Civil Engineering in the Oceans VI

There has been an explosion of development in new nonparametric methodology in the last several decades, as workers in statistics sought to escape the tyranny of parametric and normality assumptions for problems that were clearly often not Gaussian and not easily described by the usual standard distribution functions. Methods have been developed which allow one to proceed from raw data sets directly to simulations of possible future new data with a bare minimum of parametric assumptions. Many of these techniques are now being introduced into engineering practice and decision-making. The presentation reviews the univariate and multivariate methods growing out of the resampling procedures, and their extensions for use in extremal statistics and the estimation of risk.

Ocean engineering technology is essential to the U. S. Navy's mission. This paper presents a broad overview of the civil engineering-related challenges using two emphases. The first part of the paper illustrates the remarkable diversity of Naval ocean facilities, ranging in scale from deepsea burial of millimeter diameter fiber optic cables to the hydrodynamics of two kilometer long floating SeaBases. The second part of the paper outlines how fundamentally different the Navy's objectives and constraints are from industry, which in turn has introduced Navy-unique challenges, and the use and advancement of technologies not commercially available.

Houston described the economic value of America's beaches. Few understand the large contribution beaches make to the national economy. Similarly, few realize the contributions maritime transportation and oil and gas production make to the national economy. Engineers that design infrastructure supporting beaches, maritime transportation, and oil and gas production make an important contribution to improving America's standard of living.

For accurate and consistent estimate of the directional spreading parameter and mean wave direction of directional seas based on a cosine-2s model, a new approach is proposed, which employs a Maximum Likelihood Method (MLM) to estimate the directional spreading function and then the angular Fourier coefficients. Because a MLM is more tolerant of errors in the estimated cross spectrum than a directional Fourier transfer used in the conventional approach, the proposed approach is able to estimate the directional spreading parameters more accurately and consistently, which is examined and confirmed by applying the proposed and conventional approach, respectively, to the time series generated by numerical simulation or recorded in the field.

The values of the model parameters α and β of the Boussinesq-type equations for coexisting waves and currents over porous beds are determined via optimization of the fundamental properties for wave propagation. A suitable optimization function is first sought to attain the improved accuracy indicated by a prior expansion analysis, then the function is utilized to investigate the sensitivity of the model parameters to the hydraulic properties of the porous medium. Optimization is applied for relative depths up to deep water and relative porous thicknesses up to 10. The optimization results indicate that α controls primarily the celerity property while β influences the celerity as well as the spatial porous damping properties. Results of numerical simulations for a submarine porous trench are shown to illustrate the effectiveness of the optimization technique.

In this paper a method is introduced to predicts the height for waves propagating over a bed with arbitrary shape. The method is based on dividing the domain into two sub domains. The potential in the outer domain is represented by a series. The wave height and any other required quantities in the inner domain are found by using an integral representation of the potential. Other quantities such as water particle velocity can be calculated from the potential. This quantities may be used in the study of the sediment transport.

Smoothed particle hydrodynamics (SPH) is a meshfree method that is well suited to the simulation of complex and free-surface flows. SPH uses control masses and provides a means by which the conservation equations, written in the Lagrangian form, can be discretised. In this paper an SPH numerical wave tank is described in which waves are generated by specifying the initial state using a second order solution for solitary waves. Solitary waves with a range of amplitudes are created and the performance of the model is discussed. Comments are made on the quality of the waves, in particular on the wave profiles just after generation, and on the change in profile during propagation. It is concluded that the model used here cannot simulate low amplitude waves, because the model is computationally too expensive to run at the high resolutions required. The model cannot simulate waves propagating over long distances because waves experience significant losses in height and because a large domain is required which is too computationally expensive to consider, at least for current desktop computers. These limitations mean that this SPH model is not appropriate for simulating waves in wave tanks. However where complex flows are to be modelled it may provide a good alternative to established modelling techniques. Further developments to the theory of SPH and to the algorithms employed here may result in improvements that mean the model is more useful.

