South Louisiana is vanishing. Subsidence due to relative sea level rise with erosion of weak wetland soils together produce devastating rates of land loss for this area. It is believed that high rates of erosion are due to weak strength properties of fine-grained sediments in the beaches, marshes, and other wetlands in coastal Louisiana. Wave action is known to initiate the movement of weak coastal soils in a manner that is related to the difference between the shear stresses applied by waves and the critical shear strength of erosional sediments. Direct shear tests were performed on samples obtained from the field at Fourchon Beach, Louisiana, as well as on samples that were cultivated in a known soil media within a controlled environment. The role of plant roots on soil shear strength was studied by examining changes in the shear strength of vegetated soil-root composites (SRCs). Two species were used to create SRC direct shear test specimens: Scirpus americanus and Scirpus acutus. Samples were grown in fully-saturated conditions in a greenhouse, and tests were conducted on samples after 4, 8, and 12 weeks of growth after planting. A matured sample of Scirpus acutus, which contained a highly developed root system, was also sampled and tested. Both species were observed to add benefits in shear strength with increased effectiveness after longer growth periods. Findings indicated that Scirpus americanus, being more resilient during cultivation and having higher growth rates, provided the most benefits by increasing shear strength upwards of 30 percent in as little as eight weeks after planting. Field samples were obtained from five areas at Fourchon Beach across an elevational gradient from the intertidal shoreline area to the heavily vegetated marshes containing a variety of plants, specifically Avicennia germinans and Spartina alterniflora. A sample of relict marsh clay was also obtained from the shoreline area and tested in addition to beach sand that had been treated by workers in the aftermath of the BP oil spill. Erosion rates were calculated using a method developed for fine-grained estuarine sediments.

In this research a framework is developed for modeling route choice in hurricane evacuation. Two behavioral hypotheses are evaluated which together with the route choice model, constitute the contributions of the research. The first hypothesis states that beside congestion, other variables such as familiarity with the route, availability of fuel and shelter, facility class, and length of route have an effect on an evacuees' route choice. The second hypothesis states that as time passes and storm conditions change, the impact each variable has on route choice changes. The logit structure was used for modeling the choice process and stated choice data previously collected from the New Orleans area on hypothetical storms was used to calibrate the model. The study found that accessibility of a route, familiarity with a route, facility class, length of a route, and availability of services (gas stations and hotels) had an effect on evacuation route choice. The magnitude of the coefficients of perceived service, accessibility, and distance differed among those evacuating in the first half of the evacuation period versus those that evacuated in the second half but coefficients of facility class were not significantly different between two time intervals. Observed traffic count data from hurricane Katrina evacuation was used to validate the model. Comparison of traffic volumes predicted by the model with actual traffic volumes from hurricane Katrina shows error percentages of 17.5, 0.01, and 28 percent of error for volumes on I-10, I-55, and US-61 respectively.

To evaluate the effect of high moisture content on the performance of weak subgrade soil and improve the engineering properties of weak subgrade soil through using cementitious materials, five different soils that represent range of subgrade soil in Louisiana (based on plasticity indices) were collected and considered in this research study. All tests on raw soils and treated/stabilized soils were performed on the soil laboratory at the Louisiana Transportation Research Center (LTRC). Ordinary Portland cement and hydrated lime were selected in this study to treat/stabilize the subgrade soils depending upon the soil type and plasticity index. The repeated load triaxial (RLT) tests were performed on the laboratory molded treated/stabilized specimens in order to evaluate their resilient modulus and to study their deformation behavior under cyclic loading. In order to simulate the field conditions for the pavement construction over weak subgrade layer to create working platform and/or subbase layer, the soil/stabilizers were mixed at three different moisture contents in the wet side of optimum moisture content. A total of 84 resilient modulus tests and similar number of single-stage permanent deformation tests were performed under cyclic loading conditions. Moreover, 54 multi-stage permanent deformation tests were also performed to characterize the behavior of the material based on shakedown limits. A good relation was observed between the water/stabilizer ratio and the repeated loading characteristic of the specimens tested from resilient modulus, single-stage permanent deformation, and multi-stage permanent deformation tests. The soil specimens compacted at low water/stabilizer ratio showed better performance than those compacted at high water/stabilizer ratio having identical unconfined compressive strength (UCS). Regression analyses were also performed on the available models to predict resilient modulus based on the results of laboratory tests and the regression coefficients (k1, k2, k3) were evaluated for all soil/stabilizer conditions.

