Earth & Space 2008: Engineering, Science, Construction, and Operations in Challenging Environments

The Constellation Project's planned return to the moon requires numerous landings at the same site. Since the top few centimeters are loosely packed regolith, plume impingement from the Lander ejects the granular material at high velocities. Much work is needed to understand the physics of plume impingement during landing in order to protect hardware surrounding the landing sites. While mostly qualitative in nature, the Apollo Lunar Module landing videos can provide a wealth of quantitative information using modern photogrammetry techniques. The authors have used the digitized videos to quantify plume impingement effects of the landing exhaust on the lunar surface. The dust ejection angle from the plume is estimated at 1–3 degrees. The lofted particle density is estimated at 10⁸–10¹³ particles/m³. Additionally, evidence for ejection of large 10–15 cm sized objects and a dependence of ejection angle on thrust are presented. Further work is ongoing to continue quantitative analysis of the landing videos.

We investigate by means of laboratory experiments crater evolution in a bed of loose particles caused by an impinging subsonic jet. Attending physical considerations, which may apply to rocket-propelled vehicles during landing and take-off operations, are based on a simple force balance between the fluid forces and particle weight and account for the effects of bed permeability on cratering. Three bed materials were used with mean diameter ranging from 134-μm to 6-mm and particle density ranging from 0.9 g cm^–3 to 2.65 g cm^–3. We show that the equilibrium crater depth is weakly influenced by permeability of the bed material and introduce a Reynolds number, based on bed permeability, which captures this effect. Finally, we provide an empirical means to the estimate the maximum crater sidewall slopes and evolving crater depth as a function of jet strength.

A mathematical model and software implementation developed to predict trajectories of single lunar dust particles acted on by a high velocity gas flow is discussed. The model uses output from a computation fluid dynamics (CFD) or direct simulation Monte Carlo (DSMC) simulation of a rocket nozzle hot gas jet. The gas density, velocity vector field, and temperature predicted by the CFD/DSMC simulations, provide the data necessary to compute the forces and accelerations acting on a single particle of regolith. All calculations of trajectory assume that the duration of particle flight is much shorter than the change in gas properties, i.e., the particle trajectory calculations take into account the spatial variation of the gas jet, but not the temporal variation. This is a reasonable first-order assumption. Final results are compared to photogrammetry derived estimates of dust angles form Apollo landing videos.

Roberts' model of lunar soil erosion beneath a landing rocket has been updated in several ways to predict the effects of future lunar landings. The model predicts, among other things, the number of divots that would result on surrounding hardware due to the impact of high velocity particulates, the amount and depth of surface material removed, the volume of ejected soil, its velocity, and the distance the particles travel on the Moon. The results are compared against measured results from the Apollo program and predictions are made for mitigating the spray around a future lunar outpost.

A series of experimental tests were performed with the aim of reproducing the in-situ geotechnical measurements conducted on the Surveyor lunar missions. An excavation and bearing test rig was set up that provided controlled high force actuation, and high resolution force and position measurement capabilities. Emphasis was placed methods of repeatable soil bin preparation. A replica of the returned Surveyor III excavator scoop, which is also identical to the Surveyor VII scoop, was fabricated and used in the test setup. Bearing forces using the replica model are compared with the Surveyor VII data. The forces and performance of a flat blade excavator and the SMSS in Nevada sand and JSC-1a lunar simulant are examined.

This paper describes a recently developed multi-sleeve friction penetrometer that has the potential to play an important role in future Lunar and Martian terrain assessment studies to better measure and understand the mechanical properties of soils, as they relate to compaction and shear under a wheel or track. In contrast to other terrain assessment systems, this device allows for multiple simultaneous measurements of soil response in a single test sounding and thus the interpretation of the test results can be performed in terms of both absolute as well as relative response values. This is possible since interchangeable friction sleeves with surfaces of different roughness values allow for soil response as a function of shear surface characteristics to be evaluated. Testing with the newly developed device can be performed simultaneously with other well established technologies (e.g. cone penetration testing, shear wave velocity testing). In addition, the design of the device is well suited for deployment using remotely controlled robotic systems. An overview of the multi-sleeve friction penetrometer is presented, along with typical results obtained using the device.

The identification of constitutive parameters by inverse analysis of limited experimental information is investigated. In order to ensure the quality of measurements, all the data come from a thick wall cylinder test performed on a saturated sand sample. A numerical FEM-simulation considering a linear elastic perfectly plastic model (Mohr-Coulomb) is carried out in order to determine the pressure — cavity deformation relationship. Two kinds of optimization algorithms, a deterministic and a stochastic one, are presented and implemented in the inverse procedure. The performance of theses algorithms taking for identifying three parameters (Young's Modulus, friction angle and dilatancy angle) is compared. The two kinds of algorithms provide a quite similar response for the mathematical optimum, but some parameters sets did not have an acceptable physical meaning. Contrary to the deterministic algorithm, the genetic method provides an assembly of "satisfactory" individuals. Some of the parameters sets have acceptable physical meaning and the expert has to choose the best one considering his scientific and technical background.

Due to the physical constraints and limitations of existing measurement technologies, accurate and continuous distribution of the vertical stress underneath granular material columns has not been determined experimentally. The grid-based tactile load/force sensor, a new stress measurement technology of high accuracy, is adopted in laboratory-scale experiments to capture the stress distribution underneath sand columns. It has been observed evidently that the stress distribution is non-uniform and there exists stress concentration zone at approximately half-way between the center and the circumference of the column. The results are discussed with reference to previous theoretical and experimental work of other researchers.

We present a study on investigation of fundamental properties of granular media as gravity levels are reduced. Probes and rovers are sent to different solar-system bodies encountering surfaces covered with granular materials. Questions of how deep probes sink in or how well rovers can drive on such surfaces can only be answered if the fundamental properties of the granular material and its behaviour under reduced gravity conditions are known. We are interested in the static and dynamic characteristics and especially at which lower boundary in g-level particles become dominated by cohesive forces. The experiments were performed in the Bremen Drop Tower facility using the microgravity environment so that a substitute `gravity' field could be applied via a rotating centrifuge. The rotation rate could be varied to adjust for different acceleration levels. Surface flow effects were simulated in two flat (quasi-2D) sandglass experiments, in a rotating tumbler and in an avalanche box. We will present results from 15 microgravity experiments in an acceleration range between 0.01g and 1g.

Lunar regolith is characterized by very low mechanical strength and thermal conductivity due to the small inter-particle contact area and the vacuum environment. This poses challenges to future lunar exploration effort involving thermal processing of lunar soil to extract useful resources. The low thermal conductivity leads to low efficiency for heat recovery, and thus bigger equipment size, which is likely one of the limiting factors for manned exploration at larger scale with longer duration. This paper describes an experimental and analytical study of bulk solid thermal conductivity taking into account of the effect of properties of base solid, the filler gas, void fraction, and the vacuum conditions. A semi-empirical model has been developed that can be plugged into a proprietary solid-to-solid heat exchanger simulation software. Preliminary results show that the heat recovery efficiency can be dramatically increased by using high thermal conductivity gases such as hydrogen and helium as the filler gas.

Granular segregation is a common phenomenon that occurs when binary (two grain sizes) granular materials are subjected to vibration or mixing agitation. Practical examples occur in materials handling applications from pharmaceuticals to construction and the result is usually undesirable. Although much research exists on this phenomenon, previous predictive models appear to be based on visual observations. The authors have found no models that establish a cause and effect relationship. Recent (summer 2007) research reveals that an energy-related phenomenon is occurring during granular segregation. Experiments were conducted using black beans and rice as the granular material in a horizontal rotating tube. Decreased rotational torque required to turn the tube is consistently detected and correlates well with visual observations of the progression of segregation. Copious amounts of literature exist regarding the segregation phenomenon. Literature on the physics of fluids and gases seem to have more energy related theories regarding segregation of binary granular mixtures. However, none have either predicted or observed a decrease in rotational torque. Our observations provide new parameters with which to model the segregation phenomenon and may lead to a better understanding of the physics involved.

The mechanical properties of the lunar soil are critical parameters in predicting vehicle performance on the Moon. In preparation for Man's return to the Moon, surface vehicles must be tested on terrain that represents the mechanical strength of the lunar ground. Terrain that simulates the lunar trafficability conditions must have similar compaction and shear response underneath the wheel. This paper discusses the development of a soil (called GRC-1) and soil-preparation method to emulate the measured compaction and shear characteristics of the Moon's surface. A semi-empirical design approach was used incorporating particle sieve and hydrometer analyses as well as triaxial strength testing. Soil preparations were developed to match stress-strain curves resulting from in-situ lunar experiments. Additionally, results of laboratory strength tests with returned lunar soil samples and lunar soil simulants were compared to provide insight into the material's relative strength properties.

Tribocharging of particles is common in many processes including fine powder handling and mixing, printer toner transport and dust extraction. In a lunar environment with its high vacuum and lack of water, electrostatic forces are an important factor to consider when designing and operating equipment. Dust mitigation and management is critical to safe and predictable performance of people and equipment. The extreme nature of lunar conditions makes it difficult and costly to carryout experiments on earth which are necessary to better understand how particles gather and transfer charge between each other and with equipment surfaces. DEM (Discrete Element Modeling) provides an excellent virtual laboratory for studying tribocharging of particles as well as for design of devices for dust mitigation and for other purposes related to handling and processing of lunar regolith. Theoretical and experimental work has been performed pursuant to incorporating screened Coulombic electrostatic forces into EDEM^TM, a commercial DEM software package. The DEM software is used to model the trajectories of large numbers of particles for industrial particulate handling and processing applications and can be coupled with other solvers and numerical models to calculate particle interaction with surrounding media and force fields. In this paper we will present overview of the theoretical calculations and experimental data and their comparison to the results of the DEM simulations. We will also discuss current plans to revise the DEM software with advanced electrodynamic and mechanical algorithms.

"Moon Dust" is expected to become one of the most mission critical problems for both astronauts and machineries for the planned extended stay on the Moon. The challenges associated with the mitigation of the charged fine moon dust have been identified in the wide range of areas ranging from nano-toxicology to failed seals. In this preliminary simulation study, negatively charged particles are injected to a container that is filled with positively charged particles. Each negatively charged particle carries the same amount of charge; however, the amount of charge carried by a positively charged particle is scaled with its surface area. This feasibility study addresses issues associated with the effects of particle surface on the rate of coagulation.

Planned Lunar missions have resulted in renewed attention to problems attributable to fine particulates. While the difficulties experienced during the sequence of Apollo missions did not prove critical in all cases, the comparatively long duration of impending missions may present a different situation. This situation creates the need for a spectrum of particulate sensing technologies. From a fundamental perspective, an improved understanding of the properties of the dust fraction is required. Described here is laboratory-based reference instrumentation for the measurement of fundamental particle size distribution (PSD) functions from 2.5 nanometers to 20 micrometers. Concomitant efforts for separating samples into fractional size bins are also presented. A requirement also exists for developing mission compatible sensors. Examples include provisions for air quality monitoring in spacecraft and remote habitation modules. Required sensor attributes such as low mass, volume, and power consumption, autonomy of operation, and extended reliability cannot be accommodated by existing technologies.

In light of the environmental differences (such as: gravitational fields, surface temperatures, atmospheric pressures, etc.), the mechanical behavior of the subsurface soil on Moon is expected to be different from that on Earth. This paper investigates the possible effect of surface energy forces on the shear strength of lunar soil. A method of modeling granular material by considering interactions at particle level has been developed which can accurately reproduce the overall mechanical behavior of soils under terrestrial conditions. The model is extended here to include surface energy forces between particles in order to describe the possible behavior of lunar soil under extremely low atmospheric pressure conditions. Given these conditions, the model shows an increase of the shear strength of the soil due to the effect of surface-energy forces. The magnitude of increased shear strength is in reasonable agreement with the observations of lunar soil made on the Moon's surface.

A three-dimensional computer model of the Mars Exploration Rover wheel interaction with soil has been developed using the discrete element method. This simulation incorporates the important geometric aspects of the rover wheel and has the ability to perform specific soil tests such as compaction and excavation of layered soil and to vary soil properties such as grain size and shape, particle cohesion and friction. In addition, in simulations the effects of reduced Martian and lunar gravity can be explored. The rover wheel has a rather intricate non-uniform geometry because of a cavity used to attach the rover to the lander that is captured in the model. We investigate the effect of reduced gravity, the effect of the presence and absence of the attachment point, and qualitative variations in the model soil used in the simulations. Finally, we compare the simulated rates of excavation and torque to experimental results.

This paper describes how to predict the impact force and the penetration at landing on lunar sandy surface by SPH (Smoothed Particle Hydrodynamics) method. Before the calculations by SPH method, we conducted experiments about the landing on the lunar sandy surface. In experiment, 1/6 scale model of foot pad of landing gear, which was designed according to the 1/6 scaling laws, was dropped on the Regolith simulant foundation in vacuum chamber, and the impact acceleration and the penetration were measured. In calculations, the test bed of lunar simulant was modeled as Bingham fluid which had Mohr-Coulomb's failure criteria and the impact acceleration and the penetration of foot pad model was calculated. The results of computations by SPH method are in good agreement with the experimental results.

Efficient and safe processing of Lunar Soil is necessary for a sustainable stay on the Moon. The ability to predict and understand the mechanical properties of Agglutinates will ensure the development of novel machinery to extract and process the regolith. We have developed a simulation methodology to model the behavior and properties of lunar soil found in the laboratory experiments and the ways they may break into finer particles. These models will provide us with an initial insight of the importance of our better understanding of the mechanical properties of Agglutinates. These models will evolve with the experimental data that are expected to become available in the near future.

A lunar surface soil sample from Descartes highland (No. 60501) is investigated by micro X-ray CT. Based on the obtained 3D information on particle shape and enclosed voids and cracks together with the information from microscopic images, we classified the particles into four groups: (1) monomineralic particles mostly corresponding to plagioclase, (2) micro breccias composed of a lot of mineral fragments, (3) agglutinate particles with relatively smooth surface and enclosed voids and (4) spherical glass beads. The detailed shape indices such as elongation ratio, flatness ratio and sphericity are computed for representative particles by image processing. Furthermore, in order to evaluate the mechanical properties of lunar soil from the particle information, image-based DEM is applied to directly model the particles, and simple shear simulations with such modeled particles are demonstrated. The computed shear resistance is in good agreement with the best estimate of Apollo model. Coupling such numerical tool with the above-mentioned particle statistics, we can evaluate the mechanical properties of various lunar soil from their petropraphic information.

Contact laws are required for the numerical modeling of the mechanical behavior of granular media, and such models can be made considerably more realistic if the contact laws are 1) tied to the physical and mechanical properties of the constituent grains, and 2) developed independently of the numerical model. To produce realistic contact laws for geologic materials and lunar simulants, on-going work is developing the necessary laboratory techniques for grain-to-grain contact experiments, incorporating the resulting laws into discrete element models and validating the simulations. Our initial experimental efforts addressed the stiffness and friction of normal contacts, and sliding contacts are now being examined, with other modes of deformation to follow. This presentation focuses on our findings with regard to normal and sliding contacts subjected to both monotonically increasing and cyclic force. The experiments yield force-displacement measurements which are analyzed to determine stiffness as a function of loading conditions, and frictional loss (as quantified by analysis of the hysteresis loops observed under cyclic loading). The presentation gives an overview of the experimental and analytical methods that we have developed to date, the results for several materials are presented and their interpretation and implications with respect to numerical modeling are discussed. Of particular interest is the nature of the power law that governs normal contact stiffness. The sliding contact experiments quantify the shear stiffness and frictional loss as a function of the normal force on the contact and the amplitude of the cyclic shear force. Shear stiffness values at very small deformations (e.g., microns) are seen to be on the order of the normal stiffness at low normal forces. In some cases, however, stable sliding can occur, leading to significant reductions in shear stiffness with increasing amplitude of the shear force. Such stable sliding under cyclic loading demonstrates one potential mechanism for permanent strain accumulation (ratcheting) and relevant data are presented and discussed. The materials of interest include a gneiss that has been the subject of previous contact mechanics experiments, triaxial testing and numerical modeling, and the lunar simulant JSC-1A. The experimental work is on-going and results for additional materials (lunar simulants in particular) that are available at the time of the meeting will be presented.

Both image-charge forces and surface-energy (i.e. van der Waals) interactions contribute to the adhesion of charged dust particles on conducting surfaces. In-situ lunar regolith is charged (positively on the sunlit side of the moon, from UV photo-ionization, and negatively on the dark side, from electrons in the solar wind). Furthermore, mechanically disturbed regolith can attain a triboelectric charge which is different than its charge-state before the disturbance. The expected size dependence of the charge-to-mass ratio for fine lunar particulates differs depending on which mechanism caused the charge. Based on current theories and measurements, it is expected that, as the size of dust particles decreases, the adhesion forces acting on particles in contact with conducting surfaces will be dominated by van der Waals' forces, or by image-charge forces, depending on whether the fine particles attained their charge from solar sources (i.e., photo ionization or solar wind) or from triboelectric (i.e., mechanical) means, respectively. At present we have insufficient information on the size dependence of charge-to-mass ratios of insitu or mechanically disturbed lunar regolith particles to resolve this uncertainty.

This paper introduces simulated experiments conducted to investigate two major issues related to luna soil behaviors. The first one is related to the electromagnetic properties of lunar soils at microwave frequency (dielectric permittivity, magnetic permeability and electrical conductivity) which aims to identify specific problem that might arise when applying electromagnetic wave based geophysics tools such as Ground Penetration Radar (GPR) for lunar subsurface survey. The second issue investigated is the orginal of cohesion in lunar soils. Measurement of electromagnetic properties is conducted using Time Domain Reflectometry (TDR), which is a guided electromagnetic wave technology. TDR utilizes the propagation of electromagnetic wave to measure material properties. It works by generating a small-magnitude electromagnetic field excitation and measures the material response. By using a fast rising pulse of a few picoseconds by the current electronics, TDR measures the broad frequency band material responses from a few megahertz to gigahertz. A detailed analyses indicated that the magnetic permeability for Ferite Oxide at TDR frequency range is around 7. Magnetic components are believed to attribute to the cohesion in lunar soils. A method to differentiate their contribution to cohesion from other sources such as molecular attractions is if mixing them randomly, the cohesion will disappear due to disturbance of the alignments of these "small magnets". The cohesion will increase, however, as Ferite grains are re-magnetized at their new locations.

This paper presents the results of the structural design and analysis of the upper pressure shell section of a carbon composite demonstration structure for the Composite Crew Module (CCM) Project. The project is managed by the NASA Engineering and Safety Center with participants from eight NASA Centers, the Air Force Research Laboratory, and multiple aerospace contractors including ATK/Swales, Northrop Grumman, Lockheed Martin, Collier Research Corporation, Genesis Engineering, and Janicki Industries. The paper discusses details of the upper pressure shell section design of the CCM and presents the structural analysis results using the HyperSizer® structural sizing software and the MSC Nastran® finite element analysis software. The HyperSizer® results showed that the controlling load case driving most of the sizing in the upper pressure shell section was the internal pressure load case. The regions around the cutouts were controlled by internal pressure and the main parachute load cases. The global finite element analysis results showed that the majority of the elements of the CCM had a positive margin of safety with the exception of a few hot spots around the cutouts. These hot spots are currently being investigated with a more detailed analysis. Local finite element models of the Low Impact Docking System (LIDS) interface ring and the forward bay gussets with greater mesh fidelity were created for local sizing and analysis. The sizing of the LIDS interface ring was driven by the drogue parachute loads, Trans-Lunar Insertion (TLI) loads, and internal pressure. The drogue parachute loads controlled the sizing of the gusset cap on the drogue gusset and TLI loads controlled the sizing of the other five gusset caps. The main parachute loads controlled the sizing of the lower ends of the gusset caps on the main parachute fittings. The results showed that the gusset web/pressure shell and gusset web/gusset cap interfaces bonded using Pi-preform joints had local hot spots in the Pi-preform termination regions. These regions require a detailed three-dimensional analysis, which is currently being performed, to accurately address the load distribution near the Pi-preform termination in the upper and lower gusset caps.

To develop a deployable optical telescope, composite tape springs were designed to replace the traditional metal support truss of a Newtonian telescope. Tape springs are thin-walled beams composed of layers of carbon-fiber-reinforced plastic and are noted for their high specific strength and deployability; both properties are advantageous in aerospace applications where weight savings outrank material costs. Testing and finite-element modeling of the composite telescope demonstrate that the horizontal displacement is small enough to allow the telescope to function adequately for ground-based observations after stowage and subsequent deployment. The composite parts were fabricated in the Air Force Research Laboratory at Kirtland Air Force Base. Testing of the structure was performed with the telescope at both a horizontal and vertical position. To enable both tests, the tape springs were attached to aluminum rings. Vertical-orientation testing allowed for the deployment accuracy of the structure to be examined by recording positions on the telescope before and after deployment using dial gauges. For the horizontal testing, dial gauges and weights were used to measure the displacement due to the measured self weight (optics and housing) of the secondary mirror housing. The paper will discuss the design challenges posed by the conflicting demands for deployability and stiffness and findings from testing and FEM analysis.

Fiber-reinforced polymer (FRP) panels, with sandwich or cellular configurations, are steadily gaining popularity in highway bridge applications due to their favorable performance for minimum unit weight. One of the most likely uses of FRP panels is FRP decks over steel or concrete girders. Adequate connectivity should be achieved through shear connections between FRP decks and steel girders, and their development is critical in order to achieve partial or full composite actions. For applications in practice, an effective deck-to-girder connector design is needed, validated by full investigation of strength, stiffness, and fatigue performance characteristics. In this paper, the design and performance of a sleeve type shear connection for FRP decks is presented. This shear connection can accommodate both sandwich and cellular FRP decks with various heights. It has the ability to sustain interface shear to achieve composite action in FRP deck-and-steel girder bridges, while maintaining simplicity in manufacturing and installation. The tests conducted on this shear connection are at both component and system levels, to investigate its strength, stiffness, and fatigue performance. This sleeve type shear connection has shown to have both practical and technical attributes for adoption in bridge engineering, and implementation in field projects.