A 2D fully nonlinear Numerical Wave Tank (NWT) is developed based on potential theory, Boundary Element Method (BEM)/Constant Panel Method (CPM), MEL-nonlinear free surface treatment, and Runge-Kutta 4^th-order (RK4) time-marching scheme. The inner pneumatic chamber is modeled by the volume-dependent pressurized air and its flow through outlet causing damping. Using the developed 2D NWT, the damping effect of the pneumatic floating breakwater was simulated and its wave-blocking performance is assessed against various damping coefficients. The developed NWT was utilized to investigate the variation of transmission coefficients for various kinds of mooring and wave conditions. It is seen that a significant damping effect can be achieved up to 50% if the breakwater is stationary. When the breakwater is floating against incident waves, the maximum transmission coefficient reduction ratio is much smaller since the floating body tends to follow the vertical motion of incident waves and the resulting volume-change effect is small. The fully nonlinear simulations are also compared with linear ones.

Resonance and frequency-domain effects are well documented for floating bodies such as barges and moored ships. If a body's waterplane dimensions are small in comparison to the wavelength, it can be treated as a point absorber, and its response can be found in terms of response amplitude operators (RAO's) which are functions of the wave frequency. However, for wave-energy devices and breakwaters, the waterplane dimensions of the body are often of the same order as the wavelength, so wavelength effects become important. Simple relationships between the wavelength and the response in different degrees of freedom would be very useful in the design of floating structures. In the present study, a numerical integration scheme is used to solve an initial-value problem and simulate the motions of a floating barge in regular waves. Wave forces are calculated numerically at each time step. Response amplitudes in heave, pitch, and surge are plotted versus wave frequency (normalized by the barge undamped natural frequency in the appropriate degree of freedom) and simultaneously versus wavelength (normalized by the barge length). The simulated data agree well with expectations, and they show that the wavelength-to-body length ratio is an important factor in the design of floating bodies.

An entire-area survey conducted during spring tide in Tokyo Bay on November 21^st, 2002 revealed a vertically well-mixed density at the bay mouth. An Acoustic Doppler Current Profiler (ADCP) was deployed to a depth of 40 m at a location 10 km landward from the mixing. The ADCP survey results indicated suppression of estuarine circulation during the spring tide may have been due to the mixing. We used a three-dimensional non-hydrostatic flow model (MEL3D-Tide) and a two-dimensional two-layer model and we carried out field experiments with a Turbulence Ocean Microstructure Acquisition Profiler to evaluate the mechanism responsible for the mixing. We attempted to clarify the criteria of the tidal amplitude when the mixing appeared in Tokyo Bay. Interestingly, computation results indicated that the mixing was not due to the tidal front; it was due to the instability of internal waves caused by topographical effects. The criteria whether a well-mixed density appears or not were also evaluated successfully in terms of the tidal amplitude.

The understanding of air-sea coupling dynamics is of vital importance to Navy operations as well as to other concerns such as global warming and pollutant transport. Considerable work has been done to model the turbulent boundary layers at the atmosphere-ocean interface. Nevertheless, essential mechanisms of the air-sea turbulent interactions at small scales remain elusive. Existing modeling and parameterization all rely heavily on empirical input. Therefore, a detailed understanding of the small scale physics is necessary to provide a bridge between the small-scale processes and large-scale modeling and predictions. In this work, we use direct simulation of both the air and water turbulent flows to investigate the air-sea coupling mechanisms. We aim at fully resolving and capturing the coupled air-water dynamics at small scales. Our objectives are to identify and assess key transport processes at the air-sea interface and to establish a physics basis for the characterization and parameterization of the momentum and mass transfer within the atmosphere-ocean boundary layer.

In this paper we study a shape monitoring of the oil slicks caused by operational and accidental discharges of ship tanks. We assume that spreading of oil slick is axially symmetric and describe its motion by the system of the equations for the three-dimensional, axisymmetric, non-viscous fluid with the horizontal planar upper and low boundaries. When the oil slick is spreading along the sea surface the vertical components of its particle velocities of the slick and its upper boundary coincide this mathematical model yields the nonlinear differential equation for the prediction of the shape in depending on a thickness of the oil slick with respect to time. In order to get it we firstly derive the formulas for a stream function and a velocity potential depending on the thickness and its derivative with respect to time. Then using the Cauchy integral and taking into account the surface tension at the interface of the fluids we find the differential equations for the oil slick radius and thickness functions of time. The solutions of the both equations are obtained by the numerical methods. It is shown that the slick oil radius has a limited value due to the tensile forces distributed along the surface.

