Bridges built today are larger, but also lighter, more slender, and more efficient structures than they were a century ago. As the free span of future suspension bridges increases, so does the need for reducing dead loads. Using Fiber Reinforced Polymer (FRP) deck for suspension bridges is one way to achieve significantly lighter dead loads. Although the cost of FRP materials is more than double the cost of conventional concrete and steel deck, the hypothesis of this research is that the savings in the anchoring system and foundation and the reduction in weight of the main cables and suspenders will result in an overall cost reduction. It is also the hypothesis of this research that the use of FRP deck will impair the aerodynamic stability of suspension bridges. Significant studies have been performed on the use of FRP materials in bridge structures. The Federal Highway Administration initiated research on FRP composite bridge decks in the early 1980s, primarily focused on deck strength and stiffness. In addition, several research projects have been conducted for health monitoring and to assess the long-term performance of FRP materials in bridge construction. Overall, the results suggest that long-term structural response was consistent and well within acceptable strength and serviceability design limits. For the research described in this dissertation, a parametric study was performed considering several bridges of different spans, materials, soil conditions, and material unit prices to study the economic and aerodynamic implications of using FRP deck in suspension bridges . Two groups of suspension bridges with 200 m, 400 m, and 600 m free spans were designed, one group using a reinforced concrete deck and the other group using the much lighter FRP deck. Since soil conditions affect the design of the anchorage and the overall cost of the bridges, three different soil types were considered in this research. The three soil conditions that were considered in this research were sound rock, medium sand, and stiff clay. Then, the aerodynamic stability was examined for all of the bridges using Selberg’s approach. Three-dimensional finite element analyses was performed for each bridge to obtain the values for the torsional moment of inertia and the vertical and torsional frequencies. These values were used in Selberg’s equation to determine the flutter speed of each bridge. A linear elastic analysis was performed to validate the three-dimensional finite element analysis results. The predicted flutter speeds obtained from the linear elastic approach and the finite element approach were within 9% for all the spans and deck materials. The use of FRP deck reduced the predicted flutter speed of the 200 m span bridge, 400 m span bridge, and 600 m span bridges by 35%, 36%, and 37%, respectively. Sensitivity cost analysis was performed of the 200 m, 400 m and 600 m span bridges founded in three different soil types. The three soil types considered were sound rock, medium sand, and stiff clay. The maximum savings was realized in the case of the weakest soil with the least resistance to the main cables tension force: stiff clay. Consistent with the research hypothesis, the cost of the FRP deck is more than twice the cost of the concrete deck, yet the overall cost savings for using an FRP deck were 30% to 42% of the cost using a concrete deck depending on span length and soil conditions. While earlier studies have demonstrated that the life cycle cost analysis could be advantageous in the long term because it requires less maintenance, the findings of the research described in this dissertation showed that the use of FRP deck could result in a 30% to 42% reduction in initial construction cost.

A number of studies have been done in the field of driver distraction, specifically on the use of cell phone for either conversation or texting while driving. However, till now, researchers have focused on the driving performance of drivers when they were actually engaged in the task, i.e. during the texting or phone conversation event. The primary objective of this study is to analyze the post event effect of cell phone usage in order to verify whether the distracting effect lingers on after the actual event had ceased. The research utilizes a driving simulator study of thirty-six participants to test whether a significant decrease in driver performance occurs during and after cell phone usage (texting and conversation). The standard deviations of lane position and mean velocity was used as dependent measures to represent lateral and longitudinal control of the vehicle respectively. Linear mixed model with subject as a random factor and F-test for the equality of variance were used as statistical measures. The results from the study suggest that there was no significant decrease in driver performance during and after the cell phone conversation both laterally and longitudinally. On the contrary, during the texting event, a significant decrease in driver performance was observed both in the lateral and longitudinal control of the vehicle. The diminishing effect of texting on longitudinal control ceased immediately after the texting event but the diminishing effect of texting on lateral control lingered on for an average of 3.388 seconds. The number of text messages exchanged did not affect the magnitude and duration of the diminished lateral control. This indicates that the distraction and subsequent elevated crash risk of texting while driving linger on even after the texting event has ceased. Such finding has safety and policy implications in the fight to reduce distracted driving.

