Earth and Space 2010: Engineering, Science, Construction, and Operations in Challenging Environments

We have assembled a 2D model to study the dynamics of eolian soil entrainment at the particle scale. This model couples a lattice-Boltzmann computational fluid model with a discrete element model (DEM) to represent individual particles. Grains are entrained into the fluid flow by the computed aerodynamic forces and grain-grain collisional forces. The coupling was implemented using an immersed boundary condition to calculate the fluid forces on grains, and vice versa. The computational model uses a large eddy simulation (LES) turbulence closure model to allow simulations of relatively high Reynolds number, subsonic flows. This model is used to simulate two conditions: flow parallel to the bed, and a planar jet impinging the bed. Results from both of these cases are presented along with comparisons to experimental data and observations.

Dust accumulation on thermal radiator surfaces planned for lunar exploration will significantly reduce their efficiency. Evidence from the Apollo missions shows that an insulating layer of dust accumulated on radiator surfaces could not be removed and caused serious thermal control problems. Temperatures measured at different locations in the magnetometer on Apollo 12 were 38 °C warmer than expected due to lunar dust accumulation. In this paper, we report on the application of the Electrodynamic Dust Shield (EDS) technology being developed in our NASA laboratory and applied to thermal radiator surfaces. The EDS uses electrostatic and dielectrophoretic forces generated by a grid of electrodes running a 2 μA electric current to remove dust particles from surfaces. Working prototypes of EDS systems on solar panels and on thermal radiators have been successfully developed and tested at vacuum with clearing efficiencies above 92%. For this work, EDS prototypes on flexible and rigid thermal radiators were developed and tested at vacuum.

Lunar surface missions will rely on In-Situ Resource Utilization (ISRU) technologies for a sustained presence. These technologies will be enhanced by the use of beneficiation approaches of lunar regolith to increase efficiency and performance of regolith processors for oxygen and water production. An experimental investigation to determine the performance of size sorting concepts of lunar simulants was performed under terrestrial and lunar gravity on the Zero-G aircraft. Two hardware concepts were tested which were based on screen sieving techniques. The effects of vibration and sifting agitation, use of JSC-1a and NU-LHT-2M lunar simulants, and different mesh sizes were investigated. The sieving percentage was determined by simple weighing of passing particles. Imaging of the sieving process to provide physical insight was also provided during the flight tests. Despite the limited low-g period (approximately 20 seconds) the data provided sufficient information to determine the performance and operational issues of operating over longer periods in a relevant low-g environment. The results of sieving performance, hardware operation, and testing in terrestrial and lunar gravity will be discussed.

The lifetime of reactive sites on the surfaces of irradiated lunar dust grains is of interest to anyone studying human health effects because of the free radicals and toxic compounds that may be formed and may not passivate quickly when exposed to habitat/spacecraft air. One of the major activators of lunar regolith grains may be ultraviolet (UV) radiation, but the contribution of UV radiation to space weathering appears to have been neglected, to our knowledge. The work reported here describes the novel use of time-resolved Raman spectroscopy to measure changes in reactivity caused by UV irradiation. The change in the dominant Raman spectrum peak centers of San Carlos olivine versus time was measured to determine the rate of decay of polished samples exposed to UV radiation in various levels of ambient humidity. The decay time of the reactivity was observed to decrease as the relative humidity increased from 0% to 100%. The chemical reactivity caused by UV exposure appears to passivate after approximately 50 minutes in air containing 45% or higher relative humidity at approximately 25 °C. Experiments such as these will provide guidance in the design and fabrication of living facilities on the Moon.

Discrete Element Method (DEM) simulations of rotating drum flows, aimed at developing simulation models for the deformation and flow of lunar regolith, tested the effects of particle shapes (spheres, particles comprised of 8-spheres in a cubical arrangement, and clusters of 4-spheres in a tetrahedral arrangement) and a variety of cohesive pull-off force values. In these simulations the calculational-material comprised of purely spherical particles flowed much more readily than did the regolith simulants being used as guides for this study. The simulated samples comprised entirely of cubical-cluster particles appeared to have higher shear resistance than observed in physical tests of JSC-1A simulant. The samples comprised of tetrahedral cluster particles responded in a manner that most closely resembled the observed behavior of the simulant powder. Linear, quadratic and cubic scaling of the model cohesive pull-off force parameter with particle size was examined to see which scaling with particle size would come closest to preserving the overall mode of the bulk powder flow if larger-than-nature calculational particles were used in the simulations. Theoretical cohesive force models, such as JKR or DMT, predict that actual pull-off forces due to van der Waals interactions acting between particles will scale linearly with particle size. The aim of this study was to see what scaling of the cohesive force with particle size would allow larger calculational particles to exhibit bulk deformation similar to a material comprised of much smaller physical particles. Not unexpectedly it was found that scaling the pull-off force parameter with the square of the particle-size produced flows that remained the most similar, as the size of the calculational particles was increased. This scaling keeps the bulk tensile strength per unit area of the bulk powder approximately constant as the calculational particles vary in size.

The modeling of mobility and excavation on mars and the moon requires a thorough understanding of the planetary regolith. In this work, a discrete element (DEM) based model of a triaxial cell was created that closely represents the complex processes and properties of granular media. This model relies on a triangular lattice membrane covered triaxial cell for determining the macroscopic properties of the modeled granular material as well as a fast and efficient contact detection algorithm for a variety of grain shapes. This enables direct comparison to an actual triaxial test of the proposed material. We compare simulations and experiments using Vicksburg sand that can be closely replicated by poly-ellipsoidal (asymmetrical ellipsoidal) grains in the model. Then we compare experimental triaxial tests done on lunar simulant (JSC-1a) to DEM triaxial simulations. This comparison gives us a basis to begin scaling DEM grain size, shape and size distributions to practical values for extraterrestrial mobility and excavation modeling.

Previous researches have revealed that the lunar surface soil (regolith) has a very wide range of grain size distribution. The mechanical properties of such a granular material may be quite different from those of poorly-graded granular materials. This paper proposes a method to reproduce the mechanical properties of a well-graded granular material by replacing it with a binary mixture of different particle sizes and evaluates systematically the effects of grain size distribution. A series of maximum and minimum density tests and direct shear tests with a lunar soil simulant, FJS-1, proved that the model effectively simulates the void ratio range and the shear strength of original material.

In order to realize a long-term lunar exploration, it is essential to develop a technology for transporting lunar soil for in-situ resource utilization. We are developing a particle transport system that uses electrostatic traveling-waves. The conveyer consists of parallel electrodes printed on a plastic substrate. Four-phase rectangular voltage is applied to the electrodes to transport particles on the conveyer. Ultrasonic vibration was applied to the conveyer to transport particles efficiently. The following points are the outline of our investigation: (1) The observed transport rate in air was 2 g/min. Through numerical calculations based on the 3D distinct element method, we predicted that the system performance would improve in the high vacuum and low-gravity environment on the moon. (2) The power consumption of this system is very less. It was only 4 W for a 1-m² area of the conveyer. (3) We demonstrated an inclined and curved transport path as well as a flat and straight transport path. In addition, we demonstrated that transportation of particles through a tube and accumulation of scattered particles were also possible.

The Lunar Airborne Dust Toxicity Assessment Group (LADTAG) is working to determine the permissible limits for exposure to lunar dust. This standard will guide the design of airlocks and ports for EVA, as well as the requirements for filtering and monitoring the atmosphere in habitable vehicles and other modules. Rodent toxicity testing will be done using the respirable fraction of actual lunar soils (particles with physical size of less than 2.5 micrometers). We are currently separating this fine material from the coarser material that comprises >95% of the mass of each soil sample. Sieving is not practical in this size range, so a new system was developed for this task. Collection and separation efficiencies are tracked as development and tests proceed. LADTAG's recommendation for permissible exposure limits will be delivered to the Constellation Program in 2010.

Preparations for lunar missions involve the extensive use of simulants of lunar surface materials. Since many planned operations engage the mechanical properties of the regolith, it is of utmost importance to assure that the simulants adequately represent the engineering properties of actual lunar materials. To address this critical issue, we are conducting an experimental and modeling effort to quantify and compare the grain-scale properties of lunar materials and their simulants. Given the scarcity of lunar regolith for experimentation, we employ an approach to material characterization based on grain-to-grain contact experiments and use numerical modeling to extend the work to the engineering scale. This paper describes the experimental methods, compares the contact properties of the materials under study, and discusses our on-going DEM modeling efforts. We present the results of an initial set of contact experiments conducted on the plagioclase component of the lunar simulant NU-LHT, and a number of highlands plagioclase grains obtained during the Apollo 17 mission. Our initial experiments indicate that the normal contact stiffness of the simulant plagioclase can be up to 2–3 times higher than the lunar highlands plagioclase, which appears to be primarily in the form of relatively weak micro-breccias. This difference is substantially lower for more intact lunar grains. Sliding contact experiments indicate that the shear stiffness at low force levels is close to the normal stiffness. These preliminary experiments indicate that lunar highland simulants produced by simple crushing and grinding of plagioclase rock may not capture the actual strength of lunar highlands plagioclase. Continuous micro-meteorite space weathering of soil on the Moon can weaken grains considerably more than simple crushing/grinding. Additional experiments are in progress with plagioclase from contrasting maturity of soils, as well as with lunar rock plagioclase.

The exploration of the lunar surface will rely on properly designed excavation equipment for surface preparations and for collection of lunar regolith in In-Situ Resource Utilization (ISRU) processes. Performance efficiency, i.e minimizing loading forces while maximizing material collection, and mass and volume reductions are major design goals. The NASA Glenn Research Center has embarked on an experimental program to determine the flow characteristics and dynamic forces produced by excavation operations using various excavator bucket designs. A new large scale soil bin facility, 2.27 m x 5.94 m x 0.76 m (nominally 8 ft. x 20 ft. x 27 in.) in size, capable of accommodating moderately large test implements was used for the simulations of lunar operations. The soil bin is filled with GRC-3simulant (a mixture of industrial sands and silt with a particle size distribution and the bulk mechanical (shear) strength representative of an average of lunar regolith from different regions) and uses motorized horizontal rails and a vertical actuator to drive the implement through the lunar simulant soil. A six-axis load cell and encoders provide well resolved measurements of the three dimensional forces and torques and motion of the bucket. In addition, simultaneous video allows for the analysis of the flow behavior and structure formation of the regolith during excavation. The data may be useful in anchoring soil mechanic models and to provide engineering data for design consideration.

This paper presents a study of the material response of a granular material under different gravity fields. A numerical tool, the discrete element method, is used to perform the drained triaxial compression simulations. The gravitational effect is examined with this numerical tool without using multiple samples. The results are compared with previous numerical simulations with zero gravity. The granular material is bi-dispersive porous medium. It is composed of two different kinds (shape and size) of ellipsoids. They are randomly generated and deposited with 1-g (or 10-g) conditions. Conventional drained triaxial compression simulations are performed on these samples. The simulations are loaded to very large strain until the critical state is reached. Two different loading paths are applied such that the major principal stress is either along the gravity field or perpendicular to the gravity field. The effect of the magnitude of gravity field and the effect of anisotropy of the sample due to gravity can be investigated.

Dust exposure and control is the number one concern in returning to the Moon. Calculations show that respirable particles, if released in a habitat, would remain suspended in the air for extended periods of time. The Lunar Airborne Dust Toxicity Assessment Group (LADTAG) has been assigned the mission of evaluating dust hazards to humans and producing exposure standards for lunar dust suspended in breathing air. Dust exposure standards, similar to those established for quartz and asbestos on Earth, will determine the design, mass, power, and cost of engineering dust control systems incorporated into lunar habitats and shirtsleeve rovers. Despite its potential hazards, lunar regolith provides tremendous opportunities for both science and resources. The lunar regolith is a "witness plate" for solar system history over billions of years. A record of solar variability, supernovae, and gamma ray bursts may be found in regolith layers. The search for and retrieval of ancient regolith samples will likely be a major lunar science activity. In addition, the regolith is a resource of water and oxygen for future explorers, and major effort may be devoted to locating, excavating, and processing of regolith to extract these and other resources.

Lunar samples are not readily available for In-Situ Resource Utilization (ISRU) studies, necessary for preparations for a return to the Moon with landers, robots, and astronauts. Lunar soil simulants have been produced as substitutes for the real thing; BUT how good are they? JSC-1 and 1A were produced only to approximate the geotechnical properties of lunar soil, with its natural glassy component. This welded volcanic tuff is neither highlands- or maria-like in composition, being at best only half-way between in FeO content, and is only typical of a 2–3 % by area of the lunar surface. Indeed, JSC-1A has the wrong mineralogy [e.g., it has no ilmenite, yet has been used for hydrogen reduction of ilmenite, as well as for as feedstock for several other oxygen-production and ISRU processes.] And largely because of the blessings of NASA in the production of JSC-1, similar lunar simulants have been effectively duplicated by other nations (e.g., China, Japan). The Minnesota Lunar Simulant (MLS-1) was a reasonable hi-Ti mare soil simulant in composition, yet has been abandoned by NASA. When NASA MSFC got into the lunar simulant business, lunar soil experts repeatedly advised that "one size does not fit all", meaning that each lunar soil simulant should only be used for very specific purposes. But the education of the engineering community has not been sufficient such that "high-quality studies are still being performed on the wrong simulants". Also, lunar soil simulants are being produced supposedly with certain properties, which are in reality definitely not proper lunar simulants For example, simulants with nanophase metallic Fe are far from being similar to lunar soils; JSC-1A made with nanophase Fe has an order of magnitude more nanophase magnetite than metallic Fe, so what good is this product? Indeed, most people questioned are not really sure what or why they are trying to simulate nanophase Fe: magnetic susceptibility? Dielectric properties? Toxicity? A review of the unique properties of lunar samples required for studies in engineering and applied sciences (exclusive of biology) is conducted here. This naturally leads to an evaluation of current simulants and the requirements for simulants that must accurately reflect all properties of lunar soils. If not possible to synthesize suitable materials, it may be necessary to use the soils from the Apollo lunar sample collection.

An acoustic method of determining the size of loose particles has been developed at the breadboard level. This is intended as a precursor to a planetary flight instrument that can conduct grain-size analyses using a highly miniaturized sensor head requiring no complex sample processing or handling. When a particulate material (sand, dust) in actively being crushed, it emits a sound or acoustic signature that is diagnostic of the particle size distribution of the material, as well as the hardness of the grains. This principle hβas been applied in the breadboard development which has confirmed the ability of the technique to discriminate between samples based on their size distribution. A brief anecdotal comparison serves to illustrate the principle underlying the proposed instrument. It has probably been most people's experience that sugar spilled on a tabletop creates a distinctive crunching sound if a cup is pressed down onto it. But if flour is spilled on the tabletop, the same cup will generate only a muffled "squeaky" sound. The human ear can readily distinguish the sound of crushing sugar, salt, and flour without having to see what the cup is sitting on. In other words, this simple tabletop "experiment" can do first order grain-size discrimination by registering diagnostic acoustic signatures for each material. We are proposing to take the next, considerably more sophisticated step by replacing the human ear with highly sensitive acoustic transducers that can explore both audible and non-audible frequencies.

At Earth & Space 2008, we presented a numerical model that predicts trajectories of lunar dust, soil, and gravel blown by the engine exhaust of a lunar lander. The model uses the gas density, velocity vector field, and temperature predicted by computational fluid dynamics (CFD) or direct simulation Monte Carlo (DSMC) simulations to compute the forces and accelerations acting on the regolith particles, one particle at a time (ignoring particle collisions until more advanced models are developed). Here we present significant improvements to the model, including the implementation of particle drag and lift formulas to account for the rarefaction and compressibility of the flow. It turns out that the drag force is reduced due to the rarefaction, but the lift is increased due to several effects such as particle rotation. A data matrix of particle sizes, engine thrusts (descent and ascent values for Altair), horizontal and vertical starting distances, and lander height above ground, have been tested using the latest version of the software. These results suggest that the previously reported 3 degree trajectory angle limit can be exceeded in several cases by as much as a factor of five. Particles that originate at a height of 1 cm above the surface from an outer crater rim can be propelled to angles of 5 degrees or more. Particles that start at 10 cm above the surface can be ejected with angles of up to 15 degrees. Mechanisms responsible for placing particles at starting heights above the surface may include the kinetics of horizontal collisions, as suggested by Discrete Element Method (DEM) simulations. We also present results showing the distance particles travel and their impact velocities. We then use the model to evaluate the effectiveness of berms or other methods to block the spray of soil at a lunar landing site.

A subscale landing site alteration program was conducted in support of future Mars landed Missions to provide site alteration data including soil erosion mechanisms and dependency on throttle level, altitude, and ground slope. A 25% scale Viking Lander Engine was fired into a representative Mars stimulant soil-media test bed. The test facility was operated at ∼633 Pa to match the supersonic plume expansion at mars ambient pressure. The test apparatus utilized quarter symmetry with the use of baffle planes. A media that is 1/3 the density of Mars silica was used to match the 1/3 gravity Mars ballistic coefficient and particle trajectories. Key findings include soil bulk shear failure as the primary erosion mechanism, nonlinear dependence of erosion with throttle level and ground slope, and particle size. Another key finding is that we observed significantly larger erosion rates for supersonic jets (under-expanded) at Mars atmospheric pressure as opposed to jets (highly over-expanded) at Earth atmospheric environment. The highest ground pressures were also observed in the Mars atmospheric regime with jet expansion ratios greater than 2.

We measured the spatially varying flow field and entrainment flux under an axisymmetric jet impinging on a particle bed. We found that the erosion of the bed is driven by excess turbulent surface shear stress, readily quantified by the turbulent kinetic energy of the flow. This observation differs from uniform flow parallel to the bed wherein the horizontal flux of particles depends linearly on the local surface shear stress computed from the time-averaged flow and in excess of a critical value. Our findings suggest a more general approach for relating the entrainment flux to the bead shear stress: use the time-dependent shear stress acting on the erodible soil bed. In the case of uniform flow the shear stress is for all intents and purposes invariant in time and space; for non-uniform flow this is not the case and the shear stress based on the turbulent fluctuations (second moments) of the flow should be used.

Rover-mounted geotechnical systems are of paramount importance to lunar trafficability assessment, construction, and excavation/mining toward establishing permanent human presence on the Moon. These tools can also be used to determine density, when the regolith is used as radiation shield, for example. Two popular in-situ devices for establishing geotechnical properties of soil are the Static Cone Penetrometer (SCP) and Dynamic Cone Penetrometer (DCP). However, both systems have shortcomings that may prevent them from being robotically-deployed in a low gravity environment. In this paper we describe an alternative system, called the Percussive Dynamic Cone Penetrometer (PDCP) that can be used to robotically-measure geotechnical soil properties in a low gravity environment. It is shown that PDCP data correlates well with the data obtained from both SCP and DCP testing, and by extension with California Bearing Ratio (CBR) and soil bearing strength.

With NASA's planned return to the moon and possibly with lunar outposts being formed, repeated landings at the same site will be necessary. Understanding rocket plume interaction with lunar and Martian surfaces is of paramount importance in order to safely land and protect hardware surrounding the landing site. This work will report on results of three small experiments intended to explore plume impingement onto lunar and Martian surfaces: Handheld Observation of Scour Holes (HOOSH), Handheld Angle of Repose Measurements of Lunar Simulants (HARMLuS), and Mars Artitechture Team study (MATS). The first two experiments were performed during two sorties of reduced gravity flights. HOOSH was designed to investigate crater formation as a function of gravitational level (lunar and Martian gravity). HARMLuS was designed to measure the Angle of Failure (related to the angle of repose) at lunar and Martian gravity. Both experiments have complex findings indicative of the hysteretic behavior of granular materials, especially resulting from reduced gravity. The MATS experiment was designed to investigate the effects of regolith compaction on the granular mechanics of crater formation. In general, the granular mechanics is a much stronger function of compaction than gravitation acceleration. Crater formation is greatly enhanced at reduced gravity (resulting in much larger craters). The angle of failure of the lunar simulants increases with decreasing gravitational acceleration, and occasionally becomes infinite for some compactions at lunar gravity. The angle of failure also increases with increasing compaction. While compaction does play a role in the time development of crater formation, the asymptotic behavior is largely unaffected.

Small scale jet-induced erosion experiments are useful for identifying the scaling of erosion with respect to the various physical parameters (gravity, grain size, gas velocity, gas density, grain density, etc.), and because they provide a data set for benchmarking numerical flow codes. We have performed experiments varying the physical parameters listed above (e.g., gravity was varied in reduced gravity aircraft flights). In all these experiments, a subsonic jet of gas impinges vertically on a bed of sand or lunar soil simulant forming a localized scour hole beneath the jet. Videography captures the erosion and scour hole formation processes, and analysis of these videos post-test identifies the scaling of these processes. This has produced important new insights into the physics of erosion. Based on these insights, we have developed an erosion rate model that can be applied to generalized situations, such as the erosion of soil beneath a horizontal gas flow on a planetary surface. This is important to lunar exploration because the rate of erosion beneath the rocket exhaust plume of a landing spacecraft will determine the amount of sand-blasting damage that can be inflicted upon surrounding hardware. Although the rocket exhaust plume at the exit of the nozzle is supersonic, the boundary layer on the lunar surface where erosion occurs is subsonic. The model has been benchmarked through comparison with the Apollo landing videos, which show the blowing lunar soil, and computational fluid dynamics simulations of those landings.

Numerical simulation of lunar regolith and simulant is of significant interest given the planned effort to establish a long term presence on the Moon. The granular behavior of these materials requires the representation of discrete particle interaction which is angular in shape. This paper describes Discrete Element Method (DEM) simulations with polyhedral particle shapes to reproduce recently conducted experiments on JSC-1A, a lunar soil simulant. In order to account for the highly angular JSC-1A particle shapes, a new DEM element library was developed from scanning electron microscope photos of JSC-1A particle. DEM model parameters were developed from available geotechnical properties, such as grain size distribution, or calibrated using selected experiments, such as contact damping ratio. The paper will discuss in detail the modeling approach and the results of a suite of simulations intended to reproduce experimental observations. The small particle size in the JSC-1A experiments would require the use of very large number of particles in the DEM simulations which is computationally very costly. Therefore, larger particle sizes have been employed while maintaining the general character of the grain size distribution curve. The simulation results show an overall good agreement with the experimental measurements, although limited stick-slip fluctuations in the force measurements are observed due to the larger size of particles in DEM simulations.

For the return of humans to the lunar surface, there is need for a more comprehensive understanding of the strength properties of the lunar regolith in order to reduce risk to the explorers. Spacecraft will land on, shelters and bases will be constructed in, materials will be mined from, and exploration vehicles will traverse extensive regions of the undisturbed lunar regolith. Previous lunar missions included soil mechanics studies, but did not provide sufficient information to estimate regolith strength in unexplored regions of the Moon. This paper describes the design of a system to measure the strength characteristics of lunar soil simulants in an analog lunar environment. In this system, the simulant is tested in high vacuum to replicate the ambient pressure experienced by lunar regolith particles. Within the vacuum chamber, soil samples reside in a copper bin that can be heated or reduced to near liquid nitrogen temperature using a temperature controlled contact plate. While monitoring chamber pressure and simulant temperature, the strength of the regolith simulant is analyzed by means of an externally driven bevameter device capable of performing plate-sinkage, cone penetration, and annular shear tests within the vacuum chamber. Principles of similitude are applied to account for the effects of gravity. The design of the lunar environment simulation chamber and initial strength testing experiments are discussed. Additionally, the application of this system to lunar regolith strength characteristic prediction of previously unexplored regions of the Moon is examined.

This paper describes a method to deduce in situ soil density from ripping and raking force measurements. A clear understanding of the properties of the substrate — including density — is required for effective preparation of any site, whether on Earth, the Moon, or Mars. When the substrate is soil or regolith, the density often must be modified through compaction to meet stability requirements. Scaled experiments conducted with JSC-1A lunar regolith simulant form the basis for a potentially useful relation between soil or regolith density and ripping force, ripper tine spacing, and number of tines. The high data acquisition rates of modern instrumentation thus permit high-resolution density mapping of any site being subjected to ripping or raking. This would be valuable for scientific study. It also would provide calibration in situ for some aspects of remote sensing.

We have studied several field geotechnical test instruments for their applicability to lunar soil simulants and analog soils. Their performance was evaluated in a series of tests in lunar simulants JSC-1A, NU-LHT-2M, and CHENOBI each prepared in carefully controlled states of compaction through vibration on a shake table with overburden. In general, none of the instruments is adequate for a low-cohesion, frictional soil, but we find that a modified version of a shear vane tester allows us to extract several of the important soil parameters. This modified instrument may be useful for use on the lunar surface by astronauts or a robotic lander. We have also found that JSC-1A does not behave mechanically like the other lunar soil simulants, probably because its particle shapes are more rounded. Furthermore we have studied a soil material, BP-1, identified as very lunar-like at a lunar analog location. We find this material has a natural particle size distribution similar to that of lunar soil and arguably better than JSC-1A. We find that BP-1 behaves very similarly to the high fidelity lunar simulants NU-LHT-2M and CHENOBI.

A lunar surface soil sample from Descartes highland (No.60501) was investigated by micro X-ray CT. On the basis of obtained 3D information on particle shape, the particles were classified into four groups: (1) monomineralic particles, (2) breccias (fragmentai matrix), (3) breccias (crystalline matrix), and (4) agglutinate particles which have a lot of reentrant surfaces and enclosed voids. The content ratio of these particles obtained in this study was in good agreement with those reported in the previous study by Houck (1982). The detailed 3D shape indices such as the aspect ratio, the flatness ratio, the elongation ratio and the sphericity were computed for all the particles and their statistics were discussed. An image-based DEM in which the particles were directly modeled from the 3D information was employed to quantify the effects of agglutinate content on the mechanical properties of lunar soil under the simple shear condition. The analysis revealed that the minimum void ratio increases with increasing agglutinate content, but that the shear resistance is irrelevant to the agglutinate content. The angle of shear resistance obtained is about 50 degrees, which is in good agreement with those referred in preceding studies.