Flow past a fixed and freely-vibrating circular cylinder is studied numerically using an unsteady, overset-grid (Chimera), Reynolds-Averaged Navier-Stokes (RANS) method. The VIV flows selected for study correspond to low mass ratio and low damping at high Reynolds numbers. Some numerical results using large eddy simulation (LES) are also presented for transitional flow.

A Reynolds-Averaged Navier-Stokes (RANS) method has been employed in conjunction with a chimera moving grid approach to provide accurate resolution of four-quadrant propeller flows under both the design and off-design conditions. Time-domain simulations were performed first for the DTRC 4118 propeller under ahead, bollard-pull, crash-ahead, crash-astern, and backing conditions and compared with the available experimental data. Preliminary numerical results were also presented for the DTRC 4383 propeller to illustrate the applicability of the chimera RANS method for highly skewed propellers.

A major capital component of future ocean research will be single-point surface moorings, which will be "hard-wired" to the sea bottom with electro-optical-mechanical (EOM) cables. We consider an alternative to traditional high-modulus EOM cables for single-point surface moorings that is based on using low-modulus Nylon fibers as the strength member. High-modulus EOM cables, such as those that use Vectran fibers as the strength member, are usually constructed with the conductors and optical fibers in the core and the strength member on the outside. The key aspect of the design that uses Nylon fibers is that the strength member is placed in the center of the cable and the conductors and fibers are wrapped around the outside with a high helix angle. When the cable stretches, the conductors and fibers can alter their geometry without straining themselves. In a comparison of the static and dynamic responses of moorings constructed with Nylon and Vectran EOM cables (the Vectran EOM cable uses a rubberized "snubber hose" at the top to offset the effects of the high elastic stiffness of the Vectran cable), our results show that the maximum total tensions were lowest for the mooring constructed with a Nylon EOM cable. In comparison, the maximum total tensions for a mooring constructed with a Vectran EOM cable and snubber hose were 79% higher at the anchor and 21% higher at the surface buoy. The substantially lower anchor tensions for the Nylon mooring are due to the hydrodynamic damping that occurs over the length of the Nylon EOM mooring cable. Most of the motion of the Vectran/snubber mooring is confined to the short snubber hose. Since there is little hydrodynamic damping over the length of the Vectran EOM cable, the tensions pass from the surface buoy to the anchor without attenuation.

A numerical scheme, known as CABLE3D, originally developed for the simulation of dynamics of steel mooring lines is extended to allow for special properties pertaining to polyester ropes, such as relatively large elongation under tension, dependence of the modulus on loads and energy dissipation under cyclic loads. The modified CABLE3D is then integrated into a numerical package, known as COUPLE, for computing the interaction between a floating structure and its polyester mooring system. A classical SPAR is chosen in this study as a representative of deepwater floating structures. By considering large elongation in polyester ropes, the static offset curve of a polyester mooring system is found to be softer than that calculated under the assumption of small elongation. The effects of the mean loads on the modulus of polyester ropes are much greater than those of the dynamic loads. The energy dissipation in polyester ropes under cyclic loading does not play a significant role in the responses of the SPAR and tensions in a polyester mooring system. The above observations though made based on a classical SPAR may still have important implications to other floating structures moored by a polyester mooring system.

This paper focuses on two specialized classes of ship mooring problems, i.e. transient loadings and loadings from long period waves. Transient loadings include rapid changes in speed and/or direction of wind or current. Also considered are transient loadings associated with changes in mooring system geometry and motions arising from passing ships. This paper emphasizes the risks posed by these loadings in practical applications. The first transient example illustrates the large loads on tankers moored to single point moorings (SPM) resulting from shifts wind and current directions. The second long wave example involves seiche problems in the Port of Long Beach, California. The third transient problem considers loads from passing ships. The final transient example involves a moored floating drydock used to launch vessels built at a shipyard.