This study presents a numerical modeling procedure for the pullout of FRP bar from concrete cylinder, when the bond failure of concrete/FRP occurs mainly within the bar surface. From the governing equation of bond-slip, the normal force along the bar is defined in terms of a local bond stress-slip law and the relative displacement between concrete and bar surface. A shear stress-slip relationship that was successfully used for interface between concrete and externally bonded FRP sheet is modified and adopted as the local bond stress-slip law for FRP bar in concrete. Then values of parameters in that expression are determined by minimizing the difference between bond-slip (normal force vs. slip at the loaded end of the bar) from the analytical method and experimental result. Finite element analysis is also carried out to model the bond-slip of bar in concrete. The interaction between FRP bar and concrete is defined using a nonlinear spring element. The force-deflection curve of the spring element is determined by the local bond stress-slip law. With the proposed procedure, the local bond stress-slip law can be quickly determined, avoiding tedious computations, and the development length for FRP bar can be easily obtained.

The development of decision support system for monitoring dam behavior is an important approach to implement the real-time analysis and reasonable diagnosis for dam safety based on prototype observations, thereby realize the effective control of dam life process, viz. construction, operation, aging and end of its useful life. With systems engineering, mathematical and mechanical methods, a decision support system for monitoring dam behavior is developed. It is used to resolve problems over factual data and employ heuristic techniques with the accumulated knowledge. This system was composed of integration control module, intelligent inference engine, support base cluster, information management and input/output modules. Metadata base based on object oriented data model is used to implement the integration of dam safety data from different information sources. The multilevel link style was used to manage model base. Intelligent inference engine is the central processing unit. It can be used to monitor the operation characteristics and diagnose the unexpected behavior. It includes monitoring models, inference model and evaluation model for dam behavior. The proposed system has been used to monitor dam safety successfully. The applications show that the system structure is feasible, the adopted key technologies are effective, and the results are reasonable.

Quantitative analysis of monitoring data obtained from concrete dams can provide useful information about the behavior of dams, permit prediction of the future values by considering the corresponding actions, and detect abnormalities (or irregularities) as early as possible to enable a timely response. It can also contribute to options regarding the building process and to control of the construction program during construction. As a rule, the traditional statistic models can be used in quantitative analysis of monitoring data. A statistic model is established on the basis of all monitoring data. After a long time (maybe several years), the coefficients in the model are updated. Before updating, the old coefficients are always used without considering the new measurements added. As a result, the reliability and accuracy of the prediction with the models are doubtful. Therefore, the models are essentially static. To monitor the dam in real time, it is necessary to update the models dynamically. To overcome the drawback of the traditional statistic model, a dynamic model for dam monitoring, based on a recursive method, is set up. An example is provided, and it shows that the quality of prediction of the dynamic model presented is better than that of the static model. If the dynamic model is used along with automatic monitoring system, it can monitor a dam in real time and predict the behavior of the dam more accurately.

In the field of dam safety monitoring, quantitative analysis of monitoring results is a very important task. It can offer useful information about the behavior of dams, permit prediction of the future values by consideration of the corresponding actions, and detect anomalies as early as possible to enable a timely response. To date almost all work has been focusing on quantitative analysis of monitoring results obtained from dams in service, but quantitative analysis of monitoring results obtained from dams during construction has been neglected. In fact, the quantitative analysis of monitoring results obtained during construction is very important because it can contribute to options regarding the building process and to control of the construction program during construction. For the purpose of quantitative analysis of monitoring results obtained during construction, it is necessary to establish a mathematical model. However, such a model does not exist yet. This paper presents a model and derives the formula in the mathematical model for the quantitative analysis of monitoring data obtained during the construction. As an example of the application of the model, the monitoring results obtained from the Three Gorges dam, which is the largest and the most important dam under construction in China, are used. The example shows that the model is well established and can be applied to analyze quantitatively the monitoring results obtained during construction.

The stability of the dam-abutment is reflected synthetically by its deformation observation, so it can be evaluated qualitatively with the deformation trend and speed. At the same time, because the evaluation is unquantifiable, the dam-abutment safety is hard to quantitatively estimate and comparer. For that, a quantitative analysis of the dam-abutment safety based on the deformation observation is presented in this paper. At different load conditions extracted from observation analysis, the elastoplastic finite element method based on the shear strength reduction (SSR) technique is applied to analyze the stability of the dam-abutment. Then the deformation fields and the safety factors are obtained by c- reduction algorithm in critical stability of the dam-abutment. Based on the sample about the critical deformation and the safety factor, a BP artificial neural network model is established. In the end, the safety quantitative degree of the dam-abutment stability is obtained by BP artificial neural network trained. Through a series of case studies, the applicability of the proposed method is clearly exhibited.

In this study, the stability of gravity dam on a sloping layered rock foundation is analyzed, and the stability problem of gravity dam against deep slide is particularly focused. The commercial finite element software ADINA is used to develop the constitutive law of anisotropic layered materials, such as the sloping layered rock foundation. Based on a strength reduction method, the stability of gravity dams on sloping layered rock foundation is evaluated, and a criterion for evaluating the instability is proposed. As an application, the proposed methodology for stability analysis of gravity dams against deep slide is applied to a gravity dam in ArHai Hydraulic Power Station in Yunnan Province, China. The complexity of dam structures as well as the anisotropic nature of layered rock foundation is tackled with a finite element simulation, from which the deep sliding mechanism of gravity dam and its stability against slide are analyzed. By using the different vertical and horizontal parameters in the layered rock foundation model, the stability of gravity dam against deep slide is analyzed. From the thorough numerical parametric study, it indicates that the methodology is effective, feasible and generally applicable. The methodology and numerical analysis presented provide a better understanding of stability of gravity dam on layered rock foundation and can be used as a valuable reference for design analysis of gravity dam.

The traditional method of determining the dam safety monitoring index uses the hypothesis of small deformation and continuity of deformation, it can not band the stability against sliding of the gravity dam and the deformation of the dam together organically. Here the discontinuous deformation analysis (DDA) based on block theory is introduced into studying the relationship between stability of dam and its deformation. Considering the whole stability against sliding of the dam and its foundation, the whole stability against sliding of the 3# dam section of the Three Gorges left-bank workshop is analyzed in detail by use of the intensity reduced factor method, and the inner relation between the factor of safety and the displacement of dam is obtained. According to the destabilization criterion and the relation curve between the dam displacement and the intensity reduction coefficient, the dam structure behavior is determined, and the deformation early warning index of the dam under elastic condition and the load-bearing limiting condition are estimated.

The paper briefly introduces the basic principles of the double-curved arch dam geo-mechanical model's stability test and proposes a new solution in which the induction displacement measuring system is applied into the multi-point displacement measurement of the geo-mechanical model test. With the reasonable calibration and post data-processing, the induction displacement meter can be used in the non-linear area. The measuring range is extended and the size is reduced, so it's easier to be embedded in the model. The multi-point, high-precision data can be acquired by I/O control, and It's low-cost. The author expatiates the test process through various aspects: the choose of model materials, the making of the batholith and the dam, the similarity of model, load method, structure simulation and measuring points distribution etc. The paper also concerns the application method of the system in the geo-mechanical model test, the displacement curve of some measuring points, the data processing method and the synthetic errors analysis of the system.

Production of aerogel under bead form at Aspen Aerogels Inc. has made possible utilization of this material in various forms, such as pourable, formable, and sprayable insulation with excellent versatility in a variety of applications with critical low weight requirements. Flowable aerogel insulation showed lower thermal conductivity with decreasing the bead size, increasing the packing density and at lower pressures. Formable bead binder panels showed superior thermal performance compared to the bead foam insulation, while the latter showed superior mechanical strength, outperforming the Sprayed on Foam Insulation (SOFI) used on the External Shuttle Tank. Sprayed aerogel insulation has lower thermal conductivity than the SOFI foam at various temperatures and has good mechanical integrity under high enthalpy at 100°C. Aerogel insulation showed improved thermal and dimensional stability compared to polyurethane foams at cryogenic conditions and after heating at 200°C.

This paper presents a simplified method to calculate pushover curves for an asymmetric structure with displacement-dependent passive energy dissipation devices (DDPEDDs). The deformations of a symmetric structure are analyzed in translation and torsion, respectively. These results are then combined in order to calculate the pushover curve for an asymmetric structure with DDPEDDs. The numerical results obtained by using the simplified analytical method are then compared to those obtained from the analysis of the models using the software SAP2000. The results show that the simplified analytical method can be an effective tool for engineering analysis of an asymmetric structure.

Two contributors to the high cost of access to space are the use of disposable launch vehicles, and the extreme maintenance required by the U.S. Space Shuttle's thermal protection system (TPS), whose tiles can be easily damaged and thus, must be carefully inspected and frequently replaced between missions. However, high temperature materials currently under development for gas turbine compressors and hypersonic missiles may play a role in cutting the high cost associated with launch vehicles. Application of these high temperature materials to reusable launch vehicles (RLV) could lead to a simpler and less maintenance intensive TPS. This paper reevaluates the current state of the art materials with regards to their structural and thermal properties in an effort to determine if they hold the potential to lower the cost of space access. Relevant material properties and scenarios were combined and analyzed using a MATLAB based program which uses the diffusion equation to approximate heat transfer. This allows a designer to quantify the thermal transients and gradients during reentry. The program allows for a quick comparison of the proposed materials to the traditional shuttle design. The basic configuration of the proposed materials is similar to that of the TPS system currently used on the U.S. space shuttle, consisting of an outer non-structural layer for maximum thermal mitigation efficiency protecting an inner layer which provides structural strength and stiffness. The key difference lying in the idea that the application of high temperature materials allows for higher external and internal structure temperatures than traditionally allowed, reducing the demand on the TPS, and allowing for a shorter reentry duration.

The interface bond strength, curling and delamination due to early age volume change are critical for selecting high-performance concrete (HPC) overlays for reinforced concrete bridge decks. In this study, as part of a large scale program for West Virginia Department of Transportation (WVDOT) to develop overlay specifications, four types of HPC overlays was investigated for curling, delamination under volume change and bond strength under tensile load. Two types of specimens were tested: Pre-cracked rectangular prismatic specimens for early age delamination and butterfly notched specimens for bond strength test. The bi-layer specimens were cured and exposed to temperature 35°C and 50% relative humidity. The specimens were monitored for curling at the corners and peripheries. The ultrasonic pulse signals were recorded for evaluation of interface delamination. Results show that the delamination and edge curling depends on overlay types. Silica fume modified concrete with shrinkage reducing admixtures curled and delaminated less than silica fume modified-only overlay. The latex modified and fiber reinforced concrete overlay performed better than silica fume modified-only concrete. The testing method adopted was sensitive enough to evaluate and compare among overlays.

Based on chloride ion penetration test (CIPT), ultrasonic test, abrasion resistance test, scanning electron microscope (SEM) and mercury porosimetry method (MPM), the fractal dimensions of cast concrete specimens in lab under controlled permeability formwork (CPF) inner-liner was measured, and the effects on concrete durability were analyzed. The results show that CPF inner-liner with suitable physical characteristics is useful to improve concrete compactness, anti-permeability and durability. Meanwhile, CPF inner-liner can decrease the ratio of water to cement and blow-holes distribution during hydration.

The investigation focused, in the paper, on developing a method of the improvement in the capacity and deformation of a concrete shear wall reinforced with high-strength rebars under the actions of the horizontal forces. For the cantilever shear walls, the ultra strength rebars were placed both in the two boundary columns using as transverse stirrups and longitudinal reinforcements, and in the central part of the wall using as horizontal and vertical distributed steel. To validate the proposed method, a nonlinear FEM model for the shear walls was set up and a numerical simulation was finished for the understanding of the parametric influences and failure mechanism. To examine the efficiency of the FEM model and the results of the numerical simulation, a pseudo static test, which included five high-strength concrete shear walls reinforced with the ultra strength rebar, was tested under cyclic lateral loads combined with constant vertically axial forces. The results of the experiments and numerical simulations both showed that the capacity and the ductility of the concrete shear wall were effectively increased by using the high-strength rebars.

Concrete exhibits significant strain softening beyond the peak or initial failure stress and the failure criterion of concrete is not easy determined under complex stresses state. To incorporate this behavior and also reflect the entire failure process, two advancements of Mazars isotropy damage model in strain space have been proposed. To reflect the failure criterion of concrete under multiaxial stresses, based on the idea of Hsieh-Ting-Chen strength failure criterion in stress space, a new four-parameter failure criterion in strain space is presented. Two numerical examples are used to explain the ideas proposed in this paper and compared with experimental data. The results of computation were generally in good agreement with the experimental observations. It is showed from the computed results that the criterion and equivalent strain presented in this paper is reasonable.

The interfacial stresses of FRP-RC hybrid beams were studied by analytical methods. An approximate model of the hybrid beam was developed and a closed-form solution for interfacial shear stress was derived out. Then the finite element calculations were carried out for validation of the analytical solution. The comparisons between present solution and other ones in existing literatures were also performed. It is shown that the analytical solution for the interfacial shear stress is agreed well with the corresponding finite element result.

According to actuality that softening process has no stable model and mode 1 fracture has been investigated rarely, this paper utilizes the smart properties of CFRC to attain initial load of three-point bending beam. Double-K criterion was imported to compute K_ICⁱⁿⁱ and K_IC^un, which can explain toughening effect of fiber effectually. Results suggest that the smart properties of CFRC can be used to research mode 1 fracture of three-point bending beam after analysis of relationships between fractional change in resistance and load, deflection and CMOD, which are accord with Lorentz fit. The curves of fractional change in resistance before maximum load can illustrate three stages such as elastic deformation, stable fracture and unstable fracture.

In this study, the effect of hybrid microfiber reinforcement on fracture energy and crack propagation in cement matrix composites is evaluated. The cracks in cement matrix composites are allowed to fracture under Mode I loading using a notched three-point bending beam (3PBB) specimen. Influence of fiber type and their combination is quantified using fracture energy and toughness index. It is demonstrated that a hybrid combination of steel fibers and polyvinyl alcohol (PVA) micro-fibers enhances the resistance to both the nucleation and growth of cracks. A micromechanical model of hybrid composites based on a fiber bridging law is used to compare with experimentally measured data. The influencing role of the fiber combination becomes manifest in the fracture tests. The fundamental fracture tests are very effective in characterizing and developing high performance hybrid fiber composites.

In this study, an improved bi-material beam theory with adhesive interface is presented to evaluate the interface stress distributions of a concrete beam reinforced by an externally bonded fiber-reinforced plastic (FRP) composite plate. Both the adherend normal and tangential deformations induced by interface stresses are considered by introducing two interface compliances, from which an improved solution of interface stress distributions is obtained. Closed-form solutions of interface stresses are presented, and favorable agreements between the present solutions and those of the literature for a carbon FRP-strengthened concrete beam are achieved, thus demonstrating the validity of the solutions. The present improved bi-material beam theory provides a better prediction of the interface stress distributions, especially for adherend materials (i.e., beam and bonded plate) made of relatively low stiffness properties (e.g., wood material as the originally strengthened beam and thin FRP composite as the strengthening plate), and it can be used to analyze the interface debonding in the beams with externally adhesive-bonded plates.

Since water is not a universal commodity on the moon as it is on Earth, sulfur concrete, which does not require water to make, can be used as an alternative building material. Sulfur concrete consists of molten elementary sulfur and aggregates. The aggregates in lunar environment will be lunar soil and rocks. Sulfur is present on the moon in Troilite soil (FeS) and by oxidation soil iron and sulfur can be produced. Sulfur concrete specimens were cycled in two conditions: between room temperature and –27, and room temperature and liquid nitrogen (∼–191°C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression. Test results showed that due to severe temperature cycling (between room temperature and ∼–191°C), compressive strength of cycled specimens was 20% of those non-cycled. Similar sulfur concrete mixtures were strengthened with short and long glass fibers. The glass fiber was derived from lunar regolith simulant. Glass fibers were pulled from the melted lunar regolith simulant and were used to reinforce sulfur concrete. Prisms beams strengthened with glass fibers were tested in 4-point bending test. Beams strengthened with glass fibers exhibited an increase in the flexural strength by as much as 40%.

Recent applications have demonstrated that fiber-reinforced polymer (FRP) honeycomb sandwich panels can be effectively and economically applied for both new construction and replacement of existing structures. In this paper, free vibration analysis of an as-manufactured FRP honeycomb sandwich system with sinusoidal core geometry in the plane and extending vertically between face laminates is presented. A higher-order vibration model for sandwich beams is formulated using energy method. The analytical solutions in term of frequency and mode shapes are compared with the results of experimental testing and numerical finite element modeling of an "as-manufactured" FRP honeycomb sandwich beams. The present vibration analysis demonstrates the accuracy and capability of the higher order dynamic sandwich beam theory, and it can be used in analysis, design applications, and potential health monitoring of efficient honeycomb FRP composite sandwich structures.

Based on a combined multi-objective optimization and homogenization approach, effective transverse shear moduli of composite honeycomb cores are optimized, from which the corresponding optimum core configurations are obtained. The effective transverse shear stiffnesses of three typical honeycomb cores (i.e., sinusoidal, hexagonal, and tubular) are predicted using a two-scale homogenization technique, and a multi-objective method is then employed to obtain optimal designs of periodic cellular cores. The optimization problem is solved using a sequential quadratic programming algorithm. An optimization procedure using finite element analysis and a response surface algorithm is also conducted to verify the proposed approach. The present multi-objective optimization approach combined with the explicit prediction of transverse shear stiffness from homogenization can be effectively used to maximize transverse shear material properties of composite honeycomb structures.

Every system can fail. Systems in harsh or challenging environments, like radiation, chronic and frequent use, and weather variations, also can fail. At perihelion, the Sun is close to the Earth and could be associated with earthquakes. Gravitational forces increase, when the Sun is close to the Earth, and the magma, crust, surface, plates might be affected like Io is affected by close approach of Jupiter. Should we shut down the nation's bridges or evacuate the coasts during such times so that there is no risk of loss of life on bridges or from tsunami? Such a response leads to new problems like food distribution and evacuation questions. The poster will list types of radiation that a spacecraft or astronaut can encounter from gamma, cosmic rays, UV, alpha, beta, photons, etc. The idea of responding with multiple tools and shields to protect a spacecraft or astronaut from damage will be discussed. The idea of multiple responses can be applied to bridge design as well. One could imagine putting a secondary bridge or pontoon system separately supported underneath unstable bridges. Does the risk of failure increase as the supporting environment around the bridge is utilized for supporting a unique structure? Bridges on Io and Europa are looked at. Possibilities of success/failure with each design is discussed. The interaction of multiple responses themselves can lead to system failure. A radiation protection device like a heat shield could increase temperatures and secondary radiations too much and lead to system failures. Multiple responses are useful /helpful, but can create problems as they can increase system and structure stresses and failures.

As a result of the increase in use of composites in the Aircraft Industry, use a better knowledge and behavioral prediction is desired. This can be done through computational models and/or physical testing. Numerous FEA programs are used to aid in the design process and to predict the performance and behavior of composite structures. There are also many non destructive methods of investigation (NDI) which are used in both quality control and behavioral observations. A composite flight structure common to many airplanes is a radome, which can be defined as a structural enclosure used to protect an antenna from the environment which includes the aerodynamic loading and weather. FEA model validation is performed by comparison to vibration testing as well as internal pressure testing. Shearography allows us to measure the surface deformation of an object when under a stress. Shearography was completed to determine any possible defects caused in manufacturing (or transporting) the radome. De-lamination will possibly cause unpredicted response in the vibration or pressure tests. Areas of different construction as well as defects will deflect non-uniformly. There were no flaws detected in the composite radome tested. Laser Doppler Vibrometry (LDV) is a non-contact vibration measurement that is used to determine the natural frequencies and mode shapes of the Composite Radome Structure. The vibration testing was completed using a few different boundary conditions which include approximately free-free BC's and fixed BC's. The testing has corresponded accurately in comparison to the FEA model however; it is suspected that there is some slight error caused by the fixed fixture for vibration testing.

Despite, significant work over many years (utilizing either one of the micromechanics based or phenomenological approaches; see Lagoudas et al. 2006; Patoor et al. 2006), there are still prospects of much improvements to be made in constitutive modeling of Shape Memory Alloys (SMA), specially if we target sufficiently general scope in the modeling; i.e., including such important attributes as, (i) multiaxiality, (ii) possible asymmetry in tension and compression, (iii) accounting for pseudoelasticity and pseudoplasticity, (iv) rate dependence, and (v) effects of shape memory training under cyclic loading. The theoretical formulation employs two main ingredients; (i) multiplicity of hardening mechanisms, and (ii) the partition of the energy storage/dissipation that is so vital in capturing the extremes of pseudoelasticity and pseudoplasticity in SMAs. In this presentation, we describe our recent efforts in extending the approach utilized in (Saleeb et al. 2001) to the modeling of the inelastic response of SMA materials.

Although the water projects in China are first class in quantity, type, construction technique and experience, the safety control technique relatively lags. The management level does not match the construction level. The existence of many dangerous projects and the construction of extra large scale water projects demand the establishment of a safety assurance system which focuses on water engineering health and early warning to find the engineering abnormality and the hidden dangers in time. Firstly, this paper reviews the current situation of study on hydraulic engineering safety. Based on dangerous projects and the safety of large scale water projects, the conventional philosophy on water engineering safety is changed. The development trend of safety assurance technology is introduced in aspects such as basic theory and analysis method, monitoring, inspection and experimental instrument, new material and technology and so on.

