In the USA alone, about 27% of the bridges are classified as structurally deficient or functionally obsolete. Bridge owners are continually investigating methods to effectively retrofit existing bridges, or to economically replace them with new ones. Modern composite materials for structural applications, at one time only in the domain of aerospace engineering, are increasingly making their way into civil engineering applications. In addition to retrofitting current concrete and steel structures using FRP sheets or plates, a great deal of work is being conducted to develop versatile, fully-composite structural bridge systems. To reduce the self-weight and also achieve the necessary stiffness, sandwich panels are usually used for bridge decks. However, due to the geometric complexity of the FRP sandwich, convenient methods for bridge design have not been developed. The present study aims at developing finite element modeling techniques for sandwich structures. Parametric studies are carried out with the objective of developing equivalent elastic properties, which would be useful parameters in design. A distinction is made between in-plane and out-of-plane behavior, and properties are derived accordingly. The performance of the sandwich, such as the interface stress between the flange and wearing surface can be evaluated. Therefore, through finite element modeling, optimization can be achieved in order to minimize the interface stress. The contribution of stiffness of the wearing surface to structural performance, a factor which is not usually accounted for in typical design procedures, is also examined. An effort is also made to analyze the temperature effects on the structures performance. A conceptual approach aimed at studying the thermal performance of the panel due to both uniform and gradient temperature variations is presented.

In hydrological frequency analysis, it is difficult to apply standard statistical methods to derive multivariate probability distributions of the characteristics of hydrologic or hydraulic variables except under the following restrictive assumptions: (1) variables are assumed independent, (2) variables are assumed to have the same marginal distributions, and (3) variables are assumed to follow or are transformed to normal distribution. Relaxing these assumptions when deriving multivariate distributions of the characteristics of correlated hydrologic and hydraulic variables. The copula methodology is applied to perform multivariate frequency analysis of rainfall, flood, low-flow, water quality, and channel flow, using data from the Amite river basin in Louisiana. And finally, the risk methodology is applied to analyze flood risks. Through the study, it was found that (1) copula method was found reasonably well to be applied to derive the multivariate hydrological frequency model compared with other conventional methods, i.e., multivariate normal approach, N-K model approach, independence transformation approach etc.; (2) nonstationarity was found more or less existed in the rainfall and streamflow time series, but according to the nonstationary test, in most cases, the stationarity assumption may be approximately valid; (3) the multivariate frequency analysis coupling nonstationarity indicated that the stationary assumption was valid for both bivariate and trivariate analysis; and (4) risk, defined by both flooding event and the damage caused by the scenario, showed the difference from that defined by T-year return period design event and the probability of total damage with the comparison indicating that only one character, i.e., T-year event or probability of total damage was not adequate to define the risk.

The objectives of this study were to investigate the variability in the physical and mechanistic properties of HMA due to production, characterize and compare the mechanistic properties of roadway cores and laboratory compacted samples, develop the relationship between modulus from in situ NDT and those obtained from laboratory tests on roadway cores, and compare air voids measurements between laboratory and field test methods. Six ongoing rehabilitation projects in Louisiana were selected, in each of which several test sections were tested. Comparative analyses were conducted on density measurements between two laboratory (AASHTO T-166 and ASTM D6752-02, or Vacuum sealing) and one in situ test (Pavement Quality Indicator) methods. Three types of nondestructive in situ test (NDT) devices, Falling Weight Deflectometer (FWD), Light Falling Weight Deflectometer (LFWD), and Potable Seismic Pavement Analyzer (PSPA) were conducted on asphalt layers. Four laboratory mechanistic tests including Indirect Tensile Strength test (ITS), Indirect Tensile Resilient Modulus test (ITMr), Frequency Sweep at Constant Height test (FSCH), and Loaded Wheel Tracking (LWT) test were conducted on roadway cores and/or Superpave Gyratory Compactor (SGC) samples. High variation was observed in mixture composition and air voids, as well as mechanistic properties along the mixture production. A strong correlation was observed between the two laboratory air void measurement methods. In general, SGC samples had higher mechanistic properties than those of roadway cores. Good correlations were observed between roadway cores and SGC samples in terms of complex shear moduli and indirect tensile resilient moduli. A methodology was developed for the prediction of laboratory resilient modulus from the in situ PSPA test parameter. Field test results indicated that the LFWD test might be used as an alternative for the FWD test in pavement structure evaluation. Pavement Quality Indicator (PQI) results did not correlate well with laboratory air void measurement methods.