The capture of wave energy by point-absorber floats has been a popular topic in the wave-energy conversion field for more than two decades. Analysts have undertaken many studies devoted to the optimization of the absorbers and the prediction of their capture widths — the crest width from which the wave energy is supplied. Although this concept is somewhat difficult to exploit for energy conversion due to a combination of power take-off and transmission problems, the concept has promise for coastal protection, where the point absorbers are tension-moored spar buoys. When the wave properties are known at a near-shore site, a tension-moored buoy with motion controls, operating at resonance, can (theoretically) capture the incident wave energy from a crest width of 1/2π to 3/2π times the design wavelength, depending on the number of motion-modes excited by the waves. The characteristic dimensions of the moored body are relatively small compared to the design wavelength, making the absorber easy to deploy and minimizing the possibility of creating a navigation hazard. In this study, a heaving tension-moored can-buoy is studied as a point-absorber partial breakwater.

This paper describes the underwater installation and monitoring of artificial frond mats around the pile supports of a scientific data monitoring tower in Nantucket Sound. The purpose of this investigation is to verify the effectiveness of the mats to reduce and/or prevent scour around offshore monopilestructures proposed for the Cape Wind Project, located on the outer continental shelf approximately five miles off the coast of Massachusetts. The artificial frond mats contain overlapping continuous lines of fronds composed of buoyant, high tensile strength material that provide an unbroken viscous drag layer above the seabed. The viscous drag layer induced by the fronds reduces water velocities exerted by tides, currents, and waves, thereby minimizing the transport of sediments along the bottom and reducing scour. In October 2003, engineer-divers installed two Seabed Scour Control Systems (SSCS) Type-12 Frond Mats at the base of southwest mono-pile of the tower. Follow-up inspections to monitor the performance of the system were conducted by engineer-divers in the summer of 2004.

In this paper, a two-layer model of a stream of water wave body on a sloping bed presented. In this model, the velocity of upper layer has forward direction, but the lower one has backward direction. The effect of lower layer on upper layer is defined with a partial coefficient. The input parameters are obtained from the height and celerity of wind wave with a sine curve. Two essential continuity and momentum equations are used to derive the necessary equations. The continuity equation is discrete with a forward condition respect to time and the momentum equation is derived at an instant of time. With a suitable inserting method, there is a diagonal system of equations and the thickness profile of upper layer is inserted in the unknown matrix as well as the velocity of upper layer, velocity of lower layer and the thickness of upper layer in the tip elements is inserted in the known matrix and therefore with solution of existing implicit system the thickness of moving particles is shown with a variable profile on sloping bed. This theory of run-up is derived from the system of particles and variable mass laws and with this method a relationship between movement of particles and impact and interaction of water particles is developed and finally the results are determined for rock slopes and gravel beaches under wave attack. The results of computational methods are compared with experimental measurements and available standard codes, SN 92-60 from the Russian references.

A Reynolds-Averaged Navier-Stokes (RANS) numerical method has been employed in conjunction with a chimera domain decomposition approach for time-domain simulation of wave runup around offshore structures. Simulations were performed first for a simplified two-dimensional TLP configuration under two different incident wave conditions. The results are in very good agreement with the available data obtained from the particle image velocimetry (PIV) measurements. The method was then extended for the simulation of wave runup around single and multiple vertical cylinders. The simulation results clearly demonstrated the capability of the chimera RANS method for time-domain simulation of wave runup including both the viscous and fully nonlinear wave effects.

Accurate prediction of responses is critical to complete a successful design of any offshore structure. Field measurements are crucial in order to confirm the numerical modelling methods used in design. Normally, free-wave components are used as inputs for analytical predictions of responses of offshore platforms. The paper discusses a method for resolving incident free-wave components from wave elevations measured around a spar offshore platform. The importance of the process is proven using full-scale measurements of motions for the Boomvang Truss Spar. The study also presents a comparison between the full scale data and analytical predictions. Two events were selected for analysis, and particular attention was placed on responses from high frequency waves. Results reveal an excellent match between the measured and analytically predicted spar responses when the measured waves are adequately decomposed into incident free-wave components and inserted into the numerical model.