This paper discusses the use of vibrating wire strain gages with large civil structures. A two-hundred ft. section of tunnel liner has been instrumented with twenty-five vibrating wire strain gages. The section of liner will be monitored long term to develop a better understanding of the thermal stresses in the liner, and as part of ongoing health monitoring. The twin tunnel is bored in soft rock. The liner is a polypropylene fiber reinforced shotcrete, which, in the test section, is a minimum of 2 in. thick. The tunnel is a dedicated dual track light rail transit tunnel, and is 3.5 miles long. The test section is near an entrance portal, and temperature gradients exist between the rock subsurface and the shotcrete liner surface. The liner, the experimental program and the objectives of the study are discussed.

The most remarkable feature of rock masses is the existence of discontinuities of various size, orientation, and spacing. The algorithm developed on the concept of "composite element method" has the ability to contain discontinuity segments such as faults and joints within elements. In this way the discontinuities can be simulated explicitly without special elements deployed along the discontinuities. The composite elements can be incorporated into the conventional finite element analysis procedure easily. If there are no discontinuities in the calculated domain, the algorithm is degenerated back to the conventional finite element procedure. Baozhusi gravity dam on a complicated rock foundation is studied in the paper, from which the advantage of the CEM can be shown and the reliability of the CEM can been verified.

The finite element model for reinforced-concrete frame beam to resist progressive collapse was established by ADINA program, which geometrical and material non-linearity considered. Axial forces are often present in reinforced-concrete beam at the ultimate load as a result of the boundary conditions and geometry of deformation of the beam segments. So the ultimate load-carrying capacity of reinforced-concrete frame beam was increased because of the arching and cable action (compressive and tensile membrane action). The influence of the beam to resist progressive collapse has been discussed such as steel ratio, span-depth ratio. It shows that the finite element model presented is feasible and can be applied to further research on engineering practice for reinforced-concrete frame structure to resist progressive collapse.

In this paper, considering the characteristic of geological and synthetic materials disobey the associated flow rule and the elastic parameters change with the plastic strain, the incremental of plastic strain can be divided into two parts: the one part comply with associated flow rule and Drucker postulation, which can be established on the basis of traditional incremental plastic theory; the surplus part, resulting from elasto-plastic coupling, is presumed to be reversible strain. Therefore, more prevalent stress-strain constitutive model based on the increment plastic theory is deduced. The wide applicability is proved through two projects in the end.

Today, the adjacent cases increase rapidly; the influence of two engineering is the objective existence, and also the influence factors are quite many, which are considered with difficulty in the design stage completely. The useful data are getting to guide the construction of Dongshankou station through 3D numerical construction process analysis on deep excavation and tunneling of Guangzhou subway line one.

In general, it is difficult to obtain all the information in each part of a complex structure during the dynamic analysis due to the CPU time and memory costs. In fact, only parts of the structure are most really concerned in many cases. The present work is concerned with a time-saving finite element dynamic sub-modeling approach based on the local mesh refinement technique, and it can be carried out in a quite easy way in the dynamic structure analysis through three steps. First, the analysis for the whole original model should be accomplished on a fairly coarse mesh. Second, the key part of the structure which is most concerned with is taken out as the sub-model. The local mesh refinement technique is then employed to the sub-model to get the acceptable fine mesh. At the same time, the interface displacement distribution on the fine mesh is obtained from the original coarse mesh model analysis. Finally, the dynamic analysis for the selected structure is performed with the interface displacement boundary conditions obtained in the previous step. The accuracy and efficiency of the presented procedure is examined by a numerical example. It is concluded that the interface displacement boundary condition is enough for the sub-model dynamic analysis.

In finite element analysis, the mesh coarseness and the type of elements used are vitally important to the accuracy of the final result. Obviously, high accuracy can be achieved by imposing high order elements and dense meshes. However, the computational cost in these cases would be considerable, especially for physically large or three dimensional models. In order to achieve satisfactory results within reasonable computational time, low order elements and local refinement is usually applied. There are two problems to be solved: i) the elements which need refinement are located. This is usually done through various kinds of error estimation. ii) the method for refining without ill composed elements is used. For two dimensional models, local refinement in a mesh consisting of triangular elements is easier than that of quadrilateral element which has better element properties; but using traditional methods for local refinement of quadrilateral elements, is virtually impossible without misshaped elements and/or meshes with ill composed valences occur. In this paper, an alternative low-cost refinement technique for refining both two and three dimensional problems using quadrilateral and hexahedral elements is present. The technique is applicable to linear as well as non linear problems, though in this paper, we focus on implementing the technique in the non linear soil problem of predicting failure mechanisms and collapse loads in soils.

A model was set up using element-free method (EFM) to trace crack propagation of concrete acted by transient temperature field. The time-varying rules of temperature, stress and stress intensity factor at concrete crack tip were analyzed to get the time of crack initiation and the whole process of crack propagation. In addition the effects of the change rate of external temperature and crack depth on crack propagation were discussed. The results show that surface crack can possibly develop into penetrative crack acted by variable external temperature, which would wreck structural stability, and surface crack propagation is more likely to initiate in shorter period when the change rate of external temperature is higher. What's more, the deeper crack is, and the easier and the rapider crack initiation are.

Dynamic direct tensile damage tests of plain concrete specimens are carried out on MTS in order to investigate the effect of strain rate on dynamic damage behaviors of concrete. About forty dumbbell shape specimens were tested in tension with the axial strain rate range from 10^–5/s to 10^–1/s. With the damage of concrete denoted by the reduction of tangent modulus, damage evolution of different strain rates are studied systematically. Results show that the inner cracks of concrete expand slowly and the number of cracks decreases when the strain rate increases. The damage threshold stress of concrete increases with increasing of the strain rate. Also, the effect of strain rate on other dynamic behaviors of concrete was studied. The tensile strength and critical strain of concrete increase with the strain rate and the relationships can be simplied approximately linear with the logarithm of strain rate. The poisson's ratio of concrete is independent on the strain rate.

Reinforced concrete hollow slabs are among the most common structural elements. In spite of the large number of slabs designed and built, the effect of holes on their punching shear behavior are not always appreciated or properly taken into account. The present work reports the testing results of 9 reinforced concrete hollow slabs and analysis results of 80 reinforced concrete solid slabs which were designed to against punching shear. The deformation of slab, stress of steel reinforcement and crack development are analyzed. Curved cracks, bending and shearing cracks, punching shear ring cracks and horizontal cracks between steel reinforcement and concrete are observed in the tests. The testing results show that punching shear strength of reinforced concrete hollow slab is affected by effective thickness of slab, the ratio of hollowness, the concrete strength, the strength and reinforcement ratio and loading area. The punching shear strength model of reinforced concrete hollow slab is also proposed.

Due to the steel radial gates' characteristics of structural and acting forces, the investigation on parametric resonance of radial gates' arms has always been the hot topic in the research field of radial gate's dynamic stability. In this paper, the simplified space frame is taken as the analytical model, and according to the elastomer perturbation equation and beam element model of thin-walled structure, the dynamic instability region of radial gates can be obtained by the finite element method, then the computational method is applied to calculate the main regions of dynamic instability for a working radial gate. Furthermore, combing with the physical and numerical models, a new method recognizing the parameter resonance of steel radial gates is proposed. The investigations, in this paper, are not only important improvement for the radial gates' parametric vibration computational method, but also a solid foundation for further study on the dynamic stability of radial gate structure.

The structural types, geometry properties, force transfer modes and performance of various key grooves are thoroughly evaluated, and the important factors, such as single key groove, two-way key groove, and multi-way key groove, are considered in modeling. The relationships between the initial normal and shear apertures of the key groove are derived. A nonlinear constitutive law, so called the key groove shear transfer model, is presented, in which the initial aperture of the joint is included. In the modeling and analysis, the direction, shape, and shear strength of the key grooves are considered, and the variation law and the contact characteristics of the key grooves are fully revealed, shedding light on critical component analysis and design of concrete key grooves in hydraulic structures. Further, a variable incremental search method used for the solution of the nonlinear space contact problem is proposed, from which the stability of calculation is assessed. The analytical models and results presented in this study provide a benchmark for design analysis of concrete key grooves in hydraulic structures and can be better utilized in optimum design of key grooves.

There is a 333.586 m length tunnel for parking and cross-over track at the north Gulou station between Gulou station and Xuanwumen station, which the largest span is 17.358 m. The spacing interval is small, and the smallest is 0. The tunnel has many chambers, and the section area is varied. A 320.6 m length tunnel goes through the soft muddy and silty ground at the south Xuanwumen station. The tunnel crown is located 8 m to 9 m below the ground surface, where there are structures on the ground, pipeline and built-constructions under the tunnel. All the constructions therefore must be secure and steady in the process of excavating. The paper analyzes both the construction difficulty and features of large span and parking cross-over track tunnel in the soft flow mucky ground. The construction method of bench cut method, center diagram method (CD method) and both side drift method are adopted on the base of the theory. Finally the paper introduces the construction scheme and support method in the soft flow mucky ground. From the effect of construction, it is concluded that the construction method and the reinforcement method are right. In a word, the constructions are secure and steady in the whole process of construction.

The objective of the paper is to present a practical bridge condition evaluation method for the decision making of whether a bridge should be replaced, repaired, or routinely maintained. The bridge conditions are classified into four types (i.e., First, Second, Third, and Fourth) corresponding to different required maintenance levels determined by Multilevel Fuzzy Identifying Synthetical Appraisal theory. The inspection and statistical analysis of 88 deficient reinforced concrete girder bridges in China are first introduced. Then, the bridge deficient classifications and their weight coefficients are discussed. Finally, the type of condition and the maintenance level of an existing concrete bridge are evaluated based on Multilevel Fuzzy Identifying Synthetical Appraisal theory. Results show that the proposed method is reliable and can be used in evaluating the existing bridge conditions.

In order to increase the rated power and improve the efficiency, the old runner of hydraulic turbine generator unit is replaced by a new and improved design, from which the dynamic performance is altered. In this study, in situ test is conducted to inspect the operation stability of the new hydraulic turbine generator unit. The transducers (i.e., laser Doppler vibrometer (LDV) and proximity probe) are used to measure the vibration and swing magnitude of the unit. The test results show that the vibration amplitude becomes bigger with the hoist of rotating speed, but it is not proportional to the square of rotating speed. The mass of rotating component of hydraulic turbine generator unit is thus balanceable. At the same time, the vibration and swing amplitudes are less than the design limit of hydraulic turbine generator unit, and the primary frequencies of vibration and swing are relevant to the rotating speed. Based on the in situ vibration test conducted, it is concluded that the new hydraulic turbine generator unit can be run stably.

Karkheh earth dam is located in the south-western part of Iran. The nominal capacity of the reservoir is eight billion cubic meters with three electrical generators at pick hours. To control the behavior the dam layers, cell pressure and inclinometers were used. The results obtained through applying these instruments at a depth of 140m were disturbed during development period due to an increase in pressure incurred by embankment layers and a squeezing of pipes. Based on 44'000 recorded data, interaction graphs of the vertical settlement in terms of height are drawn. Then engineering mathematics and SSM were applied on the data registered and thus elasticity module was obtained for each layer. Lines slope indicates the variable potential of embankment as well as consolidation interaction behavior. Using the mentioned graph, one may draw stress- strain curve of the vertical axis. Joining these broken lines at the bottom part of the graph with the stress-strain curve, an enclosed curve named Turk elliptical criterion 2008. This criterion may predict the final deflection of dam at any time and correct the mistake records.

For the safety of power station and people living in downstream area of the river, safety of the dam must be evaluated and monitored on the basis of prototype observation data. Among the evaluation indexes, displacement is proved to be the most convenient and efficient. Therefore it is important to forecast displacement of dam based on the observation data and the causation. Basically, the ANNs (Artificial Neural Networks) are numerical structures inspired by the learning process in the human brain. They are constructed and used as alternative mathematical tools to solve a diversity of problems in the fields of system identification, forecasting, pattern recognition, classification, process control and many others. Genetic algorithm (GA) belongs to a class of evolutionary computation techniques based on models of biological evolution. It has been proved useful in domains that are not well understood, or for search spaces which are too large to be efficiently searched by standard methods. Recently, it is popular to improve capability of neural network by genetic algorithm and apply the model in engineering field. Taking advantage of excellences of genetic algorithm and neural network, a GA neural network model is designed which combines neural network's self-studying, error revising with genetic algorithm's comprehensive searching ability. In the paper, standard genetic algorithm is modified at some aspects including coding, selection, crossover and mutation. Then the modified GA is used to calculate weight and threshold values of neural network and to determine the best network structure at the same time. By using this GA neural network model, displacement of dam is calculated on the basis of prototype observation data. To prove the performance of the model, capability and forecast precision are also analyzed. This kind of method provides useful technical support for safety monitoring of dam.

As one of the most important concrete arch dam of upper reaches of the Yellow River, Lijiaxia concrete arch dam is 155 meters high. The reservoir, which capacity is 1.65 billion cubic meters, began to store water at Dec 26, 1996. According to the loads occurred on the dam and its foundation, safety monitoring indexes can be established to assess condition of the dam and to predict probable loads the dam can bear. Because a displacement observation system of Lijiaxia concrete arch dam was established and the continuity and reliability of observation data are proved, secondary safety monitoring indexes for displacement of Lijiaxia concrete arch dam are calculated and analyzed in this paper. In this paper, three-dimension nonlinear finite element model of Lijiaxia arch dam, considering some major faults and foundation treatment measures, is established. The stress, strain, positions and scopes of yield zone and failure zone of the dam under different critical load conditions are obtained by structural calculation method, and the secondary safety monitoring indexes for displacement of Lijiaxia arch dam are determined. By analyzing the indexes, safety operation of the dam can be ensured. This paper also provides an effective way to determine other kinds of safety monitoring indexes.

The main factors of influencing the crack change of concrete dams can be reduced to three parts of water pressure, temperature and aging, but it is very difficult to get the effects of this three parts respectively. The nonlinear time-varying relationship between the crack change and its influencing factors is very strong. Using the unique ability of data analysis and learning of artificial neural network, and through the intercrossing of dam construction knowledge, then a good approach to solve these problems can be offered. In this paper, based on in-situ monitoring data of concrete dams, from the angle of machine learning, the time varying analysis model for causality of cracks of concrete dams is introduced, and the evolution law of load cracks with the change of time and load is analyzed and forecasted. The example indicates that the model can finely describe and forecast the time varying characteristic of cracks causality in concrete dams, and can give each factor's contribution to crack opening.

For polymer matrix composites subjected to large strain rates, it is important to correctly characterize the nonlinear and strain rate dependent response of polymers. For this purpose, viscoplastic constitutive equations originally implemented for metals have been modified to account for the effects of hydrostatic effects and inelastic strains in polymers. The resultant stress in the composite can then be obtained by using a mixture theory that averages the individual stresses of the polymer and fiber (assumed to be elastic) constituents. The implementation of such analytical models using finite element methods constitutes one of the first objectives of the current effort. A continuum model that combines the individual constituents is defined using mixture theory. Experimental tests will be used to validate the preliminary analytical model and verify its efficiency and applicability for engineering applications.

A framework is presented for analyzing the low-temperature inelastic behavior of a class of amorphous polymers with full account taken of finite deformations and inertial effects. Viscoplastic constitutive equations are used and supplemented with a new model for craze initiation, growth and breakdown. The capabilities of the framework are illustrated by finite element solutions of initial/boundary-value problems under plane strain conditions. Three illustrative benchmark problems are used to evaluate the proposed implementation: shear band formation and propagation under compression, dynamic response under impact and quasi-static response of a polymer composite unit-cell subject to uniaxial tension transverse to fibers.

Metal failure in many applications, such as ballistic impact, containment, shielding, and crashworthiness, with the exception of thin shells, occurs while the metal is in a three dimensional state of stress. Many previous definitions of triaxiality use two invariants to define the relative stress state in a virtual element, leading to a characterization that can be better thought of as biaxial. An additional, second parameter, based upon the third stress invariant is defined, which extends the characterization of the state of stress to three dimensions and to true triaxiality. The relation of the two parameters is explored and limits are found in the failure surface which aid in defining critical failure regions. Standard tests are compared to these regions of interest and new tests are proposed which envelope the limits of the failure surface, and thus define this failure surface.

The deformation (plastic) and failure of 2024-T351 is studied under a wide range of loading conditions. Uniaxial tension and compression tests and pure shear tests have been conducted over a wide range of strain rates. The results show no significant strain rate effect on plastic deformation up to strain rate of about 2000s^–1. Surface finish in tensile test has a noticeable effect on the strain to failure. Specimens with a rougher finish failed at a smaller strain than specimens with a smooth finish. Equivalent stress strain plots from tension, compression and shear tests do not coincide, which indicate that a plasticity model (either time independent or time dependent) that is based on J-2 flow theory will not be suitable for modeling the plastic deformation of the material. All the specimens that were tested were machined from plates. Specimens for tensile tests were machined in different orientations relative to the rolling direction of the plates. The results show that the plates have anisotropic properties with regard to plasticity and failure. Initially round cylindrical specimens tested in compression ended up with an elliptical cross sectional area. The objective of the testing program is to generate accurate and diverse data that will be used for developing accurate plasticity and failure models that will be incorporated in numerical codes that are used for simulations of impact events.

Uncontained aircraft engine failure can cause catastrophic damaging effects to aircraft systems if not addressed in the aircraft design. Mitigating the damaging effects of uncontained engine failure and improving the numerical modeling capability of these uncontained engine events are crucial. In this paper, high strain rate material behavior of one of the most extensively used materials in the aircraft industry is simulated and compared against ballistic impact tests. Ballistic limits are evaluated by utilizing explicit Finite Element (FE) simulations based on the corresponding ballistic impact experiments. LS-DYNA is used as a non-linear explicit dynamics FE code for the simulations. Johnson-Cook material model is employed as a thermo visco-plastic material model coupled with a non-linear equation-of-state and an accumulated damage evaluation algorithm for the numerical simulations. Predictive performance of the numerical models is discussed in terms of the material characterization efforts, material model parameter sensitivities and mesh sensitivities.

In accordance with the FAA certification requirements, all modern commercial turbofan engines must successfully demonstrate its ability to withstand a Fan Blade-Out (FBO) event through actual test. Possibility of losing a rotating fan blade from a running engine is a flight safety consideration, which must be addressed during the design phase of the engine. A typical Fan Blade-Out event involves a very complex non-linear transient dynamics with large deflection of the release blade and large rotation of the trailing blade as well as progressive failure and fragmentation of various components. Given the high strain rates, the solution to the problem should also address dependence of material behavior via strain rates. In short, the transient dynamic analysis of a fan blade-out event highlights the complexity of the numerical technique, which includes all the nonlinearities of structural dynamics; plastic behavior of the materials, large displacements, and contact interaction between structural elements. In this paper, we present the results of a LS-DYNA simulation of a FBO (Fan Blade Out) event on a full-engine analytical model, which covers both the primary as well as secondary damage.

Composite materials made with triaxial braid architecture and large tow size carbon fibers are beginning to be used in many applications, including composite aircraft and engine structures. Recent advancements in braiding technology have led to commercially viable manufacturing approaches for making large structures with complex shape. Although the large unit cell size of these materials is an advantage for manufacturing efficiency, the fiber architecture presents some challenges for materials characterization, design, and analysis. In some cases, the static load capability of structures made using these materials has been higher than expected based on material strength properties measured using standard coupon tests. A potential problem with using standard tests methods for these materials is that the unit cell size can be an unacceptably large fraction of the specimen dimensions. More detailed investigation of deformation and failure processes in large unit cell size triaxial braid composites is needed to evaluate the applicability of standard test methods for these materials and to develop alternative testing approaches. In recent years, commercial equipment has become available that enables digital image correlation to be used on a more routine basis for investigation of full field 3D deformation in materials and structures. In this paper, some new techniques that have been developed to investigate local deformation and failure using digital image correlation techniques are presented. The methods were used to measure both local and global strains during standard straight-sided coupon tensile tests on composite materials made with 12 and 24 k yarns and a 0/+60/–60 triaxial braid architecture. Local deformation and failure within fiber bundles was observed, and this local failure had a significant effect on global stiffness and strength. The matrix material had a large effect on local damage initiation for the two matrix materials used in this investigation. Premature failure in regions of the unit cell near the edge of the straight-sided specimens was observed for transverse tensile tests in which the braid axial fibers were perpendicular to the specimen axis and the bias fibers terminated on the cut edges in the specimen gage section. This edge effect is one factor that could contribute to a measured strength that is lower than the actual material strength in a structure without edge effects.

The paper presents the research that is devoted to analyzing the lateral crash of triaxial braided composite tubes. An existing unit-cell based material model for axial crushing of tubes is modified to model the response of the tri-axially braided composites under lateral loads. Matrix, fiber-tension and fiber-compression failures have been considered to account for lateral crash. "DyCrush", an user-defined material module which can be interfaced with ABAQUS/Explicit, is used to simulate the present conditions. A four-point bending problem is simulated using the "DyCrush" module in the quasi-static case and the results are compared with experimental results. The effect of load rate on the lateral crash response is presented by comparing the load-displacement curves for different dynamic loadings. An active sensing scheme is employed in the experiment to verify the progressive damage development in the structure.