The physical state of the lunar soil in the permanently shadowed craters of the moon is inferred from experimental investigation. The permanently shadowed craters do not undergo the same thermal cycling experienced by other parts of the moon and therefore could be slightly less compacted. This study is significant because excavating, roving, and landing interactions, along with the energy budgets and deployment schedules for associated technology, need to be scaled and designed properly. Results indicate that the degree of compaction due to thermal cycling is a function of the depth in the soil column.

Various high temperature chemical processes have been developed to extract oxygen and metals from lunar regolith. These processes are tested using terrestrial analogues of the regolith. But all practical terrestrial analogs contain H₂O and/or OH^–, the presence of which has substantial impact on important system behaviors. We have undertaken studies of lunar regolith simulants to determine the limits of the simulants to validate key components for human survivability during sustained presence on the moon. Differential Thermal Analysis (DTA) yields information on phase transitions and melting temperatures. Thermo-Gravimetric Analysis (TGA) with Fourier Transform Infrared (FTIR) analysis provides information on evolved gas species and their evolution temperature profiles. The DTA and TGA studies included JSC-1A fine, NU-LHT-2M and its proposed feedstocks: anorthosite; dunite; HQ (high quality) glass and the norite from which HQ glass is produced. As an example, the DTA and TGA profiles for anorthosite follow. The DTA indicates exothermic transitions at 355 and 490°C and endothermic transitions at 970 and 1235°C. Below the 355°C transition, water is lost accounting for approximately 0.1% mass loss due to water removal. Just above 490°C a second type of water is lost, presumably bound in lattices of secondary minerals along with other volatile oxides. Limited TGA-FTIR data is available at the time of this writing. For JSC-1A fine, the TGA-FTIR indicates at least two kinds of water are evolved in the 100–500 and the 700–900 °C ranges. Evolution of carbon dioxide types occur in the 250–545, 545–705 and 705–985 °C ranges. Geologically, the results are consistent with the evolution of "water" in its several forms, CO₂ from break down of secondary carbonates and magmatic, dissolved gas and glass recrystallization.

Aiming at the key design problems of large pumping station in area of high seismic-intensity on weak foundation, this paper proposed a new type of reinforcement scheme combining with plate rib underground continuous wall and soil grouting technique based on China's South-to-North Water Diversion Project. According to the layout characteristics of jointed structure, a three-dimensional nonlinear finite element model was established, and the static and dynamic finite element analysis of the plate-rib underground continuous wall were achieved with consideration of different rib width, grouting depth and soil strength parameters. The displacement principles of structure and foundation, contact state of construction joints, the influences of different arrangement modes of retaining wall and grouting effect on the overall safety performance of structure were studied respectively. The results showed that the reinforcement method is feasible and effective, and it can solve the base consolidation problem of soft-based foundation of large pumping station in meizoseismal area.

Externally bonding of FRP plates or sheets has become a popular method for strengthening reinforced concrete structures. Stresses along the FRP-concrete interface are of great research interest because high interface stress concentration can lead to debonding along the FPR-concrete interface and premature failure of the structure. In this study, we develop an analytical solution of FRP-concrete interface stresses in a curved structural beam strengthened by a thin plate through externally bonding. Unlike existing studies in which the adhesive layer is modeled as a two-parameter elastic foundation, this study simulates the adhesive layer as a three-parameter elastic foundation by introducing an extra independent parameter, the deflection of the mid-plane of the adhesive layer. In this new model, the interface shear stress is assumed constant through the thickness of the adhesive layer; while the interface normal stresses along two adherend/adhesive interfaces are assumed different. The equilibrium equation of the adhesive layer, which is violated in two-parameter elastic foundation model, is satisfied by this new model. Closed-form solutions of interface stresses and beam forces are obtained and verified by finite element analysis.

This paper presents an efficient frame finite element (FE) able to accurately model reinforced concrete (RC) beams strengthened in flexure with externally bonded fiber reinforced polymer (FRP) strips and plates. The proposed element employs a force-based formulation and considers distributed plasticity with fiber-discretization of the cross-sections. The FRP strip/plates are modeled as an additional layer with linear elastic-brittle behavior in tension and zero-strength in compression. The failure strain in tension is the lower value between the rupture strain of the FRP material and the strain at debonding. The cross-section stress resultants are obtained under the Euler-Bernoulli kinematic assumption. Realistic nonlinear hysteretic constitutive models are used for both concrete and steel materials. The presented FE is used to predict, based on very coarse FE meshes, the ultimate load-carrying capacity of beams subjected to three- and four-point bending loading, for which experimental results are available in the literature. Comparison of numerical and experimental results are presented in terms of the ratio between the numerical prediction and the experimental value of the maximum shear force for several sets of tests from different authors. The experimental configurations considered cover a wide range of different geometry, material properties, steel reinforcements and FRP reinforcements. The obtained numerical results compare remarkably well with the experimental results. The proposed FE is able to model flexural collapse (steel yielding, concrete crushing), collapse due to FRP rupture, and FRP debonding. The major features of this frame FE are its simplicity and its efficiency in terms of mesh refinement. In addition, the proposed frame element can be used without modification for FE analyses based on cyclic and dynamic loadings. Thus, this FE is suitable for modeling and analyzing flexural rehabilitation of FRP-strengthened RC frame structures. FRP-strengthening is particularly useful for structures subjected to demanding environmental conditions.

Since the anisotropic characteristic of deformation and strength of layered rock masses, giving the reasonable constitutive model is of great significance for numerical analysis of the rock engineering concerned of layered rock masses. Based on the McLamore & Gray strength criterion, the isotropic Drucker-Prager strength criterion which is widely used in rock engineering is extended to be an anisotropic elastoplastic constitutive model for layered rock masses by making use of the conversion relationship between the Mohr-Coulomb strength criterion and the Drucker-Prager strength criterion. Then the presented anisotropic constitutive model is embedded in ABAQUS for its numerical implementation based on the derivation of the implicit integration algorithm and consistent tangent modulus. Numerical example is given for demonstration of the validity of the proposed constitutive model and its numerical implementation.

As the intake sluice pier is a massive concrete pier structure, the existences of injury cracks are inevitable and these cracks may expand further to affect the stability of the structure. Using the element-free method as the numerical method and the theory of fracture mechanics as the analysis tool, this paper determines the necessity of using the mechanical-hydrological coupling technology. Through the establishment of the dual medium model including the cracks, this paper focuses on tracking the tracing of the crack propagation at the heel of pier under the load of the water pressure. The results show that after the occurrence of the cracks at the heel of pier, the cracks will continue to propagate and affect the stability of the structure.

The allowance crack length is the distance from the dam heel to centerline of drainage holes. The real crack length is varied with the hydraulic pressure acted on the dam and material mechanical properties. Nonlinear FEM analysis is used to obtain the real crack length, and the Mohr-Coulomb criterion with lower tensile strength is used to simulate the cracking and yielding state on the interface between dam and foundation. The limit state equation of crack reliability for gravity dams is established with the computation length and the allowance length. The hydraulic pressure, parameters for Mohr-Coulomb criterion, and mechanical parameters for dam and foundation are taken as random variables. The linear response surface method is used to obtain the iterative result of the reliability and the orthogonal test design method is used to reduce the number of finite element analysis. The LongTan RCC gravity dam is taken as an example and the crack reliability is given.

The propagation of cracks in concrete structures is always accompanied by energy dissipation and redistribution. This kind of energy dissipation and redistribution can be characterized by entropy. In this paper, cracked concrete structures are considered as dissipative structures. The mechanism of energy transformation and dissipation in the propagation of cracks is studied. Structural information entropy is then defined for concrete structures. Finally, compact tension test is conducted and numerical simulation is carried out to analyze entropy variation in the propagation of cracks in concrete structures. The test results show that the entropy in the fracture process zone increases with the increase of applied load and that the propagation of cracks can be characterized by structural information entropy.

In order to control the formation and expansion of cracks, artificial inducing joints are set up near upstream heel of Xiaowan arch dam to release the tensile stress. Based on the qualitative analysis, this paper analyzes the inducing joint behavior of Xiaowan arch dam during reservior filling by using statistical model, which extracts the componets of main influencing factors on the inducing joint deformation. With stress meter and osmometer monitoring data, the deformation behavior of inducing joints are evaluated. It suggests that below 1160m water level, temperature is the main factor and correspondingly the reservior filling process has no obvious effect, but some osmometer measured values are still worthy close attention.

Many high arch dams are in service with cracks, which degraded the integrity and ultimate bearing capacity of arch dam. In this paper, based on natural vibration frequency, the possibility for monitoring the ultimate bearing capacity of cracking arch dam in service was discussed theoretically using finite element numerical analysis. The effect of typical crack on the ultimate bearing capacity of arch dam was analyzed with hydro-pressure over-loading method. The relationship between the overload factor and natural vibration frequency of arch dam under different crack condition was studied. The calculation result shows the natural frequency variation caused by load-induced structure crack is obvious in hour scale. So it is feasible to assess the ultimate bearing capacity of cracking arch dam in service based on natural frequency monitoring. The natural frequency of arch dam measurements would be carried out by ambient excitation such as water discharge, operation of hydropower station and small earthquake.

A unified approach is proposed to evaluate the compliance and energy release rate (ERR) of generic beam-type interface fracture specimens. Based on a sub-layer Timoshenko beam theory and three different joint deformation models, the compliance and ERR of the generic beam-type fracture specimens are obtained. The effects of the crack tip deformation on the ERR of the interface crack are compared among the three different joint models, from which the evolving accuracy of the joint models to the ERR predictions of beam-type fracture specimens is manifested. The derived explicit formulas and improved solution for the compliance and ERR of the common beam-type fracture specimens can be effectively used to reduce data in interface fracture experiments and increase accuracy of fracture toughness evaluation of dissimilar material interfaces.

Luanshigang landslide is located in Sichun province of China. This paper introduces the influencing factors about the stability of landslide, which include the characteristics of landslide topography, regional geological structure, geological conditions, as well as rainfall, earthquakes, human activity and so on. Therefore, the failure mechanism of the landslide can be divided into many types. The mode and the cause of Luanshigang landslide are analyzed, the whole process of the creep — cut landslide mode is simulated. The present landslide stability is conducted and evaluated by numerical simulation. Furthermore, the seismic response and stability of the landslide is researched. Based on the analysis results, the stability of the landslide is evaluated and the reinforced method is suggested.

The fundamental theory of generalized plasticity is proposed in detail. With the framework of the theory, irreversible plastic deformations during loading and unloading are introduced without specifying any yield or plastic potential surfaces explicitly and the soil behavior under complicated stress path can be simulated. Based on the theory, a finite element code with concerning the model is programmed and tested. By using the numerical code, all the parameters that the model needs are obtained for a ultra-high rockfill dam and the static response of the dam is simulated. The results show that PZ-III model possesses considerable adaptability for simulating high rockfill dams.

In this paper the FEM is used to analyse how the interface shear stress affects the tension in geomembranes with biaxial displacement loaded at the specimen's boundaries. And the numerical solution is based on two models, one is interface shear stress (SS) — shear displacement (SD) response between the geomembranes and soil; and the other is the biaxial stretching stress-strain response of geomembranes. And the result indicates that the shear stress should not be disregarded in design and construction, especially at where the displacement of the geomembranes is relatively biger than somewhere else.

Buckling of shallow spherical shells made from composites, and subjected to external pressure, can be a design limitation in a number of applications, e.g., in pressure safety devices, shallow mirrors, energy concentrators/inflatable space antenna. The magnitude of buckling pressure in shallow spherical caps is strongly dependant on the boundary conditions applied at the cap's outer edge. The current paper examines the use of toroidal shells with closed, circular and non-circular cross-sections, as means of supporting/constraining the outer edge of the cap. This implicitly aims at preventing buckling of the cap or at increasing the cap's buckling load. The toroids can also be internally pressurized, differently laminated, etc. Additionally the point of cap's attachment can be chosen in such a way that buckling load is as large as possible. The effect of some of these parameters on the buckling pressures of spherical caps is quantified. This is an entirely numerical study.

Combined with triaxial test data of coarse-grained material, rationality verification and study of constitutive model used commonly in earth dam indicates that Duncan's E-B model and SHEN Zhujiang's double-yield-surface model both well reflect the stress-strain relationship of pre-broken coarse-grained material under general triaxial test. Using general triaxial test parameters, deformation of coarse grain calculated under the path of equal stress ratio is done; whose decrease of volume strain and increase of shear strain is great difference compared with the experimental result. Nonlinear elastic model and Shen Zhujiang's double-yield-surface model could fit the result of triaxial test under equal stress ratio well when they are modified combined with the stress path of equal stress ratio. the main reason of great calculation error is that elastic parameters obtained by general triaxial experiment are applied to calculate them under complex stress path in high rockfill dam, by assuming the elastic parameters independence on stress path. Reasonable stress-strain constitutive model must reflect dam's real loading stress path objectively.

In the coupled analysis of arch dam with trial load method and finite element method, the author presents a new method to solve the incompatibility of the nodal displacement at dam-foundation interface. The translation and rotation displacement of the arch-cantilever base nodes on the interface between dam and foundation are interpolated by the translation displacement of the finite element nodes which have relation with those base nodes. A new relationship between the translation and rotation displacement of arch-cantilever nodes and the translation displacement of finite element nodes is derived. The stiff coefficients about the displacements of the base nodes are transformed into the stiff matrix of the finite elements. After assembling all stiff matrixes, the total equilibrium equation can be established and solved. An example about typical cylindrical arch dam proves correctness and feasibility of the proposed method.

The concrete arch dam is a high hyper-static structure. Its deformation acted by forces is very complicated, and the early-warning for dam safety is very difficult because of the effect of structure, restraint, environment and loading condition etc. The Particle Swarm Optimization (PSO) has been applied in the dam safety monitoring, where it was widely used to solve the problems of inversing parameters, optimizing functions and optimizing components etc by searching optimization. But when it is applied to high dimension solution space, the precocious phenomenon will occur with the convergence rate slowly. In order to overcome the shortcomings, the PSO is improved in this paper. According to the changing of influence fitness of each particle, an improved PSO (IPSO) is presented by adjusting the acceleration factors by adapting and combining. In the meantime, by merging the crossover and mutation operators of genetic algorithm (GA) with PSO, the population diversity of searching optimization solution is improved when calculating. The IPSO is used to set up the deformation prediction model of a concrete arch dam. It is shown that the IPSO can avoid the precocious phenomenon and effectively improve the convergence rate of PSO. Furthermore, compared with the least square regression (LSM), the precision of deformation forecasting model of concrete arch dam based on IPSO is higher and the calculation results can be more corresponding with the practice operating condition of the dam.

This paper describes the utilization of veneer-mill residues from hardwood species, being discarded by the furniture industry, into value-added composites. These residues come from high quality logs and currently are being discarded as waste. This study describes the development of production methods for a corrugated web panel for I-joists. Using standard ASTM testing methods, an assessment of the physical and mechanical properties of the composite web panel was performed. The structural application of these panels as web material in prefabricated I-joists was studied. Composite I-joists were produced using flanges of structural composite lumber and a proposed corrugated web produced from veneer-mill residues. The purpose of the corrugated web was to increase the buckling capacity and in-plane stability of the joists. To manufacture structural size samples, corrugated panels were joined in length. The strengths of the web-to-web connection and two different flange-to-web connections were explored. A basic investigation into the bending performance of the I-joists was carried out. This research was carried out as a preliminary investigation into the production methods and characterization of composite panels produced from discarded hardwood decorative veneer clippings. The test results will be used to validate analytical and numerical models for characterization of this new product, including stiffness, strength, and buckling.

The Xieka hydropower station is located on the Taka River in Sichuan province China, where the design earthquake intensity is 7 degree. Its concrete face rockfill dam is about 108m high with about 45m to 100m thick overburden layer. According to the actual engineering conditions of Xieka dam, the 3-D non-linear FEM dynamic model of the dam is set up for calculating earthquake response. By simulating the process of the filling of dam and reservoir impounding, the original static stress field of dam body is obtained firstly under the normal water level. Then by the dynamic time-history analysis method, the earthquake response of the dam is calculated and obtained for inputting the design earthquake with peak acceleration of bedrock 109cm/s², including acceleration response, displacement response and stress response etc. The acceleration response along the up-downstream direction is the maximum with 7.6m/s², the one along the dam axis is secondary with 4.8m/s², and the one along vertical direction is the minimum with 2.9m/s² . The maximum displacement responses of dam are 56mm, 31mm and 17mm respectively in aforesaid three directions, and the maximum principle stress responses of rockfill are 871kPa, 678kPa and 598kPa respectively. The maximum stress response of face slab is about 4819kPa in the dam slope direction. It is shown that the earthquake response of the dam is consistence with the general law. The analysis results show that the design of the dam is reasonable in technique.

The application of Fiber-Reinforced Polymer (FRP) composites for retrofitting deteriorated concrete structures has been highly successful, but there are concerns with long-term performance and durability, particularly when chloride ions are still present for two possible reasons: (1) no chloride ion extraction is performed when a bridge is initially retrofitted; and (2) even if chloride ions are initially extracted, they will again accumulate from available sources such as continual application of de-icing salts. Leaving chlorides within concrete will exacerbate the onset of corrosion during the post-repair service life of the structure. Therefore, it is desirable to study whether the Electrochemical Chloride Extraction (ECE) technique, which has been proven to be an effective tool for removing chloride ions for regular concrete structures, can be effectively used for FRP repaired structures, which is the objective of this study. A total of 28 beams were tested. Testing variables included different ECE techniques, i.e., intermittent vs. continuous; different FRP repairing schemes; and applying ECE before and after FRP repair. Parameters monitored during the study included chloride content, pH value around the steel, and current resistance and density. The effectiveness of ECE was determined by changes in chloride levels and the pH value around the steel. At this stage of the study, only partial results for concrete beams without FRP are reported, while the overall scope of the research is described. Based on this study, the effects of different testing variables will be evaluated, a modified ECE technique will be proposed, and guidelines for how to implement the technique on FRP repaired structures will be provided.

Green high performance concrete can be obtained with the mineral admixture produced by industry waste residue for saving resource and energy sources. Workability, mechanical properties and durability of concrete can be greatly improved with the advanced mineral admixtures such as steel slag powder. Mechanical properties of steel slag concrete and cement mortar with different steel slag kinds and different dosage of admixtures are studied. Experiments results show the effect of steel slag powder on performance of cement mortar and concrete. When compound mineral admixtures with steel slag powder and blast-furnace slag powder are mixed into, the performance of cement mortar and concrete can be improved further due to the synergistic effect and activation each other. The mineral admixture will be a perfect component of green concrete and its utilization will be a valuable resource for recycling.

Uniformly distributed loads are usually adopted in structural design. An equivalent distributed live load on slabs has been proposed by the Chinese Load Code for the Design of Building Structures (GB50009-2001) to simplify calculations, where it specifies that the maximum absolute value of bending moment produced by the equivalent uniformly distributed load should be equal to that generated by local loads by assuming that the slab is simply supported on all four edges under both loading conditions. This assumption has large error for two-way reinforced concrete slab structures which are usually fixed on all edges. In this paper, based on classical thin plate theory, an analytical solution for equivalent uniformly distributed live load is derived for two-way slabs either fixed or simply supported on all edges and subjected to local distributed load. The resulting equation is simple but with high accuracy. The analytical solution can be applied easily for design of slabs

Latex modified concrete (LMC) overlays are placed over normal concrete substrates to increase the life of bridge decks. However, the property mismatch between these two concrete types gives rise to interfacial stresses that cause premature delaminations, corner lifting, and cracking. No systematic studies are available to properly evaluate the placement process and failure mode of LMC overlays at prototype scale. This study measures and evaluates the bond-strength, displacements, and delaminations of the interface during the entire placement and curing process. The findings will be used for full-scale studies and developing performance based specifications to eliminate or reduce the potential interface failures.

During the construction of South-North Water Transfer Project in China, many structures are poured with high performance concrete. But the over standard stress caused by temperature always bring potential safety trouble. On the way to solve such problem, boundary heat transfer coefficient is the very important parameter. Two experiments are designed to get the parameters. One is the non-adiabatic temperature rising experiment of cubic concrete block whose six surfaces are covered with different thick polystyrene insulation board. Another is the pipe cooling experiment of rectangular concrete block whose surfaces are covered with different formworks and some insulation materials. Based on the experiment data, the inversion analysis is carried out with genetic algorithm to get the boundary parameter of these materials. The achievements are applied in the temperature control research of a large aqueduct, and no crack appears again. The conclusions also suggest the selection of thickness for insulation material and cooling pipe.

Panelized systems are prefabricated components that brought to the site and assembled into the finished structure. Traditional constructions are often subjected to termite attack, mold buildups and have poor penetration resistance against wind borne debris. To overcome these problems, new type of composite structural insulated panels (CSIPs) was developed and is analyzed in this study. The concept of the panel is based on the theory of sandwich construction. The proposed composite panel is made of low cost thermoplastic glass/polypropylene (glass-PP) laminate as facesheet and Expanded Polystyrene Foam (EPS) as a core. The EPS core provides excellent insulation against heat, sound and vibration and withstands shear stresses while FRP facesheets primarily resist bending stresses. This study provides an analytical modeling for the CSIP floor member based on the experimental work previously conducted at the University of Alabama at Birmingham on full scale CSIP floor panels. A theoretical analysis was conducted to predict defection, flexural strength, and facing stresses of the CSIP floor member and results found were in a good accordance with the experimental ones.

Through experimental tests of 9 groups of recycled concrete specimens under large eccentric compression, issues were discussed concerning the effects of recycled aggregate displacement ratio on recycled concrete column's ultimate load, damage stage, and mid-span deflection under the same eccentricity. It was concluded from the experiment that the ultimate load of recycled concrete column decreased gradually as recycled aggregate's percentage rose from 0 to 80%. However when this percentage maintained 50%, the ultimate load mentioned above increased. Conclusions could also be drawn from the test that recycled concrete large eccentric compression column possessed obvious elastic stage, crack stage and fracturation stage, satisfying plane cross-section assumption in the process of buckling. Its mid-span deflection increased with the increment of recycled aggregate displacement ratio. Tensile area reinforcement basically varied linearly. When load reached 100kN and 200kN, the concrete cracked and the strain of tensile reinforcement increased suddenly. The larger the recycled aggregate displacement ratio, the larger the increment of reinforcement strain, deriving thus the conclusion that the ductility of recycled concrete column was a little bit higher than that of ordinary concrete column, and that the strain of compressive area reinforcement changed linearly before the exertion of ultimate load, and yielded with the exertion of ultimate load. The maximum strain of compressive area reinforcement conformed to that of ordinary concrete column. It was suggested the application of concrete structures with 50% recycled aggregate in engineering.

According to phenomenon that the physical properties have great effect on electric capability of carbon fiber reinforced mortar, the author researched relationship between DC resistance of carbon fiber reinforced mortar and curing age using the two-probe method. Then the effect of insulative area, location and quantity on DC resistance of carbon fiber reinforced mortar was investigated at different curing age. The results suggest that DC resistance inceases greatly with its curing age, which illustrates relationship like Sigmoidal curve. Because of bulk conduction and surface conduction like that in crystal isolator, DC resistance shows that increase first and then decrease with the increase of insulative area. The quantity of insulation has few effect on DC resistance, but the shorter the distance between electical pole and insulating trip is, the stronger its conductibility is.

A new organosilicone was adopted to improve the freeze-deicing salt resistance of cement concrete pavement. According to CDF test — Test method for the freeze-thaw resistance of concrete with sodium chloride solution, the deicer salt scaling resistance and microstructure of two kinds of concrete were investigated in this paper. The results show that after painted with the organosilicone, the scaled mass of two kinds of concrete in water-cement ratio (0.40, 0.32) were only 1% of those of concrete without organosilicone and all decreased 99% and the loss rate of dynamic elastic modulus of concrete with the organosilicone reduce by 32% – 42% of the control concrete after 56 freeze-thaw cycles. SEM observations demonstrated that the organosilicone distinctly decrease the formation of cubic NaCl crystals and microcracks inside concrete.

Crack is one of the common diseases in hydraulic concrete structures. Its traditional safety monitoring models only consider the loading factors such as hydraulic head, temperature and time without taking into account the parameters of the crack itself. The crack depth and initial opening are considered here besides the usual factors based on further analysis of the impacting factors of crack opening displacement (COD) according to Fracture Mechanics. In this way, the improved safety monitoring model can reflect both the mutation and the gradient of crack. Due to the fact that in the usual cases the crack depth and initial opening are not easily detected and measured, a method is designed to inverse them based on the finite element method (FEM) and the artificial neural network (ANN), and then a criterion of abnormality diagnosis for crack is established. Finally, based on the improved safety monitoring model and the criterion of abnormality diagnosis, a case of concrete gravity arc dam is accomplished.

The structural dynamic behavior is becoming increasingly important in order to determine the structural optimization design. Maintaining safety and integrity of the structures require a better understanding of structural dynamic properties and response. In this study, in situ test is conducted to inspect the structural dynamic behavior of gate in ship lock. The real ship is used to crash against the gate to make structural vibration. Using the free vibration response to obtain structural dynamic properties provides the foundation of structural optimization design. The special fender is used as collision protection system of the gate. The test results show that the vibration amplitude changes greatly between gates with and without the fender. The vibration amplitudes of gate with fender are less than the one without fender. Based on the in situ vibration test conducted, it is concluded that the installation of fender as collision protection device is an effective method to make the gate in ship lock safer.

The pollution of the geological environment around landfills has received increasing amounts of attention from researchers. The factors in this issue are very complex, and vary not only with the nature of MSW, but also with the type of landfill, which is closely related to the geological environment. In order to demonstrate the influence of MSW landfills (in terms of leachate, heavy metals and other harmful substances) on the surrounding geological environment (atmosphere, groundwater environment, and soil environment), literature and experimental data were studied and analyzed after field investigations. The results show that landfill leachate is the most important factor impacting the surrounding geological environment, so the mechanisms and control methods of leachate pollution of surface water and groundwater pathways are discussed. Leachate also carries heavy metals and contaminates soil. The remaining amount of heavy metals in the soil profile gradually decreases with depth. Heavy metal pollution of the soil also shows accumulation and lag patterns, and the amount of pollution increases over time. This paper proposes specific control measures for different forms of pollution and pollution patterns.