The design of deepwater offshore structures is often significantly influenced by the analysis of model basin data from large scale physical model tests. In these tests, great care is taken in the design, construction and verification of the model details. A test matrix typically includes regular waves, white noise spectrum tests and multiple realizations combining wind, wave and current conditions to simulate realistic design environments at a proposed offshore site. The objective clearly being to obtain enough quality data sets under well controlled laboratory conditions to reliably predict the extreme platform response statistics of interest. Great care is taken in selecting and executing the tests for each design environment, especially with regards to the specification of site specific conditions and assuring an adequate number of time series realizations are obtained. In sharp contrast, field data is obtained using the ambient environment with particular interest on the response of the ocean structure during events such as storms and eddy events. Those measurements reflect the often directional nature of the environmental excitation. This of course is quite different from the model basin tests data where the wind, wave and current environments are developed under controlled conditions. The measurement systems deployed offshore are generally keyed to sample at regularly scheduled intervals and are expected to capture samples from major design events including the build up and decay of a storm or other site specific events. This article focuses upon the statistical characterization and graphical interpretation needed to compare and contrast laboratory data with field measurements. Both single and sequenced data sets are analyzed and particular attention is directed at a time delayed sequence of field measurements.

In this paper we describe how to use the shooting method in combination with a continuation method to give a numerical treatment of the equilibrium and buckling of axisymmetric, simply-connected, nonlinearly elastic shells and membranes under hydrostatic pressure. We employ a general, geometrically exact theory accounting for flexure, mid-surface extension, and shear relative to the mid-surface. The shells we treat have a single edge, which is circular. The governing equations in cylindrical coordinates consequently have a polar singularity, which is complicated by the quasilinearity of the governing equations resulting from the nonlinear material response.

Stiffened plates found wider application in many branches of civil and structural engineering such as retaining walls, storage tanks, railway cars, large transportation carrier panels, steel lock gates, slender ship hulls, box girder bridges, bridge decks, offshore oil platforms and helidecks in which high strength to weight ratio is important. The main objective of this study was to determine the ultimate load of stiffened plates with initial imperfections using finite element analysis that were tested under axial compression. The analysis was done using ANSYS, the finite element software by considering both material and geometric nonlinearities. The geometric initial imperfections in the plate in between the stiffeners and in the stiffeners were measured after fabrication and that were modeled in the analysis using shell elements. The ultimate load of stiffened plates was also calculated using semi-empirical solutions. The analytical results obtained from the finite element analysis and semi-empirical solutions were compared with the experimental data. It was found that the proposed method underestimated the ultimate load while ANSYS overestimating.

With the increasing demand of multi-purpose use of coastal and offshore zone, the floating breakwaters are being constructed as a good and cost effective substitute for the conventional type of breakwaters. In the case of deep water areas, floating breakwaters are easier to build than gravity type breakwaters made of concrete caissons. It has gained significance in recent years because of its basic advantages, such as flexibility, easy mobilization, installation and retrieval. A rectangular-shaped floating breakwater is proposed here to reduce the transmitted wave height and to control the incoming wave energy. An experimental study is carried out in a two-dimensional wave tank to evaluate the performance of the proposed breakwater. Three different types of mooring systems, with three different inclination anchorage of each system, are adopted in this experimental study. Two of them are perforated wooden plates. The other one is chain mooring system that was adopted for comparison. The experiments are carried out for 3 different water depths, 3 different wave steepnesses and 10 different wave periods, that result a total 810 cases of experimental runs. The reflected and transmitted wave heights, water particle velocities and the displacements of the floating body (sway, heave and roll) are measured during the experiment. It is observed that a good amount of the incoming wave energy is dissipated by the breakwater in most of the cases. Comparisons among the performances of the floating body with three different types mooring systems with various inclination of the mooring anchorage are done. All the results and analyses are presented in this paper. The very good performance of this type breakwater to absorb the incoming wave energy, its easy installation and mobilization characteristics and less construction and maintenance cost demand and justify its use in the real field of coastal engineering.

A floating system consisting of three pontoons equispaced, rigidly interconnected and taut moored to act as a single breakwater is analyzed. The problem is formulated based on the assumptions of irrotational fluid flow, an inviscid fluid, and small incident waves. The breakwater is assumed to be long and uniform in the direction parallel to the incident wave crests. The diffracted and the scattered potentials are obtained from the solution of boundary value problem using Green's identity method. The potentials and hence the free surface oscillations in between the spacing are also determined. The results of parametric study of varying space and drafts of the pontoons have been presented as a function of relative width of breakwater (Ratio of width of the breakwater to the wavelength). It is evident from the results that the spaces between the pontoons have a definite effect on transmission and reflection characteristics of floating breakwater system. As the draft of the floating breakwater increases the bandwidth of incident wave frequencies for which Kt (Ratio of transmitted wave height to incident wave height) is less than 0.2, also increases, thus ensuring a wider spectrum of operation. With the increase in gap form G/W_p=0.5 to G/W_p=1.5 the minimum transmission increases 25%, 27% and 38% for d/h=0.2, d/h=0.4 and d/h=0.6. In addition the paper discusses on forces, oscillations in the interspaces and reflection coefficient.