This work, standing as an attempt to understand and mathematically model the small scale materials thermal and mechanical responses by the aid of Materials Science fundamentals, Continuum Solid Mechanics, Misro-scale experimental observations, and Numerical methods. Since conventional continuum plasticity and heat transfer theories, based on the local thermodynamic equilibrium, do not account for the microstructural characteristics of materials, they cannot be used to adequately address the observed mechanical and thermal response of the micro-scale metallic structures. Some of these cases, which are considered in this dissertation, include the dependency of thin films strength on the width of the sample and diffusive-ballistic response of temperature in the course of heat transfer. A thermodynamic-based higher order gradient framework is developed in order to characterize the mechanical and thermal behavior of metals in small volume and on the fast transient time. The concept of the thermal activation energy, the dislocations interaction mechanisms, nonlocal energy exchange between energy carriers and phonon-electrons interactions are taken into consideration in proposing the thermodynamic potentials such as Helmholtz free energy and rate of dissipation. The same approach is also adopted to incorporate the effect of the material microstructural interface between two materials (e.g. grain boundary in crystals) into the formulation. The developed grain boundary flow rule accounts for the energy storage at the grain boundary due to the dislocation pile up as well as energy dissipation caused by the dislocation transfer through the grain boundary. Some of the abovementioned responses of small scale metallic compounds are addressed by means of the numerical implementation of the developed framework within the finite element context. In this regard, both displacement and plastic strain fields are independently discretized and the numerical implementation is performed in the finite element program ABAQUS/standard via the user element subroutine UEL. Using this numerical capability, an extensive study is conducted on the major characteristics of the proposed theories for bulk and interface such as size effect on yield and kinematic hardening, features of boundary layer formation, thermal softening and grain boundary weakening, and the effect of soft and stiff interfaces.

Synchrotron Micro Tomography (SMT) is a powerful, non-destructive scanning technique for studying the internal structure of materials. SMT was utilized for two applications in this thesis. The first application involves tracking particle rotation of aluminum powder under different compaction strains. The experiments were conducted on two geometrical configurations by applying axial load to compact the powder in the die and acquiring SMT scans at different strain levels. The SMT scans were processed using AVIZO visualization software for further analyses. The analyses included tracking the same particle at different compaction strain levels, analyzing their volume compressibility, and then quantifying their rotational behavior with respect to the z-axis and xy plane. Particles were first tracked, colored, and then 3D volume was generated. The main findings of this analysis include: 1) the volumetric strain of the particles decreased at high compaction strain due to breakage of the particles into small fragments and elastic volumetric strain of aluminum powder; 2) initially, particles showed no rotation, followed by significant rotation, due to an increase of compaction strains; 3) the majority of the particles exhibited significant rotations near the loading plate and the curved boundary; 4) the 3D shape of the tracked particles under different compaction strains provided a significant contribution to the research area of powders by demonstrating that particles change their shape during the application of compaction. SMT was utilized to quantify sand particles position during a Cone Penetration Test (CPT) as a second application. CPT is a fast and reliable in situ method for characterizing soil properties. A CPT was conducted on a sand specimen and the scans were acquired at different penetration depths using SMT. AVIZO was used to analyze the SMT scans with an objective of identifying how the particles change their position under different penetration depths. Individual particles were tracked and colored to perform this analysis. The results of the analyses include: 1) most particles near the top of the specimen moved upward during initial penetration, due to a small overburden pressure; 2) particles belonging to the middle and bottom of the specimen showed a downward movement with CPT advancement; 3) the tracked particles provided an insight into particle interaction with advancing cone penetration.