In this study, a trip distribution model for hurricane evacuation using the intervening opportunity method was developed. Post Hurricane Floyd survey data was used for model calibration and comparison. To model the behavior that people tend to evacuate away from the path of the hurricane, a new concept of equal destination attractiveness was introduced and an extended intervening opportunity model was built on this basis and implemented in TransCAD. The gravity model, intervening opportunity model and its extended version were compared using several statistical measures. This study demonstrates that it is possible to use the intervening opportunity theory to model trip distribution in hurricane evacuation. The results also show that the gravity model performs slightly better than intervening opportunity model, while the extended intervening opportunity model performs the best among the three models.

In this study a Classification and Regression Tree (CART) classification system method was developed as an alternative to the HPMS conventional method of VMT estimation. Louisiana Highway Performance Monitoring System (HPMS) data from Federal Highway Administration (FHWA) and Louisiana highway network data from Louisiana Department of Transportation (LADOTD) were used to carry out the analysis. The CART classification was derived based on link attributes that effectively distinguished the homogeneous traffic volume sections. VMT estimation on individual links as well for the different systems was calculated using the CART classification system and the values were assigned on each link. The default MOBILE6 VMT values were also assigned on each link. The entire procedure was carried out using GIS Developers kit in TransCAD. The whole procedure was automated by creating a customized add-in program to TransCAD. <br> <br> The resulted AADT estimates from the CART classification system equation were compared with the HPMS conventional method estimates and with the observed values on the HPMS sample sections. This comparison was done graphically and statistically by the paired sample T-test. The results indicated that the HPMS conventional method performs better in estimating AADT than the CART classification system method. <br> <br> The study also included the demonstration of the CART classification system add-in the East Baton Rouge non-attainment area. The developed add-in can also be used on any other traffic count data for any region, state or country. The GIS program developed during this study provides a framework, which can be built upon further and shared with other researchers in future.

The heat straightening method of repair for damaged steel structures has been employed for many years. The method was based on the experience of practitioners. Recent research has given an engineering background for the technique and established certain procedures and guidelines to be followed while using heat straightening. Although a scientific basis has now been established, there still exist some major gaps in the data. Misuse of the heat straightening technique has produced fractures in the steel during repair.There are two parameters that may be keys to limiting fracture sensitivity: degree of damage and application of jacking force stress during the repair of the damaged steel. Currently, research data supports repairing damaged steel strained to 100 times yield strain if jacking forces used in repair are limited. No data exist for more severe damage such as caused by high impact. The formation of a link between degree of damage and jacking ratio may lead to a performance-based design. The purpose of this research is to investigate behavior of plate elements bent about their weak (minor) axes and then heat straightened. Specifically relationships between material properties, jacking force, degree of damage and amount of movement during straightening will be investigated. The results will be used to develop recommended heating and jacking patterns for repair of localized damage. This research will provide a method of repair for fracture critical situations such as damaged rigid beam-to-column connections and damaged steel subjected to dynamic behavior for machinery and fire damaged structures. The damaged plates were repaired using heat straightening technique. The movement of plates was compared to strain ratio and jacking ratio. Movement was found to be directly proportional to jacking ratio and inversely proportional to the strain ratio. Degree of damage did affect material properties of repaired plates. A locally damaged flange was repaired using new heating pattern developed by finite element modeling. More widespread use of the heat straightening technique would lead to both efficient and economical repair of damaged steel structures since the process is fast and minimizes disruptions related to use of the structure.

A large strain finite element analysis is performed to analyze the effect of soil anisotropy on the inclined piezocone penetration test in normally consolidated cohesive soils. The piezocone penetration is numerically simulated using the commercial finite element code ABAQUS. The saturated clay is modeled as a two-phase material and the effective stress principle is used to describe its behavior. A frictional contact interface utilizing Mohr-Coulomb's theory was chosen to represent interactions between the surface of the cone and the soil. The Anisotropic Modified Cam Clay Model (AMCCM) by Dafalias (1987) was chosen and implemented into ABAQUS through user subroutine UMAT. The piezocone penetration is numerically simulated by the three-dimensional finite element method using different inclination angles at different initial stress states. A field testing program of inclined cone penetration is also developed and performed in three different locations with varying soil characteristics in Louisiana, using the Continuous Intrusion Miniature Cone Penetration Test System (CIMCPT). The following conclusions are drawn from this study: 1) As compared to the previously conducted calibration chamber tests, the finite element analysis results based on Anisotropic Modified Cam Clay Model (AMCCM) are overall in good agreement with the actual measurements. This indicates that the soil anisotropy plays an important role during piezocone penetrations. 2) Initial stress state strongly affects the tip resistance, sleeve friction and generated excess pore pressures. Coefficient of lateral earth pressure K indicates the degree of initial stress anisotropy. If K=1, no difference is expected between inclined and vertical penetrations. However, for K1, the tip resistance, sleeve friction and generated excess pore pressures tend to increase (K<1) or decrease (K>1) when the orientation of penetration changes gradually from vertical to horizontal. Also, the soil classification derived from inclined penetration data may require special consideration. 3) The effect of anisotropic permeability on the tip resistance, sleeve friction and excess pore pressures during inclined penetrations is negligible for soils with very low hydraulic conductivities. However, it has significant effect on the dissipation of the excess pore pressure at the cone tip.