Various Geosystems like geotubes, geocontainers are being increasingly used as marine structures for coastal applications like revetments, gryones, spurdikes, breakwaters and longitudinal reefs. They are considered as superior alternatives in comparison with more traditional methods (i.e. rocks, prefabricated concrete units, block mats, etc.) due to reduction in cost, work load and execution time; greater use of local material, low-skilled labour and predominantly locally available equipments and providing eco-friendly solutions. The stability of geotubes against dynamic loads like wave forces, current actions has been explored through full-scale physical modeling and verified through analytical modeling. Various methods for enhancing stability of geosystem like using stacked arrangement, developing appropriate strapping system and anchorage system, erosion protection system like apron system has been explored. The final objective of developing superior geosystem having enhanced stability and economically cheaper has been explored through this paper. The main hindrance in application of geosystem is the lack of proper design criteria. The knowledge of real shape of the tube after filling and placing is essential for calculation of required number of tubes for a given height and for calculations of stresses in the geotextile. The major design problems are related with integrity of units during release and impact (impact resistance, seam strength, burst, abrasion, durability etc.), the accuracy of placement on the bottom (especially at larger depth). There are still uncertainties in the existing design methods. Thus, further improvement of design methods and more practical experience is required in application of geotube. The water movement on marine structures can endanger the soil. The dynamic analysis has been conducted for stability of the geotubes.

Wave forces acting on slender cylinders are normally estimated using Morison equation. When a structural member is near the free water surface, it experiences the slamming force. Wave slamming on horizontal members of any ocean structure is crucial to its design. API Recommended Practice 2A-WSD (2000) recommends slamming coefficient C_S equal to π for circular cross sectional members near the still water level. The horizontal cylinders in the inter tidal zone for Port craft jetties are subjected not only to slamming force in the vertical direction and horizontal direction but also berthing force in the horizontal direction. If two cylinders are kept in close spacing, then the load on each member will be different compared to force on a single member kept alone. In this paper, the results of investigations of the effect of tidal variation on slamming forces are reported. The comparison of single circular member and twin circular members with c/c spacing varying from two to four times the diameter of cylindrical member in random waves is also included in this paper. The slamming coefficient is found to be not a constant value and it varies with respect to the spacing between the cylinder and free water surface, the incident wave height and wave period.

The regular wave interaction with a double concentric porous circular cylinder system consisting of an inner impermeable cylinder and an outer perforated cylinder was studied through physical model study. The experiments were carried out on the the double cylinder model in a wave flume to study the runup and rundown at the leading and trailing edges of the perforated cylinder. It was found that the maximum wave runup on the perforated cylinder is almost the same as the incident wave height. The predictive formulae were also developed for the wave runup and rundown on the perforated cylinder, which can be easily used for design applications.

During recent experiments, which were sponsored by the Office of Naval Research, a number of different kinds of test were carried out to measure the insitu strength of the sea bed. These included quasi-static cone penetration tests, tests utilizing a freely-falling probe with a 1 to 2 m long shaft and tests with a small, expendable penetrometer. During the course of these tests significant differences were noted between the penetration resistance recorded by the quasi-static probe as compared with the output of the dynamic probes even though repetitive tests were done at the same site and conventional strain-rate factors were applied. Subsequent laboratory tests, as well as comparisons using the results of the field tests, suggest that the rapid penetration rate of the dynamic probes plays a key role in determining their response in different types of sediment. For example, in granular sediment such as sand, deformation involving shear strain can result in volumetric strain owing to dilation with the result that there is a significant change in pore-water pressure, inter-granular normal stress and, therefore, shearing strength. The exact nature of this dilative response for a given set of experimental conditions is both strain-rate and permeability dependent. Results of various penetrometer tests are presented and criteria are proposed for estimating shear strength when loading is carried out dynamically. This information is important when predicting the impact burial of mines and other objects and in a variety of other activities where the geotechnical properties of the sediment must be determined.