This paper provides an overview of rotorcraft crashworthiness research being conducted at NASA Langley Research Center under sponsorship of the Subsonic Rotary Wing (SRW) Aeronautics Program. The research is focused in two areas: development of an externally deployable energy attenuating concept and improved prediction of rotorcraft crashworthiness. The deployable energy absorber (DEA) is a composite honeycomb structure, with a unique flexible hinge design that allows the honeycomb to be packaged and remain flat until needed for deployment. The capabilities of the DEA have been demonstrated through component crush tests and vertical drop tests of a retrofitted fuselage section onto different surfaces or terrain. The research on improved prediction of rotorcraft crashworthiness is focused in several areas including simulating occupant responses and injury risk assessment, predicting multi-terrain impact, and utilizing probabilistic analysis methods. A final task is to perform a system-integrated simulation of a full-scale helicopter crash test onto a rigid surface. A brief description of each research task is provided along with a summary of recent accomplishments.

Based on the structural model for wave-controlled impact, a modified Hertzian contact law was used to investigate impact responses of composite laminates. The original nonlinear governing equation was transformed into two linear equations using the method of asymptotic expansion. Closed-form solution can be derived for the first linear homogeneous equation, which is the equation of motion for single degree of freedom system with viscous damping. The second linear non-homogeneous equation was solved numerically. The overall impact responses for wave-controlled impacts can be obtained semi-analytically and agree well with the numerical solutions of nonlinear governing equations. The proposed methodology is useful for providing guidance to numerical simulation of impact on complex composite structures with contact laws fitting from experimental data.

This report will discuss the use of advanced simulation techniques to optimize the performance of the proposed Orion Crew Module airbag landing system design. The Boeing Company and the National Aeronautic and Space Administration's Langley Research Center collaborated in the analysis of the proposed airbag landing system for the next generation space shuttle replacement, the Orion spacecraft. Using LS-DYNA to simulate the Crew Module landing impacts, two main objectives were established and achieved: the investigation of potential methods of optimizing the airbag performance in order to reduce rebound on the anti-bottoming bags, lower overall landing loads, and increase overall Crew Module stability; and the determination of the Crew Module stability and load boundaries using the optimized airbag design, based on the potential Crew Module landing pitch angles and ground slopes in both the center of gravity forward and aft configurations. This paper describes the optimization and stability and load boundary studies and presents a summary of the results obtained and key lessons learned from this analysis.

A key element of the President's Vision for Space Exploration is the development of a new space transportation system to replace Shuttle that will enable manned exploration of the moon, Mars, and beyond. NASA has tasked the Constellation Program with the development of this architecture, which includes the Ares launch vehicle and Orion manned spacecraft. The Orion spacecraft must carry six astronauts and its primary structure should be reusable, if practical. These requirements led the Constellation Program to consider a baseline land landing on return to earth. To assess the landing system options for Orion, a review of current operational parachute landing systems such as those used for the F-111 escape module and the Soyuz is performed. In particular, landing systems with airbags and retrorockets that would enable reusability of the Orion capsule are investigated. In addition, Apollo tests and analyses conducted in the 1960's for both water and land landings are reviewed. Finally, tests and dynamic finite element simulations to understand land landings for the Orion spacecraft are also presented.

A review of astronaut whole body impact tolerance is discussed for land or water landings of the next generation manned space capsule named Orion. LS-DYNA simulations of Orion capsule landings are performed to produce a low, moderate, and high probability of injury. The paper evaluates finite element (FE) seat and occupant simulations for assessing injury risk for the Orion crew and compares these simulations to whole body injury models commonly referred to as the Brinkley criteria. The FE seat and crash dummy models allow for varying the occupant restraint systems, cushion materials, side constraints, flailing of limbs, and detailed seat/occupant interactions to minimize landing injuries to the crew. The FE crash test dummies used in conjunction with the Brinkley criteria provides a useful set of tools for predicting potential crew injuries during vehicle landings.

In this paper, the concept of through thickness integration points in the available shell element of LSDYNA, as well as considering fiber tow size and direction, are used to realize the complex fiber tow undulation in braided composites. A previous model will be modified and further developed to simulate the braided carbon reinforced epoxy composite materials. The work scope will include the following specifically defined tasks: Develop a unit cell model of a 0/60/–60 tri-axial braid with quasi-isotropic architecture; predict basic composite material mechanical property; perform test and analysis correlation; enhance the micromechanical model after the test and analysis correlation.

A ballistic impact test program was conducted to provide validation data for the development of numerical models of blade out events in fabric containment systems. The impact response of two different fiber materials — Kevlar 49 (E.I. DuPont Nemours and Company) and Zylon AS (Toyobo Co., Ltd.) was studied by firing metal projectiles into dry woven fabric specimens using a gas gun. The shape, mass, orientation and velocity of the projectile were varied and recorded. In most cases the tests were designed such that the projectile would perforate the specimen, allowing measurement of the energy absorbed by the fabric. The results for both Zylon and Kevlar presented here represent a useful set of data for the purposes of establishing and validating numerical models for predicting the response of fabrics under conditions simulating those of a jet engine blade release situation. In addition some useful empirical observations were made regarding the effects of projectile orientation and the relative performance of the different materials.

Test methods to obtain constitutive material properties of fabrics used for containing high-speed projectiles are presented. The material models are general enough to be used for both static and dynamic/explicit finite element analyses. Tension Tests were conducted to develop the longitudinal and transverse material properties. Trellising Picture Frame Shear Tests were used in investigating the shear resistance properties of the fabrics, followed by friction tests to determine the coefficient of friction between fabric layers. In addition to these basic material tests, experiments were conducted on systems built with fabric wraps. Ballistic tests of containment wraps subjected to a high velocity projectile were carried out at NASA-Glenn Research Center. These tests have provided benchmark results to validate the finite element methodology used for the analysis of the containment systems.

The development of a robust and reliable material model for fabrics used to prevent fan blade out events in propulsion engines has significant importance in the design of fan-containment systems. Currently Kevlar is the only fabric approved by the Federal Aviation Administration (FAA) to be used in fan-containment systems. However, very little work has been done in building a mechanistic-based material behavior model especially one that can be used to quantify the behavior of Kevlar when subjected to high-velocity projectiles. Experimental static and high strain rate tensile tests have been conducted at Arizona State University (ASU) to obtain the material properties of Kevlar fabric. In this paper we discuss the development and verification of a constitutive model for dry fabrics for use in an explicit finite element program. Results from laboratory tests such as Tension Tests including high-strain rate tests, Picture Frame Shear Tests, and Friction Tests yield most of the material properties needed to define a constitutive model. The material model is incorporated in the LS-DYNA commercial program as a user-defined subroutine. The validation of the model is carried out by numerically simulating actual ballistic tests conducted at NASA-GRC and fan blade out tests conducted at Honeywell Aerospace (Propulsion Engines).

This paper deals with the dynamics and control of multi-body systems in which their linear, rotational, and elastic motions are coupled. We model a multi-body spacecraft system as two rigid bodies that are connected by a nonlinear, elastic spring. It is assumed that the system travels in a planar orbit around a planet with a uniform gravitational field. The methodology developed in this paper leads to a simple nonlinear control law that allows us to control the coupled orbital, attitude, and elastic dynamics, and precisely maintain a prescribed tumbling trajectory for the spacecraft system. We show that complex motions like the precision tumbling of elastically vibrating spacecraft in orbit can be accomplished with considerable ease and accuracy. The proposed methodology reveals a systematic technique for controlling complex nonlinear, multi-body systems.

In past two decades, two intriguing classes of problems, having a wide range of applications in engineering, have been of interest to many researchers: (i) coupled dynamics of distributed parameter system carrying one or more moving oscillators, and (ii) transient dynamic analysis of axially moving media (and associated phenomena of parametric resonances). Bridge vehicle interaction falls into the first class of problems and flexible appendage deployed from a satellite or a spacecraft is typical of the second class. Mathematically, these two problems are dual to each other, and they often are highly non-linear in nature and typically involve large overall motion in space with complex effects of convective inertia terms in their governing equations of dynamic equilibrium. Many researchers are trying to formulate the response of these problems, each having a different approach, but applicable only to certain specific details. Moreover, few researchers have concluded that these problems are beyond the scope of present commercial finite element software packages. However, we believe that if the nature and details of these problems are studied properly and carefully, it is immediately possible to simulate these problems in available commercial finite element software packages. An added advantage would also be the avoidance of many unrealistic simplifying assumptions that are often introduced to reduce the mathematical complexity; e.g. neglecting possible separation in beam-moving vehicle problem (Yang & Yau 1997), assuming linear behavior of suspension system, restriction to beam configuration only, etc. For demonstration, we use ABAQUS in a large number of test cases to be presented. The results are compared with those presented in literatures.

NASA is currently challenged with the development of a new family of spaceflight vehicles which need to fly as soon as possible after the Space Shuttle is retired in 2010. Consequently, it is faced with converting or constructing facilities across multiple NASA centers enabling support to a new family of space flight vehicles. Testing, verification and manufacturing facilities need to be constructed or modified on critical path schedules supporting new hardware certifications and processing. Ground Operations facilities need to be customized to the new family of vehicles. NASA is planning to return to the Moon in 2018 to begin building a permanent lunar base. Lunar hardware will require engineering development and testing facilities which simulate the dusty lunar vacuum environment. Testing technologies related to newly developed materials will need facilities which allow the development and certification of thermal protection systems and heat shields. New flight vehicles are significantly larger than Apollo Program vehicles and further drive facility sizing decisions. The range and complexity of these facility requirements requires intensive planning and project management efforts. This article will outline the extent of these facility needs, the best practices used to develop the projects, and lessons learned thus far from these efforts.

This paper will summarize the phase one lander conceptual design study that was conducted during the spring of 2006 under the auspices of the National Aeronautics and Space Administration (NASA), lead by Johnson Space Center's Engineering Directorate in support of the Lunar Lander Preparatory Study (LLPS) as sponsored by the Constellation Program Office (CxPO), Advanced Projects Office (APO). This study was prior to the establishment of the Lunar Lander Altair Project Office at JSC. This study was conducted in two phases. Six NASA teams collaborated on numerous lunar lander concepts in phase one during the spring of 2006, with each team conceptualizing a range of four to six concepts each. At the end of phase one, each team performed additional design analysis of one APO selected concept. This paper will describe the JSC led multi-center phase-one design team efforts and their six lander concepts. The lunar lander conceptual design and analysis was intended to provide an understanding of requirements for human space exploration of the Moon. Recommendations, results, and conclusions in this paper do not reflect NASA policy or programmatic decisions.

On January 11, 2007 the Chinese military successfully demonstrated the technology to physically hit a 2 meter sized spacecraft at a closing speed of 8.0 km/s. It is postulated this "hit-to-kill" technology can serve as the basis for a "hit-to-deliver" space transportation system. A key innovation is to convert the kinetic energy (KE) of an arriving spacecraft into electricity via regenerative braking, liberating hundreds of MW of electrical power while simultaneously stopping the relative motion of an arriving spacecraft with accelerations below 10 m/s². A space transportation architecture exploiting these KE converter stations (named Impulse Engines) is presented, with results that compare favorably with conventional rocket travel. If further developed, a promising method of converting asteroidal bodies into Impulse Engines can potentially open vast regions of the solar system to exploration activities.

The Zero Boil-Off Tank (ZBOT) Experiment investigates zero boil-off pressure control strategies in microgravity. The primary objective is to validate and verify numerical models used to design more efficient cryogenic storage tanks for use in long-duration space missions. A key challenge of the experiment is to characterize and control the fluid flow and energy balance in the experiment system so they can be used for boundary conditions in the models. In this manner the performance of the numerical models can be directly compared to experimental results in microgravity and improved to extrapolate beyond the experimental boundaries. To date, a ground-based breadboard system has been developed with the primary objective of verifying flight concepts in the areas of fabrication and thermal performance. The breadboard consists of an acrylic fluid test tank that is thermally isolated from the outside environment. Heaters on the tank introduce controlled energy into the fluid, a room temperature refrigerant used as a cryogenic fluid simulant, whose temperature and pressure rise is accurately measured over time. A mechanically pumped fluid loop circulates the refrigerant in the chamber to distribute heat and control pressure, and velocity flow fields are measured using Particle Image Velocimetry (PIV). The test tank is constructed of stainless steel and acrylic materials. The transparent acrylic portion of the tank allows velocity flow field measurements, at rates of 1 μm/s to 2 mm/s using PIV. The lower stainless steel portion of the test tank provides a structural mounting platform while facilitating the installation of fluid fittings and a pressure transducer. The test tank is mounted within a sealed vacuum jacket to limit convective and radiative heat transfer. The enclosure is constructed of aerospace grade aluminum that has been electroless nickel coated. The internal surfaces have been highly polished for low emissivity to reduce radiative coupling between the test tank and vacuum enclosure; temperature matching the jacket to the tank further reduces the radiative heat loss. Hermetic connections provide fluid line and sensor access to the test tank. Strip heaters mounted to the test tank and vacuum enclosure allow precise power input. Eighty-seven high precision RTDs are mounted internally and externally to the test tank and vacuum jacket to provide a detailed mapping of the system's thermal profile.

Long term space habitation on the moon or mars will require a constant food and water supply. Struvite, the precipitate formed in urine, can be used as a nutrient source for the growth of crops. The supernatant remaining after precipitation is a water source that must be reclaimed in order to maintain a constant water supply. The objective of this investigation was to characterize the urine supernatant in order to facilitate the development of a water reclamation method. Additionally, the investigation sought to identify any potential benefits of the urine supernatant for other applications on a space habitat. The high levels of organic contaminants found within the urine supernatant indicated that a combination of biological, physical, and chemical treatments must be employed in order to reclaim the urine supernatant as potable water. The urine supernatant also displayed a buffer capacity that could be useful in applications such as maintaining pH within the wastewater collection tank.

A full-scale mockup of the future Lunar Lander habitat was constructed based on the dimensions defined in NASA's November 2005 Exploration Systems Architecture Study (ESAS). An initial goal of the project was to establish methods and procedures for constructing a rapidly reconfigurable engineering prototype while concurrently using the analogue as a means of developing systems-level requirements based on anticipated operational concepts. The use of cost effective materials in the mockup provided a simplified approach for construction of system concepts and readily allowed subsequent configuration changes. The application of rapid prototyping provides a means of incorporating a hands-on `human in the loop' component to spacecraft system design and technology test bed. This ongoing effort is intended to be used to help evaluate vehicle configuration options, determine subsystem mass and volume budgets, reduce risk factors and derive requirements before the Lunar Lander preliminary design review (circa 2013).

The Interphase Transport Phenomena laboratory (ITP) at Texas A&M University (TAMU) has developed and tested a microgravity dehumidification system. This system utilized the Microgravity Vortex Separator (MVS) developed at TAMU to significantly reduce humidity levels in air, separate and accumulate the water removed from the air, and reduce air temperature through direct contact heat exchange. This device operates by producing and managing fluid vortices within a cylindrical separation volume. For the Vortex Dehumidification System (VDS) separator, a liquid vortex provides a replacement for gravitational acceleration in the form of centrifugal acceleration. Warm and humid air passes through cold water. Thermal energy is rapidly exchanged between the two phases, lowering the air temperature to that of the water and removing water vapor present in the air through condensation. This condensate is separated to the liquid layer and either accumulated or removed and recycled. Testing of this concept was conducted both in the laboratory facilities at TAMU and aboard a reduced gravity aircraft. For air with an inlet temperature of 23.3 degrees Fahrenheit with an absolute humidity of 22.5 g/m³, 0.02 g/s of water vapor was condensed from a constant air flow rate of 25 SLPM while maintaining complete phase separation during microgravity periods. Moreover, TAMU has tested MVS designs with volumes in excess of 2 L that are capable of processing hundreds of SLPM of gas flow with no loss of separation performance.

The National Aeronautics and Space Administration's (NASA) future plans for long-term spaceflight will require a wastewater recovery system in order to supply enough water to complete missions. The primary sources for wastewater in manned spacecraft are humidity condensate, hygiene water and urine. Prior to wastewater collection, urine is pretreated in order to prevent clogging of the small diameter collection tubes by biofilm formation and solids precipitation. The current urine pretreatment chemicals are toxic and contaminate the other sources of wastewater preventing the reclamation of potable water. The objective of this research was to identify nontoxic urine pretreatment agents that best prevent solids precipitation and bacterial growth. Two acids, glycolic and acetic, were chosen based on their desirable oxidative properties and low pKa values. Both chemicals maintained constant concentrations of Total Suspended Solids (TSS), which indicates that urine precipitation was prevented, and pH levels in the range of two to four. Conflicting test results for the prevention of bacterial growth were inconclusive based on the nitrate and ammonia concentration trends.

One of the most powerful techniques for the characterization of mineral samples is Electron-induced Energy-Dispersive X-ray Fluorescence Spectroscopy (EDX-XRF). If used for resolving the elemental composition for samples in their natural state, high spatial resolution data will provide insight into geological processes and formation mechanisms of planets and other solar system objects. By correlating the XRF with other spectra (eg XUV and optical luminescence) additional information could be obtained about the bonding structure and oxidation states for the minerals. To date, all in situ missions have carried some form of an XRF instrument. For example, the APXS instrument aboard the Mars Pathfinder and MER determined bulk" averaged elemental composition over areas of several cm in diameter. The spectrum acquisition time required to resolve the XRF spectrum was several hours. In order to obtain spatial maps, the spectrum acquisition time must be decreased and the spatial resolution of future XRF instruments increased in comparison to the current methods.

The miniature instrument with a triple measurement system, works as a robotic field geologist on remote planetary surfaces such as Mars or the Moon. This Mineral Identification and Composition Analyzer (MICA), employs XRF, XRD, and visual imaging for in-situ nondestructive determination of mineralogy and elemental composition of rock or regolith samples. Its key feature is characterizing geological materials without destroying, damaging, or removing the sample from its in-situ location. MICA addresses two key issues: 1) Mars geology/astrobiology relating to physical and chemical evidence of water and its processes and 2) lunar in-situ resource utilization (ISRU). A 1.5 kg MICA prototype was developed and built under NASA MIDP (Mars Instrument Development Project) and demonstrated with calibration samples and natural rocks on the NASA Ames K-9 test rover robotic arm. MICA serves as a reconnaissance sensor, providing rapid, 10–30 minute analyses for making decisions about further analysis, sample collection, or sample return from a planetary surface.

The lunar surface habitat will serve as the astronauts' "home on the moon," providing a pressurized facility for all crew living functions and serving as the primary location for a number of crew work functions. Adequate volume is required for each of these functions in addition to that devoted to housing the habitat systems and crew consumables. The time constraints of the LAT-2 schedule precluded the Habitation Team from conducting a complete "bottoms-up" design of a lunar surface habitation system from which to derive true volumetric requirements. The objective of this analysis was to quickly derive an estimated total pressurized volume and pressurized net habitable volume per crewmember for a lunar surface habitat, using a principled, methodical approach in the absence of a detailed design. Five "heuristic methods" were used: historical spacecraft volumes, human/spacecraft integration standards and design guidance, Earth-based analogs, parametric "sizing" tools, and conceptual point designs. Estimates for total pressurized volume, total habitable volume, and volume per crewmember were derived using these methods. All methods were found to provide some basis for volume estimates, but values were highly variable across a wide range, with no obvious convergence of values. Best current assumptions for required crew volume were provided as a range. Results of these analyses and future work are discussed.

Airlocks for lunar Extravehicular Activity (EVA) will be significantly different than previous designs. Until now, airlocks operated infrequently and only in the "clean" weightless environment, but lunar airlocks are planned to be used much more often (every other day) in a dusty, gravity environment. Concepts for airlocks were analyzed by the NASA, JSC Habitability Focus Element during recent lunar outpost studies. Three airlock types were identified; an Airlock (AL) or independent pressure vessel with one hatch to the outside and the other to the Habitat. A Suitlock (SL) which shares a pressure bulkhead with the Habitat allowing rear-entry suits to remain on the dusty side while the crew enters/exits the Habitat. The third option is the Suitport (SP) which offers direct access from the habitable volume into an externally mounted suit. The SP concept was not compared, however between the AL and SL, the AL was favored.

The Lunar Habitat Configuration Assessment evaluated the major habitat approaches that were conceptually developed during the Lunar Architecture Team II Study. The objective of the configuration assessment was to identify desired features, operational considerations, and risks to derive habitat requirements. This assessment only considered operations pertaining to the lunar surface and did not consider all habitat conceptual designs developed. To examine multiple architectures, the Habitation Focus Element Team defined several adequate concepts that warranted the need for a method to assess the various configurations. The fundamental requirement designed into each concept included the functional and operational capability to support a crew of four on a 6-month lunar surface mission; however, other conceptual aspects were diverse in comparison. The methodology utilized for this assessment consisted of defining Figures of Merit (FOMs), providing relevant information, and establishing a scoring system. In summary, the assessment considered the geometric configuration of each concept to determine the accessibility to the lunar surface and the complexity of unloading, handling, mobility, leveling, aligning, and mating to other elements. In theory, the assessment was designed to derive habitat requirements, to determine potential technology development needs, and to identify risks associated with living and working on the lunar surface. Although the results were more subjective than objective, the assessment provided insightful observations for further assessments and trade studies of lunar surface habitats. This overall methodology and resulting observations will be described in detail and illustrative examples will be discussed.