Recycling of asphalt shingles in flexible pavements has received interests in recent years due to economic, environmental, and social reasons. The objective of this study is to introduce a new approach to recycle asphalt shingles in asphalt paving construction in which RAS is ground to ultra-fine sizes and blended with asphalt binder through a wet process. In this method, the ground recycled material is blended with the binder at high temperature prior to mixing with the aggregates. Two unmodified binders that are classified as PG64-22 and PG52-28 were blended with two contrasting sources of RAS, originating from tear-off and manufacturer wastes, at a modification content ranging from 10 to 40% by weight of the binder. The use of RAS modification through the proposed wet process was successful. The use of RAS modification through the proposed wet process would generally improve or not influence the high temperature grade of the binder but it may reduce the low temperature grade of the binder. An optimum shingle content may be identified that will improve the high temperature grade without influencing the low temperature grade of the binder. Using Confocal Laser-Scanning Microscopy, wax crystals were detected. However, wax crystals were not detected in the RAS-modified binder, which may indicate that the wax molecules are absorbed by the RAS material. Results of HP-GPC showed that the proposed wet method of modification caused a slight increase of the High Molecular Weight (HMW) content in the prepared blends especially at high content of RAS modification. Use of RAS resulted in an increase in viscosity ranging from 3 to 130%. The increase in viscosity was proportional to the RAS content with greater increase at RAS content of 30% and in blends prepared with RAS from tear-off. The temperature susceptibility of the binder in the range from 95 to 135°C decreased with the use of RAS. Thixotropy and shear thinning were observed concurrently in the asphalt binder blends at 25°C. In addition, RAS-modified asphalt binders showed greater susceptibility to thixotropy than the base binder. Thixotropy increased with higher RAS content.

Fiber reinforced polymer (FRP) composites have found extensive applications in the field of Civil Engineering due to their advantageous properties such as high strength-to-weight ratio and high corrosion resistance. This study presents a simple and efficient frame finite element (FE) able to accurately estimate the load-carrying capacity and ductility of reinforced concrete (RC) circular columns confined with externally bonded fiber reinforced polymer (FRP) plates and/or sheets. The proposed FE considers distributed plasticity with fiber-discretization of the cross-sections in the context of a force-based (FB) formulation. The element is able to model collapse due to concrete crushing, reinforcement steel yielding, and FRP rupture. The frame FE developed in this study is used to predict the load-carrying capacity of FRP-confined RC columns subjected to both concentric and eccentric axial loading. Numerical simulations and experimental results are compared based on experimental tests available in the literature and published by different authors. The numerically simulated responses agree well with the corresponding experiment results. The outstanding features of this FE include computational efficiency, accuracy and ease of use. Therefore, the proposed FE is suitable for efficient and accurate modeling and analysis of RC columns confined with externally retrofitted FRP plates/sheets as for parametric studies requiring numerous FE analyses.

Breakwaters have been constructed in many areas along Louisianas coastline to protect the shoreline from wave energy and erosion. During normal conditions, these breakwaters can typically be analyzed using traditional empirical methods for emergent breakwaters. However, Louisianas coastline is under constant threat from tropical storms and hurricanes, during which breakwaters can frequently become overtopped or submerged systems. Recent studies show that the type of shoreline response to a breakwater system may vary depending on the crest height of the breakwater in relation to the mean water level. Though emergent breakwaters typically induce sediment accretion along the shoreline, studies using laboratory and numerical models indicate that overtopped or submerged breakwaters may increase erosion of the shoreline. This variation of the hydrodynamic patterns and shoreline response is of particular interest for breakwaters along shorelines that can be impacted by hurricanes and other events that trigger large variances in water level, as the breakwaters may periodically shift between emergent and submerged states. The Holly Beach Breakwater System has been constructed to protect a vital piece coastline in southwestern Louisiana. These breakwaters are typically emergent, but can frequently be inundated by surge events and become submerged, and therefore may not always perform as intended. This study uses topographic survey data, aerial photography, and wave and surge information associated with Hurricanes Rita and Ike to identify the sediment transport patterns generated by emergent breakwaters impacted by storm surge and waves. The results of this study show that during a storm event the sediment transport patterns within the breakwater system are very different from those of an emergent system and vary with the geometry of the breakwater system. During Hurricanes Rita (2005) and Ike (2008), breakwaters near the shoreline exhibited extreme erosion and very little accretion, while breakwaters farther from the shoreline showed more accretion which, in some cases, offset the erosion of the beach. Erosion to accretion ratios for segments of breakwaters near the shore were 20 to 50 times higher breakwaters farther from shore. The cause of these erosion patterns is investigated based on the hydrodynamic conditions of Hurricanes Rita and Ike.