This paper studies the influence of the working gap on the magnitude and distribution of the magnetic flux density and the shear stress of a magneto-rheological coupler. The results of the Finite Element Analysis (FEA) and experiments indicate that the magnitude of the magnetic flux density decreases with the increase of the working gap, while the distribution of the magnetic flux density and the shear stress becomes more uniform along the axial length direction. Because of the magnetic saturation and the existence of the stress yield of the Magneto-Rheological Fluid (MRF), the working gap, for the range of 0.6mm to 2.0mm, has limited influence on the magnetic flux density and stress. The experimental results show that the transmission torque only decreases 25% during this range. Based on these findings, the working gap should be chosen properly to obtain a sufficient magnetic field and transmission torque for a given device with consideration of machining and assembling costs associated with a smaller working gap.

Based on the insights of high efficiency and accuracy, and avoiding influences of various user-defined parameters in mixed finite element method for solving contact problems, how to solve contact problems of multi-body by that is studied. Generalized Mohr-Coulomb law is adopted instead of classical Coulomb law as friction condition in solvable and judged conditions. Then relative spacing equation and compatibility equation in incremental form of mixed finite element method for solving contact problems of multi-body (FEM of multi-body) are presented, which can deal with rigid displacements of any bodies. For the characteristic of the relative slipping of contact nodes in any direction on the contact surface in 3D contact, contact states and slipping friction coefficient components are judged simultaneously in the program by which iteration and convergence are fast and accurate. For the common non-smooth contact namely corner problems in contact problems of multi-body, more appropriate and reasonable approaches are proposed by corner classification and real contact state of corners. Finally, the validity and accuracy of the developed method is demonstrated using a number of numerical examples, and from which a conclusion is drawn that the proposed method can be obviously applied to solving contact problems of multi-body in the hydraulic and civil engineering practice.

Rehabilitating and retrofitting concrete structural members using externally bonded Fiber Reinforced Polymer (FRP) strips has been gaining steadily use in recent years because of its many advantages, such as ease and speed of construction, low cost, low maintenance, and high strength to weight ratio. An important design issue with significant performance and safety implications is the debonding of externally bonded FRP strips in flexural members, where the delamination is primarily due to Mode-II facture. A lot of research has been done in this area, but there are concerns about interface durability. This study is based on a fracture mechanics approach using Mode-II single shear test specimen to evaluate the durability of Carbon FRP (CFRP)-concrete interface subject to two environmental conditioning effects: (1) immersed in deionized water varying from 0 to 13 weeks; and (2) controlled temperatures varying from 25°C to 60°C (77°F to 140°F) of samples while immersed in water. A new method to obtain the fracture energy release rate and the traction-separation law is proposed based on J-integral approach, by measuring load and slip at the debonding end only, which is verified by the traditional strain-based method. The durability of the interface is characterized by the fracture energy release rate. By comparing the results with those from unconditioned companion specimens, it was observed that considerable degradation of the interface integrity resulted with increased moisture duration and temperature. The test results will be further used to develop a model to predict the long-term behavior of the interface based on Arrhenius or similar relation.

Based on an interface deformable piezoelectric bi-layer beam model, a bonded piezoelectric bi-material beam with an interface crack perpendicular to the poling axis is analyzed within the framework of the theory of linear piezoelectricity. The layer-wise approximations of both the elastic displacements and electric potential are employed, and each sub-layer is modeled as a single linearly elastic Timoshenko beam perfectly bonded together through a deformable interface. The closed form solutions for energy release (ERR) and crack energy density (CED) are derived for the layered piezoelectric beam subjected to combined uniformly distributed electromechanical loading. Loading dependence of the total CED with respect to the applied electric field is revealed with the analytical results, showing that there is a transformation from an even dependence to an odd dependence for the normalized CED when the applied mechanical loading increases. The proposed model provides improved explicit solutions for fracture analysis of piezoelectric layered structures and sheds light on the loading dependence of the fracture parameters (i.e., the ERR and CED) with respect to the applied electromechanical loadings.

Controlled permeability formwork liner (CPFL) is used commonly on numerous major concrete structures for durability due to its functional compacting concrete surfaces. However, existent problems of CPFL according to series test in-situ and laboratory by author are claimed. Firstly, the effective expelling excess water and air from fresh concrete discounted obviously, and will no longer been reusing because of clogging rate of liner increased seriously after pouring with formwork two or three times continued. Secondly, concrete block surface cast subsequently is formed unsmooth due to wrinkles caused by CPFL deformation and hydroscopic properties changed and thirdly, the improvement for bottom surfaces are far less than both inclined and vertical surfaces because of weak expelling on horizontal formwork. Some efficacious methods and engineering measures are presented to solve above problems according to author's study.

This paper describes a synthesis of findings pertaining to rehabilitation of concrete T-beam bridges with externally bonded FRP composites from a Pennsylvania Department of Transportation District 3 (PennDOT D3) project, with the purpose of answering common questions of concern mainly by state Department of Transportation (DOT) engineers and officials. A method for selecting applicable candidate bridges for suitability of repair with externally bonded FRP composites is described. Three levels of repair are identified, Level 1 (contract), Level 2 (contract/Department force), and Level 3 (Department force). From this classification, a candidate bridge was selected for a contract repair project. Field and laboratory testing of existing bridge materials is described. Pre-repair tests included ultrasonic pulse velocity and rebound hammer on beam concrete, compressive strength tests on deck concrete cores, carbonation tests for both beam and deck concrete, SEM-EDX analyses for beam and deck concrete, and tension tests of the extracted reinforcing steel. Structural analysis was based on AASHTO specifications. Finite Element (FE) modeling was performed to determine existing capacity and the FE model was calibrated by testing of the bridge using applied truck loads. The FRP design was based on strengthening the bridge to sustain an HS-20 AASHTO truck loading. The FRP repair system was designed based on current ACI 440.2R-08 design guidelines. Repair work and post-construction load testing were completed. Supporting full-scale lab studies were conducted to evaluate the most effective concrete substrate repair method and FRP strengthening scheme for laboratory damaged concrete beams by accelerated corrosion, to assure better long-term performance under static and fatigue loads. Results from the rehabilitated bridge and supporting testing were used to develop draft PennDOT design standards and construction specifications and to apply "lessons learned" to the design and constructability of nearly 1,000 concrete T-Beam bridges in Pennsylvania, USA.

Numerical methods and rigid block limit equilibrium methods for rock slope analysis are introduced and the evaluation methods of static and seismic stability are discussed. Combined with an application example, the stability of a complex high rock slope in a hydropower station is evaluated under static and seismic loads, which is located in southwest China. With several analysis methods, the general stability of the slope with several blocks is first analyzed, then the stability for a key block is further studied. The results obtained by different methods are compared, and the causes of the difference between the results are explained. the research results show that the safety factors of the slope under the action of gravity and earthquake are less than that requried and some strengthening measures should be taken.

Using the 3-D topology optimization theory and the feature of high arch dam to design the homologous program to build the 3-D model and design the body type for high arch dam with the fixed arch dam upstream face. The initiative result showed that the topology optimization can be used to the reasonable body type research for high arch dam.

The Wanjiazhai is a half monolithic concrete gravity dam. The power plant has been completed and generated electricity in 2002. Several issues such as the unstable dam slope, settlement, crack, seepage etc., are discovered in the operation process. Because the existence of these series of safety problems, a comprehensive safety evaluation is needed to be carry on to understand the present security state and provide scientific basis for the safe operation, the management and the full engineering benefit. Static and dynamic structural calculation is the main appraisal method. Combining with the monitoring data of scene security check, the concrete testing, the stress, the deformation and the displacement in situ, an appropriate mathematical model is established through the back analysis. The deformation, the strength and the stability of dam under static and dynamic conditions are computed to reexamine the requirement of specification can be satisfied. The Main evaluation parameters are the stable safety factor, the maximal stress and the maximal displacement.

According to the characteristics of the underwater high-rise structure of the 2^nd spillway tunnel intake tower of Zipingpu hydro-junction, a 3-D tower-foundation dynamic analysis model was built up by using ANSYS software. This study analyzed the different modes of action of water load inside and outside of intake tower, and also achieved the application of these two sorts of water load by conducting the secondary development of APDL language in ANSYS. The new checked design earthquake parameters before and after 5.12 Wenchuan Earthquake were adopted to analyze the dynamic response of this intake tower. The seismic weak parts have been pointed out by the analysis of its dynamic displacement and stress, which provided necessary reference for the seismic reinforcement of the intake tower.

To evaluate the seismic safety of long-term operating concrete dams, we first obtain the stress and displacement relationship of concrete dams according to an evolution equation for creep damage in static condition. Then, based on the static results, the bilinear damage evolution model is adopted to combine with viscous-spring artificial boundary to investigate the failure pattern of concrete dams under the action of earthquake. This method proposed in this study can consider the effect of creep-related degradation on the safety assessment of long-term operating concrete dams. Finally, the method is validated by a comparison with the existing project data, and the results show that the method exhibits reasonable and important improvement for the existing seismic safety evaluation of large concrete dams.

Lateral deformation is one of the most important indexes which can reflect the working performance of geosynthetic reinforced segmental soil retaining wall. There are many influencing factors of the lateral deformation of wall facing. And most of the factors possess characteristics of uncertainty, randomicity and ambiguity. Taking a six-meter-high geosynthetic reinforced segmental soil retaining wall as an example, orthogonal design and finite difference method were used to analyse the global sensitivity of wall performance to design parameters of the wall. The sensitivity sequence of lateral deformation to all influencing factors and the optimal design parameters were obtained. In the end, more detailed calculation and analysis were conducted to find out the optimal length and vertical spacing of geosynthetic reinforcements, which was a problem urgently needed to be settled in practical project.

The flat shape of geotube which is used to construct dam for reservoir for fresh water supply at estuary in China is different from round shape of that in Europe and America on stability. The unstable model of the former is sliding, while that of the latter is overturning. The stability of geotube dam with modeled length scale of 30 is studied by wave experiment in a flume. The archetypal heights of model are 6.6m, 7.8m, 8.4m, 9.0m and 10.8m with slope ratios of 1.0, 1.25, 1.5, 2.0, 2.5 and the geotube dams are subject to regular wave by using constant wave steepness of 1/15, 1/20 and 1/25. Wave pressure in front of dam and up pressure at bottom of geotube affected by wave height, wave steepness, and overtopping are studied and the critical wave heights when geotube dams are unstable are obtained under different conditions. The formula of wave pressure in front of dam without overtopping is given by regressing. On the other hand, site experiments of eighteen geotubes filled with slurry of sludge clay, silt and fine sand from nearby area are performed at estuary of the Yangtze River. The results of observation on total pressure and pore water pressure show process of dewatering and consolidation of geotube with fine sand filling is suitable to geotube filling under tide condition at site. According to experiment and analysis, the dam of 9.9m high has constructed on the foundation of slurry clay to form reservoir of 3.56 x 106 m³ at estuary of the Yangtze River.

Electrical switch cabinets are widely used in power control systems. In order to ensure the seismic performance of electrical switch cabinets, seismic test must be taken. Through check calculation, the acceleration response of the measurement point can be used to check the response of strain measurement points, and the result shows that the check value is consistent with the actual measurement result. Analysis and contrastive studies are made on the natural vibration characteristics of the structure with white-noise wave transfer function, seismic wave transfer function and white-noise wave auto-power spectrum function. Legitimacy assessments are made on mechanical structure and filed installation of electrical switch cabinets by analyzing structure transfer function curves and cross-correlation function curves. It also provides basis for evaluate the seismic performance of electrical switch cabinets and installation brackets.

Cangzhou iron lion was the first batch important heritage site under state protection. Being very complicated, it is very significant to study the structure of the iron lion. Reverse engineering CAD technique was used to found the mechanical simulation model of Cangzhou iron lion; stress and displacement of iron lion was studied under 8 degree seismic fortification intensity earthquake action, the results showed that iron lion is on safe by ordinary earthquake action.

Surface compactness poured with controlled permeability formwork liner (CPFL) depends on deformability and permeability of fresh concrete consequentially and subject to variation of wrapped formwork, self-weight stress of concrete and vibratory stress. In this paper, bulk modulus and vertical permeability coefficients are acquired from triaxial test and variable head permeability test for the first time with different mixing designs of fresh concrete. The impact factors changed, i.e. water blinder ratio from 0.4 to 0.5, mixed duration from 1 hour to 2.5 hours, coarse aggregate type with gravel and pebble, mixed volume of pulverized fuel ash from 10 to 30 percent and ambient temperature from 15°C to 30°C, were studied by orthogonal experimental design. Triaxial test results indicated that secant modulus is more suitable than tangent modulus of bulk deformation, elastic deformation and Poisson's ratio of freshly mixed concrete. Besides, permeability coefficient of mixed concrete freshly is the most influenced by water blinder ratio. It is crucial and helpful to study rheology of fresh concrete cast with CPFL in depth.

Under action of water pressure and self-weight, the stress concentration is occur at the heel of high arch dams. It forms the oblique principal tensile stress and will cause the concrete to crack because of the combination of shearing stress and normal stress. Taking the xiluodu high arch dam as an example, suppose dam damage only occurs nearby the foundation plane. The dam self-weight is simulated with the change of the construction process, the water pressure and temperature loads are applied after the dam construction. For the Gauss points where crack failure happen, the stress along the maximum principal tensile stress direction reduces to zero, and the stiffness also adjusts to zero. For the Gauss points where compressive failure happen, the stress along the maximum principal compressive stress direction reduces to the compressive strength of concrete, the stress along other principal stress direction remains unchanged, and the stiffness adjusts to zero. Three strength criterions of uniaxial, blaxial and triaxial are used to check the influence of the strength criterions. The failure regions of the dam with three kinds of different strength criterions are compared and analyzed, the safety of the dam is evaluated.

In this paper, the artificial neural network (ANN) and support vector machine (SVM) methods which are commonly used in data mining are introduced, both the advantages and disadvantages of between them are detailedly discussed in engineering application. Two forecasting models based on ANN and SVM are derived from the main factors for slope stability, in which the nonlinear relations between slope stability and main influencing factors are obtained from the finite empirical data. Compared the results with maximum likelihood estimation in details, it is concluded that SVM forecasting model has more advantages to slope stability evaluation over ANN model under the condition of limited data.

In order to guarantee the strength and stability safety of dam, it is need frequently to replace weak rock structure with concrete in the process of excavation of arch dam foundation plane. Usually there are two kinds of replacement way, one kind is taking this part of replacement block as the part of dam, which has the advantages of convenient construction and the disadvantages of irregular form of the dam; The other kind way is taking the replacement block as the part of foundation, it means pouring the replacement block in advance, and then pouring dam body when its internal temperature fall at the same as the bedrock, which has the advantages of regular form of the dam and the disadvantages of complex construction lead to influence construction progress. Therefore, the engineering designers pay more attention to the issue that rational evaluation on the influence on the strength and deformation of dam by these two different construction ways. In this paper, as an example of xiluodu, the full-process emulation calculation and study is conducted for the temperature and stress of the high arch dam during construction period period, so as to figure out the distribution and variation rule of temperature and stress and make a rational evaluation on the influence of two kinds of construction scheme on the strength and deformation of the dam. The study provides the helpful evidence for the choice of the concrete pouring ways of the foundation replacement of xiluodu dam.

The forecast of structure invalidation of ocean engineering construction items is a fuzzy and complex issue, which related with many uncertain factors. In this article gray and comprehensive evaluation method, the Back Propagation (BP) Artificial Nerve Network (ANN) and the MATALAB software are introduced to solve the forecast issue of structure invalidation in marine engineering construction. Fully considering the coordination and the mutual predominance of man-machine system, it proposes a structure invalidation forecast system including the gray comprehensive evaluation method, the BP artificial nerve network, the MATALAB software, and the multi-expert decision-making system.

A direct algorithm of heat interchange between concrete and water pipes is considered to simulate the cooling effect is presented in this paper. The heat propagated from cooling water pipes to concrete is obtained directly after the internal temperature field of concrete is solved. Then the water temperature along the cooling water pipes can be obtained directly instead of the temperature gradient around the pipes. An example is used to verify the validity of the method. What the mesh density influences the calculation result is also discussed.

A field investigation of the May 12, 2008 Wenchuan earthquake-affected areas in China was conducted. The objective of the study was to evaluate the effects of the event on brick masonry structures, concrete block masonry structures, stone masonry structures, adobe structures, concrete structures and timber structures. The causes of structural failures due to the earthquake included bad site choice, bad material choice, soft story, non-ductile detailing, unreinforced masonry, inadequate construction quality, etc. Traditional timber structures survived with minimum structural damage due to high ductility, low stiffness and light mass. It is concluded that structures constructed and designed according to the provisions of current codes with attention to detailing would have survived the ground motion without collapse.

Based on the continuum damage mechanics, an anisotropic elasto-damage model for predicting the residual strength of concrete under fatigue biaxial compression with constant confined stress is presented in this study. The model utilizes the concept of multiple bounding surfaces, with a varying size limit fracture surface defining fatigue loading. In expression of damage modulus, D is a constant which depends on the concrete strength under monotonic loading or low cyclic loading. However, in process of high-cycle fatigue, the attenuation of residual strength of concrete is larger, so D in the damage modulus expression is not a constant under high cycles. It is a variable which depends on the residual strength. The calculation parameters of the model are given according to the fatigue test results. A total of 101 specimens of plain concrete are tested under biaxial compressive fatigue loading with constant confined stress. In this test the constant confined stress and maximum stress of fatigue loading are both considered. The residual strength attenuating curves are also shown in the paper. Residual strength predictions of the model are compared with the experimental data. The residual strength predicted by the model seems to be in close agreement with results of experiment.

A meso scale three dimensional finite element model was setup to model two dimensional tri-axially braided composites. Unit cell scheme is used to take into account of braiding architecture as well as mechanical behavior of fiber tows, matrix and fiber tow interface. 0°/±60° braiding configuration has been studied. A failure criterion and progressive damage evolution model taking into account fiber tow and tow interface has been applied to theoretically predict inter laminar and intra laminar failure mode. Straight sided specimen testing was carried out in both axial and transverse direction. Results obtained in the tests as well as finite element approaches will be discussed. This paper will also discuss the main feature of the model through an extensive parameter study.

A micromechanical model is presented in order to model effective properties and microstructural inhomogeneity of CNT/SMP composites. It is assumed that the CNT is elastic and the SMP obeys a thermo-mechanical constitutive law. The aggregated effect of CNT in a composite, which frequently encounters in real engineering, is considered by a two-step homogenization approach. The aggregation degree of CNT is described by an aggregation coefficient. The effective properties of CNT/SMP composites with aggregated inclusions are estimated by Mori-Tanaka method. It is shown that the aggregation of CNT can influence dramatically the effective properties of the CNT/SMP composites.

Scheduled to launch in the fall of 2011 with arrival at Mars occurring in the summer of 2012, NASA's Mars Science Laboratory will explore and assess whether Mars ever had conditions capable of supporting microbial life. In order to achieve its science objectives, the Mars Science Laboratory will be equipped with the most advanced suite of instruments ever sent to the surface of the Red Planet. Delivering the next mobile science laboratory safely to the surface of Mars has various key challenges derived from a strict set of requirements which include launch vehicle performance, spacecraft mass, communications coverage during Entry, Descent, and Landing, atmosphere-relative entry speeds, latitude accessibility, and dust storm season avoidance among others. The Mars Science Laboratory launch/arrival strategy selected after careful review satisfies all these mission requirements.

This paper discusses the larger view on lunar settlement creation. Such an endeavor is exceeding complex, requiring the talents of all disciplines, from physiology to engineering to human factors. While narrow sub-problems can be tackled in isolation, any significant aspect of lunar settlement creation needs to be solved as a multi-disciplinary endeavor. And here multi-disciplinary means across classes of disciplines, for example, technology and psychology.

A multi tier barcode based system was designed and implemented for the construction management of industrial and military emplacements and equipment in remote locations. The developed system offers much potential as valuable tool in the construction management of Lunar and Martian outposts. The purpose of the study was to ascertain if it was possible to implement a symbology based inventory control system that would allow both project direction to control and team members at all levels to have access to better information. The findings of this project can be applied to further similar projects and have widespread potential for the optimization of space related outpost construction.

The parallels between an actual Antarctica South Pole re-supply traverse conducted by the National Science Foundation (NSF) Office of Polar Programs in 2009 have been studied with respect to the latest mission architecture concepts being generated by the United States National Aeronautics and Space Administration (NASA) for lunar and Mars surface systems scenarios. The challenges faced by both endeavors are similar since they must both deliver equipment and supplies to support operations in an extreme environment with little margin for error in order to be successful. By carefully and closely monitoring the manifesting and operational support equipment lists which will enable this South Pole traverse, functional areas have been identified. The equipment required to support these functions will be listed with relevant properties such as mass, volume, spare parts and maintenance schedules. This equipment will be compared to space systems currently in use and projected to be required to support equivalent and parallel functions in Lunar and Mars missions in order to provide a level of realistic benchmarking. Space operations have historically required significant amounts of support equipment and tools to operate and maintain the space systems that are the primary focus of the mission. By gaining insight and expertise in Antarctic South Pole traverses, space missions can use the experience gained over the last half century of Antarctic operations in order to design for operations, maintenance, dual use, robustness and safety which will result in a more cost effective, user friendly, and lower risk surface system on the Moon and Mars. It is anticipated that the U.S Antarctic Program (USAP) will also realize benefits for this interaction with NASA in at least two areas: an understanding of how NASA plans and carries out its missions and possible improved efficiency through factors such as weight savings, alternative technologies, or modifications in training and operations.

The Sample Acquisition/Sample Processing and Handling subsystem for the Mars Science Laboratory is a rover-based sampling system scheduled to launch in 2011. The sampling system consists of a powdering drill and a scooping, sieving, and portioning device mounted on a turret at the end of a robotic arm. The turret also contains a dust removal tool for clearing the surface of rocks prior to science observations, and two scientific instruments mounted on vibration isolators. Using its drill, the system acquires powder from depths of 20 to 50 mm in a wide variety of rocks from very soft rocks such as kaolinite to basalts with compressive strengths up to 230 MPa. The system also picks up loose soil with its scoop. Sample acquired by either method is sieved, portioned, and delivered to two instruments inside the rover for analysis. Multiple portions of 45 to 65 mm³ are created from a sample sieved to contain only sub-150 micron particles. A single portion of 45 to 130 mm³ is created from a sample sieved to contain only sub-1 mm particles. The sampling system operates in the cold temperature, low pressure, and reduced gravity environment of Mars for the primary mission duration of one Martian year.

The proposed paper summarizes a recent (August 2009) workshop at the NASA Johnson Space Center discussing lessons learned from traverses, driven largely by science objectives, in the Earth's polar regions. These lessons will be used as one facet of NASA's preparation to explore, over extended periods of time, the surface of the Moon and Mars as part of the Constellation Program. Over 50 years of extensive traverses in both the Arctic and Antarctic provide a potentially rich source of lessons for future planetary missions under analogous conditions. For both lunar and Mars missions, it is anticipated that both crew and robotic equipment, which could arrive on different vehicles, will land in a fairly benign location. But "benign" can also translate into "uninteresting" from a scientific or exploration perspective, resulting in the crew exhausting the scientific potential of a particular site before returning to Earth. This is especially true for Mars mission crews who will spend 18 months at a given location. By providing a capability to move long distances across the surface removes the need to risk a landing at a more challenging, but interesting, surface location. The proposed paper summarizes the workshop presentations and discusses several of the key findings or lessons, including: (1) A recognition that NASA's current approach for long duration planetary surface operations has fundamental differences from any of the operational approaches described by the invited speakers. These approaches drive the crew size and skill mix to accomplish basic objectives and, in turn, drive the logistical pyramid needed to support these operations. NASA will review the operational approaches of the organizations represented to understand the differentiating factors. NASA will then decide if it should alter its current approach to surface exploration. (2) There are potential parallels between key characteristics of the systems used for exploration in these environments, such as heated volume as an analog for pressurized volume or energy usage for various activities. NASA will look at these characteristics to identify which could help with preliminary planning and gather raw data from the presenters to model these characteristics. (3) New technologies are being applied and design approaches are being tailored to take advantage of these technologies on both sides. Interactions between these two communities has begun or is expanding to understand how these new technologies are being leveraged: NASA habitation designers are exchanging ideas and approaches with the Antarctic station designers; Antarctic support contractors have put together a list of areas where NASA could benefit from their experience and vice versa; discussions have begun to compare the equipment used for the National Science Foundation (NSF) South Pole Station resupply traverses to identify possibly functional similarities for NASA.

This paper documents NASA's habitation approach for the Constellation Architecture Team `Scenario 12.1' lunar outpost concept. The architecture team defined an outpost scenario optimized for intensive mobility that uses small, highly mobile pressurized rovers supported by portable habitat modules that can be carried between locations of interest on the lunar surface. A compact vertical cylinder characterizes the `12.1' habitat concept, where the large diameter maximizes usable flat floor area and allows for efficient internal layout. The `Scenario 12.1' system integration approach is described where habitability, mass, power, logistics, and Extra Vehicular Activity (EVA) systems are defined under a mobility intensive operations scenario. In addition to baseline design features, modular addition and expansion concepts were also explored and are documented in this paper.

This paper will describe an overview of the Constellation Architecture Team Lunar Scenario 12.0 (LS-12) surface habitation approach and concept performed during the study definition. The Lunar Scenario 12 architecture study focused on two primary habitation approaches: a horizontally-oriented habitation module (LS-12.0) and a vertically-oriented habitation module (LS-12.1). This paper will provide an overview of the 12.0 lunar surface campaign, the associated outpost architecture, habitation functionality, concept description, system integration strategy, mass and power resource estimates. The Scenario 12 architecture resulted from combining three previous scenario attributes from Scenario 4 "Optimized Exploration", Scenario 5 "Fission Surface Power System" and Scenario 8 "Initial Extensive Mobility" into Scenario 12 along with an added emphasis on defining the excursion ConOps while the crew is away from the outpost location. This paper will describe an overview of the CxAT-Lunar Scenario 12.0 habitation concepts and their functionality. The Crew Operations area includes basic crew accommodations such as sleeping, eating, hygiene and stowage. The EVA Operations area includes additional EVA capability beyond the suitlock function such as suit maintenance, spares stowage, and suit stowage. The Logistics Operations area includes the enhanced accommodations for 180 days such as enhanced life support systems hardware, consumable stowage, spares stowage, interconnection to the other habitation elements, a common interface mechanism for future growth, and mating to a pressurized rover or Pressurized Logistics Module (PLM). The Mission & Science Operations area includes enhanced outpost autonomy such as an IVA glove box, life support, medical operations, and exercise equipment.