The Lunar Architecture Team Phase 2 study defined and assessed architecture options for a Lunar Outpost at the Moon's South Pole. The Habitation Focus Element Team was responsible for developing concepts for all of the Habitats and pressurized logistics modules particular to each of the architectures, and defined the shapes, volumes and internal layouts considering human factors, surface operations and safety requirements, as well as Lander mass and volume constraints. The Structures Subsystem Team developed structural concepts, sizing estimates and mass estimates for the primary Habitat structure. In these studies, the primary structure was decomposed into a more detailed list of components to be sized to gain greater insight into concept mass contributors. Structural mass estimates were developed that captured the effect of major design parameters such as internal pressure load. Analytical and empirical equations were developed for each structural component identified. Over 20 different hard-shell, hybrid expandable and inflatable soft-shell Habitat and pressurized logistics module concepts were sized and compared to assess structural performance and efficiency during the study. Habitats were developed in three categories; Mini Habs that are removed from the Lander and placed on the Lunar surface, Monolithic habitats that remain on the Lander, and Habitats that are part of the Mobile Lander system. Each category of Habitat resulted in structural concepts with advantages and disadvantages. The same modular shell components could be used for the Mini Hab concept, maximizing commonality and minimizing development costs. Larger Habitats had higher volumetric mass efficiency and floor area than smaller Habitats (whose mass was dominated by fixed items such as domes and frames). Hybrid and pure expandable Habitat structures were very mass-efficient, but the structures technology is less mature, and the ability to efficiently package and deploy internal subsystems remains an open issue.

This paper will describe an overview of the Lunar Architecture Team phase 2 (LAT-2) Option-4 architecture surface habitation definition performed during LAT-2. The LAT-2 architecture study focused on three primary habitation strategies. The three strategies are 1) habitats that are small, modular, and unloaded from the lander to create an outpost, 2) a monolithic habitat strategy that remained on the lander, and 3) habitats that remain on the lander and are mobile. This paper will describe the 2.75 meter diameter by 5 meter long mini.habitats that were defined for the Option 2 architecture. Each mini-hab is an aluminum.lithium pressure shell with an integrated cargo frame used for handling, integration with the lander, and surface emplacement. Each mini.hab contains 27.5 cubic meters of volume and 5 mini-habs are used to make up the outpost. The modular mini.habs allows for flexibility and adaptability to the lander integration and emplacement on the surface. This paper will describe the mass and master equipment list of the systems. The internal architecture and configuration will be described.

This paper will describe an overview of the Lunar Architecture Team phase 2 (LAT-2) Option-4 architecture surface habitation definition performed during LAT-2. The LAT-2 architecture study focused on three primary habitation strategies. The three strategies are 1) habitats that are small, modular, and unloaded from the lander to create an outpost, 2) a monolithic habitat strategy that remained on the lander, and 3) habitats that remain on the lander and are mobile. The option 4 architecture focuses on the mobility aspects of a lunar outpost. Each habitation unit is 3.0 meters diameter by 8.5 meters long. Each is an aluminum-lithium pressure shell integrated with the lander and mobility system. Each habitat unit contains 55 cubic meters of volume and 3 habitats are used to make up the 165 m3 outpost. As part of the outpost architecture a mobile habitat and laboratory was defined to provide the long range mobile exploration capability. This paper will describe the mass and master equipment list of the systems. The internal architecture and configuration will be described.

In the eve of a manned return to the Moon and following the requirement for a permanent base design proposals and alternatives must be evaluated before a final decision is taken. In this paper we want to define a design proposal based on architectural as well as technological requirements, based on a minimum number of missions and the definition of design parameters that could help during the evaluation process. The resulting design is a permanent base built with the hardware and equipment provided by two missions, one for a habitat unit the other for a cargo unit. The habitat unit is a three story facility of 5,50m diameter and 6.5 m height that can be stored in the proposed Ares V spacecraft and containing all requirements and spaces for an independent unit. The cargo unit, while being of the same size contains all equipment and hardware for life support, rover and external components. All design details are described in the technical paper.

A three-dimensional (3-D) frame-membrane structure covered with regolith shielding and pressurized internally has been proposed as a possible lunar habitat. This paper presents results from the dynamic impact analysis of the structure using nonlinear (large deformation) finite element technique. Results are presented taking into account the effect of the added mass of regolith and stress stiffening due to applied internal pressurization load. The impact load is considered arising from a moving object/debris/projectile hitting a membrane panel of the structure. The results show that both pressurization and added mass affect the displacement and stress response of the structure under the impact load. At the membrane node, the internal pressurization (prestressing) has greater effects to reduce the amplitude of oscillation of the vertical displacement in the case of without the added regolith mass than that in the case of with the added regolith mass. However, for the frame member nodes, when there was no added mass of regolith the amplitude of displacement seem to reduce slightly or remain the same due to pressurization. However, the effect due to pressurization is observed to be just the opposite (i.e. the displacement amplitude increased) when there was added mass of regolith.

Pneumatic, pliable membrane structures have found a variety of useful applications on Earth and in space to provide rapidly and easily deployable large volume enclosures that can be transported in compact forms. These characteristics offer particularly important advantages for habitats destined for remote and inhospitable sites where erection times are critical and construction equipment and labor resources are minimal. Such conditions characterize locations where housing shelters are needed following natural and man-made disaster events as well as orbital and lunar/planetary surface facilities. This paper will discuss fundamental differences and similarities between design requirements for terrestrial and extraterrestrial pneumatic structures and will offer illustrative examples of both. An obvious and defining characteristic of any space habitat is a need to retain large internal pressures in an external vacuum environment without significant atmospheric leakage. Means to provide radiation, meteorite/debris and thermal protection in harsh space environments also present vital design priorities. All of these requirements add complexities and weight that distinguish them from much simpler alternatives on Earth. Terrestrial membrane structures can rely upon very small internal pressure differentials between inside and outside atmosphere for support, or alternatively, can incorporate rigidizing structural air tubes into the envelope. The second option eliminates a need to continually add air into the structure, can eliminate the requirement for an air trap at the entrance, and affords structural redundancy in the event of localized damage to the envelope or an air supply failure. The relative volumetric spatial advantages of all pneumatic membrane structures increase with size, and particularly as a function of diameter (in space) or floor span (on Earth). This makes them particularly well suited for large-scale applications to accommodate long-term, crew-intensive space missions or multi-family, community-sized disaster victim populations. Representative design concepts for both types of circumstances will be presented along with general planning considerations.

Sustainability is a key consideration in the design and establishment of human habitats on the Moon (and on Mars as well). One hazard faced by such habitats is the damage that can be caused by the impact of a meteoroid on a critical habitat structure or structural component. In this paper we discuss various approaches to meteoroid shielding for lunar habitats, focusing on approaches that use resources mined or extracted from the moon. Advantages and disadvantages of these various techniques are also presented and discussed. The Moon's mineralogy is highlighted, and suggestions are presented for materials that can be used to develop meteoroid shielding for lunar habitats and which are comprised primarily or entirely of lunar materials. The paper concludes with recommendations for continuing work in optimizing the design of meteoroid shielding for lunar habitats, including suggestions for a test program that can be performed to garner data on the effectiveness of some of the proposed shielding approaches.

This paper will draw parallels and define differences between factors that drive the planning and design of human surface facilities in space and in extreme environments on Earth. Primary emphases will highlight influences upon general habitat requirements, constraints upon delivery and construction, and special provisions for safety and hazard interventions. The overall intent is to identify important lessons that can be applied across different settings which present common priorities, issues and challenges. Such environments include future bases on the Moon and Mars, offshore surface and submersible facilities, polar research and oil/natural gas exploration stations, military desert operations, and natural and man-made emergency shelters. Important topics of emphasis include the following considerations: 1) Design influences driven by transport to remote sites; 2) Environmental influences upon facilities and construction; 3) Influence of crew sizes, types activities and occupancy durations; 4) Influences of construction methods and support infrastructures; 5) Special safety and emergency response requirements. This presentation will draw upon research and design experiences and examples at the Sasakawa International Center for Space Architecture (SICSA). Information is also taken from a SICSA-sponsored conference "International Design for Extreme Environments One" (IDEEA-One) at the University of Houston which attracted more than 400 interdisciplinary participants from 12 countries representing diverse professions and environmental settings.

A series of studies is conducted to develop a systematic approach to optimizing—both in terms of the distribution and scheduling of tasks—scenarios in which astronauts and robots accomplish a group of activities on the Moon, given an objective function (OF) and specific resources and constraints. An automated planning tool is developed as a key element of this optimization system. For the first two studies, astronaut safety is given foremost priority, and the automated planner's primary OF is minimizing the amount of time spent in extravehicular activity (EVA), with minimization of intravehicular activity (IVA) as a secondary OF. This is accomplished through the use of a robot, teleoperated from Earth, which relieves the astronauts of some of the work. For the third study, currently in progress, the OF is revised to maximize scientific productivity, achieved by having astronaut geologists work the most EVA hours that are deemed consistent with safety. Minimizing the robot's idle time, when it wastes power waiting for the astronauts to enable its next activity, becomes an additional element of the OF. A much more complex scenario is developed for a better demonstration of the value of an automated planner.

This paper summarizes the major themes and ideas presented at a 4 1/2 day symposium on lunar settlements held at Rutgers University in June, 2007, sponsored by the Department of Mechanical and Aerospace Engineering and organized by Haym Benaroya of that department. Presentations covered the political and economic aspects of lunar settlements, structures and transportation, the lunar environment, energy and power, medical aspects of lunar settlements, outpost site selection, and use of the Moon as a platform for astronomy. A keynote paper by H.H. Schmitt covered topics including legal aspects of lunar settlements and possible economic products such as helium-3, demonstrably valuable for production of short-lived medical isotopes and perhaps for thermonuclear energy. Potential medical problems, discussed by several speakers, including J. Logan and W. Rowe, included radiation exposure and the effect of long-term hypogravity, Lunar resources discussed by several speakers include lunar water from possible polar ice deposits, hydrogen, helium-3, and oxygen from the lunar regolith. Outpost site selection has been narrowed to the south polar regions, with Shackleton Crater and Malapert Mountain the most-favored candidates. Lunar settlement shelters were proposed by several speakers, a consensus being that these must be largely underground because of the radiation problem. The feasibility of agriculture in lunar settlements has been demonstrated by operating greenhouses in the Antarctic. The overall result of the symposium was a summary of the problems, prospects, and practicality of such settlements, now benefiting from three decades to assimilate the lunar experience of the 6 Apollo landing missions and the many robotic missions, American and Soviet.

The research described in this paper is developing a high performance computing simulation testbed to produce a Virtual Autonomous Navigation Environment (VANE). The VANE will facilitate virtual testing of unmanned systems for evaluation of autonomous navigation systems and their associated hardware/software subsystems. The research is using mature, new, and emerging technologies to advance a physics-based, terrain-enriched, virtual environment for ground vehicle and terrain interactions based on sensor perceptions. This research is being conducted by the US Army Engineer Research and Development Center (ERDC), and it is leveraging capabilities of the Institute for Maneuverability and Terrain Physics Simulation (IMTPS). IMTPS research has been used to develop a successful high performance computing simulation testbed that produces realistic synthetic images that include the effects of geoenvironmental influences involving the ground surface and subsurface, vegetation, and meteorological conditions on sensor responses. The application of the IMTPS research for vehicle, terrain, and sensor interactions is the VANE product. This virtual environment will supplement field evaluations at a reduced cost and with better control and repeatability than can be obtained from physical testing. This paper provides an overview of the approach for developing the VANE.

Missions to Mars aim to characterize rock and subsurface soil samples and possibly bring some back to Earth for more thorough and sophisticated examination. The Martian surface is known to be partially covered with basalt which has high compressive strength, and is more difficult to drill than the much softer sedimentary formations. The experiments were designed to study the tool-wear mechanisms and to understand the associated effects on drilling of basalt. Core drilling experiments were conducted under different cutting conditions on the Martian simulant, basalt. Thrust force and torque were monitored and drill-wear was measured for each drilling test condition for a series of successive depth-increments. Based on the experimental results an optimization model was developed for maximizing the drilling depth at minimum tool-wear. This preliminary work is expected to help the development of smart drills for sustainable dry drilling applications in future NASA missions to Mars.

This paper details the engineering development and testing of the SAMURAI manipulator and AVATAR autonomous vision system. A number of developmental challenges were met and overcome, including severe limits on in-water weight and power available from the carrier AUV, selecting sensors for actuator positional feedback capable of operating at pressures up to 8000 psi, and keeping the system robust enough to survive the rough handling expected on shipboard. Extensive use was made of technologies developed for space flight in the SSL's Ranger Telerobotic Shuttle Experiment, leading to the first-ever use of distributed "intelligent" actuator modules and a modular manipulator design for underwater applications. Although external events prevented the planned sea trials in 2006, work is ongoing to integrate SAMURAI/AVATAR to various undersea vehicles for operational use. This paper further discusses potential applications of the SAMURAI/AVATAR architectures and technologies to planetary exploration tasks beyond those of Europa-type oceans. Extensions of the Arctic sampling system would enable a number of high-priority near-term objectives in planetary exploration, most specifically a Mars sample collection and return mission.

Robotic planetary exploration missions are becoming increasingly sophisticated and ambitious, with future missions contemplating the collection and return of surface and subsurface samples to Earth for detailed analysis. In many ways, collecting and returning samples from a planetary surface mimics geologic and soil sampling in remote terrestrial locations. This paper provides a review of lessons learned from geotechnical field investigations in remote areas and areas with difficult access that can be applied to future robotic field investigations. Specifically, the pros and cons of digging and sampling exploratory trenches are weighed against potential drilled sample collection techniques.

Resistance to lateral forces will be critical to shaping the lunar surface on manned or robotic missions. The development of an efficient and stable regolith anchor will require significant research and experimentation prior to a lunar mission. This paper describes experimental research into the behavior of helical anchors as a function of depth, shaft size, and anchor plate diameter in the context of the lunar surface. Through the application of the principles of centrifuge modeling in soil mechanics, scaling effects and the difference between the earth-based model and the lunar prototype are rigorously accounted for. Using a crude lunar simulant, a series of experiments were undertaken to investigate varying installation parameters and their respective effects on anchor behavior. Soil test beds were compacted inside a containment bin using a plate compactor in multiple lifts in order to simulate a typical lunar surface condition. Anchors were then installed vertically and lateral loads were applied to them at the sample surface; measurements of horizontal and vertical displacements, and magnitude of the applied lateral load were made. These results can be used as a preliminary basis for designing screw-in anchors for use in various operations on the lunar surface.

Grading and excavation machines of the future will possess greater autonomy. For these machines to operate safely, especially in human-occupied environments, it will be necessary for them to possess real-time, automated perception. We are currently engaged in a cooperative project between NASA, Caterpillar Inc., and TRACLabs Inc., which includes the development, integration and testing of 3d vision on a Caterpillar-MTL (Multi-Terrain Loader). Recently, a milestone in this project was achieved when the MTL was intentionally driven (via remote control) toward a human subject. As the machine approached, it sensed the human and appropriately signaled with its headlights. If/when the human failed to evacuate the intended path, the MTL would then revert to "safe-mode" in which it appropriately halted. Herein we discuss the vision technology used in this experiment as well as adaptations to the MTL's control system which enabled modular integration. Critical features of the 3d, LIDAR-based, vision system include the ability to operate in real-time and under a variety of conditions including total darkness. Real-time, processing of 3d data is achieved through a novel implementation of the ICP (Iterative closest point) algorithm. A brief overview of future goals for the on-going project is included.

A variety of space applications require the delivery of power into sealed structures. Since the structural integrity can be degraded by holes for cabling we present an alternative method of delivering power and information using stress waves to the internal space of a sealed structure. One particular application of this technology is in sample return missions where it is critical to preserve the sample integrity and to prevent earth contamination. Therefore, the container has to be hermetically sealed and the integrity of the seal must be monitored in order to insure to a high degree of reliability the integrity of the sample return vessel. In this study we investigated the use of piezoelectric acoustic-electric power feed-through devices to transfer electric power wirelessly through a solid wall by using elastic or acoustic waves. The technology is applicable to a range of space and terrestrial applications where power is required by electronic equipment inside sealed containers, vacuum or pressure vessels, etc., where holes in the wall are prohibitive or may result in significant structural performance degradation or unnecessarily complex designs. To meet requirements of higher power applications, the feasibility to transfer kilowatts level power was investigated. Pre-stressed longitudinal piezoelectric feed-through devices were analyzed by finite element models and an equivalent circuit model was developed to predict the power transfer characteristics to different electric loads. Based on the results of the analysis a prototype device was designed, fabricated and a demonstration of the transmission of electric power up to 1.068-kW was successfully conducted. Efficiencies in the 80–90% range were also demonstrated and methods to increase the efficiency further are currently being considered.

The paper provides a summary review of the properties, modeling and applications of piezoelectric polymers. Attention is focused on the results of a consistent experimental program directed to characterize the mechanical response of polyvinylidene fluoride (PVDF) under static and cyclic loading conditions. Experimental results demonstrate that, within certain limits, the properties of PVDF can be represented by the constitutive law of linear viscoelasticity. The behavior of PVDF subjected to combined static and cyclic loads is characterized by much higher creep rates as compared with creep deformations under static loading conditions. This phenomenon is attributed to creep-fatigue interaction effects. Practical implications of these findings and future research directions are discussed.

Future NASA missions are increasingly seeking to actuate mechanisms to precision levels in the nanometer range and below. Co-fired multilayer piezoelectric stacks offer the required actuation precision that is needed for such mechanisms. To obtain performance statistics and determine reliability for extended use, sets of commercial PZT stacks were tested in various AC and DC conditions at both nominal and high temperatures and voltages. In order to study the lifetime performance of these stacks, five actuators were driven sinusoidally for up to ten billion cycles. An automated data acquisition system was developed and implemented to monitor each stack's electrical current and voltage waveforms over the life of the test. As part of the monitoring tests, the displacement, impedance, capacitance and leakage current were measured to assess the operation degradation. This paper presents some of the results of this effort.

The limited travel capability of conventional piezoelectric actuators has prevented their adoption in many longer-travel applications where magnetic actuation remains dominant. But the subatomic resolution, high acceleration, cool operation, vacuum compatibility, fieldlessness, stability, reliability and inherent stiffness of piezoelectric mechanisms present many valuable benefits. Recent innovations in piezoelectric-based actuation break through the former travel constraints, bringing the benefits of piezoelectric actuation into applications requiring many millimeters of travel. The novel actuation concepts are proving to be enablers for next-generation applications in fields as diverse as aerospace, semiconductor microlithography, data storage, life sciences and photonics. This paper briefly reviews the fundamentals of piezo actuation, the origins of its characteristics, and the classical approaches employed to address its shortcomings. We then explore several recent advances which form the basis of entirely new piezo-based mechanisms, some with essentially unlimited travel but which retain the rest of piezo actuators' signature benefits. Several of these new mechanical approaches are of potential value for innovative active structures. In addition, significant progress has been made in further burnishing the reliability of conventional layered piezo actuators and reducing their susceptibility to humidity; these approaches are reviewed and the reliability benefits are presented quantitatively.

Identification and delineation of Land use/ Land cover, location, extent and their spatial distribution patterns are possible through Remote Sensing (RS) because of its synoptic view and its ability to resolve both macro and micro details on a single imagery. The preliminary objective of this paper is to evaluate watershed parameters using remote sensing and geographic information systems for Palleru sub basin (K-11) of River Krishna, Andhra Pradesh, India for a period of 1989 to 2002. NDVI concept has been used to evaluate land use/ land cover in this study area. Spatial and temporal variations were analyzed. Four classes were identified in the study area. Further, the secondary objectives of the present study is to develop different maps like slope map, soil map, contour map, flow direction map, flow accumulation map, mandal wise administrative boundary map, Digital Elevation Model (DEM) map, Thiessen polygon coverage, Aspect map, Viewshed map and drainage map in GIS environment. To prepare Land use /Land Cover map using ERDAS through Satellite imageries. The extracted watershed parameters will be useful in watershed hydrology and irrigation water management effectively.

In his 1872 fictional story "From the Earth to the Moon", Jules Verne imagined the Moon as a favorite destination for tourists and a great place for commerce. Since then, we have seen the emergence of big airplanes and space flight has attracted private citizens to pay millions of dollars to visit the International Space Station. Indeed, space holds an attraction to people and industry that go far beyond satellites and short visits. As Jules Verne predicted, people want to reside on the Moon and Mars, living and working on research or high-tech fabrications. While Korea has already successfully deployed satellites, it is looking to step further. This paper presents the result of a survey designed to get a feeling of what the common people believe the status of the Korean space program is. Based on 324 analyzed questionnaires it was found that ordinary people opinion not only appropriate space development about commercialization in Korea. A follow up and expansion of the survey is planned for after the launch of National Space Development in the fall of 2008.

Construction in space is a very specialized process that requires a number of steps to guarantee its success and safety. Appropriate space construction policies and laws should include a conscientious concern about the health, safety, and educational welfare of those building in space. Space builders must take more precautions than normally exercised on Earth. Adding to the level of difficulty is dealing with minorities such as Hispanics, Asians, etc. They require social, psychological, and language needs that are unique to that population, and appropriate construction safety laws must consider these characteristics. Only translating from one language to another will not result in the needed goals; complete immersion with minorities at a work site, along with special consideration of their demographic characteristics, is essential aspect to any training program in order to reduce fatal injuries at a work site. This paper will address the needs of space construction safety policies and laws that are especially geared toward minorities' needs and will help them participate actively in the safety programs that OSHA or any other space agency manages. The paper is based on the social, cultural, and religious aspects of minorities as well as the language differences and space policies related to minorities. Additionally, the research related to this paper will produce a "work site sensitivity study" that may form the basis for future policies related to training minorities at space construction sites.

Space is the final frontier. It has been forty years since mankind ventured into this frontier but since the moon landings the advancement towards space settlement seems to have halted. One of the main reasons has been the phenomenal costs associated with space travel. A viable solution has been proposed in this paper in the form of creating a global entity for the exploration and settlement of space. It is discussed that with one global organization coordinating the efforts of space exploration and settlement the barrier of costs would be overcome. The importance and significance of a global organization is highlighted along with the goals which the organization would follow. The paper also discusses the commercial aspects which such an organization might be able to venture into.