Increasing concerns on environment and greenhouse effect, coupled with increased construction prices led to the development of new technologies by the Asphalt industry to produce Asphalt Concrete (AC) pavements. Extensive research is being done to evaluate the impact and performance of these new technologies. Warm Mix Asphalt (WMA) is one of these technologies that allow mixing, production, placing and compaction of asphalt mixes at significantly lower temperatures as compared to the traditional Hot Mix Asphalt (HMA) practice. Lower temperatures result in reduced fuel usage, fume exhausts, greenhouse gas emissions, wear and tear at plants; while enhancing worker health and safety conditions. The performance characteristics of asphalt mixtures containing WMA technologies may be affected and should be quantified. A detailed laboratory study has been conducted to evaluate and quantify the performance of different WMA technologies. Eleven mixes from three overlay field projects across Louisiana were taken into consideration. Evotherm, Rediset, Foaming and Latex were different warm mix technologies used. Each project included a companion HMA mixture section to allow comparison of WMA to conventional HMA. Mechanistic tests were conducted on plant producedlab compacted (PL) specimens to evaluate Rutting (permanent deformation), Fatigue/Fracture and Low temperature cracking performance of the mixtures at high, intermediate and low temperatures respectively. The testing factorial included Dynamic Modulus, Indirect Tensile Strength (ITS), Flow Number (FN), Loaded Wheel Tester (LWT), Beam Fatigue, Semi-Circular Bend (SCB), Dissipated Creep Strain Energy (DCSE), Thermal Stress Restrained Specimen Test (TSRST) and Modified Lottman Test. A Life Cycle Assessment (LCA) has been performed to evaluate the economic and environmental benefits of WMA. Overall, the WMA mixtures showed similar performance compared to that of control HMA mixtures. Asphalt mixtures with Rediset and Latex showed better performance than conventional mixtures with respect to fatigue and permanent deformation. The use of WMA technologies resulted in lesser aging of the binder. Energy assessment has shown a 12-15 % energy savings. On average, $1.61 of cost savings per ton of produced asphalt was observed along with a considerable reduction in air pollutants without any reduction in the mechanistic performance of these mixtures.

The use of composite materials such as Fiber Reinforced Polymer (FRP) to strengthen concrete structures has surged during the past two decades as an alternative for conventional methods of structural strengthening and repair. FRP materials are light and relatively easy to install. They are noncorrosive, durable and less vulnerable to environmental conditions in comparison to other construction and retrofitting materials. The knowledge and applications of composites for strengthening steel structures are relatively smaller when compared to concrete strengthening applications. Strengthening-By-Stiffening (SBS) is a new strengthening alternative that was developed at Louisiana State University. SBS has proven to be a practical technique for inhibiting local buckling in shear-controlled steel beams. This technique relies on the out-of-plane stiffness of pultruded composite sections as opposed to the in-plane strength of thin composites that is often reported in the literature. Preliminary results showed that gains in shear strength of more than 40% are achievable using SBS. The objective of this study is to establish a coefficient for the efficiency of FRP stiffeners as compared to steel stiffeners. This coefficient can be multiplied by the capacity of steel stiffened structures to obtain the capacity of an FRP stiffened member using a SBS design approach, which is lacking in the current codes that do not address FRP stiffening. Four steel beams were first experimentally tested to verify the developed analytical model under a single point loading over the first internal stiffener and the results were compared to those obtained from a nonlinear finite element (FE) analysis. The beams were designed to evaluate the effects of bonding area between pultruded Glass Fiber Reinforced Polymer (GRFP) stiffener and the web of steel plate girders in addition to the effect of web slenderness and the aspect ratio of the shear panel. The results show that there is a good agreement between the FE model and the experimental results. The average estimated strength of the tested beams was about 98% of the experimentally obtained capacities. The parametric studies show that the predicted shear capacity of the SBS beams was almost identical with the shear capacity of steel stiffened beams.