Detection of exterrestrial ice or water is among the most important tasks for space exploration. The resources are invaluable to build permanent base on the Moon or on the Mars. There are different processes governing the migration, formation and accumulation of ice under exterrestrial environment. Especially, this involves coupling of multiple fields such as thermal, hydraulic and mechanical fields. This paper describes the development and implementation of a coupled thermo-hydro-mechanical model for unsaturated porous materials. The coupling integrates the Fourier's laws for heat transfer, Richard's equation for fluid transfer, and linear constitutive relationship. Coupled parameters were utilized to transfer information within or between field variables. Additional relationships, such as the similarity between drying and freezing processes, Clapeyron equation for ice balance were incorporated to consider the effects of frost action. Numerical simulations were implemented in multiphysical platform to solve the coupled nonlinear partial differential equations. A simulation case was carried out on a relatively simple geometry, using accepted models for thermal, hydraulic and mechanical properties. Results of multiphysical simulations, (such as the freezing induced moisture redistribution, the thermal stresses, etc) are consistent with the basic laws and experience. The results indicate under terrestrial environment, ground freezing will cause moisture to migrate toward ground surface. By incorporating the unique phase transition mechanism under exterrestrial environment, the simulation model can potentially be used to guide the exploration of water resources under exterrestrial environment.

Increasingly, NASA exploration missions are including in-situ sampling tasks. The difficulties of acquiring samples have been identified by the designers of the 2007 Mars Phoenix Scout and the 2011 Mars Science Laboratory missions. In particular, it has been indicated that planetary drilling faces great challenges. The associated challenges grow significantly with the depth of drilling and it is the objective of the current study to develop an autonomous wireline rotary-percussive drill (called Auto-Gopher) that can reach a depth of several meters. In developing the Auto-Gopher efforts are made to take advantage of the hammering capabilities of the Ultrasonic/Sonic piezoelectric mechanism to fracture rocks using low preload. This mechanism was demonstrated in 2005 to reach about 2-m deep in ice at Lake Vida, Antarctica. The augmentation of the hammering by rotation of the bit having flutes provides both effective cuttings removal and faster drilling. The progress in developing the Auto-Gopher will be described and discussed in this paper.

The desire to colonize the moon has prompted an examination of ways to mine lunar regolith to create a solid foundation for NASA's 2020 Lunar Base and/or recover O₂, water, or He-3. Accordingly, NASA created a Centennial Challenge directed at various North American groups to design excavators to mine regolith. Several mechanical and operational challenges exist because of the unique physical properties of regolith — high internal friction angle, high compressibility, and a very-fine particle size distribution leading to dust entrainment in excavator components. UBC-Thunderbird Robotics Team TREAD — a University of British Columbia student club — has been working for two years on a viable approach to this problem. This paper presents an effective design based on a scraper excavator from Miskin Scraper Works. Details about the NASA Centennial Challenge will also be given.

Processing of lunar regolith into oxygen for habitat and propulsion is needed to support future space missions. Direct electrochemical reduction of molten regolith is an attractive method of processing, because no additional chemical reagents are needed. The electrochemical processing of molten oxides requires high surface area, inert anodes. Such electrodes need to be structurally robust at elevated temperatures (1400–1600°C), be resistant to thermal shock, have good electrical conductivity, be resistant to attack by molten oxide (silicate), be electrochemically stable and support high current density. Iridium with its high melting point, good oxidation resistance, superior high temperature strength and ductility is the most promising candidate for anodes in high temperature electrochemical processes. Several innovative concepts for manufacturing such anodes by electrodeposition of iridium from molten salt electrolyte (EL-Form^TM process) were evaluated. Iridium electrodeposition to form of complex shape components and coating was investigated. Iridium coated graphite, porous iridium structure and solid iridium anodes were fabricated. Testing of electroformed iridium anodes shows no visible degradation. The result of development, manufacturing and testing of high surface, inert iridium anodes will be presented.

Returning humans to the Moon for prolonged periods will require extensive information on the properties and compositions of the lunar regolith, its resource potential, and in-situ characterization of the effects of space weathering of the soil and equipment. To address these concerns, we are developing a miniature Scanning Electron Microscope (mSEM), a project led by the NASA Marshall Space Flight Center (MSFC), for use on the lunar surface. Working within the lunar environment and at low-power provides opportunities to simplify the instrument, as well as sample preparation. The natural lack of an atmosphere eliminates the need and complexity of a vacuum chamber on the instrument and introduces the possibility of a "point-and-shoot" configuration for the mSEM. Imaging with low-power does not require sample coatings of carbon or gold, or the use of a gas, to mitigate surface charging on the sample; this low-power greatly simplifies sample preparation. Engineering and science activities on the lunar surface will benefit from the presence of an mSEM and its ability to determine particle size distribution (PSD), mineral chemistry, and the general characteristics of the regolith.

Fundamental to NASA's Mars Exploration Program (MEP) is an ongoing development of an integrated and coordinated set of possible future candidate missions that meet fundamental science and programmatic objectives of NASA and the Mars scientific community. In the current planning horizon of the NASA MEP, a landed mobile surface exploration mission launching in the 2018 Mars launch opportunity exists as a candidate project to meet MEP in situ science and exploration objectives. This paper describes the proposed mission science objectives and the mission implementation concept developed for the 2018 opportunity. As currently envisioned, this mission concept seeks to explore a yet-to-be-selected site with high preservation potential for physical and chemical biosignatures, evaluate paleoenvironmental conditions, characterize the potential for preservation of biosignatures, and access multiple sequences of geological units in a search for evidence of past life and/or prebiotic chemistry at a site on Mars. Candidate science measurements and payload sizing implementation options for this concept are identified and described for the purpose of identifying overall rover mass and power scenarios for such a mission. A description of plans for use and possible modification of NASA-developed entry, descent and landing capabilities will be included and is fundamental to meeting the budget and landing site access goals for this mission concept. This mission concept also intends to make concrete steps towards a possible future mission to return Martian samples to the Earth. This latter objective anchors the potential 2018 mission in a sound Mars exploration strategy that is also consistent with NASA's primary goals for the subsequent decade of exploration (2020 – 2030), namely; a potential international collaboration for the return to Earth, and subsequent detailed analysis, of carefully selected Martian samples. The proposed 2018 Landed Mission concept includes near sub-surface access and acquisition of sample cores, as well as encapsulation and caching of cores for possible recovery by a potential future mission. Here we describe the mission concept and the technology planning and development efforts underway to enable meeting the proposed mission objectives. Potential international collaboration opportunities and implementation strategies for this mission concept and potential launch opportunity are also outlined.

There is a significant consideration to include humans as part of the NASA future missions aimed to explore the solar system. The current NASA plans consist of permanent habitation of the Earth's Moon and a visit to Mars. An extended presence of humans on other planets is quite challenging and requires establishing of the critical infrastructure to support the essential needs for such a presence. A critical requirement for such a presence is to have a robust In-Situ Resource Utilization (ISRU) capability. This manuscript covers the current state of the art and the challenges of implementing ISRU technology on Mars.

In-situ planetary exploration of the solar system is one of the key objectives of NASA future missions and Venus is one of the significant scientific targets in the NASA plans. However, the extreme environment on Venus of high temperature (460°C) and high pressure (∼91 atm) poses enormous challenges. Tools are needed that can be operated at these conditions and acquire subsurface samples for analyzers. Potentially, piezoelectric materials can be made to actuate samplers and be operational over a wide range of temperatures. In this reported study, the development of a piezoelectric actuated drill is underway for operation at temperatures as high as 500°C is investigated. Several prototypes of Ultrasonic/Sonic Drill/Corers (USDC) were made with actuators consisting of high temperate piezoelectric ceramics as well as single crystals of LiNbO3. The results of this study are reported and discussed in this manuscript.

We tested an off-the-shelf electrical power connector in a dusty environment and in a clean environment. It was assumed that the exposure to lunar simulant dust would result in a significantly shortened life span for the connector, but this was not observed. During mating and demating of both connectors through 5000 cycles, decreases were noted in both mating and demating loads. However, the electrical resistance of the connectors did not change significantly—neither connector had a resistance change of more than 0.02 Ω. Although it seems from the results of this test that lunar dust may not be a grave concern for electrical connectors, more testing is required. This test was not performed in a representative environment, nor are we certain that the mechanical properties of the simulant represent the worst-possible properties of all lunar soils. We still need to learn more about what to expect when we arrive at the lunar surface with electrical equipment.

For long term space exploration it will be necessary to build a safe infrastructure and experimental research facilities for human scientists providing efficient working conditions and protecting against the environment. To construct structures on the moon one has to select proper materials considering strength and cost of production and supply. Concrete is a widely used material for building any kind of structure on the earth. Concrete is also a good candidate as construction material on the moon, but has to fit the lunar environment and the economic realities. This paper presents a pilot effort to investigate the efficacy of waterless concrete using mostly ISRU material for the robotic fabrication and installation of prefabricated elements. The first concrete bricks have been "cast" by the small research group. The results of testing the first lunar concrete specimens using polymers as binder will be presented at the conference.

An analog of a lunar habitat has been constructed that will allow for remote monitoring and control of lights, temperature, air quality, and video in the 2009 NASA Desert Research and Technologies Simulations (D-RATS) field tests. The analog facility, known as `Microhab,' is also designed to function as a payload for the All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) robotic lunar mobility system, allowing for a mobile habitable environment that can be tested while the vehicle is deployed in field operations. The instrument suite and technologies applied to the Microhab analog have inheritance with systems used in previous field tests conducted at McMurdo Station in Antarctica. Results of the 2009 field test will inform the development of ISHM technologies in the NASA Lunar Surface Systems Habitat Demonstration Unit (HDU) in the 2010 D-RATS and beyond. This paper describes the Microhab ISHM system, including Commercial Off-The-Shelf (COTS) components and operations, and reviews challenges and lessons learned from the 2009 field test.

High resolution hydrogen surface mapping is essential for locating and characterizing water ice and other hydrogenous volatile deposits in permanently shadowed lunar craters. This is especially important for potential in-situ resource utilization. Although orbital remote sensing can provide much information, prospecting for near-subsurface resources can only be performed directly on the surface. The small HYDRA neutron spectrometer has been successfully integrated onto the K10 Black planetary rover, operated by the Intelligent Robotics Group at NASA Ames Research Center [1,2]. The system was used to assess hydrogen content in an initial set of field tests at Ames. During these tests, we successfully detected and mapped targets of various hydrogen contents and burial depths.

NASA systems engineers require an accurate assessment of excavator mass, power and energy requirements to correctly design lunar surface systems' overall architecture. In order to properly determine excavator mass and energy for various excavation tasks, we recommend a 5-step process. It starts with selection of appropriate soil that is analogous to lunar regolith. The second step refers to soil preparation methods; the desire is to make the soil's relative density similar to in-situ lunar regolith's relative density. The third step requires measuring excavation forces by deploying instrumented digging end effectors in carefully prepared soil bins and preferably in vacuum. After forces are measured, they need to be scaled for lunar gravity. The scaling factor varies depending on soil properties (cohesion and friction angle) and also on the size of an excavating blade/scoop. Once the forces are scaled they can be used to accurately estimate excavators' parameters for various tasks. This paper describes in detail all of the 5 steps mentioned above.

Utilization of in-situ lunar resources will decrease launch mass and thus the expense of missions to the Moon, and will also give a lunar base a degree of self-sufficiency. Geothermite© reactions utilize an in-situ mixture of minerals and a reducing agent as reactants in a thermite-type chemical reaction. The geothermite© reaction investigated within this study used a mixture of JSC-1A series of lunar regolith simulant and aluminum powder as reactants. The JSC-1A series of simulant is an approximation of chemical and mineralogical characteristics of actual lunar regolith. Upon application of heat, an exothermic reaction initiated, and a coherent ceramic-composite material was produced. Experiments have shown that a geothermite© reaction occurred within the regolith-aluminum mixture over a range of reactant proportions. XRD analysis indicated that silicon, corundum (Al₂O₃), grossite (CaAl₄O₇), and spinel (MgAl₂O₄) were common species present in the reaction product. SEM/EDS analysis of samples reacted in a standard atmosphere showed formation of nanoscale whiskers containing aluminum, oxygen, and nitrogen. XRD results indicate that the whiskers are likely to be composed of aluminum oxides and aluminum nitrides. The compressive strength of products formed in a standard atmosphere was observed to vary depending on reactant proportions and particle size of the simulant. The largest mean compressive strength was found to be 18 ± 3.7 MPa. To better simulate conditions on the lunar surface, further experiments were conducted in a vacuum environment. No whisker formation was observed within samples reacted in a vacuum environment. It is hypothesized that the removal of gases by the vacuum environment decreased overall interparticle contact by preventing solid-gas chemical reactions. Neutron radiation transmission measurements were conducted on two samples to determine the preliminary radiation shielding capability of the reaction product.

Unmanned deep space explorations have received a lot of attention in recent years. Some missions to land safely and explore on the surface of the moon or other planets are proposed and planned in the world. In Japan, lunar lander-rover missions have been earnestly studied. In these missions, it is required to perform sampling, conduct in-situ analysis of geological samples and deploy devices for measurement and observation. Many researchers have studied and developed sample acquisition systems and driller or corer systems. Recently deep drillers or penetrating systems have been required to obtain deep data for subsurface exploration. In lunar or planetary mission, it is needed to excavate the regolith layer, which covers the lunar surface, in depth of several meters. Some suggestions for drilling on the lunar surface have already been made. However, there are few schemes that can satisfy the requirement. This paper, to begin with, describes lunar or planetary mission scenarios and scientific requirements. A detailed surface and subsurface exploration by a mobile explorer is presented. Then a smart manipulator with new actuators to collect samples is proposed. The proposed manipulator is actuated by ultra-sonic motors, which can lead to a light-weight system with low-power consumption. The developed manipulator has an end-effecter to collect regolith, pick up stones, etc. The effectiveness of the developed smart manipulator is shown by some experiments. This paper also proposes a mole-like robot which is maneuverable in regolith. A new mechanism to move forward in the soil is described. The drilling function is studied by analyses and some experiments. The experimental results show the feasibility of the proposed robot.

The Pacific International Space Center for Exploration Systems (PISCES) of the University of Hawai'i at Hilo was founded in 2007 to pursue research, education and analog testing of new technologies designed to sustain life on the Moon and beyond. PISCES operates a test site on the lower slopes of Mauna Kea on the Big Island of Hawaia'i. In November, 2008, scientists from the United States (KSC, JSC, JPL, Lockheed-Martin, Carnegie-Mellon University), Canada (NORCAT, Canadian Space Agency [CSA]), Germany (DLR) and Switzerland (Michelin) gathered for an International Lunar Analog Test in Hawai'i. In 2010, these groups will be joined by others, including the European Space Agency, in a second series of international tests. Tests include in situ resource utilization (ISRU) production of water, oxygen and other volatiles, and robotics as well as studies of the process of analog test operations and management and base design. Fuel cell integration, space medicine techniques, lunar mining and numerous other experiments will be conducted in an environment which has already proven itself as a lunar analog site. The lunar analog tests in Hawai'i are characterized by a high degree of scientific integration and international collaboration. Robots from several agencies will be transporting devices constructed by other agencies to conduct site-preparation studies, regolith transport, and related activities. Between fifty and seventy scientists from around the world will be joined by undergraduate students, graduate students, scientists and operations workers. All personnel from the participating countries work side by side. PISCES will also coordinate a public outreach and education program which serves the dual purpose of (1) educating the public in current efforts to create a sustainable human presence on the Moon and (2) generating local support for lunar analog testing. We will describe briefly the tests which are conducted on the Hawai'i site and the ways in which groups of scientists and engineers from around the world come together in common endeavor.

With NASA's goal of returning to the Moon in a sustainable way, utilizing the local resources is an obvious thought. To be able to utilize the local resources, they need to be gathered and delivered to a target location. At the Colorado School of Mines several excavation system prototypes have been developed over the past several years. The systems include a bucket wheel, a bucket ladder/chain and a backhoe scaled to be able to excavate 50 – 1600 kg/hr using less than 70 Watts during peaks or less than 200 Watts including the mobility platform. This paper will show the prototypes and discuss lessons learned from participating in NASA's centennial challenge and experimental tests.

With 1 rover, 2 astronauts and 3 days, the Apollo 17 Mission covered over 30 km, setup 10 scientific experiments and returned 110 kg of samples. This is a lot of science in a short time and the inspiration for a barebones, return-to-the-Moon strategy called Daylight Exploration. The Daylight Exploration approach poses an answer to the question, "What could the Apollo crew have done with more time and today's robotics?" In contrast to more ambitious and expensive strategies that create outposts then rely on pressurized rovers to drive to the science sites, Daylight Exploration is a low-overhead approach conceived to land near the scientific site, conduct Apollo-like exploration then leave before the sun goes down. A key motivation behind Daylight Exploration is cost reduction, but it does not come at the expense of scientific exploration. As a goal, Daylight Exploration provides access to the top 10 science sites by using the best capabilities of human and robotic exploration. Most science sites are within an equatorial band of 26 degrees latitude and on the Moon, at the equator, the day is 14 Earth days long; even more important, the lunar night is 14 days long. Human missions are constrained to 12 days because the energy storage systems required to operate during the lunar night adds mass, complexity and cost. In addition, short missions are beneficial because they require fewer consumables, do not require an airlock, reduce radiation exposure, minimize the dwell-time for the ascent and orbiting propulsion systems and allow a low-mass, campout accommodations. Key to Daylight Exploration is the use of piloted rovers used as tele-operated science platforms. Rovers are launched before or with the crew, and continue to operate between crew visits analyzing and collecting samples during the lunar daylight.

Future human or robotic landed missions to the moon will provide an opportunity for rigorous in-situ measurements and sample acquisition on the Moon to answer key science questions and provide information to support human exploration. The Lunar Regolith Characterization Kit (LRoCK) described in this paper is designed to provide the flexibility, modularity, and capabilities to make crucial in-situ measurements and collect samples to support science studies on the Moon. The LRoCK consists of an integrated suite of surface and subsurface geophysics instruments that can be deployed during a human mission by astronauts and then run semi-autonomously or be carried on a rover for robotic missions. LRoCK instruments and tools strongly support concepts to characterize polar and non-polar regolith properties and to understand the lunar interior (through heat flow and seismic measurements). LRoCK also supports those concepts that require collection of rock and regolith samples and preliminary analysis of those samples. Data and analysis results from LRoCK are intended to be available through a display (Mapper) and analysis/decision support system software (DSS) to provide scientists, engineers, and astronauts a near real-time way to communicate results and plan their next steps.

Between 2006 and 2009 Magna Parva performed a European Space Agency (ESA) study "Ultrasonic Tools for Planetary Surface Exploration". It was partially funded by the ESA Technology Research Programme (TRP) framework. During the course of the work Breadboard and Engineering Model drill concepts were designed, developed and tested in a range of media and environmental conditions. The tools were demonstrated to drill and collect samples from various mediums. The abilities of the devices and phenomena encountered during experimental testing were documented and through an iterative development and test programme, the Engineering Model concept's material removal rate was improved by 3600%. Effects encountered during testing included: ultrasonic erosion machining (including particle disintegration), ultrasonic consolidation of fine powers, vibro-fluidisation of granular medium, ultrasonically induced atomisation of water, phenomenologically modified frictional characteristics, alleviated jamming of mechanisms in the presence of granular medium, and ultrasonic particle/fluid transport. From the experimental evidence presented, four ultrasonic drilling mechanisms were proposed along with recommendations for improving the efficiency of ultrasonic drilling devices. The Autoresonant Control System developed by Magna Parva facilitated stable control of the ultrasonic tools during the study (even when subjected to an inherently nonlinear and ill-defined loading) and a description of the control strategy was given. Finally, a potential future capability of the ultrasonic tool was introduced - its ability to act as a ranging/sonar type device to interrogate both solid rocks and subterranean geological features.

The exploration of remote planetary surfaces calls for the advancement of low-power, low-mass, highly-miniaturized instrumentation. Multi-functional instruments of this nature will prove to be particularly useful in preparation for human return to the moon, and in exploring increasingly remote locations in the Solar System. To this end, our group has been developing a miniaturized Scanning Electron Microscope (mSEM) capable of remote investigations of mineralogical samples through in-situ topographical and chemical analysis on a fine scale. Specifically, the fabrication and testing of a proof-of-concept assembly has begun, and consists of a cold-field-emission electron gun and custom high-voltage power supply, electrostatic electron-beam focusing column, and scanning-imaging electronics plus backscatter electron detector. The functioning of an SEM is well known: an electron beam is focused down to nanometer- scale onto a given sample resulting in emissions such as backscattered and secondary electrons, x rays, and visible light. Raster-scanning the primary electron beam across the sample results in a fine-scale image of the surface topography (texture), crystalline structure and orientation, with accompanying elemental composition. The flexibility in the types of measurements the mSEM is capable of makes it ideally suited for a variety of applications. The mSEM is appropriate for use on multiple planetary surfaces, and for a variety of mission goals (from science to non-destructive analysis to in-situ resource utilization). The current status of the development and potential mSEM applications for planetary exploration are summarized here. This effort is funded through the NASA Research Opportunities in Space and Earth Sciences - Planetary Instrument Definition and Development Program (PIDDP).

The MOONBIT experiment investigated the capability to obtain structural and stratigraphic information of planetary subsoil using Seismic While Drilling (SWD) - a geophysical technique used for Earth subsoil exploration. The basic concept of SWD uses the drill bit as a seismic in-depth source of seismic waves, recorded by geophones as surface receivers gathering digital seismograms at different depths: signal processing provides seismic images known as Reverse Vertical Seismic Profiling (RVSP). MOONBIT's target medium is the regolith layer on the Moon surface, covering basaltic bedrock. As innovatively RVSP SWD method, a passive Downhole Hammering Mechanism (DHM) actuates the drill bit, which becomes the borehole source of seismic waves. Two main tests were conducted in regolith simulant with buried geophones: the first test characterized the propagation velocity of seismic waves; the second test used a 1.5 m drill over a container. Drill control strategies and robustness towards signal transmission problems of future unmanned Moon drills of missions, Earth remote controlled, were also assessed and simulated with an error generator and a remote supervisor prototype. Test results with consistent seismic signals of good quality and resolution and comparative analysis showed that the DHM drill bit is an adequate source of SWD signals for RVSP planetary purposes and may support steering, drilling planning and scientific investigations.

This paper relates a story about efforts to develop a heat transfer concept which proved to be unfeasible, and how the search for alternatives to solve the heat transfer challenges led to new solids conveying concepts with several potential applications. Under vacuum conditions the effective bulk conductivity of loose regolith (k_eff ∼ 0.001 W/m-K) is nearly 100 times lower than it is when an interstitial gas, at atmospheric pressure, is present. After evaluating alternatives, two new, solids conveying technologies were proposed to increase convective solids motion, and provide better conductive and more direct radiative heat-flow paths in a novel coaxial, counter-current, centrifuging-flow screw-like conveyor. A compact modular design, with the option for separate optimization in different temperature zones, was proposed that could utilize radiation-dominated or conduction-dominated modes when each is most effective. In the proposed design, mechanically-induced solids convection would maximize heat flow into and through the flowing regolith. The heat-exchanger was not selected for funding, but one of the proposed conveying techniques, a flexible screw conveyor, may be able to provide a robust method for transfer of regolith from mining or collection points to final utilization locations without the need for wheeled vehicles to make multiple trips. For shorter distances, the other new technique, a centrifuging step-screw conveyor, offers new options for robust vertical or horizontal transfer of granular solids independent of gravity. The analysis behind the centrifuging step-screw conveyor is described in this paper.

We conducted a series of numerical simulations to investigate the efficiency of a pneumatic method to convey lunar soil under earth (9.8 ms^–2) and lunar (1.62 ms^–2) gravity field. This numerical modeling was based on PFC2D with a fluid and particle coupling functions. During simulations, air jet at various pressures was injected into a 0.2 m diameter and 2m long tube that was filled with 8 mm diameter spherical particles. It was determined that the pressure of 5 x 10³ Pa was enough to loft particles at lunar gravity but not at earth gravity. Thus the jet-lifting method under reduced gravity conditions will be more efficient and will require the utilization of less injected gas than when used under Earth gravity conditions. Increasing the pressure to 10⁴ Pa was enough to loft particles at earth gravity. When the air injection pressure was decreased to 10³ Pa, the lofting under both gravitational fields ceased. We postulate that one of the important parameters in the fluidization of a bed of particles is the friction acting between neighboring particles. If the injected fluid cannot overcome such frictional forces, the sample would not be fluidized. As the more detailed observation suggest, this may be the major reason why at lower air pressures only the particles subjected to lunar gravity can successfully be jet-lifted.

Two contemporary issues foretell a shift from our historical Earth based industrial economy and habitation to a solar system based society. The first is the limits to Earth's carrying capacity, that is the maximum number of people that the Earth can support before a catastrophic impact to the health of the planet and human species occurs. Estimates of the Earth's carrying capacity vary between 14 and 40 billion people. Although at current population growth rates we may have over a century before we reach Earth's carrying limit our influence on climate and resources on the planetary scale is becoming scientifically established. The second issue is the exponential growth of knowledge and technological power. The exponential growth of technology interacts with the exponential growth of population in a manner that is unique to a highly intelligent species. Thus, the predicted consequences (world famines etc.) of the limits to growth have been largely avoided due to technological advances. However, at the mid twentieth century a critical coincidence occurred in these two trends — humanity obtained the technological ability to extinguish life on the planetary scale (by nuclear, chemical, biological means) and attained the ability to expand human life beyond Earth. This paper examines an optimized O'Neill-Glaser model for the economic human population of space. Critical to this model is the utilization of extraterrestrial resources, solar power and spaced based labor. A simple statistical analysis is then performed which predicts the robustness of a single planet based technological society versus that of multiple world (independent habitats) society. The model predicts that the human extinction probability is high in this generation unless humans expand into multiple independent habitats in space.