PISCES, the Pacific International Space Center for Exploration Systems, is being developed on the Big Island of Hawaii as an integrated research facility and simulated lunar settlement for the purpose of developing new technologies needed for a sustained human presence on the Moon and Mars. PISCES was created by the University of Hawaii under the auspices of the Japan-US Science, Technology and Space Applications Program (JUSTSAP), and has recently been funded by the State of Hawaii through the Department of Business, Economic Development and Tourism (DBEDT). This new center will be built on partnerships between industry, academia and the governments of spacefaring nations, adopting a model that has seen wide success in such programs as the NASA Research Partnership Centers (RPCs), the NASA Robotic Engineering Consortium at Carnegie Mellon University, and numerous programs within NIST, the Department of Commerce and the National Science Foundation. In addition to its research and development mission, PISCES will function as an education, research and technology development center; a training center for astronauts, scientists, K-12 and university students; and a public outreach resource for local residents and tourists to experience the multitude of scientific, educational and economic benefits that space exploration could bring to Hawaii. New technologies developed in PISCES and at universities and industries around the world will require testing in an environment simulating as closely as possible that found on the Moon. Several nations plan robotic exploration missions to the Moon in the next few years, and PISCES will be an important proving ground for hardware developed through collaborative projects in science and technology. To validate space operations, new system architectures, designs, materials and mechanisms had to be developed, such as a robotic vehicle called ATHLETE (the All-Terrain Hex-Limbed, Extra-Terrestrial Explorer), and materials had to be utilized from space. This ATHLETE vehicle concept is capable of efficient rolling mobility on moderate terrain and walking mobility on extreme terrain. Each limb has a quick-disconnect tool adapter and associated tools so that it can perform general-purpose handling, drilling, scooping, assembly, maintenance and servicing tasks using any or all of the limbs. Each of ATHLETE's 6-degree freedom limbs is equipped with non-pneumatic, lunar-appropriate, compliant wheels to enable rolling mobility in soft soil. Also, new ISRU materials and designs had to be developed to accommodate the space environment to sustain human settlements, deal with moon dust, and ensure very long-duration operations. Astronauts embarking on exploration missions and long stays on the Moon will need training in the use of these new technologies to free themselves from the drudgery of routine chores and to increase their time for scientific and technological achievements. This paper describes the PISCES development plans, particularly in the areas of In-Situ Resource Utilization, Robotics and Education and Outreach.

Alvin Toffler who is a futurist predicted that jumping at space would bring fortune revolution changing. He estimated that if we invest 1 dollar in space industry, it would bring 7 to 12 dollar benefit. The USA and Russia, advanced countries in space project, has numerous experiences and technologies for space project. We analyzed cases of advanced nations, and we took a survey the instance of Japan and China which are developing countries in space development. Throughout the examples, the results lead lesson-learned and gain the advertisement strategy for newly entering countries. Therefore, we will suggest the new space development strategies for the countries that entering the space project newly.

The President's Vision for Space Exploration — National Security Presidential Directive (NSPD) # 31 and U.S. Space Transportation Policy — NSPD # 40 both require continued access to Low Earth Orbit (LEO) over the long-term. However, there is a growing possibility that changing climate trends pose risks to our Nation's critical spaceport and LEO transportation capabilities. Managing climate change risk is a growing field of study, but there are no known systematic approaches that have been applied to spaceports to date. Potential hazards to U.S. spaceports are generally recognized as changes to precipitation, temperature, sea level change, extreme weather events, and related natural hazards, but the site-specific risk characterizations required for risk management have not been systematically applied to these critical national assets. Existing tools and framework resident within NASA's own Goddard Institute for Space Studies (GISS) are well-suited for the task of better understanding NASA's spaceport and mission support risks related to climate change. The GISS approach manages uncertainty and enables risk characterization and adaptation using multi-model probabilistic forecasts tailored to users' site-specific region, variables, and timeframe. This proactive approach enables anticipatory adaptation for infrastructure planning and operations cycles, and risk reduction for our Nation's critical spaceport infrastructure.

On the moon, there is little construction facility and particles. Inflatable system is deploying the membrane and then air pressure makes it shelter. Its lightness and easy transportation is of advantages to lunar outpost. But if pressurized space is too large, material should be thick and deploying need carefully concerned. Today, actual inflatable system has 2.5 meters in diameter. This study propose that an inflatable system, which will include a large space for communal living. At first, decide a method of making large shelter. It was composed with sphere units. Units assembled by wire. Second, units' position was concerned by geometrical study. Finally, proposed figure is estimated by size and energy generation. In addition to that model and drawings show variation of transformation.

The U.S. Space Exploration Policy has as a cornerstone the establishment of an outpost on the moon. This lunar outpost will eventually provide the necessary planning, technology development, testbed, and training for manned missions in the future beyond the Moon. As part of the overall activity, the National Aeronautics and Space Administration (NASA) is investigating how the in situ resources can be utilized to improve mission success by reducing up-mass, improving safety, reducing risk, and bringing down costs for the overall mission. Marshall Space Flight Center (MSFC), along with other NASA centers, is supporting this endeavor by exploring how lunar regolith can be mined for uses such as construction, life support, propulsion, power, and fabrication. An infrastructure capable of fabrication and non-destructive evaluation will be needed to support habitat structure development and maintenance, tools and mechanical parts fabrication, as well as repair and replacement of space-mission hardware such as life-support items, vehicle components, and crew systems. This infrastructure will utilize the technologies being developed under the In Situ Fabrication and Repair (ISFR) element, which is working in conjunction with the technologies being developed under the In Situ Resources Utilization (ISRU) element, to live off the land. The ISFR Element supports the Space Exploration Initiative by reducing downtime due to failed components; decreasing risk to crew by recovering quickly from degraded operation of equipment; improving system functionality with advanced geometry capabilities; and enhancing mission safety by reducing assembly part counts of original designs where possible. This paper addresses the need and plan for understanding the properties of the lunar regolith to determine the applicability of using this material in a fabrication process. This effort includes the development of high fidelity simulants that will be used in fabrication processes on the ground to drive down risk and increase the Technology Readiness Level (TRL) prior to implementing this capability on the moon. Also discussed in this paper is the on-going research using Electron Beam Melting (EBM) technology as a possible solution to manufacturing parts and spares on the Moon's surface.

It is likely that the first structures suitable for human habitation on the Moon will be surface structures. This is because without an adequate infrastructure, especially power sources, it is very difficult to do any construction. Once we have a presence on the Moon we will be able to begin to use local resources to supplement imported materials for building. This paper summarizes some of these initial steps to utilizing ISRU for expanding the human presence on the Moon and also introduces the concept of synergistic interdependencies with Mars settlements.

Several processes to produce water and oxygen from lunar regolith have been proposed. Among these processes, hydrogen reduction process of lunar regolith has several advantages. Therefore, we have investigated the water-production mechanism by H₂ reduction for three types of lunar soil simulants. The maximum of water-production was obtained for all lunar soil simulants at 1323 K. Mössbauer spectra of FJS-1 revealed that the produced water was generated from ilmenite, Fe³⁺ phase(s), and magnetic materials such as hematite or magnetite. The cross-section observation of scanning electron microscope and BET method presented that the surface area was decreased at higher temperature owing to melting of some components in the cracks, and the surface area was increased as the progress of hydrogen reduction. The kinetic consideration using thermogravimetry indicated that hydrogen reduction for lunar soil was controlled by chemical reaction.

Structural vibration has been always a major concern and this motivates engineers to study and control the undesired vibration on many structures. This paper presents development of an interactive smart flexible beam experiment using a low cost Freescale MC9S12C32 microcontroller. Piezoceramics material is a commonly used smart material that can function both as actuator or sensor. The smart beam has two surface bonded lead zirconate titanate (PZT) patches one as an actuator and other as a sensor. The experiment demonstrates the vibration of the beam at different modal frequencies and active vibration suppression of the beam under Positive Positioning Feedback (PPF) control and Sliding Mode Control (SMC) for the first mode. An interactive user interface with LCD display, keypad and pushbuttons is also developed. Through the use of pushbuttons, the microcontroller excites the beam at the first four modal frequencies and also controls the first modal vibration of the beam using PPF control and sliding mode control. The keypad is used to input a customized excitation frequency value, ranging from 0.1 Hz to 400 Hz. The experiment is multi-functional and can be used for educational as well as research purposes. These experiments can be used in courses related to dynamics, controls, and structures to improve student learning about the subject. For research, this experiment can be used as a test bed to study various PZT based active vibration control algorithms.

In the paper, the bridge and building complex structural system is proposed as a new seismic structural system, and a steel frame complex structural model with the dissipation devices is designed in our research for a large scale shaking table dynamic test. Based on the new complex structural system and dynamic test results, the computation model, design parameters, earthquake response numerical analysis and the earthquake response decrease effect are mainly researched in our research. In this part, the basic concept system of bridge and building complex structural with energy dissipation devices is provided firstly, and a steel frame structural model with total weight 4.5 ton is designed to grasp the earthquake response of complex system. The research results show that the complex structure has a good reduction vibration effect; the acceleration response decreases nearly 50% in horizontal direction for building part. The acceleration response in deck of the bridge of the complex structure the range of decreases 9%∼30% compared to the pure bridge structure system, and the range of the decrease is 8% to 30% for the displacement responses. The dynamic test results show the new bridge and building complex structural system has ideal reduction vibration effect for both parts of bridge and building.

Smart sensors are increasingly used for health monitoring of Civil Engineering structures. Using PZT patch as smart sensor material, smart aggregates were recently developed at the University of Houston. This paper describes the experimental and analytical study of a two-story reinforced concrete frame embedded with smart aggregates at all critical locations including all the beam column joints. The frame was subjected to monotonic lateral loads up to failure. The location and sequential development of the plastic hinges were observed during the testing of the frame. A finite element model of the frame was also developed and analyzed using the computer program developed by the Open System for Earthquake Engineering Simulation (OpenSees) (Fenves, 2005). The analytical behavior of the frame closely resembled the experimental response and the progressive collapse of the frame clearly identified by the analysis. The response of smart aggregates has been utilized to also verify the state of damage of the frame at the instant of formation of plastic hinges as predicted by the analysis.

According to the excellent piezoelectric effect and converse piezoelectric effect, this paper designs and fabricates piezoelectric pivot element bars which can accomplish testing-controlling functions, that is, integrate a piezoelectric stack into the element bars playing a major role to form a so-called piezoelectric pivot element bar, and then integrate this piezoelectric pivot element bar into space steel structure thus to realize an intelligent monitoring and vibration control on space steel structure. Based on the above principle, this paper performs shaking table tests on intelligent vibration control for two models of space steel structure with the piezoelectric pivot element bars applied. By respectively inputting an acceleration record of El-Centro earthquake wave and a simple harmonic load, followed by changing the peak acceleration of earthquake wave and the frequency of simple harmonic wave, this paper investigates the influences of such factors on control effectiveness as the size of piezoelectric stack, the stiffness and deformation of model structure, the magnitude and characteristic of external excitation, and excitation voltage etc.. The experimental results indicate that: 1) the size variation of piezoelectric stack in pivot element bar is of little influence on the effectiveness of structural control; 2) when the amplitude of external excitation is big, for a flexible structure the effectiveness of control is rather conspicuous, but when the amplitude of external excitation is comparatively small, the effectiveness of control is relatively obvious for a stiff structure; 3) if the characteristic of external excitation is kept constant, the control effectiveness of pivot element bar over model structures is increasingly obvious with the increase in magnification times of excitation voltage.

In concrete technology, thermal cracking is a cause of major concern. Thermal cracking in mass concrete is related to both the rate of heat evolution and strength development at any time which are dependent on the historical time and temperature conditions at the particular point in the structure. In this research, reaction heat of concrete was determined with a developed cement hydration model. With the equivalent age method, accurate description of the strength growth of C40 concrete was presented. Then the thermal cracking analysis was carried out by means of the finite element program ANSYS. The analysis results were compared with the experiment results obtained in real practice. A good agreement has been noticed. This research will afford reliable support to design, construction and management of mass concrete structures in theory and practice.

Damping of a structure can be attained by passive or active methods. Passive methods make use of the inherent ability of certain materials (whether structural or non-structural materials) to absorb the vibration energy. Due to the large volume of structural materials in a structure, the contribution of a structural material to damping can be substantial. In this paper, some recent advances on research, development of fiber reinforced damping concrete and its structures for vibration control in mainland China, especially in Harbin Institute of Technology (HIT), P.R.China, are summarized. The main contents include the research of damping capacity (which is expressed by the loss tangent) and stiffness (which is expressed by the storage modulus) of fiber reinforced concrete, the differences on damping property at nonlinear stage, seismic behavior and destructive process and character between the plain concrete frame and fiber reinforced concrete frame were contrasted and analyzed by the experiment of uniaxial hysteresis experiment, the relationship between the damping ability of materials and the damping ratio of structure was built, then the two-story frame structures whose columns built by the fiber concrete were simulated by ANSYS software at earthquake. Finally, some issues to be further researched are pointed out.

Debonding failure has been reported as the dominant failure mode for FRP strengthening in flexure. This paper explores a novel debonding monitoring method for FRP strengthened structures by means of OTDR-based fiber optic technology. Interface slip as a key factor in debonding failures will be measured through sensing optic fibers. FRP pulling tests were conducted to verify the proposed monitoring method. It is found that the proposed method is feasible in slip measurement with high sensitivity, and would be cost effective because of the low price of sensors used, which shows its potential for large-scale applications in civil infrastructures, especially for bridges.

Based on the tunneling effect theory, a piezoresistivity model is presented to predict the resistance change of composite under multi-axis strain. Cement-based composites filled with carbon black (CB) was prepared and the electrical conduct mechanism was found agreement with tunneling effect theory, so resistance between two CB particles is a exponential function of barrier length. Conductive network is composed by infinite of unidirectional CB particles barrier. The external strain applied on composite performed various effect on each barrier because of the orientation angle. The relation between external strain and the deformation behavior of barriers was established, and then the piezoresistance model was established. The model indicated that piezoresistance property of conduct composite is multi-axis strain dependent and can be predicted. Experimental results of piezoresistance agreed well with the theoretical prediction results.

Smart material actuators, as an example, invariably exhibit hysteresis that may be either symmetric or asymmetric depending upon the actuation principle. A classical Prandtl-Ishlinskii model is normally used to describe the symmetric hysteresis. A generalized play operator is formulated and integrated to the Prandtl - Ishlinskii model together with density function to describe asymmetric hysteresis nonlinearities. This hysteresis operator is analysed using different envelop functions in order to illustrate the influence of these functions on the outputs of the generalized Prandtl-Ishlinskii model. Parameters identification for the envelope functions of the generalized play operator and the proposed density function are carried out using a nonlinear optimization technique. The validity of the generalized model is demonstrated by comparing its displacement responses with the measured asymmetric responses obtained for magentostrictive actuator. The results suggest that unlike the classical Prandtl-Ishlinskii model, the generalized Prandtl-Ishlinskii can effectively characterize asymmetric hysteresis properties.

Vibration caused by running vehicles on a highway bridge is spread to the superstructure, substructures and ground. The ground vibrates both in horizontal and vertical direction. When vehicles load at the tip of the cross beam in the T-shaped pier, rocking vibration of the pier occurs. Its ground vibration in transverse direction is the biggest. In the two-box girders bridge, which bearings are installed at the tip of the cross beam of the T-shaped pier, the ground vibration has greatly occurred due to the rocking vibration of the pier. Two measures to mitigate the vibration are proposed in this study. The evaluation the change of the vibration characteristics and effects of the measures to mitigate the vibration are also discussed in the study.

We suggest the criteria and steps on selecting scenario earthquakes for important engineering structures in this paper, the main ideas are that the scenario earthquake should be determined by considering two main factors at least, i.e., seismic environment (represented by Seismic Hazard Analysis normally) and structural dynamic property (represented by structural inherent period). The results show that it is necessary to estimate the scenario earthquake carefully by combining the structural properties with seismic environment for key engineering structures especially.

The authors performed a research using test trucks for a three-lane prestressed concrete bridge with 37.47m span that vibrated greatly. As the results of the research, the bridge had the frequency of the 1^st bending vibration (ca. 3.0Hz). And also, since the frequency and that of general vehicle's vibration (ca. 3.0Hz) is close, the bridge and vehicles had caused coupled vibration. Moreover it was clear that the bridge had vibrated greatly, only when the test truck had ran at the 2^nd slow lane. Because vehicle's suspension spring vibration had been generated by the road roughness with long space period nearby the expansion joint of the 2^nd slow lane. This paper describes the vibration characteristics of the prestressed concrete bridge coupled with the vehicle's vibration generated by the road roughness with long space period nearby the expansion joint. Besides, this study also examined the countermeasure to decrease the vibration by the dynamic response analysis due to running vehicle.

Nonlinear black-box system identification is the process of deducing a mathematical model of the internal dynamics of a nonlinear system from observations of its outputs, which represents the relationship between past input-output data and present/future outputs of the system, when very little priori knowledge is available. As a new generation of learning algorithms, support vector regression (SVR) was developed by Vapnik et.al recently, in which ε-insensitive loss function was defined as a trade-off between the robust loss function of Huber and one that enables sparsity within the SVs. The use of support vector kernel expansion also provides us a potential avenue to represent nonlinear dynamical systems and underpin advanced analysis. However, in the support vector regression with the standard quadratic programming technique, its implementation is more computationally expensive and sufficient model sparsity can not be guaranteed. In this article, particular attention is paid to the sparsity of the generated model and the model tracing ability for time-varying nonlinear systems and fuzzy linear programming support vector regression (LP-SVR) was proposed for identifying time-varying nonlinear dynamical systems identification.

Conventionally, hydraulic actuators are used in blowout preventers (BOP) to regain well pressure control in oil/gas drilling or production. As drilling moves to deeper and deeper undersea, the hydraulic actuators are not able to meet the API mandates in response time. An innovation of BOP's actuators was proposed to use the shape memory alloy (SMA) recently. This paper presents design and implementation of the Pulse Width Modulation (PWM) regulated Proportional-Derivative (PD) control using a Programmable Logic Controller (PLC) for the SMA actuators used in BOP. The SMA actuator holds a few outstanding features compared to its conventional counterparts, and thus has been used in a variety of applications. On the other hand, SMA is nonlinear, and a sophisticated controller is required to ensure its stability and robustness. In the paper, after a short review of the prototype of the SMA actuated BOP, the design and implementation of the PWM PD controller is presented, followed by the testing results of position control of SMA actuated BOP.

This paper presents a Linear Parameter Varying (LPV) gain-scheduling controller to control the response of a Semiactive independently variable stiffness (SAIVS) system. Effectiveness of the LPV Gain-scheduling controller is verified analytically. Simulation results shows that the nonlinear, time-varying stiffness properties of the SAIVS device can be tracked, even when the mathematical model of nonlinear system is only piecewise continuously differentiable, by representing the system in LPV form and by choosing the spring angle of SAIVS as the scheduling parameter. LPV controller is scheduled based on the real-time estimate of the spring stiffness of SAIVS. It is further shown that the adapted method is more effective in response reduction compared to a robust controller.

The wind-induced vibration control of high-rise buildings is an active research direction in civil engineering field. Instead of traditional controllers such as active tuned mass damper (ATMD), a new type of damper — MR-TMD called as smart TMD in this paper that combines MR damper and passive TMD is introduced to suppress the wind-induced vibration of high-rise buildings. Modified Bingham model is used to describe the mechanical characteristics of MR dampers. In the present investigation, frequency and damping are assumed as random parameters considering metrical uncertainty and structural randomness. Based on sliding mode control (SMC) theory and linear quadratic regular (LQR) control theory, one semi-active control strategy is realized to obtain the practical control force for reducing the wind vibration of building with smart TMD. When structural output state is limited, control rule is given as well. It is shown in numerical example that the controller with designed smart TMD has good control effectiveness to random high-rise structures under wind.

The suppression of regenerative vibrations on machine cutting operations is essential to avoid negative effects on surface finishing, poor machining accuracy and reduction of the tool life. In this paper, we introduce a methodology to reduce the self-excited vibration in milling cutting processes by using magneto-rheological fluids (MR) actuation. The paper provides theoretical analyses of how the MR devices can be used to suppress chatter in conjunction with the Lyapunov's direct and the Linear Quadratic Regulator (LQR) control methods. We solve the resulting delay differential equations by using Chebyshev's pseudo-spectral method and compare the solution with and without control strategies.

Aimed at the pendular vibration control problem of the suspended structure, this paper discusses the non-linear differential equation model development and control analysis of the system. Based on the classical Lagrangian principle, the system EOM can be established into two sub-types corresponding to in-plain motion mode and rotary motion mode. The analytical results indicate that different control systems should be considered owing to the diverse motions of the system. Then, theoretical results show that the Tuned Mass Damper (abbreviated as TMD) can not be used for rotary motion control owing to the coupling effect between displacement of TMD mass and structural pendulation angular velocity. Based on thorough numerical analysis, the concept of Tuned Rotary Inertia Damper (abbreviated as TRID) control system is proposed, and the differential equation of the suspended mass with the TRID system is studied. Furthermore, optimization issues of TRID system are equivalent to the classical optimization problem of TMD control. At last, conclusions were extended to vibration control of typical civil engineering structures, such as high-rising tower structure with prior bending deformation characteristics. Whenever its motion or vibration is similar to the single pendulum or inverted pendulum, the in-plain TMD control system will lose its effectiveness and the innovative TRID system should be considered for pendular vibration control of such kind of structures.