A simple empirical model for the interaction of a catenary mooring with the seabed is investigated in the frequency domain. The moorings that are considered here are low pretension moorings often used in shallow waters. In these moorings, the catenary stiffness is more important than the elastic stiffness. The empirical model includes the effects of inertia, damping, and stiffness by replacing the lower portion of the mooring with a mass-spring-damper system. In previous studies, the inertia and damping terms often have been neglected. In this paper, the definitions of low pretension and high pretension moorings are clarified, and the parameters that determine whether the catenary or elastic stiffness is dominant are identified. The paper discusses the determination of the equivalent mass, stiffness and damping as functions of static variables in these moorings, and the contribution of these terms toward the dynamic tension. It is shown that the quadratic trend that the dynamic tension amplitude shows with the forcing frequency cannot be reproduced without considering inertia in the seabed interaction model. It is also found that the aspect ratio, the ratio of the horizontal to the vertical dimension of the suspended portion of the mooring, is the critical parameter that determines whether the mooring behaves as a low pretension or high pretension mooring. In addition, it is found that, in low pretension shallow water moorings, the equivalent mass, damping, and stiffness are also functions of the aspect ratio only.

When a piece of equipment is placed directly on the seafloor, it is often important that its position and orientation remain stable. Depending on its characteristics, the seafloor soil properties and ocean currents, the item might tilt or settle excessively. The analytical tools currently available in geotechnical engineering practice do not fully address the behavior of such an object in the seafloor environment, especially regarding the unusually soft cohesive soils commonly found there. This paper presents the scale testing completed to validate a new predictive method for foundation stability under eccentric loading.

This paper presents results of experimental deployment of a large instrumented cylinder of variable nose geometry and center of mass offset. Data on three tests series in the Gulf of Mexico are presented and analyzed statistically. The stochastic nature of the problem of the cylinder free-falling through water is outlined and described as an input to the current impact burial prediction package. This predictive package is analyzed in deterministic and stochastic Monte-Carlo frameworks, utilizing the experimentally developed statistical description of all the model input parameters, including the environmental, pertaining to the strength of the sediments, and dynamic, describing the velocities and orientations of the cylinder on impact with the sediment. Significance of the center of mass offset on the behavior of the cylinder is underlined. The importance of accurate knowledge of the sediment shear strength is stressed, as an important factor in predicting penetration burial of large cylinders.

Field and laboratory measurements of wave-induced vertical motions at Barbers Point Harbor, HI, are compared with predictions from the numerical model CADET. The CADET is a Windows-based computer program based on probabilistic risk analysis techniques to evaluate the accessibility of a series of channel reaches for multiple vessel geometries and loading conditions. Prototype ship motions and environmental data were obtained in May 1999. These field measurements were reproduced in a controlled laboratory study with a model of the "World Utility" bulk carrier. In general, the CADET predictions matched the field and laboratory data reasonably well.

Global positioning system (GPS) sensors were placed on ships in Charleston Harbor to collect ship motion data. This paper focuses on the vertical motion "squat" that is the downward displacement of a ship while underway which is a function of ship draft, hull configuration and speed, and channel depth, width, and cross-sectional shape. The primary vessels of interest were containerships and bulk carriers whose length exceed 213 m (700 ft). A total of 18 ships were tracked, but only 12 were analyzed because of data collection problems. Environmental measurements consisted of wave, current, and tide levels during the period of the study. Water level information is particularly important for accurate calculation of squat. The large tidal variation (up to 1.8 m) at Charleston Harbor makes an accurate determination of the water surface elevation along the path of the ship very difficult. The procedure for obtaining these measurements required that a 3-person survey crew board the vessel and install 3 GPS antennas near the bow, and the port and starboard bridge wings. Comparisons of measured squat with three empirical predictions are presented and discussed. The evaluation of squat using GPS is a significant improvement over previous techniques. GPS not only provides precise vertical and horizontal position, but also an accurate measurement of ship speed that has been a limitation in previous studies.