The NASA Vision for Space Exploration released in February, 2004 promoted achieving four major goals and objectives: i) implementing a sustained and affordable human and robotic program, ii) extending the human presence across the solar system starting with returning to the Moon by 2020, iii) developing innovative technologies and infrastructures for human space exploration, and iv) promoting international and commercial participationin space exploration. Fundamental to achieving these goals was the need to identify and map space resources, develop new technologies to harness the Moon's and Mars' abundant resources, and develop reusable planetary landers, launch systems, and propellant depots. The ability to extract and use space resources to create products and services for propulsion, power, crew protection, and planetary surface infrastructure, know as In-Situ Resource Utilization (ISRU), is a completely new approach to human space exploration. In December, 2006 NASA released the first Lunar Architecture Team study which recognized both the benefits of incorporating ISRU as well as the uncertainty and risk associated with ISRU since no system had ever been operated in space, let alone on the ground at the time. The study also recognized that technology, design, and operational decisions for propulsion, power, and life support systems can be drastically different if ISRU capabilities are considered. The solution proposed was to establish a lunar architecture flexible enough to accommodate ISRU products and services when available, but not to rely on ISRU's benefits until it had been adequately proven. Before 2004, only small scale ISRU technology and process proof-of-concept laboratory experiments had ever been performed to provide confidence in the concept of ISRU. For ISRU to be successfully incorporated into human lunar exploration, two hurdles need to be overcome: 1) demonstrate that ISRU capabilities are possible at a scale, mass, power, and reliability relevant to future mission needs, and 2) demonstrate the critical interfaces and interconnections between ISRU systems and products with other lunar surface and transportation system elements so that technology selections and design decisions can be made across the lunar architecture to take advantage of the benefits of ISRU versus the approach to date which emphasizes delivering everything from Earth and optimizing the performance of each individual element. Through funding, partnership, and coordination between NASA, industry, academia, and other government space agencies such as the Canadian Space Agency, since 2005 a program has been underway to both develop relevant scale ISRU technologies and systems as well as to demonstrate the interaction and interconnection of ISRU with other lunar surface systems. This effort has culminated in two recent ISRU analog field test campaigns performed on Mauna Kea, on the Big Island of Hawaii in November 2008 and February 2010, involving resource prospecting, oxygen extraction from regolith, site preparation, and ISRU product storage and utilization. This paper will provide an overview of the ISRU technologies and systems developed for the analog field tests, as well as the accomplishments and lessons-learned. The paper will also present options for follow-on activities to further promote lunar surface system integration and partnerships with ISRU.

Continued exploration of the Moon and Mars will call for mobile robots that are increasingly capable in regolith; not only traversing it without getting stuck, but also manipulating and shaping it to suit mission needs. This work distinguishes issues governing performance of regolith operations, based on tasks motivated by preparatory site work for lunar outposts. Payload ratio (pound-for-pound regolith-moving capacity) of small site work robots is identified as the key parameter governing metrics such as completion time for tasks ranging from berm building to trench digging. In addition to payload ratio, driving speed also governs berm building with small robots, while soil interaction parameters including regolith cohesion and soil-tool friction dictate trench digging performance. Furthermore, 3-dimensional bucket modeling highlights cohesion and friction as risks to the viability of using the smallest proposed class of excavation robots (those with mass of 250 kg or less). For trench digging especially, machines with higher mass (500 kg or more) may be required. Results are based on parameter sensitivity analyses using REMOTE, a task-level site work simulator.

Space drilling will require autonomous systems, both for robotic exploration and to support future human exploration, as energy, mass and human presence will be scarce. A series of planetary-prototype drilling projects have developed and fieldtested drilling automation and robotics technologies for projected use in missions during the 2010s. These have demonstrated automated control of the drilling process and topside drill string and sample handling. This paper will discuss past results in field tests of drilling automation software, and the tradeoffs between the use of planetary analog sites and laboratory testing. It will also discuss several different terrestrial analog sites (Arctic, Antarctic dry valleys, US southwest, Mauna Kea, Rio Tinto) in the varying roles needed to support validation of subsurface access for exploration of the subsurface on other planetary bodies, primarily focused on operations and requirements for drilling on the Moon and Mars, as well as contrasting these locations.

Tools for extracting life-sustaining resources from the moon are needed to support the vision for space exploration. Of particular interest is the production of oxygen for life support and propulsion. On the lunar surface the only practical source for oxygen is the lunar regolith. Described in this paper is an innovative plasma reduction technique for the production of oxygen from lunar regolith. Thermodynamic calculations showed that the regolith oxides could be dissociated to yield up to 7.3 weight percent oxygen when exposed to extremely high temperatures of up to 3000 °C. Subsequently the use of a plasma flame to obtain oxygen from lunar regolith simulant, JSC-1A was demonstrated. Optimum plasma processing parameters required for oxygen production is also discussed. In addition, electron microscopy and x-ray diffraction data is discussed to demonstrate that the regolith simulant when exposed to high temperature and rapid quench, as in the case of plasma processing, transforms predominantly to a glassy phase with vesicles and dispersion of nano phase iron. This closely duplicates the agglutinitic glassy phases present in lunar regolith and therefore plasma processing provides a means to produce tonnage of high fidelity lunar simulant.

One aspect of In-Situ Resource Utilization (ISRU) in a lunar environment is to extract oxygen and other elements from the minerals that make up the lunar regolith. Typical ISRU oxygen production processes include but are not limited to hydrogen reduction, carbothermal and molten oxide electrolysis. All of these processes require the transfer of regolith from a supply hopper into a reactor for chemical reaction processing, and the subsequent extraction of the reacted regolith from the reactor. This paper will discuss recent activities in the NASA ISRU project involved with developing pneumatic conveying methods to achieve lunar regolith simulant transfer under 1-g and 1/6-g gravitational environments. Examples will be given of hardware that has been developed and tested by NASA on reduced gravity flights. Lessons learned and details of pneumatic regolith transfer systems will be examined as well as the relative performance in a 1/6^th G environment.

We present details of a precision subsampling system (PSS) under development for surface exploration of Mars and possibly other planets. The PSS combines a fine-scale solid powder extraction tool with sample collection, manipulation, and instrument analysis subsystems in a highly compact package. The system offers future landed missions the ability to selectively analyze heterogeneous surface sample composition on millimeter scales. Analysis of subsamples by mass spectrometry and other tools would then permit characterization of highly-localized chemical and mineralogical phases that could be key indicators of past or present habitability on Mars. Systematic measurements along a finely laminated sedimentary sequence would also lead to a greater understanding of surface formation processes. Following subsystem design and test, our breadboard PSS will undergo full end-to-end characterization at Mars ambient pressures using analog rock samples and integrated prototype spaceflight analytical instruments.

The NASA Lunar Electric Rover (LER) has been developed at Johnson Space Center as a next generation mobility platform. Based upon a twelve wheel omni-directional chassis with active suspension the LER introduces a number of novel capabilities for lunar exploration in both manned and unmanned scenarios. Besides being the primary vehicle for astronauts on the lunar surface, LER will perform tasks such as lunar regolith handling (to include dozing, grading, and excavation), equipment transport, and science operations. In an effort to support these additional tasks a team at the Kennedy Space Center has produced a universal attachment interface for LER known as the Quick Attach. The Quick Attach is a compact system that has been retro-fitted to the rear of the LER giving it the ability to dock and undock on the fly with various implements. The Quick Attach utilizes a two stage docking approach; the first is a mechanical mate which aligns and latches a passive set of hooks on an implement with an actuated cam surface on LER. The mechanical stage is tolerant to misalignment between the implement and the LER during docking and once the implement is captured a preload is applied to ensure a positive lock. The second stage is an umbilical connection which consists of a dust resistant enclosure housing a compliant mechanism that is optionally actuated to mate electrical and fluid connections for suitable implements. The Quick Attach system was designed with the largest foreseen input loads considered including excavation operations and large mass utility attachments. The Quick Attach system was demonstrated at the Desert Research And Technology Studies (D-RATS) field test in Flagstaff, AZ along with the lightweight dozer blade LANCE. The LANCE blade is the first implement to utilize the Quick Attach interface and demonstrated the tolerance, speed, and strength of the system in a lunar analog environment.

The developmental test program for the MSL (Mars Science Laboratory) rotary percussive drill examined the effect of various drill input parameters on the drill penetration rate. Some of the input parameters tested were drill angle with respect to gravity and percussive impact energy. The suite of rocks tested ranged from a high strength basalt to soft Kaolinite clay. We developed a hole start routine to reduce high sideloads from bit walk. The ongoing development test program for the IMSAH (Integrated Mars Sample Acquisition and Handling) rotary percussive corer uses many of the same rocks as the MSL suite. An additional performance parameter is core integrity. The MSL development test drill and the IMSAH test drill use similar hardware to provide rotation and percussion. However, the MSL test drill uses external stabilizers, while the IMSAH test drill does not have external stabilization. In addition the IMSAH drill is a core drill, while the MSL drill uses a solid powdering bit. Results from the testing of these two related drilling systems is examined.

Landing zone surface preparation is one of the first teleoperated remote lunar construction activities to occur in NASA's plans for the buildup of a lunar outpost. This paper describes a risk assessment visualization study performed for a lunar outpost landing/launch pad excavation and construction scenario. A Visualization Analysis Sequencing Technique (VAST^TM), developed by XArc Corp, was applied to the risk assessment. VAST^TM provides visual "snapshots" of the sequence of an operational process simulated over time to drive out and understand complex variables in systems planning. Presented is an illustrated sequence of the outpost buildup with pictorials of mission snapshots to play out the operational scenario and visualize the sequence of risks along the way to how the prepared landing zone gets to its ready state in time for arrival of the next crewed Altair lunar lander. The study identified and ranked operational risks according to risk matrix priority scoring using Constellation Program criteria for risk consequence scoring. Recommended mitigation strategies are discussed.

Anchoring technology to secure building structures has already been in use over 6000 years ago. In the Bronze Age boats were anchored with a large rock at the end of a rope. Anchors will undoubtedly play an important role in enabling not only the exploration of the moon but also in the construction of lunar facilities. Unlike the earth, the lunar surface is amiss of convenient means to anchor one end of a cable or rod in rocks or tree trunks. Alternative earth anchors will face much different soil conditions to be successfully installed and used on the moon. The key problem is the fact that nothing is known about the behavior of anchors in lunar regolith. This paper presents the beginning of an experimental study to assess the effect of circular wedge anchoring in compacted lunar simulant. It will introduce to key hardware that has been built and explains the models behind the planned pull-out tests with various anchor lengths and anchor sizes. The goal of the upcoming work will be to establish a function between pull-out force and theoretical models of failure mechanisms. These functions should provide the basis for experimentally verifications in lunar environments. Results of the first pull-out tests will be presented during the Earth&Space 2010 conference.

Terrestrial drills are normally deployed from massive platforms such as large trucks or stationary rigs. The drilling platform provides a reaction force for the drill, the so called Weight on Bit (WOB). Harder rocks require higher WOB to fracture, while softer rocks require lower WOB to fracture. In the case of planetary drilling, rovers and landers carrying drills have very low mass in comparison. Thus, maximum WOB that can be practically applied to a drill is highly limited for space applications. One solution to drilling with a low reaction force is to augment a rotary drill with a percussive hammer. The rotary-percussive drill requires a much lower Weight on Bit (WOB), than a pure rotary drill and it can also penetrate very hard rocks more efficiently. That is, with less overall energy. However, the downside of a rotary-percussive system is added power and complexity compared to a pure rotary system. In this paper, custom designed and Commercial, off-the-shelf (COTS) rotary-percussive drill systems are described and preliminary drilling results in various formations, including ice, limestone, and hard basalts are presented.

As space agencies throughout the world turn their attention toward human exploration of the Moon, Mars, and the solar system beyond, there has been an increase in the number of robotic sample return missions proposed as precursors to these human endeavors. In reality, however, we, as a global community, have very little experience with robotic sample return missions: 3 of the Russian Luna Missions successfully returned lunar material in the 1970s; 28 years later, in 2004, NASA's Genesis Mission returned material from the solar wind; and in 2006, NASA's Stardust Mission returned material from the Comet Wild 2. We launch many spacecraft to LEO and return them to Earth. We also launch spacecraft beyond LEO to explore the planets, our solar system, and beyond. Some even land on these bodies. But they do not return. So as we begin to contemplate the sample return missions of the future, some common questions arise: "What really happens when the capsule returns?" "Where does it land?" "Who retrieves it and just how do they do that?" "Where does it go after that?" "How do the scientists get the samples?" "Do they keep them?" "Who decides?" The questions are nearly endless. The goal of this paper/presentation is to uncover many of the mysteries of the post-return phase of a mission with respect to the samples themselves — from the time the return body enters the atmosphere until the mission ends and the samples become part of a long term collection. The discussion is based largely on the author's own experience with NASA's Genesis and Stardust missions. Of course, these two missions have a great deal in common, being funded by the same NASA Program (Discovery), having similar team composition, and being subject to United States Laws and Regulations in addition to International Agreements. The intent, however, is to use these missions as examples in order to highlight the general requirements and the challenges in defining and meeting those requirements for the final phase of sample return missions. The choices made by the Genesis and Stardust teams regarding recovery and sample handling are discussed in comparison with the handling of returned lunar samples, the Antarctic Meteorite Collection, and the Cosmic Dust Collection at Johnson Space Center.

Over the past three years NASA Marshall Space Flight Center has been collaborating with Brookhaven National Laboratory and with colleagues at Bear Fight Center to develop a modular Silicon Drift Detector (SDD) X-Ray Spectrometer (XRS) intended for fine surface mapping of light elements of planetary bodies. The SDD is ideally suited to this task, having modest power and cooling requirements and high radiation hardness. The modular form permits tailoring to multiple platforms, from orbiters to surface landers. In the former, possible targets include any airless bodies with sufficient ambient radiation to excite surface fluorescence. These include our moon, Mercury, the moons of Mars and Jupiter, asteroids and comets. Our SDD-XRS instrument can operate with a low energy threshold (i.e. is capable of detecting carbon), has comparable energy resolution to current CCDs (<150 eV at 5.9 keV) and has an order of magnitude lower power requirement. The target radiation hardness for this XRS is the Mrad level, sufficient for observations even within the Jovian system. Full details of the current status of the instrument will be presented. This effort is funded in part through the NASA Research Opportunities in Space and Earth Sciences - Planetary Instrument Definition and Development Program (PIDDP).

This paper will describe an overview of the National Aeronautics and Space Administration (NASA) led multi-center Habitat Demonstration Unit (HDU) Project. The HDU project is a "technology-pull" project that integrates technologies and innovations from numerous NASA centers. This project will be used to investigate and validate surface architectures, operations concepts, and requirements definition of various habitation concepts. The first habitation configuration this project will build and test is the Pressurized Excursion Module (PEM). This habitat configuration—the PEM—is based on the Constellation Architecture Scenario 12.1 concept of a vertically oriented habitat module. The HDU project will be tested as part of the 2010 Desert Research and Technologies Simulations (D-RATS) test objectives. The purpose of this project is to develop, integrate, test, and evaluate a habitat configuration in the context of the mission architectures and surface operation concepts. A multi-center approach will be leveraged to build, integrate, and test the PEM through a shared collaborative effort of multiple NASA centers. The HDU project is part of the strategic plan from the Exploration Systems Mission Directorate (ESMD) Directorate Integration Office (DIO) and the Lunar Surface Systems Project Office (LSSPO) to test surface elements in a surface analog environment. The 2010 analog field test will include two Lunar Electric Rovers (LER) and the PEM among other surface demonstration elements. This paper will describe the overall objectives, its various habitat configurations, strategic plan, and technology integration as it pertains to the 2010 and 2011 field analog tests. To accomplish the development of the PEM from conception in June 2009 to rollout for operations in July 2010, the HDU project team is using a set of design standards to define the interfaces between the various systems of PEM and to the payloads, such as the Geology Lab, that those systems will support. Scheduled activities such as early fit-checks and the utilization of a habitat avionics test bed prior to equipment installation into PEM are planned to facilitate the integration process.

The Lunar Surface System (LSS) Habitat Demonstration Unit (HDU) will be required to support the readiness testing operations and the remote field testing operations planned for evaluating proposed LSS architectural scenarios. From the performance of the HDU's initial subsystem evaluations to its scheduled rollout in early July 2010 at NASA's Johnson Space Center (JSC) to its shipment to the field in mid-August 2010, the HDU will benefit from well-planned strategies to mitigate risks and ensure the various phases of field test operations are successfully executed. In cooperation with the activities associated with the overall integrated design and outfitting of the HDU systems, the project's team will incorporate design features which enable robust test operations capabilities both locally at JSC and at remote field test sites. Additionally, a suite of specialized equipment will be acquired or developed to meet the demanding needs of remote field testing. This will include long-haul transportation equipment, provisions for off-loading and reloading the sizable HDU, a robust portable power supply system, and remote site test operations team support facilities. Finally, a thorough, well-developed set of operational procedures will be utilized by the team to support the different HDU field testing configurations and to ensure smooth integrated operations with the other prototype lunar surface elements being evaluated during the field test.

The Lunar Surface System Habitat Demonstration Unit (HDU) will require a project team to integrate a variety of contributions from National Aeronautics and Space Administration (NASA) centers and potential outside collaborators and poses a challenge in integrating these disparate efforts into a cohesive architecture. To accomplish the development of the first version of the HDU, the Pressurized Excursion Module (PEM), from conception in June 2009 to rollout for operations in July 2010, the HDU project team is using several strategies to mitigate risks and bring the separate efforts together. First, a set of design standards is being developed to define the interfaces between the various systems of PEM and to the payloads, such as the Geology Laboratory, that those systems will support. Scheduled activities such as early fit-checks and the utilization of a habitat avionics test bed prior to equipment installation into HDU PEM are planned to facilitate the integration process. A coordinated effort to establish simplified Computer Aided Design (CAD) standards and the utilization of a modeling and simulation systems will aid in design and integration concept development. Finally, decision processes on the shell development including the assembly sequence and the transportation have been fleshed out early on HDU design to maximize the efficiency of both integration and field operations.

Mars missions to date have interrogated the planet at very large scales using orbital platforms or at very small scales intensively studying relatively small traverses of the landscape. Long-range surveys of in situ resources on the surface of Mars could be readily accomplished with a fleet of Tumbleweeds — inflatable or deployable-structure vehicles capable of using the readily available Martian wind to traverse the surface of Mars with minimal power, while optimizing their capabilities to perform a variety of measurements over relatively large areas. These low-cost vehicles fill the niche between orbital reconnaissance and landed rovers. Fleets of Tumbleweed vehicles could conduct long-range, randomized surveys with simple, low-cost instrumentation that is functionally equivalent to conventional coordinate grid sampling. These vehicles can be suitably instrumented for surface and near-surface sensing and analysis and released to roam for the duration of a season or longer. It is anticipated that within just a few years, instruments such as gas chromatograph mass spectrometers (GC-MS) and ground-penetrating radar (GPR) will be deployable on Tumbleweed vehicles. Different Tumbleweed configurations can provide the capability to operate in varying terrains and accommodate a wide range of instrument packages making them suitable for autonomous surveys for in situ natural resources. Tumbleweeds are lightweight and relatively inexpensive, making them very attractive for multiple deployments or piggybacking on larger missions.

This paper presents the results of analysis of percussive system designed for lunar exploration using finite element modeling. The system consists of a string of hollow circular tubes driven by a mechanism delivering high-frequency impact loading so as to drive the tube forward into the lunar regolith. The tubes are attached in an end-to-end fashion with some compressive preload applied at the joint between the strings. The primary focus of this paper is to determine effects of preload and presence of joints on stress and displacement wave propagations along the length of the tube. Two types of finite element models were developed — one, a single circular tube without any joint and the second, two tubes connected end to end. Static preloads (500 N and 1500 N) were applied at the joint for the second model. Separation of tubes is seen with preloading value of 500 N for the given dynamic loading. Sudden discontinuity of stress and displacement waves is also seen. Similar analysis with 1500 N preload shows no separation between tubes. This information has considerable significance in design of joints in drill strings.

This paper explores the mechanical interactions occurring between a Piezoceramic Actuator (PA) and its host structure, the so-called "smart structures". Based on improvements of individual PA models already published, a comprehensive PA model is developed, accounting for hysteresis, non-linear electric field and dynamic effects. This model is able to determine unconstrained PA's strains due to an applied input voltage, for which experimental validation of its "standalone" behavior yields very accurate results. Two more models are also developed, able to calculate developed forces on a host structure due to an applied PA's input voltage and developed strain (via feedback measurements). These models are ideal for simulating the load exchange between the PA and its host structure, which is dependent on the geometries, rigidities and boundary conditions of both. All three models are implemented in Matlab/Simulink and their performance tested via a numerical case study of a simple mechanical system coupled to a PA, with the aim of shifting the natural frequency of the structure. Results show that the developed models exhibit greater accuracy and simplicity than some already published, also allowing the straightforward inclusion of other behavior (creep, aging, thermo-elasticity, etc.) if significant for a particular application. These models are developed in parallel to a main research, which aim is non-linear identification in mechanical structures, to be reported in forthcoming papers.

A device based on an inductive Coulter counting principle to detect metal particles in lubrication oil is presented. The device detects the passage of ferrous and nonferrous particles by monitoring inductance change in a coil. First, the sensing principle is demonstrated at the mesoscale using a solenoid. Next, a microscale device is developed using a planar coil. The device is tested using iron and aluminum particles ranging from 80μm to 500μm. The testing results show the device is capable of detecting and distinguishing ferrous and nonferrous metal particles in lubrication oil, such particles can be indicative of potential machine faults in rotating and reciprocating machinery. The design concept demonstrated here can be extended to a microfluidic device for real-time monitoring of ferrous and nonferrous wear debris particles.

A practical sensor with high sensitivity for the temperature measurement by using a highly birefringent (HiBi) fiber loop mirror (FLM) concatenated with a long-period grating (LPG) written in a photonic crystal fiber (PCF) is proposed. Only HiBi-FLM acts as a sensor head, while the PCF-LPG serves as a temperature insensitive filter to provide wavelength dependent optical power transmission. A bandpass filter is used to provide a narrow band light source, thus only one of transmission peaks of the HiBi-FLM is located within a negative linear region of the LPG's transmission spectrum. By utilizing the stable filtering function of the PCF-LPG, the resonant wavelength variation of the FLM with temperature is transferred effectively to the intensity variation of the output light. The temperature applied on the FLM is deduced by a cheap optical power. As a result, the sensitivity of the sensor is about -0.4872 dB/°C. When an optical power meter with the resolution of 0.01 dB, a temperature resolution of 0.02°C is achieved.

The ever increasing need for oil around the world has helped the offshore oil industry to grow tremendously in the last few decades. This growth has made it necessary for this industry to investigate and design new and improved drilling methods that increase the productivity and efficiency of the devices used in offshore applications. Shape memory alloys (SMA) are new materials that have great potential for significantly improving instruments used in this field. Remarkable properties, such as the shape memory effect (SME), corrosion resistance, and superelasticity, have compelled the use of SMAs in the oil industry. When the SME is correctly harnessed, this device can become a lightweight, solid state alternative to conventional hydraulic, pneumatic or motor based actuator systems. The SMA can also be used in deepwater valves, underwater connectors, seals and self-torquing fasteners. The phase transformation property enables the SMA to withstand erosive stresses, which is useful for minimizing the erosion of the downhole well bores. The conventional passive damping method suffers from various defects and limitations; however, using the superelasticity of the SMA, sufficient energy dissipation is possible. SMA actuators cannot be used for high frequency operations, however, SMA actuators remain better options for low frequency operations due to a high power density, a high fatigue life and controllable actuation as compared to their traditional counterparts, which are sometimes more expensive, less reliable and very bulky. The largest benefit comes from their potential to reduce human labor and maintenance time under the ocean. There is a growing research interest in this area, as reflected by the increasing number of related research papers and patents. This paper reviews the recent development and application of shape memory alloys in the offshore oil industry.

A practice of using FRP-wrapped Balsa wood bridge deck system to replace the original steel ones has been pioneered in Louisiana. The newly developed bridge deck system is bonded on the bridge girder, where the debonding issue in the interface is of great consideration. A debonding monitoring method using the common commercial OTDR has been proposed. By using the designed sensor configuration, the event of interface deboning will induce optic power loss in the sensing optic fiber, which is able to be detected by OTDR device. Through the experiment conducted in laboratory, it is found that the proposed method is sensitive to the event of debonding occurrence, and the slip extent can also be identified.

In this paper, acoustic emission technique is proposed to monitor the bridge cable damage. Experiments on acoustic emission characteristics of full-regime steel strands tensile failure are carried out. Acoustic emission characteristic parameters of steel strand damage are obtained. The testing results show that the acoustic emission characteristic parameter isn't apparent before fracture, the acoustic emission signal increases rapidly when approaching critical fracture point and appears a big burst signal nearby yield point1According to the correlation figure of acoustic emission accumulative energy, damage characteristic parameter of steel strand can be expressed through acoustic emission accumulative energy, the damage evolution process and law can be dynamically analyzed and broken strand numbers and time are very easily judged. Based on the monitoring data, the relationship between acoustic emission parameter and damage variables is derived. The steel strand tensile damage evolution equation is defined with acoustic emission accumulative energy relative change, the equation can be expressed using weibull cumulative distribution function, and its rightness and rationality are verified through experiments.