The research of dynamic stability involve some subjects, and was developed recent decades. It is very complex of its instability mechanization because of it is a nonlinear differential equation, so it has not achieve a uniform view. Teeming with large-span and complex structure, the dynamic characteristics of the structure gain more and more attention from scientific researchers and designers, the traditional design method which resist external load by increase cross-section area shows it's too simplistic and unreasonable. The birth of intelligent structure give a new way of the active control for the dynamic instability, in this paper, based on a three-storey smart framework struc- ture, the optimized design of the piezoelectric intelligent control equation is deduced, and give the optimal position when piezoelectric stack has the greatest efforts. After finite element equation of piezoelectric active control for dynamic instability given, a ingenious transform is used to solution active control dynamic instability region. A correspond experimental is taken, study and analysis, it show that the piezoelectric smart control of structure dynamic instability is evident, the largest ratio of active control on acceleration could induced achieved 27%, and on the displacement could induced achieve 24%, and the dynamic instability regional reduced significantly. At last, release the task of next step, all the work is helpful for practical design and useful for the further research.

An improved analytical method was proposed to assess the fastener integrity of a bolted structure. A new unsymmetrical washer was designed and fabricated, taking full advantage of piezoelectric ceramics (PZT) to play both roles as actuators and sensors, and using energy as the only extracted feature. This method doesn't restricted by the materials of the bracket, panel and base structure. A series of experiments on metallic honeycomb sandwich panel TPS were completed to detect the bolt loosing. Studies show this method can be used not only to identify the location of loosening bolts rapidly, but also to estimate the torque levels of loosening bolts. It has been found that energy is the only extracted feature in this method, which making the computation process become very simple, so the operation speed rises greatly without impacting the accuracy of the results.

In this study, brand new cement-based piezoelectric composite sensors have been developed for acoustic emission detection in a civil engineering structure. The new developed sensors have good compatibility with concrete, the most widely used construction material. Especially, the tuned acoustic impedance of the composite sensor is very close to that of concrete. Following different fabrication procedures, two kinds of sensors, sensor with 0–3 connectivity pattern or 1–3 connectivity pattern have been fabricated and characterized. The piezoelectric properties and sensitivity are investigated and analyzed using a Physical Acoustic Corporation data acquisition system. The properties are compared to that of the Physical Acoustic Corporation transducer (PAC). It is found that the cement-based piezoelectric sensor perform much better when embedded into the concrete structure. The sensor ability in detecting AE signals generated by formation of micro-cracks or dislocation in the concrete beams is improved dramatically. There is a great potential to use such type of sensor for health monitoring of civil structures.

A global status assessment scheme based on the lower eigenvalues is proposed to detect the damages in the existing structure. Firstly, a real structure is parameterized as analytical model by finite-element method, which is divided into identified part and non identified part according to chief and subordinate freedom degrees. The subordinate freedoms are condensed with Guyan reduced freedom method. The error estimator between the real structure and its analytical model is defined, and the algorithm of damage detection is developed. Finally a numerical example is presented to study the properties of the scheme by investigating the error extents of the identified results influenced by the number of measured frequency ranks in detail. The results illustrate that the proposed procedure is effective and useful.

This paper presents an intelligent computational methodology for loose bolt detection in thermal protection panels, targeted toward an active online SHM system, considering uncertainties in sensed data. The proposed methodology is based on the integration of dynamic artificial neural network, wavelet signal analysis, and Bayesian probabilistic assessment. A dynamic fuzzy wavelet neural network model is employed to perform the multiple-input-multiple-output nonparametric system identification, using time series data obtained from the panel under healthy condition. The trained model is used to predict dynamical responses of the structural system under unknown conditions. Both predicted and sensed time history data are decomposed into multiple time-frequency resolutions using a discrete wavelet packet transform method. The wavelet packet component energy is computed in terms of the decomposed coefficients and used as signal feature to detect loose bolt. The multivariate comparison in damage detection is handled by an interval-based Bayesian hypothesis testing approach. The methodology is implemented to detect one loose bolt of a prototype thermal protection system panel with four mechanically bolted joints, using experimental data collected at Air Force Research Laboratory.

A novel micro fiber Bragg grating displacement sensor is proposed and studied in this paper. A type of micro-elastic spring was used as a displacement-wavelength conversion component. According to the sensor package design established, one micro FBG displacement sensor with outer diameter of 1.3mm was constructed. Tests were designed and conducted to study the displacement and temperature sensitivity of the sensor. Results show that there are good linear relationships between wavelength and displacement, as well as between wavelength and temperature. The displacement coefficient and temperature coefficient are 10.97pm/mm, and 21.38pm/ °C, respectively.

This paper provides a tutorial on fiber-optic sensors. Since the topic spans across the many disciplines and variety of fiber-optic sensors that are researched and developed, the objective is limited to the basic technology of fiber-optic sensors. Two major classes of sensing mechanisms using optical fibers, interferometer and intensity sensor systems, are then discussed. The focus is then shifted to a review of the interferometer type of fiber-optic sensors. We begin by presenting the basic concept of the two-beam fiber-optic interferometer. This basic two-beam interferometer is then further extended to practical sensor configurations, which are widely used in many important commercial and military systems. We conclude the paper by providing the recent trends of the technology and direction of future research in this area. Finally, potential new applications will be suggested and discussed.

Erbian Dadu River Arch Bridge is located in the Erbian country, Sichuan province. In order to monitor the strain and temperature of the arch bridge and evaluate the health condition, 30 bare FBG strain sensors and 5 temperature sensors have been installed on the 15 arch suspenders, and 8 GFRP-OFBG strain sensors and 4 temperature sensors have been installed on the 4 tie cables. Techniques of FBG sensors installation have been explored. The change of arch bridge suspender strain and temperature, and the effect of the same loading traffic on different length suspender have been monitored under traffic loading with the FBG sensors. The monitoring results show that the FBG sensors can monitor correctly the change of traffic loading and temperature, possible fatigue damage. The tensile process of tie cables was successfully monitored utilizing GFRP-OFBG intelligent sensors, which supplied a great reference meaning to construction.

A novel long gauge strain Fiber Bragg Grating sensor (LG FBG sensor) has been proposed. Pretension technique and packaging method were proposed and demonstrated. Two kinds of long gauge strain FBG sensors were made, which can measure the average strain in 10cm gauge and 20cm gauge, respectively. Calibration test is conducted to obtain the strain coefficient and temperature coefficient of the sensor. Comparison tests have been carried out, and the results verify the feasibility of the proposed sensor.

A new type of optical fiber sound sensor constructed with two fiber Bragg gratings (FBG) is proposed in this paper. Because of the photoelasticity with respect to the refractive index and the elasticity of the fiber, the sound tones modulate the Bragg reflection wavelength and thus the intensity of the laser light transmitted through the sensor FBG fiber varies. Theoretical analysis of sound tone measurements is described. We use the concept of wavelength discrimination which relies on amplitude modulation of the power output with wavelength shifts of the sensing FBG. It would be beneficial if one can determine the response characteristics of a uniform FBG to an extensive list of frequency components of sound. For example, in a system where an FBG is used as a sensing element for heart sounds, the overall response can be predicted with given individual frequency responses. That is, the FBG output can be analyzed down to its individual frequency response components. In this work, a series of experiments were performed to investigate the possibility and potential use of this sensor system for heart sound detection.

A FRP-wrapped Balsa wood bridge deck system is under development in Louisiana, and the bridge long-term performance will be monitored using fiber optic sensors throughout its service. First, the instrumentation plan of the long-term monitoring system of the bridge is introduced in this paper; then a novel moisture monitoring method using FBG sensors is put forward, in which the expansion induced by moisture in the FRP wrapped Balsa wood is measured to indicate its moisture contents. A test on FRP wrapped Balsa wood specimen was conducted in which moisture penetration process was monitored through the proposed method. The feasibility of the proposed method was validated.

Bridge monitoring is conducted at the Akashi Kaikyo Bridge which is the world's longest span suspension bridge. The purposes of the monitoring are for daily traffic control, real-time monitoring during extreme events, long-term monitoring for bridge health indices and design verification. The paper presents a couple of examples of bridge monitoring and design verification results. The results showed that short- and long-term monitoring gives possible health indices to detect structural damages. In addition, study on design verification identifying vibration characteristics such as natural frequency and structural damping showed that structural damping greatly affecting flutter stability is larger than the design value.

Based on the coupling mechanism between the electrical and mechanical impedances of structure, intelligent piezoelectric sensors are used to monitor the structural health. In a certain frequency range, piezoelectric sensors are sensitive in the variations of electrical impedance of the structure, which in turn indicate physical changes in the structure. This paper presents an impedance-based structural health monitoring (SHM) circuits with telecommunication capabilities. Meanwhile, circuits are improved using microcontroller unit and direct digital synthesis (DDS) technique. It is hoped that the piezoelectric intelligent sensor circuits can be attached to a structure for real-time remote structural health monitoring.

Wireless sensor networks are now applied in many fields which deal with data-centric information or critical mission that need minimized network delay. At same time, it needs the capability of dealing with faulty situations. In this work, we propose scalable network architecture and an operating mechanism that in nature is tolerant to network structure change caused by failure, and extend our application level scheduling algorithm with the capability of healing from the failure. The algorithm achieves optimized network delay and gets close form solution that is computational simple to implement. We also look into the significance of different nodes' failure in both homogeneous and heterogeneous sensor network. Simulation results imply the effects of sensing and communication speed on significance of failure in heterogeneous sensor networks.

Acoustic bandgap (ABG) sensors are made of a periodic array of inclusions/scatterers embedded in a homogenous elastic matrix. ABG sensors can be thought of as the mechanical analogues of semiconductors. In a semiconductor the electronic bandgap arises as the result of a periodic array in electronic potentials. In an ABG sensor an acoustic bandgap arises as the result of a periodic array of differing acoustic impedances. We suggest that acoustic bandgap sensors can be used to detect and quantify submicron damage in composite laminates. Monitoring changes in the acoustic response of ABG sensors, will allow us to detect submicron damage in the substrate to which the ABG sensors are adhered. We present the results of our recent simulations demonstrating the ability of an ABG sensor made of epoxy matrix with Tungsten inclusions to detect submicron damage in a composite laminate adhered to the ABG sensor. A finite element simulation coupled with acoustic wave analysis using finite difference in time domain (FDTD) method is used to present the ability of ABG crystals to be employed as sensors for submicron damage detection.

In this study, a nano-coated Quartz Crystal Microbalance (QCM) sensor was used for moisture profiling in macro-porous media (i.e., soils). Off-the-shelf QCM was purchased and coated by deposition of carbon nanotubes. This nano coating imparted a greater surface area on the QCM sensor. An increased surface area allowed the adsorption of more water molecules for given moisture levels, thus increasing the QCM's ability to measure moisture. The resulting sensor was tested to measure soil moisture contents in controlled experiments in the laboratory. Test results indicate that the developed sensor can measure moisture inside a porous media effectively. It is hoped that this sensor can be networked in future for intelligent profiling of moisture in porous media wirelessly and remotely.

Structural health monitoring of concrete structures under seismic loads has always attracted much attention in earthquake engineering community. In this paper, a piezoceramic-based device, called "smart aggregate", is proposed for the structural health monitoring of concrete structures under earthquake loading. A concrete column instrumented with smart aggregates was used as a testing object. A shake table is used to simulate the earthquake ground motion for the testing object. During the shake table tests, the distributed piezoceramic-based smart aggregates embedded in the concrete column are used to perform the structural health monitoring. For the health monitoring purpose, one smart aggregate is used as an actuator to generate propagating waves, and the other smart aggregates are used as sensors to detect the waves. By analyzing the wave response, the existence of crack can be detected and the severity can be estimated. A damage index matrix is developed to evaluate the damage status of the structure. The experimental results demonstrate the sensitiveness and the effectiveness of the proposed piezoceramic-based approach in the structural health monitoring of the concrete structure under earthquake loading.

While optical FBG applied in long-term structural health monitoring (SHM) as strain gauge, temperature influence should be taken into account due to the fact that FBG shows strain and temperature coupling effects and the wavelength change induced by 1 degree centigrade almost equals 10 times that from 1 micro strain, so the valid and reliable temperature compensation technique is in great need for optical FBG to be applied in long-term practical field applications. By now, it is still a question whether FBG is proper for long-term SHM or not because of shortage of long-term monitoring data to illuminate the coupling effects and how to carry out reasonable temperature compensation. In this paper, based on the theoretic analysis of coupling errors, OFBG' strain and temperature cross-sensing properties, the strain sensing properties of FBG in different temperatures and the temperature sensing properties in different strain states, have been studied using experimental data. And the coupling effects caused by both strain and temperature have also been analyzed. Moreover, an absolute temperature compensation technique of the OFBG strain gauge has been brought forward to avoid the crossing coupling effect, and the reliability of this method have been validated through the long-term monitoring data. The test results show that it is valid and reliable for the OFBG to be used as sensing element for long-term SHM.

The presence of noise and vibration in structures often adversely impacts the performance of such systems. Different methodologies have been developed by researchers for vibration and noise control. The feedback techniques that have been developed for active noise control in structures have the requirement of modal parameters of the structure. In this research, loop shaping technique has been implemented along with a PZT (Lead Zirconium Titanate) actuator for active control of noise across an aluminum panel. This technique combines the advantages associated with the loop shaping technique and PZT actuators. While the loop shaping technique eliminates the requirement of modal parameters for controller design, the PZT actuators have the advantages of being cheap and compact. Non-parametric system identification was conducted and the controller was designed in the frequency domain using the sensitivity charts. The test facility consists of a panel that is coupled to an enclosure containing a noise source. The noise used for exciting the panel is broadband in nature. Experiments were conducted in an anechoic chamber to eliminate the effects of echoes and external disturbances. Experimental results proved the capability of PZT actuators along with the loop shaping technique in increasing the noise transmission loss across an aluminum panel corresponding to the modal frequencies for broadband excitations of the panel.

Traveling wave piezoelectric ultrasonic motors (PUMs) are ideal actuators for a variety of important applications including medical and space robotics, haptic interfaces, and positioning devices. Consisting of a single moving part, the motors are much simpler mechanically than other drive systems that require transmissions and brakes. Many potential PUM applications require accurate real-time control of output torque, which is difficult due to the highly nonlinear PUM dynamics. This paper reviews the development of a model-based PUM torque regulation algorithm and applications of the algorithm. The paper then examines the stability of the torque control and demonstrates it experimentally.

The Electro Discharge Machining process (EDM) is capable of producing complex geometrical features with high precision in hardened materials. This characteristic has made the process attractive for the manufacture of high precision micro components. The present study explores the use of LeadZirconate-Titanate (PZT), piezoceramic actuators to control the motion of a micro EDM electrode holder, with the goal of producing a spark with a specific voltage at a target frequency. A mechanical displacement stage delivers a coarse displacement for the electrode holder, while a PZT actuator produces fine positioning and mechanical vibration needed to facilitate flushing. The proposed arrangement provides a robust alternative for accurate control of the micro EDM process.

In this paper, a simple but optimal control method is proposed for the control of semi-active devices. The novel controller utilizes a decayed exponential function to generate the control signal for the fluid damper. There are only two parameters for adjustment: one is the decay rate, another is the response gain. Such a simple control law does not need the system modeling knowledge, also is quite straightforward for field technician to utilize in tuning-up.

This paper presents the structural control results of shaking table tests for a steel frame structure in order to evaluate the performance of a number of proposed semi-active control algorithms using multiple magnetorheological (MR) dampers. The test structure is a six-story steel frame equipped with MR-dampers on the 1^st, 3^rd and 5^th floors. In experimental tests, an EL Centro earthquake, a Kobe earthquake and a Chi-Chi earthquake (station TCU067) are used as ground excitations. Various control algorithms are used for this semi-active control studies, including the Decentralized Sliding Mode Control (DSMC), LQR control and passive-on and passive-off control. Each algorithm is formulated specifically for the use of MR-dampers. The performance of each algorithm is evaluated based on the results of shaking table tests, and the advantages of each algorithm is compared and discussed. The reduction of the story drift and acceleration throughout the structure is examined.

The use of control as an approach to mitigate the consequences of seismic events has emerged over the last forty years. During this time, this possibility has been investigated extensively. However, the findings from these studies have occurred mainly on an individual case-by-case basis. Alternatively, seismic risk assessment has been used to mitigate future losses over a region for many structures. These assessments may be conducted through the development of a fragility curve analysis. This paper examines well established techniques for structural control in conjunction with the new approach of consequence based engineering by evaluating the fragility functions of a nonlinear 20 story structure. A comparison study will be provided for the fragility function of the controlled structure with passive, active, and semi-active control implementations.

To explore the addressed issue of closed-loop vibration control using semi-active magneto-rheological (MR) fluid damper, an innovative control algorithm based on feedback of acceleration response at several points along stay cable for active/semi-active control of stay cables is firstly proposed in the present paper. Theoretical analysis, laboratory investigation, and in-situ tests are conducted in this study to verify the proposed control algorithm. Moreover, this paper presents the negative stiffness characteristic of the combined stay cable/semi-active MR damper system. These investigations indicate that the semi-active MR damper can achieve much better mitigation efficacy than the other passive MR dampers and the proposed control algorithm is proved to be practical. The effect of the negative stiffness on response reduction is demonstrated by the improved energy dissipation ability of the damper due to the enhanced displacement of the stay cable at the location attached with the damper.

As possessing character of simple structure, easy installation and steady performance, friction damper has been widely used in different fields. However, due to can not change its performance during utilization, traditional friction damper only has limited control effect to vibration of structures. Piezoelectric material and magnetostrictive material are two kinds of smart materials with ability of extending their length under excitation of electric or magnetic field respectively. Utilizing actuator made with above two kinds of smart materials to adjust normal pressure of friction damper, then to change friction force, is a good method to make friction damper to be adjustable during application. In this paper, three smart friction dampers were fabricated. The dampers have same structural parameter and their damping force can be respectively adjusted by the actuator which is made with Terfenol-D metal, polymer-bonded Terfenol-D composite and piezoelectric ceramic. Damping force and response time of the above dampers were tested. Experimental results show that, the friction damper based on Terfenol-D metal (GMM friction damper) possesses largest adjustable force and adjustable rate, the adjustable force and adjustable rate of friction damper based on polymer-bonded Terfenol-D composites (GMPC friction damper) is slightly less than that of GMM friction damper, the friction damper based on piezoelectric (PZT friction damper) possesses lowest adjustable force and adjustable rate. Experimental results also show that, the response time of GMM friction damper and PZT friction damper are close to 60–80ms and 30ms respectively.

To address the need for a reliable and cost effective nanocomposite manufacturing technique, Vacuum-Assisted Resin Transform Molding (VARTM) method was used to form four carbon nanofiber (CNF) infused nanocomposite plates with differing weight percentages of CNF in the matrix. Using Lead Zirconate Titanate (PZT) piezoceramic patches as actuators and sensors, a sweep sine excitation signal was used to vibrate the plate and frequency domain response of the nanocomposite plates were analyzed using half-band power algorithm to determine the damping ratio of the plates. The results show that as the weight percentage of CNF in the nanocomposite increased, the damping ratio of the nanocomposite plates increased and the magnitude of the vibration response decreased significantly. Between a CNF free plate and a 1.5% weight CNF plate, over a two-fold decrease in amplitude in the vibration response was observed.

Here we report on the acoustic wave propagation analyses in a layered nanocomposite structure consisting of the stacks of alternating layers of pure polymer and carbon nanofiber (CNF) reinforced polymer. A gradient in the acoustic impedance has been introduced at the interfaces as a consequence of the discrete heterogeneity of the materials and thus greatly influences the wave prorogation including the reflection and the transmission. In this paper we focus on evaluating the effect of layered structure on acoustic properties of nanocomposites. The transmission has been calculated as a function of the number of the layer repeats at a variety of frequencies. These functions share a common feature that they converge to a particular value asymptotically as the number of the layer repeats increases as if the layered composite is a homogeneous effective medium.

Recently, various nanoparticles have been paid attention as novel fire retardants. Although it has been pointed out that carbon nanofibers (CNF) have lower efficiency of fire retardancy through directly dispersing CNF in polymer resins, the cost advantage of CNF arouse our interest of exploring novel methods to improve their fire retardancy. In our work, CNF were fabricated into various freestanding carbon nanofiber sheets (CNS). They were integrated into glass fiber mat (GFM)/polyester composites through different ways. Their fire retardancy was evaluated with cone calorimeter test at an external radiated heat flux of 50 kW/m². The results show that one single layer of CNS did not benefit the improvement of fire retardancy on the top surface of composites. But, multi-plies CNS with alternate arrangement with GFM or CNF containing clay particles on the top surfaces could significantly improve the fire retardancy of composites.

This presentation covers the fabrication; characterization and potential application of electro activate shape memory polymer (SMP) containing multi-walled carbon nanotubes (MWCNTs), hybrid fillers of carbon black (CB) and short carbon fiber (SCF), and magnetic Ni power. The electrical conductivity of 8 wt% MWNTs composite is 1.25 x 10^–2 S/cm with dimension of 8.0 cm x 2.0 cm x 0.2 cm rectangle sheet, it can be triggered by passing an electrical current with a constant voltage of 200 V. While, the electrical conductivity of the composite, containing 5 wt% CB and 2 wt% SCF, reaches to 3 S/cm. Their shape recovery can be induced by passing an electrical current of 25 V voltages. SMP filled with 10 vol% Ni, induced by 20 V. Then temperature-dependent resistivity test is done to investigate the thermo-sensitive effects in conducting polymer composite, and it shows a classical negative temperature coefficient (NTC) effect ranged from 70°C to 90°C. Thus smart thermal sensor using conducting SMP composite can be realized through resistivity change.