This paper presents the results of measurements of long-period wave generated currents utilizing a horizontal looking acoustic doppler current profiler (HADCP) coupled with pressure transducer wave gages. The HADCP technology provides an opportunity to directly measure long period wave currents across a basin and provide directional information for the waves which varies by wave period due to varying seiche modes of the basin in the transverse and longitudinal directions. The data also illustrate the sensitivity for wave gage placement in relation to basin seiche nodes and antinodes. The HADCP data were used further to validate predicted wave generated currents from a numerical model of wave hydrodynamics and ship motion resulting from those currents. The ship motion modeling is the most useful for port planning since it is the actual motion of berthed containerships that impacts loading and unloading efficiency and safety. The modeling results suggest a useful tool for assessing potential ship motion issues in the harbor.

Landfills at Piers E, G, and J have been proposed as part of the Port of Long Beach's (POLB) Terminal Development Program. Both physical and numerical models of these configurations were tested and compared to evaluate optimum or preferred configurations based on harbor resonance, berth size, landfill area, and land transportation logistics.

In this paper, hydrodynamic resonant interactions of a side-by-side moored floating system have been analyzed based on the linear potential theory. Numerical results show that a partially coupled analysis cannot predict accurate responses of the side-by-side mooring system. A spiky feature in hydrodynamic coefficients including sharply negative added mass is observed, which results from a pumping resonance of the confined water column between two bodies. The sharp peaks may also cause unwanted numerical problems. In reality, the sharp variation is limited by viscosity, nonlinearity, and breaking. In order to reduce the exaggerated hydrodynamic resonance, an innovative practical method has been proposed. The present method shows a good performance to smooth out the exaggerated resonance compared to the existing lid-approach.

Sloshing motions are monitored during and outside resonance above and below the critical water depth in a square tank with base dimensions of 1 x 1 m². We investigate the free surface motion as a function of the wave steepness in shallow to deep water for different excitation cases. The test cases include sway and heave base excitation. These investigations are carried out in the depth-to-width, h/b = 0.2, 0.3, 0.6. The system is extremely sensitive to initial conditions and the system has a dynamic form of bistability for certain forcing frequencies and amplitudes. This makes it possible for the system to exhibit very interesting hysteresis effects. It is shown that the free surface behave as a soft oscillator in deep water and as a hardening spring near the shallow water limit when the tank is excited horizontally. We also identified that the Faraday peaks exhibit hardening (h/b=0.2) and softening (h/b=0.6) spring behavior when the tank is excited in a pure vertical motion with a frequency twice the first sloshing frequency. The associated wave form is "mushroom" shaped at certain time instances which resembles the Richtmyer-Meshkov instability.

In 2001 the American Society of Civil Engineers (ASCE) published ASCE Manuals and Reports on Engineering Practice No. 101: Underwater Investigations Standard Practice Manual. The manual was intended to provide guidance to engineers conducting underwater engineering investigations and assessments of existing waterfront and near-shore structures. This paper provides a practical perspective on implementing the guidelines and methods presented in the Underwater Investigations Standard Practice Manual, and will present a brief overview of the history and need for underwater engineering assessments, including the development of the Underwater Investigations Standard Practice Manual. The paper also includes examples of project experience related to the Underwater Investigations Standard Practice Manual.

Intellectual Property (IP) exists in various forms, i.e. patents, trademarks, copyrights and trade secrets. These different forms of Intellectual Property are used to protect various new ideas, new materials, new methods, and new software usable in any industry. Today, building and maintaining an IP portfolio is simpler and less expensive than in years past The first reason is due to a particular decision from the US Supreme Court that has become affectionately known as the Festo case. The second reason is because of a major legislative decision to provide for "provisional patent applications". These "provisional patent applications" are useful in protecting ideas, methods, ompositions, software, processes, and apparatus that are not yet completely tested or finished. IP is very similar to real property, in that, it can be traded, licensed and assigned like real property. The advantages of IP in protecting and growing businesses are endless. In addition, IP is used to create income from sources "outside" the traditional avenues used in a business. Beyond these reasons, Intellectual Property can be used as (1) an asset, (2) a marketing tool, (3) a tool to protect market share, (4) a source of licensing income, and (5) a tool to enhance market share with customers. The following tutorial will discuss how to identify which IP can be protected, and how to build a cost effective IP portfolio for one's business.