Piezoceramic materials have been successfully used in many fields, such as aerospace, civil and mechanical engineering, and in most cases they are used as sensors. As an actuator, piezoceramic materials exhibit non-linearities that force the use of advanced algorithms in control applications, and thus limiting the potential to move from the laboratory to large scale field applications. Moreover, piezoceramic actuators require bulky bench power amplifiers for even small applications. In this paper, a miniature piezoceramic amplifier was built to provide similar features that commercial amplifiers provide in a much smaller format and at a lower cost. The miniature amplifier is capable of running using a single battery. Additionally, a PID controller was designed and implemented to allow the reduction of hysteresis through charge feedback. Tests were conducted on a piezoceramic stack actuator with no load and verified using a laser displacement sensor.

Brachytherapy is a type of radiotherapy for localized tumors whereby radio-active substances are placed within or close to the tumor region. The procedure is extremely invasive; in the instance of prostate cancer, up to 20 needles are used to deliver 100 grain-sized capsules (usually ¹²⁵I or ¹⁰³Pd) throughout the prostate. Such a high number of needles increase the risk of damaging the rich bed of blood vessels around the prostate and also cause increased discomfort for the patient, along with other possible complications. Accordingly, an innovative shape memory alloy (SMA) based low dose rate (LDR) brachytherapy tool was designed to address this issue. Curved superelastic nitinol wires were tested on tissue simulants (Perma-gel) in order to investigate how differently curved SMA needles behave in tissue. It was found that the wires were able to create curved shapes in tissue. However, in most cases, tissue relaxation and friction caused discrepancies between the original shape of the wire and the trail it created in tissue. With the ability to create highly curved needle trajectories, it is theoretically possible to significantly reduce the required amount of external punctures normally seen in prostate brachytherapy. This study also opens up the possibility of using radically different seed planning strategies for prostate brachytherapy.

Fiber Bragg grating(FBG) sensor presents superiority in the measurement of strain in structural monitoring system since its reliability, durability, high accuracy and ease of implementation. In this work, a novel FBG strain sensor is developed and experiments are conducted on the universal material testing machine to calibrate its strain transferring characteristics and fatigue property. These FBG strain sensors are bonded onto the surface of a pipeline model to measure strain variations under the action of vortex-induced vibration(VIV) and relative frequency analysis of vibration responses are carried out. The results demonstrate that the designed encapsulated FBG strain sensor is a highly accurate and reliable method of measuring strain of model pipeline under VIV.

High precision control of single-mode fiber tapering processing, such as chemical corrosion, physical polishing, thermal tapering, etc. is challenging due to the fragility and microdimensions of the fiber. We introduce a new method based on the fiber loop ringdown (FLRD) technique to conduct real-time, on-line monitoring of the fiber etching process by using 48% hydrofluoric acid solutions. The corrosion process of the cladding of single-mode fibers (SFM-28) was monitored using the FLRD technique and the corroded surfaces of the fiber were visualized by Scanning Electron Microscopy with a resolution of 5 nm at an accelerating voltage of 1 kV. The corrosion processes monitored by the FLRD technique have a precision of 0.1 μs in terms of ringdown time, which corresponds to a 0.5 μm precision in fiber dimensions. This method can be further developed to monitor and control a chemical corrosion process, in realtime, on-line, and with high precision in many applications.

Pedestrian and bicycle (P/B) often have difficulty mixing with modern transportation modes because of big difference in travel behaviors, especially when they are crossing freeway interchanges. Fortunately, the various innovative detection and communication equipments newly developed in other fields provide great tools for traffic engineers to improve safety and efficiency for P/B crossings at freeway interchanges. In this paper, an inventory of novel devices and equipments are created based on the intensive literature review and the contacts with manufactures. The identified equipments include the Animated Display Eyes, the Microwave Detectors for Pedestrian, the Infrared Pedestrian Detectors, the Countdown Signals and so on. Problems for P/B crossings at a typical freeway interchange in Houston, Texas are identified, while the sample treatments using some of the intelligent devices and sensors are listed. The on-going works include the design of the implementation plan and conduct the cost analyses for selected test sites.

The cable plays a more and more important role in civil engineering recently. As an effective construction member, cable is used in many long-span spatial structures. The cable tension measurement is required in the construction control, assessment and long-term monitoring of cable-supported structures. The academic wireless sensing prototype co-developed at Stanford University and the University of Michigan is characterized by a powerful computational core and low power consumption characteristics. Two embedded engineering algorithm, namely the fast Fourier transform algorithm and the peak-picking algorithm, are implemented in the wireless sensing and to identify the frequencies of cables. Moreover, as a conventional method for cable tension measurement, the Fourier Transform can only be used in the static cable tension force test, but not dynamic cable tension test. It represents the intrinsic dynamic properties of cables. In this paper, wavelet transform tool that has the time-frequency analysis ability is used to analyze the signal, and obtain the cable tension dynamic change along with the time.

Sensor networks are used in the industry extensively. Most of these networks are static and do not provide standardized and systematic network management capabilities. There is no intelligence associated with the sensors and they behave as mere sensing elements. There is a need to monitor the sensor networks with the classical elements of network management in an interoperable way: fault, configuration, performance, accounting, and security. However, most of the sensor-networking approaches lack a standardized method of handling these classical elements. This paper is on the demonstration of plug and play of smart sensors using a standardized internet network management protocol (SNMP — Simple Network Management Protocol) method with IEEE 1451-based TEDS capabilities. It also demonstrates plug and play capability at different levels to provide network and sensor management in a dynamic fashion. To our knowledge, this is the first demonstration of three-level plug and play in a standardized way using SNMP and IEEE 1451.

Cavity ringdown spectroscopy and its associated techniques have been widely implemented for measurement, monitoring, and sensing in many applications in diverse fields, including energy, medicine, materials, environment, infrastructure, etc. Cavity ringdown technique has not been actually extended beyond its applications on Earth to new applications in space although ringdown instruments have been loaded to an aircraft to conduct real-time survey of atmospheric species. In addition to gas sensing, recent developments have advanced ringdown techniques for physical sensor developments by using a section of optical fiber as a conceptual high-reflectivity cavity without sacrificing the intrinsic natures of ringdown: near-real time response, high sensitivity, and measuring time constants to sense a quantity. Cavity ringdown has great potential to help address three significant issues in sensing applications associated with space science and engineering: time, logistics, and intelligence. The purpose of this paper is to introduce cavity ringdown to a new community: intelligent sensors for space science and engineering and to explore new applications, e.g., light-weight, multi-function, intelligent sensors for space vehicle structure health morning and control, real-time chemical sensors for methane, carbon dioxide, water, and carbon isotopes for extraterrestrial life exploration, and medical sensors for astronauts' metabolic status monitoring.

Magnetic nanoparticles (MNPs) have been receiving increasing attention because of its great potentials in separation. However, the separation products are difficult to be detected by general method due to their small size. Here, we demonstrate magnetic nanoparticles could greatly enhance the signal of surface plasmon resonance spectroscopy (SPR). Features of MNPs-aptamer conjugates as a powerful amplification reagent for ultrasensitive immunoassay are explored for the first time. In order to evaluate the sensing ability of MNPs-aptamer conjugates as an amplification reagent, a sandwich SPR sensor is constructed by using thrombin as model analyte. Thrombin, captured by immobilized anti-thrombin aaptamer on SPR gold film, is sensitively detected by SPR spectroscopy with a lowest detection limit of 10 ng/ml after MNPs-aptamer conjugates is used as amplification reagent. At the same time, the excellent selectivity of the present biosensor is also confirmed by using three kinds of proteins (BSA, human IgM and human IgA) as controls. These results confirm that MNPs is a powerful sandwich element and an excellent amplification reagent for SPR based sandwich immunoassay and SPR has a great potential for the detection of magnetic nanoparticles-based separation products.

Miniature, low mass actuators play an important role for practical applications in developing technologies. Having the responsive behavior to the applied current, Shape Memory Alloy (SMA) wire actuators provide cost effective solutions to many actuation problems. However there are still challenging problems need to be solved for the SMA actuators to be used efficiently, especially in applications that require precise positioning tasks. This work presents an experimental positioning application of an SMA wire actuator using μ-Synthesis controller along with a Feed-Forward (FF) compensator. The feed-forward compensator is designed as a piecewise function and used to reduce the nonlinearity of the most problematic are of the hysteresis where the steepest response change occurs. The remaining hysteretic behavior of the SMA wire actuator is modeled as a parametric uncertainty. Controller synthesis problem is defined as an S-KS mixed sensitivity problem. By minimizing the requirement of fast actuator movement using FF compensator, the overall control strategy yields good results in terms of tracking performance both at low and higher frequencies.

This paper summarizes our recent research progresses in developing optical fiber harsh environment sensors for monitoring the operating conditions of a coal-fired power plant and in-situ detection of key gas components in coal-derived syngas. The sensors described in this paper include a miniaturized inline fiber Fabry-Perot interferometer (FPI) fabricated by one-step fs laser micromachining, a long period fiber grating (LPFG) and a fiber inline core-cladding mode interferometer (CMMI) fabricated by controlled CO₂ laser irradiations. Their operating principles, fabrication methods, and applications for measurement of various physical and chemical parameters in a high temperature and high pressure coexisting harsh environment are presented.

A FRP-wrapped Balsa wood bridge deck system has been developed and installed in Louisiana. The bridge performance has been evaluated by using live load testing and its long-term performance will be monitored using fiber optic sensors throughout its service. The short-term live load test and plan of the long-term monitoring system is introduced in this paper. Preliminary results from Fiber Optic Sensors (FOS), traditional strain sensors and acoustic emission sensors are analyzed to assess the bridge performance.

In order to create a non-intrusive electric field sensor, an all dielectric electric field sensor is developed. This sensor is based on resonant coupling between a D-shaped optical fiber and a slab of non-linear optical material. A laser is tuned to have a wavelength on the edge of one of the resonant dips. The non-linear crystal causes a shift in the resonance, which causes the incident electric field to be converted into a change in the optical power transmitted through the SCOS. The SCOS is fabricated to have a size of 0.2 mm x 0.2 mm x 1.2mm and tested to have a sensitivity of 60 mV/m HZ^1/2. The SCOS is used to measure the electric field inside of an X-band waveguide and is fabricated into an array using KTP and LiNbO₃ as the non-linear optical crystals.

Classic bi-axial test specimens have typically been a cruciform design with a tapered thickness gage section. A gage section is created using a computer numeric controlled (CNC) milling machine. This milling process inflicts initial damage to the specimen which can cause inaccurate failure data. A new bi-axial cruciform test specimen has been developed using Finite Element Analysis (FEA). The new specimen was fabricated without milling the gage section. Aluminum shims have been incorporated into the design of the specimen to allow bi-axial stress to control the failure of the specimen. Uni-axial tests have been completed to accurately determine material property values. These values were then used in the Finite Element Model (FEM) developed to design the new specimen. Results from the FEM indicate that this new cruciform specimen can yield more accurate results than that of the classic bi-axial specimen.

A fiber Bragg grating (FBG) sensor was fixed on the uniform strength beam with screws and modified acrylate. The influence of fixing method on FBG strain sensor was investigated experimentally. The wavelength shifts of the FBG sensor fixed by screws and modified acrylate were measured with different strains in the temperature range 0°C–40°C. The linearity, sensitivity and their stability at different temperature of FBG sensor which fixed with different methods were analyzed. The results show that, the FBG sensor fixed with the modified acrylate has a high linearity and a higher sensitivity which is 2.04pm/με. Its linearity and sensitivity have a high stability at different temperatures. The FBG sensor fixed with screws has a high linearity and a lower sensitivity which is1.47pm/με. Its linearity and the sensitivity only have slight variation at different temperatures.

Piezoceramic materials are widely used in various applications, such as vibration control, structural health monitoring and micro-positioning devices. Piezoceramic actuators exhibit hysteresis nonlinearity due to their ferroelectric nature. This nonlinearity results in system inaccuracy and deteriorated performances for precision devices. A scalar sign function-based digital redesign control methodology is developed to establish a linear relationship between input and output of a piezoelectric actuator with absolute value state and input constraints. The scalar sign function is first utilized to obtain an optimal linear model of the constrained non-smooth state and input functions of the piezoelectric system, which has the exact dynamics of the original nonlinear system at the operating point of interest and minimal modeling errors in the vicinity of the operating point on the trajectory. A digitally redesigned optimal state feedback tracking controller with prediction feature is implemented on the nonlinear system. In addition, a prediction based digital observer is designed to estimate the unavailable state variables of the system.

The intention of the Responsive Space initiative is to develop procedures and technologies necessary to reach the goal of a six-day satellite that entails all steps from ordering to operations. The experimental test method presented in this paper performs a quality assessment of the connections between satellite panels either as an alternative to traditional vibration testing or as a precursor to in-situ monitoring of panel-to-panel connections. This technique, based on the energy of a transmitted wave across the connection, is intended for responsive satellites designed with prefabricated and pretested panels for which traditional vibration testing would be redundant. The energy used to assess the integrity of the connection is in reference to a previously taken baseline. Experiments were conducted on a functional satellite to test, in part, the feasibility of deploying this test method under realistic circumstances. This paper presents those results and an assessment of the test method.

Space operations will be the mainstream and necessity of future space activities. More and more orbital vehicles for space operations can not be described by the Kepler's laws due to man-control, and their orbits belong to the non-Keplerian orbits. The problem of non-Keplerian orbits is discussed in this paper. First, three examples of non-Keplerian orbits, the spiral climbing orbit, hanging orbit, and three-body orbit are analyzed. Then, the limitations of Keplerian theory are analyzed, while the special and general methods for studying non-Keplerian orbits are discussed. Finally, the main research areas of non-Keplerian orbits are suggested. The concept of non-Keplerian orbits put forward in this paper can help to understand and investigate the essence of motion of spacecrafts, and help to establish the basement of future space technology.

In this paper, a new general method for modeling complex multibody systems is presented. The method utilizes recent results in analytical dynamics adapted to general complex multibody systems. The term complex is employed to denote those multibody systems whose equations of motion are highly nonlinear, non-autonomous, and possibly yield motions at multiple time and distance scales. The approach considered herein opens up new routes for modeling general multibody systems by explicitly developing closed form expressions in terms of any desirable number of generalized coordinates that may appropriately describe the configuration of the multibody system. Furthermore, the approach is simple in implementation because it poses no restrictions on the total number and nature of modeling constraints required to construct the equations of motion of the multibody system. Conceptually, the method relies on a simple three-step procedure. It utilizes a new set of equations of motion developed by Udwadia and Schutte, which describes the explicit equations of motion for constrained mechanical systems with singular mass matrices. The simplicity of the method is highlighted by illustrating its use in the modeling of a multibody spacecraft system for which we provide numerical results of the system's response.

A new robust fault-tolerant controller scheme integrating a main controller and a compensator for the self-repairing flight control system is discussed. The main controller is designed for high performance of the original faultless system. The compensating controller can be seen as a standalone loop added to the system to compensate the effects of fault guaranteeing the stability of the system. A design method is proposed using nonlinear dynamic inverse control as the main controller and using nonlinear extended state observ er-based controller as compensator. The stability of the whole closed-loop system is anal yzed. Feasibility and validity of the new controller is demonstrated with simulation example.

The conventional approach used for the rendezvous-radar-based relative navigation algorithms is chiefly based on Kalman filter, which contains lots of matrix calculations. This paper presented a weighted recursive least square (RLS) relative navigation algorithm, which compared with the Kalman filter algorithms, could obviously reduce computational requirements. The observation equation of the algorithm presented was based on the rendezvous radar measurements and the state transfer matrix. In order to ensure the algorithm had a good performance, a method that calculated the initial values using the measurements was employed. For validating the efficiency and accuracy of the algorithm, a 6-state Kalman filter and 9-state filter were respectively compared with. Results of the simulation indicated the initial values were appropriate. Although the accuracy of the algorithm was poorer than the 9-state filter, it also met the demand of the relative navigation. On the other hand, the computation time needed by the algorithm was much less than the 6-state filter.

Takagi-Sugeno fuzzy modeling is well known as a practical approach for nonlinear system modeling. In this approach, a selection of membership functions makes much effect upon the model performance. It is usually determined by the experts' knowledge for the objective systems. However, it is often difficult to give appropriate membership functions for complex nonlinear system without any prior information. In this paper, a modification on the Levenberg-Marquardt (L-M) algorithm for Takagi-Sugeno fuzzy training is proposed. It has global and locally quadratic convergence and raises the convergence speed greatly. This method can adjust the parameters of each linear polynomials and fuzzy membership functions on line without relying on experts' knowledge. Then, an application to identification of NSV (near space vehicle) attitude system is considered and the availability of the proposed method is illustrated by the simulation results.

The autopilot design issue of a side-jet and aero-fin blending control air-to-air missile is discussed in this paper and a MRVSS (short for "Model Reference Variable Sliding Structure") control method is presented. The MRVSS controller generates control commands to aero-fin actuators and side-jet actuators to make the missile system to reach the desired normal load command. The control law is in the form of full-state feedback and the sliding-surface reachability condition is satisfied. GA (short for "Generic Algorithm") optimization is applied to search the optimal values of control parameters. Simulation results prove that the MRVSS controller has a good performance in tracking the desired command and it ensure the missile control system's fast time response and smooth dynamical process. Moreover, the MRVSS controller is robust to external disturbance and internal uncertainty which is meaningful in the actual industrial applications.

In this paper, a three-axis nonlinear two step attitude controller design composed of control law module and control allocation module is presented for the attitude control of hypersonic vehicle in the re-entry phase. The modified backstepping control law integrated backstepping technique and extended state observers (ESOs). In order to facilitate the backstepping design, a command filter was introduced. To deal with the large and fast-varying uncertainties, linear extended state observers were designed to estimate and compensate for the uncertainties in real time. Simulations performed using six-degree-of-freedom nonlinear dynamics in MATLAB show that design using the proposed modified backstepping attitude controller has better tracking performance and is more robust to uncertainties with fewer control demands than traditional backstepping design.

Dynamics of resonance orbits, a family of non-Keplerian orbits, is investigated and the application in orbit transfer is discussed. The study of this paper indicates that the motion of spacecraft under continuous thrust can be viewed as a kind of forced vibrations in parametric plan, and the resonance will happen in special conditions. Therefore, we can study on the motion of spacecrafts using resonance theory, and this kind of non-Keplerian orbit is named resonance orbit. Resonance orbit is studied in this paper. First, the dynamical model for resonance orbit is established via the judicious choice of orbit parameters, time scale, and thrust representation. Then, the definition and expression of resonance orbit are given. Finally, the method of orbit transfer based on resonance orbit is proposed.

This paper presents explicit and exact formation-keeping guidance schemes that use a new method to determine control inputs and state trajectories. With this approach rooted in some recent advances in analytical dynamics, explicit control inputs to exactly maintain a given formation configuration are easily determined using continuous thrust propulsion systems. The complete nonlinear problem is addressed, and no linearizations and/or approximations are made. The approach provides a marked improvement over existing results in that the control forces, which cause geometric formation-keeping constraints to be exactly satisfied for Keplerian reference orbits, are found in closed form. Extensive computational simulations are performed to demonstrate the ease of implementation and the numerical accuracy attained.

In this paper, Takagi-Sugeno (T-S) fuzzy modeling for Near Space Vehicle (NSV) is first introduced. The nonlinear dynamics of NSV are represented by a T-S fuzzy model. The fault diagnosis and active fault-tolerant control (FTC) problems for NSV with actuator fault are then investigated. An adaptive fault diagnosis observer (AFDO) is designed to detect and estimate fault. The residual is defined as the norm of the output error between AFDO and actual system to detect the actuator fault, and an adaptive fault estimation algorithm is proposed to estimate the fault. An active fault tolerant controller is designed by utilizing the diagnostic fault information to compensate for the loss of actuator effectiveness. Finally, simulation results on the longitudinal model of NSV are presented to demonstrate the efficiency of the proposed approach.

This paper presents an adaptive terminal sliding mode dynamic inversion control method. The hypersonic vehicle model is uncertain, multi-variable, unstable, and possesses significant input-output cross-coupling for its extremely wide range of operating conditions and rapid change of mass distributions. Therefore, it is essential to design flight controllers with high non-linear control ability and robustness for hypersonic air-crafts. By using a function augmented sliding hyperplane, it is guaranteed that the output tracking error converges to zero in finite time which can be set arbitrarily and by designing adaptive control law, uncertain parameters can be identified. Simulation results indicate that the proposed methodology may constitute a feasible approach towards the development of robust nonlinear controllers for this type of applications.

A gain-scheduled bank-to-turn autopilot design for a hypersonic vehicle is presented. The approach using the linear parameter varying transformations doesn't involve linearizations about operating points. Instead, the vehicle dynamics are brought to a linear parameter varying form via a state ransformation. This framework is applied to the design of a coupled longitudinal/lateral bank-to-turn autopilot for a hypersonic vehicle. First, the linear parameter varying (LPV) model of the hypersonic vehicle for bank-to-turn is obtained using state ransformation.The pitch and yaw/roll dynamics are separately transformed to linear parameter varying form, where the cross axis states are treated as exogenous parameters. Because the scheduling variables include these endogenous variables, such a plant is called quasi-linear parameter varying system. Next, using the obtained LPV model , a family of robust controllers is designed for both the pitch and yaw/roll channels, which use angle of attack and roll rate as the scheduling variables. Finally,the closed-loop simulation of the LPV controller is conducted using the original nonlinear model and also using perturbed aerodynamic coefficients. The simulation results show that the desired performance and robustness objectives are achieved across the whole turn phase.

A new guidance strategy using only the line-of-sight (LOS) rate measurement is proposed for the missiles with passive seekers. The initial relative range, initial closing velocity and their error boundaries are utilized to obtain their estimations according to the missile-target kinematics. A guidance law based on sliding mode control (SMC) theory is firstly presented, in which the boundary of target maneuvering ability is needed and the chattering phenomenon inevitably exists. In order to overcome the disadvantages above, an expression with a time-varying parameter is introduced to the new guidance law and the stability analysis is included. One of the main features of the proposed guidance strategy is that it reduces the influence of the relative range and the closing velocity on the interception and enhances the effect of LOS rate. The performance of the new guidance law is studied via a computer simulation. The effectiveness of the new guidance law is illustrated through intercepting two kinds of maneuvering target successfully.

Fault detection and isolation (FDI) technology can provide early warning of faulty sensors and actuators in order to prevent events that lead to catastrophic failures. The main objective of this paper is to describe the application of FDI techniques for vibration suppression of a space truss structure. Thus, this paper presents a Linear Matrix Inequality (LMI) based fixed-order FDI filter design theorem and approach. Necessary and sufficient conditions for the existence of a solution to detecting and isolating faults using the H_∞ formulation are provided. Furthermore, a Fuzzy Fault Tolerant Controller (FFTC) for a base isolation structure model based on the FDI filter is developed to preserve the pre-specified performance of the space truss structure in the presence of faults. A numerical example is given as well as FDI and FFTC results which demonstrate that the designed filter can successfully detect and isolate faults including displacement sensor and accelerometer failure, and that the FFTC can maintain excellent performance of vibration suppression in faulty conditions.

This paper presents a novel adaptive predictive control methodology for air-breathing hypersonic vehicles (AHVs) in the presence of dynamical thrust and parameter uncertainties. The method combines the nonlinear generalized predictive control (NGPC) with a new recurrent-functional-link- network (RFLN) adaptive law proposed here. The RFLN is a simple recurrent neural network without hidden layers, so it is suitable for the approximation of dynamical uncertainties during the hypersonic flight. The RFLN weights are online tuned by the derived adaptive laws based on Lyapunov stability theorem for the first time. The learning process does not need any offline training phase. Additionally, a robust controller whose gain can be adaptively adjusted is designed to recover the residual of the approximation error. Finally, simulation results show better performance of the controller for the AHV attitude tracking than the method compared, moreover, the robustness to dynamical parameters variations and the disturbance rejection are successfully accomplished.

In this paper, a new sliding-mode-based scheme, one-way slide mode scheme for the affined nonlinear system is discussed. For the constraint problem of the slide mode, we can make the system states satisfy the constraint condition, in the whole process of approaching and sliding on the sliding mode surface, by inducting the state constraint condition into the sliding-mode scheme. Compared with the classical sliding-mode scheme, this one-way sliding-mode scheme not only retains the advantages of the slide mode scheme such as robustness, real-time property, but also constrains the state vector during the process of approaching the sliding mode surface.

The orbit under artificial control is termed Non-Keplerian orbit which does not follow Kepler's Laws. The transfer orbit design under the continuous limited thrust is one of the most important topics in this new field. Shape-based method for Non-Keplerian orbit design is developed. Firstly the nondimensional equations of motion are established. The general equation is derived with which common curves could be utilized in orbit design with respect to polar coordinates. In addition, Forbes' spiral is presented in two assumptions, which is restrictive. So the tangential thrust assumption is ignored and then the orbit design method is described based on the assumption that the radius r is a polynomial function of time. The requisite thrust magnitude and direction are available analytically. In the end, an example of the transfer orbit is given. The result demonstrates the feasibility of shape-based method applied to orbital transfer problem under the continuous thrust.

Micro Aerial Vehicles (MAVs) and larger Unmanned Aerial Vehicles (UAVs) constitute a powerful tool for the modern warfighter and first responder. However, every developing technology must first be tested before being exported to the battlefield or hot spot to assure predictable behaviors. In today's digital age, computers give designers and testers unprecedented ability to quickly and easily test virtual models before physical prototypes are created and field tested. We have utilized emerging Free Open Source Software (FOSS) simulators and workbenches (e.g. FlightGear and AUV Workbench) to improve mission-driven MAV/UAV video and imagery capture and analysis capabilities. In this project, use of FlightGear to analyze flight trajectories and video capture capabilities of different UAVs is presented. FlightGear allows the free implementation of changeable flight dynamic models, weather, autopilot, GPS, and multiplayer to be included in the analysis of simulated flights. Another attractive aspect of FlightGear is its extensible and easy-to-modify implementation. Modifications are accomplished by changing or adding human readable XML files in the FlightGear subdirectories. In this effort, existing aerial vehicle models are incorporated into FlightGear to create flight trajectories and analyze video capture capabilities to determine the necessary toolset for analyzing imagery data to meet the mission needs. The limitations of the existing camera systems as well as effects of various flight parameters on mosaicking and georegistration are presented here. Sample analysis of the effect of aerial vehicle speed on the overlap of frames captured at the typical 30 frames/second frame rate, which provides a base for comparison of flight attributes, are demonstrated together with other parameters that affect mission performance.

