Design of fibreglass composite sheet pile seawalls is traditionally based on the flexural rigidity (EI) of the piling system. To compare with commonly used steel or wood sheet piling, there is a strong need to properly characterise the flexural behaviour of composite piling systems. Directed by this industrial need, the research reported herein is focused on the flexural response of a pultruded sheet pile seawall panel consisting of E-glass fibre-reinforced polyester. The analysis consists of an experimental investigation, analytical modelling, and finite element simulation to determine the flexural and shear rigidities of the seawall panel for use in computing the deflections of the piling system. / A novel testing method was developed to simultaneously determine the flexural rigidity (EI) and shear rigidity (kAG) of the panel using Timoshenko's beam theory. Three- and four-point bending tests were performed on six different span lengths and the results were self-consistent from the two different tests. (Abstract shortened by UMI.)

Fatigue damage due to random stress histories is typically estimated by either Rainflow range counting (a time history approach), or by the Rayleigh approximation (a power spectral density approach). These methods are not accurate in all applications. A new time history method of estimating fatigue life for a time history with undefined power spectral density is proposed. This is called the peak moment Rayleigh estimate, and it is based on the standard deviation of the random signal from knowledge of the odd moments of the peaks and valleys of the time history. This study also evaluates a recent spectral method of fatigue life estimation, the Lutes Single Moment estimate, using data from a previous experimental study by Sarkani for loadings with defined power spectral densities. This estimate is similar in form and ease of application to the Rayleigh estimate, but results in more accurate fatigue life predictions for processes with very wide bandwidths.

Utilizing simplified structural and hydrodynamic models, a parametric study is performed comparing response predictions for the Cognac deepwater platform as it is subjected to wave-and-current forces. Comparisons for the parametric study include: quasi-static versus dynamic response solutions, modal contributions to the response, impact of considering fluid-structure interaction, effects of using various empirically modified linear wave models or the Hybrid Wave Model, and correlation of the analytical response predictions with Cognac field measurements. The results of this study indicate that: (1) the dynamic response of Cognac is very moderate, (2) the dynamic response is dominated by the fundamental mode, (3) the inertia-dominated wave-and-current forces provide minimal response reductions from interaction effects, (4) of the considered wave stretching schemes, Wheeler stretching technique combined with linear wave theory produces platform response results which are closest to those obtained using the higher-order Hybrid Wave Model, and (5) the platform responses predicted using the Hybrid Wave Model are in better agreement with the measured responses for Cognac than the predictions based on the various stretched linear wave models.

The effect of top tension risers on the spar marine structure responses is studied by using time domain as well as frequency domain approaches. A simplified model of the combined dynamic system consisting of a spar, a mooring line system, and top tension risers is established. The top tension of a riser is provided by a buoyancy-can that is laterally supported by a preloaded compliant guide. The overall system is nonlinear due to the mooring line restoring force, the friction between the buoyancy-can and the compliant guides, and the friction between the risers and guides at the spar keel. The friction between the spar and riser system is represented via a continuous Coulomb model. The simplified model is numerically integrated using input time histories of force and moment that are compatible with a random representation (Jonswap spectrum) of a typical extreme environmental loading in the Gulf of Mexico. For validation, the dynamic responses of the simplified system are compared with the related responses of the combined system. The effect of the top tensioned risers on the spar responses is studied by using nonlinear time domain analysis. The responses of the simplified model are also determined by using a frequency domain approach based on the statistical linearization technique. Several parametric studies are conducted to investigate the sensitivity of the spar responses to different design parameters.

This thesis first attempts to characterize amorphous material with respect to its performance in the marine soils from an engineering viewpoint, by selecting and testing some marine soils sampled in East Canada. The second concern of this study is to develop a better understanding of particle interaction between clay and amorphous material complexes and the mechanism of soil performance. / Soil properties and behavior are not only controlled by the quantity, but also by the composition or type of amorphous materials. The mass ratio, defined as Fe$ sb2$O$ sb3$/(Fe$ sb2$O$ sb3$ + SiO$ sb2$) in units of mass, can be used as a parameter to evaluate the effect of amorphous composition. By changing the mass ratio, which in effect changes the composition, soil properties/behavior can be altered. Shear strength, consistency limits and suction all increase with an increase in amorphous content, but vary with mass ratio. Maximum shear strength and minimum consistency limits and suction are observed for soils with amorphous material composed at a critical mass ratio of 0.40. Soil properties are significantly related to the soil's acidity/alkalinity (pH), due directly to the pH dependency of surface charges of amorphous solid particles. / The basic mechanism that governs the soil's performance arises primarily from the very active surface characteristics, i.e. the large surface area and high surface charge, of the amorphous material complex. The roles played by this special soil constituent can be generalized in two functions: water holding capacity and bonding action. While the large surface area necessitates a rise in the soil's water holding capability, the high surface charge enhances the bonding action in-between clay particles. Significant cation bridging and hydrogen bonding, and strong electro-static attractive force established in the silica-iron amorphous complex, especially at the mass ratio 0.40, contribute to the high shear strength observed in the soil. / The laboratory-prepared soil samples showed a good behavioral simulation to the natural marine soils in East Canada and, hence, a much clearer picture for understanding the sensitivity of such soils as Quebec Champlain Sea clays, as well as the general soil problems related to the roles played by the amorphous materials, is achieved. (Abstract shortened by UMI.)