The fate of subsurface oiled sands collected from Fourchon Beach in Louisiana were determined while modifying biogeochemical controls on the degradation of PAHs. Groundwater on the beach has intrinsically low dissolved oxygen concentrations, which may limit natural biodegradation of the crude oil components. The intent of this research was to characterize the biogeochemical properties and degradability of oiled sands (with >10% of pore filled with MC252 oil) using a combination of laboratory flow-through reactor studies, field measurements and time-series microelectrode profiles of down-flow and cross flow geometries. Reactor experiments indicate that optimal conditions for substantial oil degradation are aerobic under advective-dispersive transport processes, and when amended with N and P (DO > 5 mg/L, > 6 mg-N/L, and > 0.6 mg-P/L). Cross-flow reactor studies, which mimic the presence of oiled sands over impermeable clayey deposits, showed no significant (P < 0.05) degradation of phenanthrenes or benzenothiophenes. Time series O2. microelectrode profiles showed that down-flow reactors had greater O2 penetration (>14 mm) than cross-flow geometries, which remained largely oxygen deficient at depths greater than 7 mm. Aerobic degradation of MC252 oil deposits on Fourchon Beach will be controlled by field transport mechanisms of available nutrients and oxygen. Due to low oxygen concentrations in natural groundwater at Fourchon Beach, in conjunction with low oxygen penetration depths and availability of nutrients, the rate of oil biodegradation in these environments is likely to be severely impeded.

UV disinfection performance was investigated under the influence of representative particle sources, including wastewater particles from secondary effluent in a wastewater treatment plant, river particles from surface water, floc particles from coagulated surface water, floc particles from coagulated process water in a drinking water treatment plant, and soil particles from runoff water (planned). Low-pressure (LP) and medium-pressure (MP) UV dose-response of spiked indicator bacteria <i>E. coli</i> was determined using a standard collimated beam apparatus with respect to different particle sources. Significant impacts of wastewater suspended solids (3. 13~4. 8 NTU) agree with the past studies on UV inactivation in secondary effluents. An average difference (statistical significance level of 5% or &alpha;=5%) of the log inactivation was 1. 21 for LP dose and 1. 18 for MP dose. In river water, the presence of surface water particles (12. 0~32. 4 NTU) had no influence on UV inactivation at all LP doses. However, when the floc particles were introduced through coagulation and flocculation, an average difference (&alpha;=5%) of the log inactivation was 1. 25 for LP doses and 1. 12 for MP doses in coagulated river water; an average difference (&alpha;=5%) of the log inactivation was 1. 10 for LP doses in coagulated process water. Chlorination was compared in parallel with UV inactivation in terms of particulate impacts. However, even floc-associated <i>E. coli</i> were too sensitive to carry out the chlorination experiment in the laboratory, indicating that chlorine seems more effective than UV irradiation on inactivation of particle-associated microorganisms. In addition, a comprehensive particle analysis supported the experimental results relevant to this study.

The objective of this study is to conduct a laboratory evaluation of asphalt mixtures and binders containing RAS prepared using the newly-developed wet process. In the proposed wet process, RAS material is blended with the binder at high temperature prior to mixing with the aggregates. The proposed wet process offers the potential to better control the Superpave Performance Grade (PG) of the binder blend, to stimulate chemical and physical interactions taking place in the blend between asphalt binder in shingles and virgin asphalt binder in the mix, and to reduce maintenance issues at the plant due to the high content of fines and fibers in RAS. To achieve this objective, asphalt binder blends with 10%, 20%, and 30% RAS were prepared using the wet process, and asphalt mixtures with a nominal maximum aggregate size (NMAS) of 12.5mm were designed according to the Superpave design protocol. The mechanistic performance of asphalt mixtures containing RAS materials was evaluated as compared to conventional asphalt mixtures. Laboratory mixture testing evaluated the rutting performance, fracture performance, and low temperature resistance of the produced mixtures using the Hamburg Loaded-Wheel Tester (LWT), the Semi-Circular Bending (SCB) test, and the Thermal Stress Restrained Specimen Test (TSRST). Results from the experimental program indicated that the proposed wet blending process allows a reduction of the virgin binder content with no detrimental effects on the laboratory performance of the mixture as compared to the conventional mixture without RAS. In addition, results suggested that the usage of RAS in its regular processed size, as processed by the recycling plant, is feasible with no foreseen adverse effects on the mixture performance. The resistance of the binder blends with RAS to fatigue and permanent deformation was evaluated through the use of the newly developed Linear Amplitude Sweep (LAS) test and the Multiple Stress Creep Compliance (MSCR) test. The effect of using different RAS amounts, as well as binder with two different PG grades, was investigated. Results of the LAS test showed that an increase in RAS leads to an increase in the number of cycles to fatigue failure. This is the opposite of what would be expected. These results indicate that the LAS test may not be suitable for characterizing RAS-modified asphalt binders. With respect to permanent deformation, it was found that the addition of RAS improved the performance of the blends by reducing the non-recoverable creep compliance and increasing elastic recovery.