This paper builds a conductivity percolation model for the carbon nanofiber composite materials. The model is based on the randomly generated cylinders, which model the nanofibers, forming clusters through the tunneling effect. When a cluster spans the substrate from one side to the opposite side, percolation happens. Preliminary simulation results demonstrate the percolation phenomenon when the volume rate of the nanofibers in the composite exceeds a critical value. The relationship between the nanofibers' aspect ratio and the critical volume rate is also studied.

A novel sensor placement method is proposed for structural health monitoring. The aim of the method is to select sensor locations from a set of possible candidate positions for achieving the best identification of modal frequencies and mode shapes. The proposed method depends on both the characteristics and the actual loading situations of a structure. It selects the sensor positions with the best subspace approximation of the vibration responses from the linear space spanned by the mode shapes. We search the best subspace approximation with a relative small subset through our recently proposed representative least squares method to approximate the original least squares estimator with the whole data set. The selected data subset is required to be representative and sufficiently approaching to portrait the scenario defined by the original full data set. The basic ideas of the representative least squares method are illustrated by a simple linear regression example. The algorithm for finding the representative subset for subspace approximation is described, and is applied to the I-40 Bridge.

An optimal assessment method for the design of accelerograph arrays to monitor the seismic response of high-rise buildings is presented. The method uses a finite element model of the structure based on a simplified multi-degree-of-freedom system model defined using the parameter identification method. The off-diagonal element of the Modal Assurance Criterion (MAC) matrix of mode is taken as the target function in order to facilitate the selection of optimum locations. An example for a high-rise building in Dalian indicates that a minimum of 15 locations provide the optimum sites for monitoring the dynamic response of the selected building in view of economic benefit.

The damage identification technique for bridge structure by vibration mode analysis is based on the precision of modal experiment. The number of the sensors and their settled locations determine the accuracy of test results. So how to distribute sensors reasonably to get the appropriate information about the changes of structure state of the bridge is the key for the health monitoring to large span bridges. Take Wenhui cable-stayed Bridge as an example and the modal date calculated by the finite element model, we adopt EI (Effective Independence) method, MAC (Modal Assurance Criterion) method and an eigenvector sensitivity based method to optimize the placement procedure of the sensors in this paper. The study begins with a detailed finite element modeling of Wenhui Bridge. Then four criteria, such as modal assurance criterion, mode energy criterion, condition number criterion and fisher information criterion, are evaluated the above three methods. The corresponding modal data at deferent locations defined by these three approaches are employed to identify the damages based on the FE model. Finally the proper locations for sensor placement are suggested for damage detection.

Negative pressure suction wall climbing robots nowadays always use air pump to get enough suction force, which has great noise and waste a great deal of power, but small animals just consume a little of power to attach or detach to wall easily. Base on studying animals' suction mechanism, a SMA (Shape Memory Alloy) actuated miniature bio-inspired multi-cavity negative pressure suction cup is designed, which is made up of SMA spring actuators, stiff margin, elastomer plate, leaders and bias spring. Then the suction cup's negative pressure analysis model is founded. Finite element method is adopted to calculate the negative pressure in suction cup. Experiments is done to validate the model and also indicate that negative pressure is bigger and response is faster with the increase of SMA actuator's actuating current.

The character of high energy density has made shape memory alloys (SMA) be applied in some smart structure as actuators. Compared with other actuator materials, SMA can produce larger driving force and recoverable strain. But a SMA actuator provides only limited recoverable displacement which can not cater some stretched out structure's requirement. When multiple shear elements assembled together are actuated by SMA springs, an efficient space stretched out structure can be acquired which also can be folded by SMA springs. This structure can be designed by the bar length of shear element, the initial angle, the terminal angle and so on; through mechanics analysis of the bars under the load of stretching or folding, a mechanics design can be implemented for SMA springs' unfolding force and folding force; wire diameter and intermediate diameter of SMA springs also can be designed according to the driving force of SMA springs; activation efficiency of the stretched out structure can be optimized by the position layout of SMA springs, fashion layout of SMA springs and number of them. The results of experiment also indicate that the structure has a good effect for large scale unfolding or folding in plane. The structure also realizes enlargement of the limited displacement of SMA springs in some degree.

Superelastic shape memory alloy (SMA) is a potential candidate for use in structural damping devices due to its unique mechanical properties. A class of novel re-centring damping device (RDD) is presented. Being configurated simply, the device comprises two functional groups of SMA strands, such as the pre-tensioned strands and the un-pre-centering strands, resulting in a perfect energy dissipation compatible with the negligible residual displacement. Based on the Lagoudas constitutive model and the mechanical analyses, the theoretical model of RDD is established, and comparisons of experiments and simulations validate its effectivity. Time history and energy analyses of an asymmetric damped single-floor building under bi-directional earthquakes are performed. Results show that with the ratio of cross-sectional area of un-pre-tensioned strands to pre-tensioned strands being 1 or 2, the RDD can provide appropriate damping and stiffness to attain the reduction of the coupled lateral-torsional response for the asymmetric structure and the lower cost simultaneously.

In this work, a Dynamic Neural Network (DNN) and an Adaptive Neuro Fuzzy Inference System (ANFIS) based hysteresis modeling and control strategy is proposed for a Shape Memory Alloy (SMA) wire with 0.001" diameter. Such thin SMA wires can achieve a few Hz operating bandwidth and can be used for surface controls in micro UAV (Unmanned Arial Vehicle) applications. Modeling and Control of the SMA wire is a challenging problem because of its dynamic hysteretic behavior. Different modeling and control techniques used in the literature to compensate the effect of the hysteresis. Several attempts have been made recently to use Neural-Network (NN) based modeling of hysteresis via different network structures. In this paper a DNN and an ANFIS based modeling method of the hysteretic effect is proposed and a comparison is made over the modeling error.

This paper is concerned about the drive of shape memory styrene copolymer through an infrared optical fiber carrying infrared laser. As one of novel actuators in smart materials, shape memory polymers (SMP) have been investigated widely. The infrared laser was chose to drive the SMP through the optical fiber embedded into the SMP. The working frequency of infrared laser was installed in 3–4μm, the working band of optical fiber was 1–6μm. An optical fiber was embedded into the SMP for delivery of 3–4μm laser light for activation. The surface of the optical fiber was etched by the aqueous solution of sodium-hydroxide in order to increase transmission efficiency of the optical fiber. The SMP based on styrene copolymer have been synthesized, the SMP was thermoset, and its T_g was the 53.7°C. The thermally activated SMP is possible to initiate an originally shape by a touch less and highly selective infrared laser stimulus. The optical fiber was treated by the aqueous solution of sodium-hydroxide, transmission efficiency of the optical fiber increased, and the total contact area between SMP and the optical fiber. The infrared laser stimulation of SMP is interest for sensor and actuator systems as well as medical applications.

Shape memory alloys (SMAs) exhibiting remarkable thermo-mechanical behaviors, such as the shape memory effect and superelasticity, have attracted much attention in the past decades. This paper presents experimental characteristics and a constitutive model of superelastic Nitinol SMAs for potential vibration damping applications in earthquake engineering. The proposed constitutive equation improves the Graesser and Cozzarelli's model and is capable of modeling the martensitic hardening effect under large amplitudes, critical for structural 'fail-safe' design for extreme loads. To verify the effectiveness of the proposed constitutive model, experiments on a superelastic NiTi wire with different strain levels were conducted. Comparisons between experimental and numerical results predicted by the proposed model show that observed and modeled behavior are in close agreement.

An improved one-dimensional, continuous, dynamic constitutive model for shape memory alloys (SMAs) to describe both the shape memory effect (SME) and the super elasticity effect (SE) of the SMAs was developed in this paper. The work presented was based on the previous work of Kazuhiko Arai, who used the energy analytical method to construct a continuous mathematical model for control analysis. The improved model, which considered the influences of the phase transformation and various strain rates of the SMAs, was set up based on a serious of experiments. Some parameters, including an error function, were determined based on the results of the experiments. The numerical simulation results using the developed model matched well with the experiment results.

Obtaining displacement responses of buildings under earthquake is important for structural damage identification in many cases. However, the sensors that measuring displacement is few. The focus of this paper is to develop a novel displacement transducer by using the strain-sensing property of austenitic shape memory alloy (SMA). This transducer can be installed on buildings for long term measurement due to the excellent ability of SMA resisting fatigue and corrosion. Another advantage of this transducer is that it can be combined with SMA damper to develop integrated SMA device with double functions of energy dissipation and displacement measurement. Large numbers of tests are carried out to measure the strain sensing property of an austenitic nitinol SMA wire, together with the basic performance characteristics, like sensitivity, linearity, hysteresis, repeatability and accuracy. Finally, this SMA displacement transducer is installed into the first story of a structural model and shaking table tests are carried out. The interstory drift at the first floor is measured by the SMA displacement transducer and is compared with the measurement results of LVDTs. All the experimental results demonstrate that SMA is a good candidate for developing displacement transducer.

Nowadays, a great number of long span cable-stayed and suspension bridges are being constructed in China. As the length of the main span increases, vibrations of these long span bridges are becoming more serious and sometimes unacceptable during the construction period. In this connection, control devices should be installed to mitigate the vibration of the pylon and the cantilever girders. Compared with the passive damper system, the AMD system has significant advantages in terms of the control of various modes of the structures, especially for close modes of the bridge at cantilever construction stage. To control the multiple modes of the structure by using multiple AMD system, the design and placements of AMD is critical. The following two issues are studied for the vibration control of the bridge at cantilever stage under seismic excitations: (a) the design and the parameter optimization of the AMD system; and (b) the optimal placements of the AMD system. Simulation procedure is carried out to evaluate the effectiveness of the designed AMD systems for the vibration control, based on the model of the 3^rd Nanjing Yangtze River Bridge. The adaptabilities of the multiple AMD system are presented and the possibilities of applying multiple AMD systems to the long span bridges under construction are investigated.

Research on the control of the structure has been done a lot already, but control-structure interaction was seldom considered. Some scholars have done research on actuator-structure interaction and developed hydraulic and linear motor model respectively and presented that there exits generally a dynamic coupling between the actuator and the structure. This paper mainly investigates the actuator-structure interaction in the active control of structures. First, Analyse the structrual dynamical characters and responses under the wind load and confirm an AMD control programme appropriate to the structure. Then Analyse and compare the control effect of coupling and uncoupling. The investigation includes three aspects aimed at the two actuators: hydraulic actuators and linear motor. First, influence of coupling and uncoupling for the structure is discussed; second, we adjust parameters of the two actuators to investigate the influence on the coupling; finally, we adjust control parameters to investigate the influence on the coupling.

One of the most effective measures for vibration mitigation of long stay cables of large span cable-stayed bridges is using mechanical dampers. In the conventional design theory for cable damper, it is assumed that the damper is linear and without any stiffness, and the cable's ends are fixed. However, actual mechanical dampers usually have nonlinear characteristics, and in addition when the span of cable-stayed bridge becomes large and the structure becomes more flexible, the effects of bridge girder and tower vibration on the cable damper performance may not be ignorable. To improve the efficiency of cable dampers, effecting factors should be taken into account when designing dampers. In this paper, the effects of damper nonlinearity, damper stiffness and dynamic interaction between cables and bridge girder were investigated theoretically and experimentally. The test results showed that these effecting factors reduced the effectiveness of cable dampers, and the proposed theoretical modal can be used for damper design.

This paper first design a multi-degree-of-freedom high-tech platform which used air springs as passive vibration isolation elements and giant magnetostrictive actuators as active vibration isolation elements. For this high-tech platform, a compound controller with feed forward and feedback compensators is designed. For making up the property of time lag of feedback control, the control system take feed forward control as the primary controller, while feedback control as the compensator. Among the vibrational disturbance of the high-tech platform received, the disturbance of ground motion and instruments and equipments on the platform can be measured, which we regard as the input and adopt fuzzy control as feed forward control; at the same time measure the dynamical response of the platform, adopt neural network control as feedback control. We take the sum of the output of feed forward controller and feedback controller as the total output U. Fuzzy feed forward control can not only make up the disfigurement of badly real-time property of neural network control, but also avoid the question of accessional disturbance that commonly feed forward control may bring. The results show that the developed compound controller has good isolation performance and better real-time property if the controller is properly designed.

The expression of equivalent stiffness in considering the geometrical nonlinearity of variable stiffness device is derived. The cubic polynomial model of the equivalent spring is obtained for analyzing the dynamic characteristic of the nonlinear system. The numerical results show that the control effectiveness of SATMD with nonlinearity is better than that with linearity as the frequency ratio is little less than 1. The existing Hertz model is adopted for constructing the equations with impact between TMD and the main structure. The investigation of impact parameters shows that the dimensionless clearance and the impact stiffness are more sensitive to the control effect of TMD than other impact parameters, such as frequency ratio, damping ratio. The robustness of TMD can be improved significantly when the frequency of TMD is detuning, if the impact parameters are reasonably designed.

A new method on vibration control and optimal design for three-dimensional building structures is presented in this paper. Firstly, the mathematical model of a typical three-dimensional shear-type structure is established which considering the damping devices installed in the structure. Then, the optimal design of damping devices is investigated in two cases, i.e. limit damping coefficient and no limit damping coefficient. The optimal parameters of the damping devices can be obtained by using the simplex optimization method and the complex optimization method respectively in the energy index of the three-dimensional structure. The optimal number and placement of damping devices can also be obtained according to the performance index of control devices. Numerical results show that the optimal design method proposed in this paper is effective and flexible. It may obviously reduce the responses of building structures.

A bilateral coupled force model is used to simulate the bilateral coupled effect of a friction pendulum system. A comparative study on the unilateral and the bilateral seismic responses of base-isolated structures with friction pendulum system is conducted in this paper. It is found that, under the bilateral ground motions, the acceleration of each floor is reduced; however, the inter-floor displacement of isolation layer becomes larger. Though the inter-floor displacements of super-structure are decreased, the maximum displacement of the bearings under bilateral components is much larger than that under unilateral component. Therefore, the influence of bilateral ground motions on seismic response of base-isolated structures and performance of bearings should be considered during aseismic designs.

Due to the shortcoming of traditional Active Mass Driver system, an innovative structural control system, direct drive active mass damper control system was put forward. The construction, characteristics and controlling principle of Direct Drive Volume Control of elector-hydraulic servo system are presented. Based on the theory of electro mechanics and fluid dynamics, theoretical models of the rotational number-mechanical relationship of the direct drive AMD system were developed which utilize the values of rotational number to predict active control force by the system. The state equation of direct drive AMD control system was put forward further. As the example with two lumped-mass structures with direct drive AMD control system at the top were simulated and studied. The result indicates that direct drive AMD control system can effectively control the seismic response of the structure.

Due to the demands of experiment on cost and repeatability, the model of nonlinear vibration of structures is difficult to establish. In this paper, an MR rotary brake was used to substitute the plastic hinge of a structure to simulate nonlinear behavior. Different nonlinear behaviors were achieved by changing the MR rotary damper's input voltage. In order to verify the performance of the intelligent algorithms presented before, a magnetorheological (MR) damper was incorporated to the nonlinear model. Adaptive fuzzy sliding mode control was applied to the MR damper using dynamic neural network as the state observer. Experimental data shows that the proposed nonlinear model can be tested repeatedly without much effort. Furthermore, through the different nonlinear case experimental results, it is proved that the intelligent control algorithm is very suitable for control of nonlinear structural vibration.

In this study, a neural networks-based structural parameters identification methodology without any mode shapes and frequency extraction is proposed and validated using vibration-induced displacement measurement from a Fiber Bragg Grating (FBG) sensor. The theoretical base of the proposed method is explained based on the discrete solution of structural dynamic response. To facilitate the parametric identification process, a reference structure is assumed firstly and its dynamic response is determined by numerical simulation. A displacement-based neural network (DNN) is constructed and trained using the simulated response to forecast the vibration displacement of the reference structure. With the support of the trained DNN and associated structures, a parametric evaluation neural network (PENN) is constructed to describe the mapping between an evaluation index and structural parameters. A two-story model frame structure on a shaking table is employed as an illustrative structure to validate the proposed approach using vibration displacement response measurement from a FBG sensor, which measure the relative displacement response of the middle point of the column of the first floor. Parametric identification results by the proposed methodology are compared with them from traditional frequencies extraction and show that the proposed methodology can identify the inter-storey stiffness of the whole frame structure within acceptable accuracy even only the displacement measurement at one point of the model structure is known. The proposed algorithm may be an applicable method in practice for and damage detection and structural model updating.

Wireless sensing systems have been proposed for structural heath monitoring in recent years. While wireless sensors are cost-competitive compared to tethered monitoring systems, their real merit lies in their embedded computational capabilities. 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. In this paper, two embedded engineering algorithms, namely the fast Fourier transform and peak-picking algorithm, are implemented in the wireless sensing and validated by laboratory and field experimental studies. Moreover, the wireless sensors are applied to the problem of identifying structural modal parameters and forces in bridge steel cables. Identification results derived from the intelligent wireless sensor using the computing core are compared with those obtained by off-line engineering analysis of the measured time-history data. Such a comparison serves to validate the effectiveness of the powerful computational core of the intelligent wireless sensor. It is shown that self-interrogation of measurement data using the two embedded algorithms greatly reduces the amount of data to be transmitted by the wireless sensing network. Thus, the wireless sensor offers scalable network solutions that are power-efficient.

Structural modal parameters identification so far has been a major issue in health monitoring system, for which damage diagnosis methods are based on. The emergence and development of smart materials have provided the more accurate techniques in structural parameters measurement. Piezoceramic material has the advantages of cheap, wide band frequency response and high sensitivity to strain variation. In this paper, PZT sensors encapsulated by cement were firstly made and the dynamic performance test proceeded on the MTS. Embedded into concrete pillar, the sensors can identify the vibration parameters of structure based on the direct piezoelectric effect. Impact test result shows that the PZT sensors signal can correctly render the regular pattern of the damped natural vibration of structure. So the modal parameters can be identified by the PZT sensors signal.

Duo to the low cost and convenient installation compared with the traditional wire-based systems, wireless sensing systems have attracted more and more researches in recent years. More validation studies on the performances of theses wireless smart sensing systems are essential so that they can serve as economical substitutes to the traditional wire-based systems. In this paper, an academic wireless monitoring system with smart sensing units developed at Stanford University and Michigan University is applied for the ambient vibration study of a steel arch bridge in China. The bridge with 324m long spans the Wuyuan Bay in Xiamen, China. Acceleration responses of the ambient vibration of the bridge measured by the wireless units are used to identify the modal properties of the bridge based on the stochastic subspace identification method. It is shown that compared with the modes calculated by the finite element model, the ambient vibration data collected by the wireless monitoring system are accurate and these data can be used for the identification of the dynamic properties of the bridge.

Bridge cables are used as critical structural components for cable-stayed bridges. It is essential to identify and monitoring the cable force of cable-stayed bridges in real time and continuously. In this paper, the design of a remote real-time cable force monitoring system including both hardware and software components are realized and the specifications of the system are also presented. The system was implemented in the Tianjin Yonghe cable-stayed bridge located in Tianjin, China, to remotely monitor the cable fore of the bridge and provide the condition assessment of the cables to the users via Internet. Experiences with this system demonstrate how effective low cost system provides a tremendous cost savings in terms of travel time, maintenance, and repair costs. This paper will also discuss the monitoring system and provides a preliminary analysis based on the data acquired from this system.

In this paper, we present a feasibility study of high-rate sensing using off-shelf wireless sensor platforms for wireless structure monitoring. The objective is to determine the key system parameters and components that limit the performance of high-rate sensing applications and provide first-hand information on design tradeoffs faced in operational systems. For the measurement studies of data bandwidth, we have identified the bottleneck of the data path as the UART communication at the sink node. Implementations of high-layer abstractions in TinyOS are shown to be inefficient in turnaround time compared to native interfaces. Finally, the wireless-based solution is shown to have comparable fidelity as wire-based approaches for mid-range sampling rates.

In recent times the interest in wireless sensor mesh networks has grown considerably from personal, to local and metropolitan areas deployment. These networks consist of several mesh routers with minimal mobility and mesh clients that can be either mobile or stationary. The clients may also form a client mesh network among themselves and with routers. The various nodes over the network are interconnected via wireless links which might possibly employ multiple radio interfaces. One major attribute of such networks is the presence of redundant links which removes the single point failure that is present in the classical star or tree networks. Most researches in this field focus on the study of various routing protocols while we sought to introduce the application divisible load theory to find an optimum data aggregation strategy that optimize the networks performance with respect to response time and network delay. We define data aggregation as the process of data sensing and reporting back to the sink nodes, typically routers. The performance of wireless mesh network with 25 sensor nodes is examined by varying network bandwidth and sensing power of sensor nodes. Basic recursive equations for sensing and data reporting are developed for the case of homogeneous and heterogeneous mesh networks and the performance results of two representative data sensing and reporting strategies are presented.

Structural health monitoring (SHM) has been an important research area for evaluating and designing reliability of engineering structures in recent years. And with recent advances in the technologies in sensing, wireless communication, and micro electro mechanical systems (MEMS), wireless sensor technique has been developed rapidly and used gradually in the SHM for engineering structures. In this paper, wireless inclinometer sensor and its Data Acquisition System(DAS) for swing monitoring of large scale structures are designed. Firstly, a kind of wireless inclinometer acquisition system structure is introduced. Secondly, the sensing unit MEME SCA100T's principles and design are discussed in detail, the development of wireless communication module and power unit are given, and all hardware units are integrated into a wireless inclinometer sensor node. Thirdly, the data acquisition system software, which can finish such the functions as data collection, data FFT, is designed. Finally, Experimental results are given to show the feasibility of the developed wireless inclinometer sensor and its data acquisition system.