This thesis presents a study of the ultimate strength capacity of two offshore platforms located in the Gulf of Mexico. The objective of the study was to validate existing non-linear finite element models for estimating the loads and strength of offshore platforms. / From August 24 to 26 1992, hurricane Andrew moved through the Gulf of Mexico with sustained winds of 140 miles per hour. Thirty-six major platforms suffered significant damage, of these, ten were completely toppled and twenty-six were leaning significantly or had significant topside damage. / Structures "H" and "K" were bridge-connected platforms, located in the ST151 field of the South Timbalier area of the Gulf of Mexico, platform "H" collapsed during Andrew, while "K" survived undamaged. They were both designed, fabricated, and installed in the early 1960's. / A push-over analysis, using the program USFOS was used to estimate the ultimate strength of the two structures in three direction: end-on, diagonal and broadside. / In the first series of analyses, all the primary members such as legs, vertical and horizontal braces, piles, soil, conductors and deck structure were precisely defined with appropriate finite elements as well as secondary members such as conductors guides barge bumpers. In the second series of analyses it was assumed that there was no horizontal or vertical movements at the level of the mudmat. In the third series of analysis the model used in the first series of analysis was modified by increasing stiffness and resistance of the piles 10 times. Finally a fourth model was investigated in which the soil resistance of the mud-level horizontal members is modelled. (Abstract shortened by UMI.)

With the advance of composite materials in the past 50 years, fiber-reinforced polymer sheet piles are becoming increasingly popular in the marine and waterfront applications. While these materials possess high strength-to-weight ratio and are corrosion resistant, their durability in water has been not well studied due to the lack of historical data for these fairly new materials. / The purpose of this research is to establish the absorption characteristics of a pultruded fiberglass-reinforced polyester composite for a sheet pile wall and quantify the effect of water on long term mechanical properties. The tests conducted were water absorption, tensile strength, flexural strength, and freeze/thaw cycling. An analytical model was developed to establish the nature of the absorption process and prediction of the change in mechanical properties. / The results indicated that the water absorption process of the material followed a combination of Fickian diffusion and polymeric relaxation. The moisture saturation was 1.72% for the flange and 3.11% for web. The absorption process modeling indicated that saturation would be reached in 4.5 years for flange and 7 years for web in tap water, at room temperature. The coefficients of diffusion calculated were 4.2 10-6 mm2/s and 3.0 10-6 mm2/s respectively. During the water absorption test at 70°C and in boiling water, a mass loss of the material occurred. Tensile strength was found to decrease with the increase in percentage of water absorbed with no further degradation seen after saturation was reached. There was a decrease of 60% in the tensile strength at saturation. On the other hand, there was no noticeable change in the tensile modulus of elasticity during the water-ageing period. The freeze/thaw cycling test revealed that there were no significant changes in the tensile strength and the modulus after 564 cycles from 4.4°C to -17.8°C.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 68-02, Section: B, page: 1152. Adviser: Samuel H. Carpenter. Includes bibliographical references (leaves 143-147) Available on microfilm from Pro Quest Information and Learning.

Ice features present one of the major obstacles to offshore development in the Arctic and Atlantic regions of Canada. Ice features have been observed to interact with the see floor creating scour features (Clark et al., 1986). In particular, when an ice feature is driven by environmental forces into the shallow water, ice scouring of the seabed may cause a danger to bottom installations such as submarine pipelines. In the present study, the ice-scour event in a centrifuge test is simulated by using PLAXIS and ADINA finite element programs. The centrifuge test data reported by (Lach et al., 1993; Yang and Poorooshasb, 1997) and the input data in their numerical study are utilized in the present work. In numerical analysis, geometric and material nonlinearities are considered. Two dimensional and three dimensional finite element models are used to calculate the stresses and deformations in the seabed soils, the deflections of the pipe, and the stresses acting on the pipe. In order to establish the validity of the finite element calculations, the experimental results and the numerical results are compared. The importance of using interface elements between the soil and the ice feature is also investigated. The FE predictions are reasonably close to the centrifuge test data. The displacements of the pipe in 3-D model are smaller than those predicted by 2-D model due to the three dimensional effects. Bending and torsion of the pipe along its long axis can only be calculated in 3-D FE analysis. Using the interface elements in the numerical analysis helps to obtain a better agreement between the calculated and measured values. In addition, convergence problems are reduced.

Submerged structures are frequently used in coastal engineering applications, such as tunnel and pipeline protection works, breakwaters, and artificial reefs. Although a significant number of research works have focused on low-crested structures, there is far less research into deeply submerged structures. In most research, lightly-sloped, uniform cross-sectioned submerged structures with specific crest elevations are considered. The present thesis deals with the three-dimensional physical and numerical modelling of the interaction of irregular waves with a large-scale three-dimensional submerged structure. It aims to advance the understanding of the structure's influence on the irregular wave field, the wave-induced velocities along the structure crest, and the wave-induced currents. The ability of a nonlinear Boussinesq wave model to simulate these processes is also investigated and assessed. Analysis was performed on a multitude of data, including---but not limited to---wave heights, wave periods, wave energy spectra, energy transfer functions, reflection analyses, and wave-induced velocities. In general, the analysis and comparison performed showed that the numerical model provided a modestly accurate representation of the physical modelling results.