Piezoelectric-based energy harvesting is an efficient way to convert ambient vibration energy into usable electric energy. The piezoelectric harvester can work as a sustainable and green power source for different electric devices such as sensors and implanted medical devices. However, its application on civil infrastructures has not been fully studied yet. This dissertation aimed to study and improve the piezoelectric-based energy harvesting on civil infrastructures, especially on bridge structures. To reach the objective, a more accurate model for piezoelectric composite beams was built first, which can be adopted for the modeling of different kinds of energy harvesters. The model includes both direct and inverse piezoelectric effects and can provide a better prediction for the dynamic response and energy output of a harvester. Secondly, to examine the piezoelectric-based energy harvesting on civil infrastructures, four concrete slab-on-girder bridges that represent the majority of bridges in the United States were modeled and used as the platforms for the energy harvesting. Piezoelectric cantileverbased harvesters were adopted for the energy harvesting performance simulation considering their wide usage. Different parameters of the bridges and the harvester were studied regarding to the harvesting performance. Two major problems for energy harvesting on civil infrastructures were identified, namely their low frequency vibrations and wide frequency ranges. Then, a multi-impact energy harvester was proposed to improve the harvesting performance under the vibration of low frequencies. The multi-impact was first introduced and theoretically proven. Theoretical and experimental studies for the multi-impact energy harvester were conducted. Both the results show an increased energy output power than the one from the conventional cantilever-based energy harvester. A parametric study was also presented which can serve as a guideline for the design and manufacture for the proposed harvester. Finally, a nonlinear energy harvester was proposed utilizing the magnet levitation. A larger band width was expected due to the stiffness non-linearity of the system. A theoretical model was built for the harvester and its energy output was simulated under the excitation of sinusoidal vibrations and bridge vibrations. The simulation results show a promising way to apply energy harvesting in the field of civil engineering.

The coastal wetlands in Louisiana are an important resource that sustains many economies and ecosystems. Subsidence, sea level rise, saltwater intrusion, storms, sediment depletion etc. have placed great strain on coastal ecosystems. Chronic wetland losses have converted vegetated lands into open waters and increased wind fetch. Locally generated wind waves acting on the marsh edge contribute considerably to wetland loss. This research seeks to implement a numerical model that can accurately describe the wave climate along Louisianas coast, which will provide a valuable tool that can be used for shore protection, environmental conservation, and resource management. Terrebonne Bay was chosen as the study area for this research because it has experienced one of the largest wetland loss rates among Louisiana estuaries. A continuous wave measurement in upper Terrebonne Bay was obtained over the course of a year. The Delft3D-FLOW and SWAN (Simulating Waves Nearshore) models are coupled to hindcast the wave climate in the estuary. An analysis of a yearlong, continuous wave measurement in upper Terrebonne Bay is presented. The coupled model system is validated against in situ measurements from the wave gauges. The wave power is calculated at different locations in Terrebonne Bay using the validated model results. Insight into the temporal and spatial variability of wave power is gained. Through the quantification of swell energy around the bay, improvements of long-term wave power computation for shoreline retreat prediction are presented. It is found the swell energy becomes the primary driver of marsh edge retreat in the southwest part of Terrebonne Bay as the barrier islands are degrading.