Target clustering forms the targets with similar attributes into several independent clusters, which is essential for the situation assessment. In this paper, a novel clustering method for the targets with mixed-type attributes is proposed. First of all, the attribute types are given according to the fundamental types of data, two new types, the "Vector-type attribute" and the "Interval-type attribute", are defined. Based on the characteristics of attribute types, the discrepancy-degree for each type is built, which extends the existing calculation method. An integrated discrepancy-degree for mixed-type attributes is established, where the quantitative or qualitative requirement of attribute is considered. The integrated discrepancy-degree solves the problem that some attributes are unsuitable for weighted sum. There is only one comprehensive comparison between individual targets and only one threshold needed to set. Several targets with mixed-attributes are selected into simulations and the results demonstrate the effectiveness of this approach.

A new optimization method named pseudospectral method for reentry trajectory was developed to transformed the original reentry trajectory generation into a nonlinear optimization problem, minimizing the accumulated heat load, which enhance the optimization greatly. Reentry orbit tracking is converted to a linear problem through feedback linearization method. The simulation under the initial error and parameter perturbation shows that feedback linearization reentry orbit tracking method has a good robust result.

This paper defines a risk analysis framework for offshore wind turbines (OWTs) and OWT farms. OWTs, due to their exposure to a demanding climatic environment, the use of particularly innovative construction methods and materials, and the relatively limited knowhow in the design and construction, are prone to elevated risk. The risk analysis problem is defined within a more global risk management framework, where several steps are foreseen in order to accomplish predetermined objectives. Starting from the establishment of the specific risk management context, the various steps for risk assessment are presented, together with the methods for risk identification, analysis, evaluation and mitigation, strictly related with the complexity of the system. As a final step, the options for risk treatment are considered. In addition, for the purpose of risk identification, a system decomposition of the relevant elements is performed, both physical related (e.g. the constituting parts) and for the external conditions and interactions.

A novel state-space formulation is presented for the dynamic analysis of rotating double-beam systems, consisting of two elastic beams continuously joined by viscoelastic springs. Although very simple, the proposed model lends itself to be used in studying the transverse vibration of wind turbine blades provided with a viscoelastic core. An efficient numerical scheme of solution is proposed, which can be further extended to include the effects of shear strain within the core, along with geometrical and material nonlinearities.

Offshore Wind Turbine (OWT) is a relatively complex structural and mechanical system located in a highly demanding environment. In this study the fundamental aspects and the major issues related to the design of such structures are inquired. The System Approach is proposed to carry out the design of the structural parts: in accordance with this philosophy, decomposition of the system (environment, structure, actions/loads) and of the structural performance is carried out in order to organize the qualitative and quantitative assessments in various sub-problems. These aspects can be faced by sub-models of different involvedness both for the structural behavior and for the load models. Numerical models are developed accordingly to assess safety, performance and robustness under aerodynamic and hydrodynamic actions.

Traditional wind resource elevation method, adopted by most commercial software like WAsP, is inapplicable for the micrositing of wind turbines in complex terrain. As the turbulence models based on Reynolds Averaged Navier-Stokes (RANS) equations could present reasonable results for the aerodynamics of blunt body, Computational Fluid Dynamics (CFD) approach is employed to assess the wind energy distribution in a real offshore hilly area. Nine wind observation towers have been installed in this area and gathered wind data per hour continuously for two years. For a reliable comparison between numerical simulation and field measurement, two strong and stable wind events were selected from field records as objects of study to verify CFD validity and accuracy. The computational domain was meshed using hexahedral grids and two horizontal resolutions of 40m x 40m and 20m x 20m. The boundary layer grids near ground were handled with great care. The performance of two RANS turbulence models Shear Stress Transport (SST) k — Ω and Re-Normalization Group (RNG) k — ε were tested. The comparison results indicate that SST k — ε model is better than RNG k — ε model, and the accuracy of 20m grid spaced results is higher. For case SST (20m), the mean relative errors of simulation and field results are 6.46% and 5.50%, which is acceptable for industry practical application. The contours of wind speed ratios at the height of 10m and 55m were also provided for wind turbines micrositing reference. At the end, by combining full-direction wind speed ratios obtained from CFD and longtime meteorological observation data from ambient flat terrain, a full-direction wind energy evaluation method applicable to complex terrain was proposed.

In recent years more and more demanding structures are designed, built and operated to satisfy the increasing needs of the Society. This kind of structures can be denoted as complex ones. Among large constructions arrangements, Offshore Wind Turbines (OWT) are definitely complex structural systems, being this complexity related to different aspects such as hard nonlinearities, wide uncertainties and strong interactions, either among the single parts or between the whole structure and the design environment. On the whole, the quality of a complex system is denoted by the idea of dependability, while for a structure the performances are connected to the property of structural integrity, considered as the completeness and consistency of the structural configuration. Even if these concepts have been originally developed, respectively, in computer science and for aerospace applications they can be applied to other high performance systems as OWT. The present paper will show some specific aspects of the modern approach for the design and the analysis of complex structural systems. In the first part of the paper, the general aspects are recalled like the System Engineering approach and the Performance-based Design. Attention is devoted to some important aspects, such as the structure breakdown and the safety and performance allocations. In the second part of the paper, a basic application of the concepts introduced is presented.

An offshore wind turbine can be considered as a relatively complex structural system since several environmental factors (e.g. wind and waves) affect its dynamic behavior by generating both an active load and a resistant force to the structure's deformation induced by simultaneous actions. Besides the stochastic nature, also their mutual interaction should be considered as nonlinear phenomena could be crucial for optimal and cost-effective design. Another element of complexity lies in the presence of different parts, each one with its peculiar features, whose mutual interaction determines the overall dynamic response to non-stationary environmental and service loads. These are the reasons why a proper and safe approach to the analysis and design of offshore wind turbines requires a suitable technique for carrying out a structural and performances decomposition along with the adoption of advanced computation tools. In this work a finite element model for coupled wind-waves analysis is presented and the results of the dynamic behavior of a monopiletype support structure for offshore wind turbine are shown.

The design of complex structures like Offshore Wind Turbines (OWTs) is commonly based on the results of deterministic structural analyses, carried out on finite element models of the structural system. However, the assessment of the structural response is affected by significant uncertainties, due to the random variability of both the environmental actions and the geometric and mechanical properties of the structure. An efficient procedure to deal with the uncertainty of modeling and loading parameters requires the characterization of the probability distribution functions of the parameters of the models of the actions and structural response, and the assessment of the probability distributions of the response parameters. Neglecting pertinent sources of uncertainty can lead to an incorrect evaluation of the stochastic structural response, and to an improper risk assessment. This paper focuses on the effects on the structural response of an OWT induced by the uncertainty of the parameters used to describe the environmental actions and the finite element model of the structure (referred to as the modeling parameters). A proper probability characterization of the parameters is assumed, and the relevance and the propagation of the uncertainty to the response are investigated. Reference is made to an OWT with a jacket support structure. Analyses are carried out in frequency domain by adopting a linear elastic finite element model, and the response uncertainty is estimated by using a sampling technique. The results presented in this paper are considered useful for the preliminary design phase, where upper and lower bounds of the stochastic structural response have to be estimated in order to select the design configuration.

Model experiment about the scour-resisting capability of natural turf reinforced with three-dimensional vegetation net was carried out in flume. The basing principle is that the turf's critical shear stress on bed and the friction velocity in model should be equal to that of prototype. Experimental research illustrate that, the relationship between shear stress above vegetative bed and mean velocity is nonlinear, which is accord with the theoretic analysis; the experimental flow belongs to turbulent flow in hydraulic rough region, since the coarseness of vegetative bed varying with the flow velocity and duration during the scouring process; the Darcy-Weisbach friction factor relates not only to the mean flow velocity, but also to the ratio of average deflected height of vegetation under the action of flow to hydraulic radius of the flume. Furthermore, the critical flow condition of vegetative revetment obtained in this paper can be applied in practical channel directly to evaluate the situation of vegetative revetment destruction.

The research studies presented focus on the influence of shear key geometries to the fatigue design of axially loaded hybrid connections in offshore wind energy converters. Within a national research project fatigue tests of grouted joints were carried out and used for the benchmark of numerical models. With the results of stress calculations from the numerical model, different local concepts for the fatigue design of steel members were implemented and evaluated. The calculation showed non-linear relations between geometric dimensions and stress concentrations. It became obvious that for future investigations linear elastic approach has to be extended taking fracture mechanic for steel and grout material into account.

The movement of oil spill, its diffusion and hydro-environmental effects have been simulated by developing a 2DH numerical model based on non-linear shallow water Reynolds averaged Navier-Stokes equations using Finite Volume Method. The new model deploys the relevant formulations for oil spill processes. Since advection and diffusion of oil pollution play a crucial role in oil spill flow pattern, it is important to choose an appropriate numerical scheme for the transport terms of N-E equations. In this work, a highly-accurate algorithm based on a 4^th degree accurate shape function has been used for the advection terms, which is not present in similar models. The solution method is based on the alternating direction implicit (ADI) scheme. The equations are then solved by a Penta-Diagonal matrix in each half-time-step. Results from the numerical model are compared with measured values. Reasonable agreement is obtained between predicted and experimental nearshore circulation patterns.

The optimal design of complex structures exposed to a high demanding environment has to be carried out in the framework of Performance-Based Design (PBD). Recently a huge research effort has been devoted at applying PBD concepts to wind engineering, and a general framework of Performance-Based Wind Engineering (PBWE) has been developed. The procedure of risk assessment has to be developed in probabilistic terms, considering the different sources of uncertainty characterizing both the actions and the structural properties: moreover the effects of the interaction between the wind field and the structure has to be properly considered. The problem is more complex in case of offshore structures, where the interaction between the wind field, the waves and the sea currents introduces additional sources of uncertainty. In the paper, the uncertainty characterizing the wind-fluid-structure interaction is discussed, and an analytical formulation of the problem of risk assessment of offshore wind turbines is proposed. The procedure, developed in the framework of PBWE, is based on the solution of a probabilistic relation between the stochastic parameters characterizing both the input and the structural response. It is applied to an example case: an offshore wind turbine with a jacket support structure.

An experimental study of the dynamic response of model offshore wind turbines founded on monopiles is presented. This exploratory set of dynamic experiments on modeled monopile foundations were analyzed by comparing the physical model test results to an analytical solution. Studied parameters included pile foundation material, water level, turbine mass, and load application. The response to free vibration decay was monitored using a vertical array of MEMS accelerometers, and the collected data were processed using Fourier analysis to assess the natural frequency of the structures. Physical model results were compared to closed form approximations using the Rayleigh energy method. Good prediction of natural frequency was achieved for turbines founded in concrete and stiff sandy soil conditions, however, the natural frequency of turbines founded in soft clays was overpredicted by up to 40%. These results highlight the importance of the sediment-structure interaction in the evaluation of the dynamic performance of offshore wind turbines.

In the recent years, research has been increasingly directed towards the design and construction of offshore wind farms (OWFs). This is mostly due to the considerably stronger, more consistent and less turbulent wind speeds offshore, something that results in increased power production. Furthermore, OWFs are characterized by a reduced visual impact as they are placed far away from the coast. On the other hand, offshore wind turbines (OWTs) destined for OWFs are relatively complex structural and mechanical systems located in a more demanding, harsher operating environment. The purpose of this paper is to present, critically and in a system manner, the main aspects influencing the basis of the design of OWT structures for an OWF in central Italy. In particular, the essential role of the structural analysis supporting the decisional process is enlightened. The project under consideration is characterized by elevated complexity due to the harsh environment (wind, wave and current actions), and the innovating characteristics, being, among else, the support structures placed in elevated depth, in the range of 20–35 meters, while up to now, the vast majority of OWFs have been set up in quite shallow waters. The support structures are designed for turbines of up to 5 MW that only recently started to enter the market.

The rising fossil energy prices and global warming phenomenon is driving researchers to look for alternative renewable and clean energy. Wind energy is considered as one of the most important alternative resources. Considering the space and other public requirements, offshore wind turbine could be larger. Technically, deepwater wind turbines are feasible since long-term viability of floating platforms has already been successfully demonstrated by the offshore oil and gas industries over decades. However, there are certain vibration issues which require critical attention for designing floating wind turbines. Flow-induced vibrations is the most important design criteria for most offshore structures and will also be important for floating wind turbines. Both the main structural elements as well as supporting structural members must be designed to withstand such oscillations. In addition to inline vibrations, the flow induced vibrations are known to initiate oscillations in a direction transverse to the general direction of motion. Most of the previous research has been concentrated on flap-wise vibration of wind turbine. This paper investigates the use of semi-active tuned mass dampers (STMDs) in controlling the edgewise vibration and the stability of floating wind turbines modeled as discrete dynamical systems in the blade rotation plane. Morison's equation is used to represent the interaction between the flow field and the offshore platform supporting the wind turbine. Numerical simulations prove that STMD has higher vibration reduction efficiency than TMD in the edge-wise blade direction under either steady or turbulent wind load, even with parameter changes such as rotation speed, nacelle stiffness loss and blade stiffness loss.

Revolving wind turbine blades are the most critical component of the wind turbine system. Structural health monitoring system is one of the most useful techniques to detect the damage before the blade fails catastrophically which could destroy the entire wind turbine. Piezoelectric transducers can sense the production and propagation of the damage effectively. Different from the previous work, the piezoelectric transducers are embedded inside of the composite blade during the manufacturing procedure in this work. This paper describes the manufacturing procedure and the experimental process and results on a 2 meters long glass fibre reinforced plastic composite wind turbine blade under the fatigue loading.

Wind turbines are complex structures that should deal with adverse weather conditions, are exposed to impacts or ship collisions and, due to the strategic roles in the energetic supplying, can be the goal of military or malevolent attacks. Even if a structure cannot be design to resist any unforeseeable critical event or arbitrarily high accidental action, this kind of systems should be able to maintain integrity and a certain level of functionality also under accidental circumstances, which are not contemplated or cannot be considered in the usual design verification. According to a performance-based design view, the entity of actions to be resisted and the services levels to be maintained are the design objectives, which should be defined by the stakeholders and by the designer in respect of the regulation in force. For what said above, the structural integrity of wind turbines is a central issue in the framework of a safe design: it depends on different factors, like exposure, vulnerability and robustness. Particularly, the requirement of structural vulnerability and robustness are discussed in this paper and a numerical application is presented, in order to evaluate the effects of a ship collision on the structural system of an offshore wind turbine. The investigation resorts nonlinear dynamic analyses performed on the finite element model of the turbine and considers three different scenarios for the ship collision. The review of the investigation results allows for an evaluation of the turbine structural integrity after the impact and permits to identify some characteristics of the system, which are intrinsic to the chosen organization of the elements within the structure.

Offshore Wind Turbine (OWT) requires demanding and costly support structures. The conception, the design and the assessment of this kind of construction must consider several interacting and controversial aspects: there is a harsh design environment, relatively wide spectrum functional requirements, and exceptional scenarios. In fact, different aspects and various performances under several load conditions have to be investigated for this type of structures. This paper shows an optimization process related to the preliminary design of support structures for an OWT farm projected in the Mediterranean Sea showing the decision criteria considered. A strutted scheme is introduced and optimized with main reference to Ultimate Limit States (ULS) to obtain a baseline design.

In the context of numerical analysis of the structural response for an offshore wind turbine an investigation procedure has been set up based on the combined use of a mesoscale atmospheric model (CSUMM) and a spectral wave model (SWAN). After calibrating parameters and testing the accuracy of both models within idealized conditions, they have been adopted for simulating extreme events for a study area in the southern part of the Adriatic Sea in front of the Puglia coast (Italy). Starting from geostrophic wind profiles recorded at the meteorological station of Brindisi, the mesoscale atmospheric model is run to obtain hourly wind velocity components over the computational domain for a two days simulation: these are used to force the wave spectral model for prediction of the sea state. Obtained results show good agreement with wind magnitude and direction recorded at 10m elevation above m.s.l. at the meteorological station for the same event; the characteristics of the simulated wave field (i.e. energy distribution and direction) are consistent with the spatial distribution of the wind forcing: comparison between simulated and observed significant height and period at Monopoli offshore buoy are in progress to obtain validation of the whole analysis procedure.

The design of long-span bridges often depends on wind tunnel testing of sectional or full aeroelastic models. Recently, some progresses have been made to find a computational alternative to replace these physic tests. A novel computational fluid dynamic (CFD) method is presented in this paper, where the fluid-structure interaction is conducted through a self-developed code combined with ANSYS-CFX solver. A new mesh control method based on block-iterative coupling is used for two dimensional (2-D) and three dimensional (3-D) bridge deck modeling. Detached eddy simulation (DES) for 3-D viscous turbulent incompressible flow was applied to the analysis of bridge deck sections. Firstly, numerical simulations of a U-shape cross section based on 2-D and 3-D models are practiced. The comparisons of aerodynamic coefficients thus obtained show that the 3-D CFD simulation is more accurate than the 2-D one. secondly, the 2-D and 3-D CFD simulations were performed for two generic deck sections to produce their aerodynamic coefficients and flutter derivatives. The computational results agree well with the available computational and wind tunnel results that shows the proposed 3-D CFD simulations are quite effective. Finally, the 3-D based flow field is obtained, which is also an advantage of the proposed 3-D CFD simulation.

Vortex-induced vibration occurs when the vortex-shedding frequency for flow past a cylinder matches with the natural frequency of the cylinder. The result can be a transverse vibration or an in-line vibration of the cylinder, or a combination of the two. Vortex-Induced Vibration (VIV) is usually an unwanted phenomenon which can lead to disastrous consequences. This paper will discuss the fundamentals of VIV and its causes. A brief history of relevant early research will be presented. Recent advances in understanding of VIV will be presented both from an experimental and computational point of view.

The aerodynamic forces due to wind turbulence indicate higher span-wise coherence as reported in the literature. To develop the buffeting response analysis method with more accuracy, and to understand the effect of turbulence on the aerodynamic forces, it is necessary to observe the coherent structure of surface pressures on a bluff body, systematically. In this study, surface pressures on a 2-D rectangular cylinder in grid turbulence were measured simultaneously at many pressure taps. Side ratio of the model cross section was selected from B/D=0.5 to 5.0 (B: stream-wise width of rectangular cross section, D: lateral height of rectangular cross section). The coherent structure of surface pressures is to be discussed. As for the relatively slender cross section, the span-wise correlation length of the lift force is found to be proportional to that of approaching wind velocity. While, the span-wise coherence of surface pressures for the side ratio B/D=0.5, the significant increase in the coherence due to the Karman vortex was observed. Temporal variation of the span-wise correlation is to be discussed as well.

A series of wind tunnel tests was conducted on the vibration and scattering behavior of full-sized model of roof tiles, which were used widely for roofings of Japanese wooden dwellings. This study has investigated the nature and source of the vibrating and scattering behavior of roof tiles with the aim of providing a better insight to the mechanism. The roof tiles were set up on the pitched roof in the downstream of the flow from the wind tunnel. Based on the consideration on the results of the measurements, there is a basic mechanism which can lead to flow-induced vibrations of the roof tiles. This mechanism is similar to that of the so-called fluttering instability, which appears as the self-excited oscillation in the natural mode of the structure at the certain critical flow speed. The values of the frequencies for the oscillating relate to the values of natural frequencies of the vibration.

Experimental study on drag-reducing characteristics of a zwitterionic surfactant additive (C₂₀H₄₃NO) in a circulation system has been carried out. It was based on the optimum concentration, temperature effect and the characteristics of resisting shear in DN27.5 pipeline. The results showed that C₂₀H₄₃NO additive has a significant drag-reducing effect depending on concentration and temperature. The most effective concentration in the tested flow loop was 900ppm at 60°C. The temperature range of the drag-reducing effect was in the range of 40 ∼ 70°C. The maximum drag reduction (DR) of 900ppm C₂₀H₄₃NO aqueous solution was 77% at the beginning of circulation with system running between 41°C and 43°C. The drag-reducing effect does not decrease remarkably after the circulation system ran for a period of seven hours, but reduces to only 5% of DR after a period of twenty-three hours. In order to study the drag-reducing characteristics of C₂₀H₄₃NO aqueous solution in the practical district heating system, the experiments with C₂₀H₄₃NO aqueous solution flow in different inner-diameter pipelines including DN50 and DN100 with rough wall were performed. The results indicated that the optimum drag-reducing concentrations are 1500ppm and 2500ppm at 45∼50°C in the DN50 and DN100 circular pipes, respectively. Finally, the technique of drag-reducing additive applying into the district heating system is discussed. And some problems in the practical application were brought forward, such as, the poor life-span of surfactant, the instabilities of drag-reducing effect and the inherent corrosion of additive itself. According to these problems, the corrosion research of C₂₀H₄₃NO aqueous solution was also conducted based on immersion method. The results show that: C₂₀H₄₃NO aqueous solution is weakly corrosive for iron-based metallic pipe comparing with CTAC aqueous solution and water.

The Shear History Extensional Rheology Experiment (SHERE) is an International Space Station (ISS) experiment designed to study the effects of a preshear history on the transient extensional viscosity of a dilute polymer solution in a uniaxial stretching flow. The absence of gravitational body forces allows us to measure the capillary thinning of the fluid filament after cessation of the extensional deformation without sagging of the liquid bridge. Understanding the deformation and thinning of polymeric solutions in complex flows containing both shearing and extensional kinematics is particularly relevant in a wide variety of industries, including fiber-spinning, injection molding, food and consumer product processing, as well as future `containerless processing' operations. The SHERE experiment offers the ability to preshear the test samples before imposing a uniaxial stretching flow in order to explore the impact of this preshearing on the sample extensional viscosity and elastocapillary thinning. After the SHERE main hardware was launched to the ISS on-board Shuttle Mission STS-120, two batches of 20 and 25 fluid samples were successively launched on-board Shuttle Missions STS-123 and STS-126. The SHERE experiments were performed by astronauts Greg Chamitoff and Mike Fincke between July 2008 and January 2009. In this talk, we will focus on the main results obtained for a well-characterized dilute polymer solution and compare them to ground-based experiments. In addition, we will show potential applications of the current microgravity experimental findings.

In this paper we demonstrate for the procedure of passively cutting viscoelastic fluids into droplets with thin ligaments in an especially-designed microchannel with T-junction inlets, serpentine mid-part and an expansion end-part. The aqueous CTAC/NaSal solution of 50ppm and 100ppm were used as dispersed phase, pinched into uniform plugs at T-junction (100μm wide, 58μm deep) and then carried by silicone oil, towards downstream where the geometric expansion helped the plugs to form rounded droplets. Both squeezing and jetting regime were observed at Capillary number of 2.31 x 10^–3 and 4.61 x 10^–3 respectively. As experimental results shown, the filaments (thin threads) between plugs always existed until the plugs flew into the expanded pocket (400μm wide, 58μm deep), making surface tension initiate the plugs' profile to shrink, promoting the thinned threads breaking. In addition, it was also shown that the breakup and coalescence process for viscoelastic fluid was distinct form that for Newtonian fluid.

In order to investigate the flow-induced vibration in the impeller clearance of centrifugal pump, and make the dynamic prediction of centrifugal pump rotor system, the flow dynamic model is put forward in the present study based on the flow characteristics in the impeller clearance. The impeller clearance rotor-dynamic force model is established based on Muszynska model and gap annular flow dynamic model. And the coefficient in this model is confirmed by quasi-steady solution of the impeller clearance flow. After the confirmation of the rotor-dynamic force model, the non-linear stability and bifurcation of the Jeffcott rotor system under the rigid support is analyzed under condition of the rotor-dynamic force. The impact of the unbalance quantity to the impeller-rotor system is discussed. The research shows that complicated alternation by turns of Hopf bifurcation and period doubling bifurcation appears on the process of spin speed rising. As the fluid pressure and rotor flexibility increasing, the fluid-induced vibration in the clearance of centrifugal pump impeller becomes a very important factor to the instability of centrifugal pump rotor system. The clearance structure and the flow feature lead to complexity of the equations of fluid dynamics (J. J. Moore, et al, 2001). And it is difficult to describe the rotor-dynamic force by analytical expression, resulting in great difficulty for the dynamics analysis. The impeller clearance can be divided into shroud passage and wearing seal based on the structure and flow feature (C. E. Brennen, et al, 2006). The bulk flow model is mainly used for the wearing seal, which is based on film assumption (D. W. Childs, 1991). The Black-Childs model (H. F. Black, 1969; D. W. Childs, et al, 1985) and Muszynska model (D. E. Bently, et al, 1988) both are given on this, and were generally applied to the dynamic analysis of rotor-seal system. But for the shroud passage, its physical dimension of channel section is not constant; and the velocity magnitude and direction between the sections are also different. So the unit radius and axial velocity cannot be used to describe the flow in it, and the existing rotor-dynamic force model of the channel fluid is limited to the shroud passage flow. Some scholars combined CFD method and hydrodynamic lubrication theory to solve the time-averaged Navier-Stokes equations of the clearance flow (R. Barrio, et al, 2008, J. Gonzalez, et al, 2006, J. Gonzalez, et al, 2006), and to get the fluid-induced vibration characteristics of the impeller clearance flow. In this paper, a rotor-dynamic force model of the impeller clearance is given based on the clearance flow feature. A quasi-steady solution is given to determine the dynamic force coefficient. Apply this method to the flow field in different whirl ratio and rotor speed, to get the dynamic coefficient with least square method. Under the rotor-dynamic force, the nonlinear stability and bifurcation problems of the Jeffcott rotor system with rigid support are also studied.

Conventional hydropower projects are generally suitable for high flow rate or high head. However, the hydro energy from small sources of water such as streams and creeks is not harvested due to a lack of instrumentation. A reciprocating hydropower system can be used at places with low flow discharge and low head to generate energy. This paper presents theoretical and laboratory test results for the estimation and calculation of the lift force in the Reciprocating Small Scale Hydropower model. Results from a finite element analysis of the lab model done to understand the forces and responses of the structure are presented in this paper.