Small-scale HEC-RAS models were used to analyze discharges used to test the Louisiana State University and the Louisiana Coastal Protection & Restoration Authority Expanded Small Scale Physical Model (ESSPM) of the Mississippi River. The HEC-RAS models extend from River Mile 228.4 (Baton Rouge) to the Gulf of Mexico that includes the ESSPM reach which begins at River Mile 173.5 (Donaldsonville). The model scales are 1:6000 horizontally and 1:400 vertically. Using the historic river discharges from 2008 through 2015, the small-scale numerical models proved capable of replicating observed stages along eleven sites of the lower Mississippi River within the targets of the statistical performance metrics: RMSE%, Bias and Pearson product-moment correlation, developed for hydraulic modeling of the Mississippi River. Specifically, RMSE% analyses of computed water depth versus the observed depth at each site was less than the 15% target all stations; the Bias metric was consistently less than 10 for all stations; and Pearson product moment coefficient was greater than 0.9 for 80% of the stations for each of the eight years of D15 modeling. Using the small-scale numerical models, the research intended to quantify the difference between a synthetic flow hydrograph used to test the ESSPM and actual flow data. Qualitatively, the stage hydrographs over the eight years indicate the actual discharge data produces six higher peak stages representing roughly 7.5 percent of the 2920 days in the model. Friction slopes for the D15 and Prototype model were compared and found to produce identical characteristics albeit the values of the D15 model friction slope was by its nature was fifteen times that of the prototype. Also, charting of the Froude Number demonstrated the expected equivalency. The HEC-RAS analyses revealed that total shear stress was equal at each of eleven observed data sites for the eight-year modeling period regardless of the inflow hydrograph. Total stream power, however, for the D15 model was roughly 15 to 20 percent higher using the actual river flows. Total stream power for the prototype model did not differ at the various data sites, while stream power at discharges above 575,000 cfs at both D15 and prototype scales were higher for the actual stream flows than for the synthetic hydrograph. The formulae for these parameters are the same except stream power is dependent on discharge where shear stress is dependent on hydraulic radius. Since the channels of both models have a relatively high width-to-depth ratio, the analyses demonstrated the maximum variance of the hydraulic radius to be approximately 12% while the maximum variance of the discharge was roughly 400%. Continued refinement and interpretation of this numerical model is an important element toward the interpretation of the results of the ESSPM and application toward understanding the dynamic hydraulic properties of the lower Mississippi River.

Crude oil from Deepwater Horizon Macondo oil spill is currently present in Louisiana coastal surface sediments and its effects on the coastal ecosystem are still being realized. Deposition of 2- and 3-ring PAHs (alkylated naphthalenes and phenanthrenes) on the exterior of Spartina alterniflora and Avicennia germinans leaves have been demonstrated in marshes impacted by Macondo spill. Whether these deposition events result from contaminated tidal water or volatilization followed by deposition onto the leaf surface has not been conclusively established. Measurements of PAH deposition on the leaf surface of black mangrove (Avicennia germinans) can provide important evidence of the mechanism of deposition since these plants are rarely submerged by tidal water. Study objectives were to quantify and observe the uptake mechanisms of PAH accumulation as a function of time, leaf age, and leaf fraction in mangrove leaves from a heavily oiled site at Bay Jimmy marsh in Barataria Basin, LA. PAHs did not accumulate over time or leaf age indicating diffusion and equilibrium processes dominated and occurred quickly. PAHs accumulated in the inner tissue of the leaf posing a potential for long-term internal cycling of PAHs in a sediment-vegetation-biota system. Semipermeable membrane devices (SPMDs) were utilized in air and marsh surface in the field as a simple analogue to investigate the transfer process. Higher correlations between leaves and SPMDs were observed for C1-naphthalenes than the other PAHs studied. The plant air partitioning coefficient (KPA) for various PAHs in field contaminated mangrove leaves was quantified using an experimental partitioning apparatus and compared to respective KPA values calculated for Spartina alterniflora. All KPA coefficients were well below 8 which supports the dominant uptake process of air phase PAHs is equilibrium partitioning between the vegetation and the gas phase.

Fourchon Beach, a 9-mile coastal headland located in Louisiana Gulf Coast, has been heavily impacted by the Deepwater Horizon (DWH) oil spill, which began on April 20th 2010. Once on the beach, the oil spill residues were moved, suspended and transported by subsequent washover events. These washover events occur during storm surges, hurricanes or other situations with high water levels; pushing oil residues from the subtidal and intertidal zone of the beach and then depositing them in the supratidal marshes and mudflat areas. In order to determine the impacts of washover events on oil residues, two complementary studies regarding degradation and transport of oil residues have been conducted. The first one is a laboratory study that has been conducted to understand the stability of oil:sand aggregates in new environments. Oil residue samples of surface residue balls (SRBs) collected from Fourchon Beach on March 7th, May 5th, and May 18th in 2016, were used in the degradation experiment. The degradation experiment was further divided into two parts: one with shaking treatment and the other without. In the static test, the stability of aggregate oil residues is negatively correlated with salinity: specifically, water with lower salinity dissolves SRBs more readily. In the shaking test, porosity was the main influencing factor of SRBs stability. SRBs with higher porosity were completely broken apart due to water energy, even if they were in water with high salinity. In the second study, data were collected for hurricanes and tropical storms that occurred after the DWH oil spill event that directly impacted the Louisiana Gulf Coast. These data were used to estimate the factors responsible for transport of SRBs. The data analysis revealed that the SRBs on Fourchon Beach were mobilized by every extreme washover event. Further, return time of washover events is also discussed at different locations with various elevations. Beach crests or coastal dunes with heights lower than 0.529 m above Mean Sea Level (MSL) would be washed over every year.