Based on the one-dimensional Saint-Venant water equation explicit difference scheme, a new explicit difference scheme is deduced to establish the evolutionary routing model of flood. The computational formula about the impact loading of flood model is deduced. The impact experiment of flood on buildings is carried on the large wave-current tank. The heights of water are 0.6, 0.9 and 1.2 meters and the distances between the building and floodgate are 3, 6 and 9 meters respectively. The model scale of buildings is 1:6 and three buildings with different ratios of holes are designed to simulate the buildings at countries and villages. Based on the experimental results, the effects of heights of water, the distances between buildings and floodgate and the ratios of holes on the impacting pressure are investigated. Finally, the numerical results are compared with the experimental results and it shows that the numerical model of impact loading is proper.

Water outburst, which often occurs in the underground construction, is one of the problems in the mountain areas in the southeast of China. Taking the JinPing cascade 2 hydropower station for example, the paper introduced the equivalent infiltration intensity method to simulate the rainfall infiltration, which based on the equivalent continuous isotropic medium model. And with the basic tool of three dimensional finite element method and the basic theory of groundwater dynamics, the water inflow and cone of depression in the zone, through the whole constructing process of diversion tunnel, are analyzed and studied. Under the influence of tunneling and without any supporting measures to deal with the seepage, the maximum water inflow value reaches 26 m³ around, and the conical depression influence radius of water cone achieves about 20KM.While adapting measures that can be concluded as "water blockage combined with water drainage", the quantity of gushing groundwater is decreasing, groundwater level can be recovered, The result of processing satisfy the engineering construction and the surface water environment.

This paper describes a water leak test of roof tiles. The 100 roof tiles were set up on 10 lines and 10 rows on the pitched roof in the downstream of the flow from the wind tunnel. The flow velocity was increased gradually from the low velocity to the high velocity, and the effects of the wind on the roof tiles were investigated by the water leak test. The situation of the water leak test was filmed by video camera. Two accelerometers were simultaneously used. The roof tiles which showed significant vibration at any velocity were found in a series of experiments and the accelerometers were attached to the two neighboring roof tiles on the model roof. The water leak phenomena in the experiment by using the artificial rainfall apparatus are discussed in this paper. Some mechanisms with relatively large amplitudes at low-frequency vibrations, which caused water leak phenomena were made clear.

A novel pendulum-generator system taking advantage of parametric resonance is proposed as an alternative way of energy harvesting in civil engineering application. A mass or length augmentation coefficient is introduced to consider the inertia effect of the generator. Theoretical analysis of the nonlinear behavior of the device is performed. It is found that there exists an optimal as well as an upper bound of equivalent viscous damping of the electrical load. The average electro-mechanical output power characteristics in terms of excitation frequency and total equivalent damping are developed for the case of parametric excitations. Two typical working modes, i.e. fixed amplitude of either displacement or acceleration of the external excitation source, are considered. Numerical results show that the output power reaches the maximal value when the equivalent damping is between 70.7∼80.9% of the upper bound of the equivalent damping. It is also shown that the proposed device may collect more energy from the source than its linear counterparts at lower frequencies.

Recently, a new method has been proposed by the authors for detecting structural local damage under limited input and output measurements. This method can be extended to detect structural local damage in complex structures based on substructure approach. In this paper, based on this structural damage detection and localization method, a two-stage damage detection strategy is developed with application to the ASCE SHM benchmark building to test its efficacy and provide a systemic solution to the Phase I benchmark problem for damage detection. In the first stage, an 8-DOF identification model is used to identify the floors and directions (X or Y) in which damages are present. Then, the detection is focused on the floors where damage occurs. A substructure approach is utilized for damage localization in the second stage. A 12-DOF identification model is used for the substructure containing the damaged structural floors to identify the exact locations of damage. Structural parameters and the unknown inputs are identified by a recursive algorithm based on sequential application of the Kalman extended estimator for the extended state vector and the least squares estimation for the unknown inputs. Only a limited number of measured acceleration responses of the benchmark structure subject to unmeasured excitation inputs are utilized. Damage detection results indicate that the new method can detect and localize various damage patterns of the benchmark problems with good accuracy.

Many competing approaches exist in literature in evaluating sensor network solutions, differing by levels of ease of use, cost, control and realism. Many existing works concentrate on simulating network protocols or emulating processing units at the machine cycle level. However, little has been done to emulate sensors and the physical environments they monitor. The main contribution of this work is the design of WiserEmulator, an emulation framework for structural health monitoring (SHM), which gracefully balances the trade-offs among realism, controllability and cost. WiserEmulator consists of two main components — a testbed of wireless sensor nodes and a software emulation environment. To emulate the excitation and response of piezo-electric transducers, as well as the wave propagation inside concrete structures, the COMSOL Multi-Physics software is utilized. Digitized sensing output from COMSOL is played back via a multi-channel Digital-to-Analog Converter (DAC) that is connected to the wireless sensor testbed. In addition to the emulation of concrete structures, WiserEmulator also allows users to choose from prestored data collected from field experiments and synthesized data. A user-friendly Graphical User Interface (GUI) is developed to facilitate intuitive configurations of experimental settings, control of the on-set and progression of the experiments, and real-time visualization of experimental results. We have implemented Wiser Emulator in MATLAB. This work advances the state of the art in providing low-cost solutions for evaluating Cyber Physical systems, such as wireless SHM systems.

Noise reduction is a main step in signal processing. However, it is not effective enough to purify the nonlinear signal by using the traditional signal denoising techniques. This paper improved the Generalized Projection denoising algorithm via calculating the optimal time delay τ and embedding dimension m, which can be regarded as an extension of the global phase space reconstruction. The de-noising effects of Lorenz signal illustrated the improved Generalized Projection method is very effective and reliable in reducing the noise and reconstructing the signals.

The purpose of model updating is to modify the finite element model of a structure in order to obtain better agreement between the numerical and field measured structure responses. In this proposed method the response surface method is used for the best experimental design of the parameters to be updated, based on which numerical analysis can be performed in order to obtain explicit relationships between the structural responses and parameters from the simulation results. The parameters are then be updated using the genetic algorithm by minimizing an objective function. After a numerical example of a simply-supported beam is used to demonstrate the concept, this developed methodology has also been applied to the model updating of an existing bridge. Results show that this method works well and achieves reasonable physical explanations for the updated parameters.

Many civil structures are subjected to damage caused by either natural disasters or man-made hazards. A large proportion of them are still in service despite the associated potential for damage accumulation. Therefore, the ability to monitor the state of current structures is of increasing importance. In this paper, vibration based damage detection techniques were employed to detect damage in reinforced concrete column after different levels of quasi-static cyclic loadings. Four main stages were carefully examined, including healthy state, concrete cracking, partial yielding and yielding at last. Modal test and analysis was carried out for the RC column in original condition at first. In order to introduce damage to this column, quasi-static cyclic test was carried out. Finally, dynamic test on the damaged RC columns was performed and changes in the dynamic characteristics of the column at different damage levels were examined. Eigen-System Realization Algorithm (ERA) was applied to identify the modal parameters of the RC column based on its impulse responses recorded in its undamaged and various damaged states using accelerometers. These identified modal parameters are then used to identify the damage in the column through a finite element model updating procedure. Results show that the identified damage is consistent with the observed damage in the composite beam.

An experimental verification of damage detection process using some of novel optimization techniques such as Latin hypercube sampling and swarm-based algorithms is presented. The algebraic differences between damage variables of numerical model and the test structures are formulated as an objective function which has to be minimized to identify damage location and its severity in the process of model updating. The profiles of modal frequency shifts become damage-sensitive features in conjunction with structural or damage variables such as mass or stiffness of numerical model. The iterative process which exploits the proposed population-based optimization algorithms successfully identifies local mass changes by updating damage variables to fit in modal data from test structures such as cantilevered beam and multi-bay truss frame.

The eigenvalues and eigenvectors decomposed from elemental stiffness matrix are related to the elemental characteristic parameters. By associating the eigenvectors with node-displacement vector, the elemental eigen-deformation shapes are defined. Each eigen-deformation shape is characterized by the cross-sectional characteristic parameters of EA, EI and GA etc. The first order Timoshenko beam element is used for illustration in this paper. The elemental stiffness matrix is decomposed to define the eigen-deformation shapes, including the axial, bending and the shear. The total deformation of each element is formulated as the weighted summation of the elemental eigen-deformation shapes together with given rigid body modes. The weights corresponding to the eigen-deformation shapes indicate the elemental deformation characteristic.The sensors to monitor the bending and shear strain are sorted and located based on the weights distribution in structure. Numerical examples are presented to illustrate the proposed method and its application.

The objective of this paper is to develop a new wireless sensing system which can provide the requirements of autonomous structural health monitoring, which include 1) reliable wireless communication data, 2) accurate signal conditioner hardware for ambient vibration sensors (VSE-15D), 3) capable for continuous long-term monitoring. Based on the prototype of WiMMS (Stanford University unit), a new generation wireless sensing unit, called NTU-WSU, is developed to meet these requirements. Besides, an embedded host node is first included in the wireless sensing system. Verification of NTU-WSU wireless sensing system was conducted using the ambient vibration data of both building and bridge. This newly developed NTU-WSU is capable to collect reliable data from high performance sensor for continuous structural health monitoring.

The structural health monitoring to large space steel structure has become more and more important and significant to monitor the performance, identifies the damage and assesses the remaining lifetime by the measurements of various kinds of sensors located in the structure. However, the acquisition method for the information of the behavior of the whole structure based on the limited measurements is still a challenge for the structural health monitoring. An approach for acquiring the whole structural stress distribution by limited strain measurements is presented in the paper. Firstly, the whole structure is divided into several substructures; secondly, the hierarchical clustering methods are used to make a decision on the number and the location of the sensors, while the fitting method introducing the definition of continuation is used to acquiring the stress distribution of baseline substructure and an amending method is used to acquiring the stress distribution of the other substructures; thirdly, the comparison of forecasting stress distribution and theoretical stress distribution from a numerical simulation example which is based on a real structure in Shenzhen of P. R. China shows that the stress distribution of the whole structure can be obtained from the limited strain measurements.

In recent decade, the electromechanical impedance (EMI) technique for structural nondestructive detection has been developed rapidly, and many researchers have carried out some experimental studies on simple structures. However, the numerical and experimental studies on relative complex structures are implemented less. In this study, firstly, a numerical EM admittance analysis of a I-type steel beam is operated by the use of the finite element method. Subsequently, the numerical results are validated by an experimental study. In this experiment, a PZT active sensor is bonded to the surface of the I-type steel beam, and the damage is detected by monitoring the variations of EM admittance measurements. Besides, a damage index, the root-mean-square deviation of real admittance (RMSDR) is defined, by which the extent of damage of the I-type beam is also evaluated. From this study it is found that the high order modes of the I-type steel beam are very dense, and the detection effect of damage extent is not ideal only depending on the EM admittance spectroscopy. By the use of the RMSDR index not only the occurrence of damage is detected clearly, but also can the damage extent of the I-type beam correctly reflect qualitatively in different frequency ranges.

This paper presents monitoring results of a two-story reinforcement concrete frame (RCF) under a pushover test by using various fiber Bragg grating (FBG) sensors, including the bare FBG strain sensors, long gage FBG strain sensors, and FBG displacement sensors . The long gage FBG strain sensors and the FBG displacement sensors are developed by the authors. The FBG sensors are either embedded in the structure or installed on the concrete surface of the frame structure to monitor the rebar strain, the concrete surface strain, or the crack width development. The testing results show that FBG sensors can measure rebar strain precisely and that the long gage strain FBG sensors can measure concrete surface average strain precisely. Destructive pushover test results show that the FBG strain sensors can detect the nonlinear strain development of the rebars. The yielding point was precisely monitored by the FBG sensors. Crack width development at certain location of the concrete structure is monitored by FBG displacement sensor, also with high precision.

The concept of smart aggregates, a distributed intelligent multi-purpose sensor network (DIMSN) for civil structures, has been developed to address three important issues including early-age concrete strength monitoring, impact detection and evaluation, and structural health monitoring. This paper mainly discusses employing smart aggregates' active sensing property to form feedback in the DIMSN to reduce damage-location detecting times for fast time-response and low power-cost. This is an optimal decision-making subject and we present concept of the Geometry Structure matching method (GSM) with the Expert System theory (ES) to build the decision-making module. The designed controller is evaluated on a 2-story concrete frame model instrumented with the DIMSN as a testing object by means of MATLAB simulations. Simulation results show that the proposed method has performed successfully in selecting an actuator in the DIMSN for detecting damage location.

For short baseline GPS positioning, the multipath effect is the major error in GPS data since it can't be reduced by traditional double differencing technique. To deal with this problem, a GPS multipath effect mitigation algorithm is proposed in the paper based on the empirical mode decomposition (EMD) method utilizing the repetition characteristics of GPS satellites in every sidereal day. More specifically, decompose first the GPS data in day 1 and day 2 separately by EMD into intrinsic mode functions (IMFs). The correlation coefficient of sum of the last a few IMFs of day 1 and day 2 are calculated and the signal with maximum correlation coefficient value represents the multipath effect. After removing the multipath effect from the original GPS data the measurement accuracy can be highly improved. Measurements from a calibration test are adopted to verify the proposed algorithm. By comparing the actual displacement of the shaking table with the calculated one, it is found that: (1) The repetition phenomena of GPS satellite can be used to reduce the multipath effect. The proposed algorithm is a reliable method for reducing multipath effect in GPS data. For all the test cases, the measurement accuracy has been improved to some extent. (2) For sine wave with low vibration amplitude and frequency higher than 2Hz, the improvement of accuracy by the proposed method is not significant.

Wireless sensor network technology has been introduced to civil structural health monitoring (SHM) systems to replace wired monitoring systems since it promises easy and flexible installation, low system cost and increased robustness. Piezo-based structural health monitoring systems have the advantages of low system cost and reliable output. Smart aggregates, which are pre-cast concrete blocks with embedded piezoceramic materials, can be used to perform SHM and impact detection tasks on concrete civil structures. The Smart aggregate (SA) based wireless SHM system utilizes the active sensing property of PZTs to realize SHM, while the passive sensing function is used to realize impact detection. In active sensing, one of the SAs is used to generate vibrations at a specific frequency range while another captures the vibration signal for analysis. Previous SA-based wireless sensor networks could be changed once the roles of the actuator (signal generator) and the sensor (signal receiver) are established during construction. To allow interchangeability between the roles of actuators and sensors, a hybrid SA-based WSN system for the SHM was designed and developed, which will be described in the paper. In the hybrid SA-based SHM system, nodes can be dynamically configured in software to take on the role of either sensor or actuator. This function can be utilized to optimize the active sensing strategy. Experimental results indicate that the designed hybrid system can dynamically configure the SA-based WSN system to realize the SHM function.

This paper mainly focuses on the parameter identification of time-varying structural system via numerical simulation. Definitions of instantaneous frequency based on Hilbert Transform in time-varying system are first introduced. Followed are the definition of Hilbert damping spectrum. Identification procedures for both instantaneous frequency and damping ratios based on their definition are then introduced. Applicability of the identification algorithm is investigated through several numerical simulations, in which time-varying frequency and time-varying damping ratios are identified respectively both in SDOF and MDOF systems under different excitations. The results demonstrate that when the system modal parameters are slowly varying, the instantaneous frequency could be easily and well identified for all cases. However, the instantaneous damping ratio could be extracted only when the system is lightly damped, and the results are more convincing for free vibration cases. When the system is under sine waves or white noise excitation, only the variation tendency of the structural damping ratio could be tracked even for noise-free situation. It is also shown that the method based on Hilbert could easily track the abrupt change of system modal parameter under free vibration.

In this paper, a new corrosion sensor using fiber Bragg grating (FBG) to monitor corrosion of steel rebars embedded in concrete structures is presented. The mechanism is based on the fact that the increase in the diameter of the reinforced steel due to corrosion can be obtained by detecting the strain variation of the optical fiber using FBG. The corresponding experimental results indicated that this new type of corrosion sensor can be effectively used for monitoring the early corrosion of a rebar, and the degree of corrosion can also be manifested. Finally, this type of sensor is applied to monitor the corrosion of steel rebars in Xiang 'an Sub-sea tunnel, which has the largest cross-section among all the sub-sea tunnels in China.

Local Scour is one of the key challenges for construction of Sutong Bridge- the first cable stayed bridge with main span over 1000m, located at downstream of Yangtze River. On the other side, though stability of riverbed is fundamental for design of riverbed protection, construction of temporary construction platform and pile group, the latter three might also effect on local scour evidently for strengthen/ disturbance on foundation soil and changing on nature flow condition. And the flow condition here is also complex due to tide influence and rugged topography. As for Sutong Bridge, Multi-beam Echo Sounder adopted to periodically measure and mapping riverbed topography, and Vibrating Wire Piezometers using to continually monitoring local scour happened within and around pile group. Then data fusion technology based on Wavelet Transformation and Geological Information System used at data processing and analysis. The result shows: 1) Multi-beam sounding system with water pressure sensors can record scour evolutionary process satisfactorily; 2) Riverbed protection does effect on riverbed and weaken the scour around pile group, but violent scour still happened near the worksite; 3) Different season, storm and tide fluctuation apply influence on siltation and scouring. And scouring/silting cause by bridge construction become stable progressively.

In recent years, the identification of modal parameters with closely spaced modes based on wavelet transform has been widely applied in the research area of structural health monitoring. But the parameters of wavelet, i.e. center frequency and its bandwidth have great effect on the results of identification. If the parameters of wavelet are inappropriate, the closely spaced modes could not be identified. In order to optimize the parameters of wavelet, a method based on adaptive genetic algorithm is proposed in this paper. The center frequency and its bandwidth are optimized with the adaptive genetic algorithm, whose objective function is the standard deviation between wavelet-ridge and fitting line. The results of numerical simulation with three closely spaced modes show that, the method proposed in this paper could optimize the wavelet parameters and the closely spaced modes could be identified by the wavelet transform with adaptive genetic algorithm.

A focusing-free ultrasonic imaging system for in-situ ground structural health monitoring (SHM) was developed using a Q-switched laser and a 2D laser mirror scanner. Two imaging methods, i.e. a frequency-selectable Ultrasonic Energy Propagation Imaging (UEPI) and Ultrasonic Frequency Tomography (UFT) methods were included. The UEPI result movie could be seen as ultrasonic energy wavefront emerging from the sensing location with concentrated energy at structural damages. The UFT generates tomograms that show different frequency components of the ultrasonic waves. Structural damages could be seen in the tomograms as high ultrasonic energy concentrated at the locations of damages. Synthesizing the UEPI and UFT could generate results with optimized frequency and dramatically improve the damage evaluation capability of the system. As demonstration, a fighter jet pod quartz/epoxy radome with honeycomb core was inspected. A 5.42J impact damage of 25mm diameter was successfully evaluated using UEPI and UFT. Improved UEPI result using synthesized UFT and UEPI shows exclusive high energy concentration at an area of which size and location agreed well with the impact damage. In conclusion, this imaging system is a robust in-situ ground SHM system suitable for complex and demanding structures.

This paper reports the recent progress in multi-functional piezoceramic-based smart aggregates research and their innovative applications in concrete civil structures. The basic operating principle of smart aggregates is first briefly introduced. The proposed multi-functional smart aggregate is formed by embedding a water-proof piezoelectric patch with lead wires into a small concrete block. The proposed smart aggregates are multi-functional and can perform three major tasks: early-age concrete strength monitoring, impact detection, and structural health monitoring. The early-age concrete strength development is monitored by monitoring the harmonic responses of smart aggregate. Impact on the concrete structure was detected by observing the open circuit voltage of the piezoceramic patch in the smart aggregate. For structural health monitoring purpose, an active-sensing sensor network is formed by embedding the smart aggregate and wavelet packet analysis is used as a signal processing tool. To verify the effectiveness and multi-functionality of smart aggregate, following research projects are performed: 1. Health monitoring of concrete columns under reversed cyclic loading; 2. Health monitoring of concrete columns under shake table excitation; 3. Wireless health monitoring of a two story concrete frame; 4. Wireless early-age concrete strength monitoring; 5. Impact detection for concrete piles; and 6. Health monitoring for concrete piles. The reported research activities were conducted collaboratively at three different institutes. The project of health monitoring under reversed cyclic loading test is performed at Missouri University of Science and Technology at Rolla, Missouri. The project of health monitoring under shake table excitation is performed at University of Nevada at Reno, Nevada. The projects of wireless health monitoring, wireless early-age concrete strength monitoring, impact detection and health monitoring for concrete piles are performed at the University of Houston. The multi-functional smart aggregates have the potential to be applied to the comprehensive monitoring of concrete structures from their early stages throughout their life-time.

A platform called Networked Structural Laboratories (NetSLab) which was originally developed for remote pseudo-dynamic test of large-scale structures and structural elements provides a relatively easier and friendlier interface for data transfer among remote monitoring stations or computers which are geographically distributed and connected by Internet for remote structural health monitoring and identification. In this study, a remote structural parameters identification strategy based on the updated NetSlab platform and the neural networks based soft identification algorithm with the direct use of structural dynamic response time series is proposed and the performance of the proposed remote identification methodology was validated for a multi-degree of freedom structural model. Results show that the updated NetSlab provides a reliable remote monitoring data transfer platform and because of the parallel computation performance of the neural networks based identification algorithm, the proposed soft identification algorithm provides a potential way for near real-time remote parameter identification for structural health monitoring.

Feasibility study on application of BOTDR (Brillouin Optical Time Domain Relectometer) to health monitoring for bridge structures is conducted in this paper. According to the monitoring requirement of bridge strucutrure, BOTDR temperature sensor and BOTDR strain sensor are proposed and studied. Temperature sensitivity and strain sensitivity test are conducted to study the feasibility of the sensor. Temperature sensitivity test results show that BOTDR temperature sensors with packaged optical fiber length of 5m, 10m and 20m can measure the temperature correctly. Strain sensitivity test results show that BOTDR strain sensor with optic fiber length of 1m and 2m can measure the strain correctly.

Extremely low frequency (ELF, up to 30Hz) electric fields play an ambivalent role in human life. Necessity of ELF monitoring is validated by the fact that the electric activity of the human brain and other organs manifest themselves in the same frequency range. The phenomenon of Brain Waves Entrainment, discovered in the 70's, also makes the role of ELF-fields socially-important. It is an established fact that subterranean water veins effect human health negatively. We will first link this fact to ELF- activity and show the mechanism of the conversion of Earth's own permanent electric fields into ELF-electric fields by a surface of turbulent waters. The strength of this field is ∼100V/m and is enough to inflict serious problems on the brain. The harmful impact of ELF-producing water veins can explain the existence of so called "black spots" on the roads. Mortality rate is as much as 5 times more in regions having subterranean waters, than regions without subterranean waters. Considering large populations that are exposed to heavy natural ELF-fields and the illnesses due to this exposure, ELF-monitoring of public domains and dwellings, as well as selected areas of the roadways, is recommended. Locating bodies of water is another very important social mission related to ELF study. The inexpensive ELF-monitoring equipment can be employed both for searching harmful ELF-zones, and water-prospecting. Observation of ELF-field activity of human muscles, (especially leg muscles) even at a slight contraction, allows us to develop techniques for searching human bodies buried under ruins at a disaster.

Karkheh reservoir earth dam is located on the NW of the Persian Gulf with a capacity of 7'8MCM. This study is based on monitoring records years 1995 to 2007. Seepages and water pressure data are used to inform the critical alarms of dam lake level. As a result of this, winter flood was discharged to fix the normal level. Useful volumes will decrease from 3'800 to 1'800MCM (fifty percent of the total volume). SSM —Step Stiffness Method- will interpret the strength of material behavior. It can be used to solve the discharge problems. Research of monitoring data will be proved to guarantee the safe behavior of the Karkheh dam. It can be concluded that winter floods may be saved to increase the water level. Water leakage and stability behavior will serve the best alarm control of dam. This correlation will show the solution that will be applied by SSM and records.

In structural health monitoring, damage detection results have uncertainty due to the measurement noise, modeling error and environment changes. In this paper, data fusion based on the Dempster-Shafer (D-S) evidence theory was employed to decrease the uncertainty level and improve the accuracy of damage identification. A weighted fusion damage index (WFDI) was proposed to perform damage identification. A two-story concrete frame was fabricated as the object for the structural health monitoring test. Experimental results have verified the effectiveness of the proposed method, which will improve damage identification accuracy and increase the reliability of damage identification.

This paper presents the system identification of the Fei-Tsui arch dam using the recorded seismic data and ambient vibration data. The modal properties of the dam under different reservoir water level are identified using the recorded seismic data from 84 earthquake events. Considering the spatial variability of input excitation, both multi-input and single-input system models are employed in the input/output subspace identification. The regression curves between the natural frequencies and the reservoir water level are developed from the statistical analysis of identification results. In order to compare the current behavior of the dam to the past, an ambient vibration experiment is performed and the output-only stochastic subspace identification method is used to identify the current modal properties of the dam. Finally, a safety evaluation is made by pointing the current identification result on the developed regression curve. Further more, the comparison between different identification algorithms in this study is made. From the stability diagram of the identification the output-only stochastic subspace identification (using ambient data) provides more clear system characteristics than the input/output subspace identification (using seismic data). Discussion on the single-input model and the multi-input model for subspace identification is also made in this study.

Determination of temperature distribution within a bridge is the first step to evaluate the temperature effect on the structure. This paper aims to investigate the temperature distribution of Tsing Ma Suspension Bridge through numerical simulation and field monitoring. A numerical analysis based on the thermodynamic theory is utilized to determine the time-dependent temperature distribution of the bridge. Via appropriate assumptions, fine finite element models are constructed for thermal analysis of the deck plates, section frames, and towers. A new solar radiation model is proposed, by which the structural temperature distribution at different components at different time is calculated. The analytical results are compared with those obtained from the long-term health monitoring system and it shows the modified solar radiation model can predict the temperature variation of the bridge more accurately than the conventional radiation model.