This thesis presents the development of a True Triaxial Testing TTT Apparatus. The TTT apparatus developed has the capabilities of applying the three principal stresses to a rectangular prismoidal specimen independently. The minor principal stress is provided by the cell pressure. The major principal stress is provided by a load actuator traveling at a constant velocity. A LabView software program instantaneously reads instrumentation, makes calculations, and commands a second load actuator to induce an intermediate principal stress that maintains a constant b-value; where b-value is equal to the intermediate principal stress minus the minor principal stress divided by the major principal stress minus the minor principal stress. The development of the TTT Apparatus included; creating a robust data acquisition system to facilitate immediate readings of all needed instrumentation, manufacturing a horizontal loading system to transmit the load from the load actuator to the specimen, constructing a pressure control system capable of providing the desired confining pressure, creating a LabView software program to interface with the data acquisition system and the load actuators to record and control the test parameters. Calibration tests were performed to quantify the correction factors for the following: volume change due to volumetric expansion of the pressure jacket and loading rams, the load due to frictional forces and pressure, and the length change due to compression of the rubber cushions. True triaxial test were conducted on F-75 silica sand at various b-values as verification of the developed TTT Apparatuss capabilities. The results of these tests compared well with the findings of other researchers conducting similar tests.

Microfocus x-ray computed tomography (μCT) is a powerful non-destructive scanning technique to study the internal fabric of granular materials. In this thesis, μCT was applied to two cases. The first case involves studying the behavior of particles in a triaxial specimen during shearing. Three-dimensional translation and rotation of the particles were tracked throughout the shearing process, and they were used to calculate the local strain distributions. Moreover, the local dilatancy angle distribution was calculated throughout experiment. These distributions were compared to study the changes in the behavior of the particles at different stages of the test. It was noticed that the radial strains ε_x and ε_y showed a similarity due to the axisymmetric conditions. It was also found that high rotation angles took place, where the vertical rotation component reached up to 30 degrees and the horizontal rotation reached up to 60 degrees. Furthermore, the rotation strain component reached up to about 50% at the end of the test. On the other hand, a wide range of local dilatancy angles was observed, where the values varied between -50 degrees and 70 degrees. The second part of this thesis aims at determining the effect of grain size distribution and consolidation pressure on the spatial porosity distribution of synthetic rock cores. Twelve rock cores were prepared with different grain size distributions and consolidation pressures, and scanned using a high resolution μCT system. Density calibration was conducted to correlate the CT numbers to the bulk density, and the porosity of the cores. 15 million porosity values were calculated for each core. μCT showed an excellent ability to track the changes in the local porosity distribution of the cores. It was found that grain size distribution has a larger effect on the porosity values, where a noticeable decrease in the porosity values was observed when using well graded grains. On the other hand, increasing the consolidation pressure did not always decrease the porosity values. This could be due to the crushing of the particles at very high consolidation pressures.

Reinforced concrete Intermediate Diaphragms (IDs) are still being used in prestressed concrete (PC) girder bridges in Louisiana. Some of the advantages of providing IDs are disputed and also use of IDs increases the cost and time of construction. There is no consistency in the practice of providing IDs among various states and codes of practice and overall there is a lack of clarity on the effectiveness of IDs and their needs in prestressed concrete bridges. The objectives of this research are to assess the need of reinforced concrete (RC) IDs in PC girder bridges and to determine their effectiveness and also to search for an alternative steel diaphragm configuration which would be as effective as RC IDs and could replace them if necessary. Systematic parametric studies for various bridge configurations, which are representative of an entire range of bridge geometries with different parameters, are analyzed through simplified and solid finite element models, which were already calibrated under live loads. This study was carried out on right and skewed bridges which are simply supported and continuous. A reduction factor which could be multiplied by a load distribution factor to account for the influence of the diaphragm in load distribution was developed. To assess the effectiveness of various diaphragms in protecting the girders against the lateral impact and to determine the design forces in the steel bracing members during construction of deck, a finite element analysis was carried out using 3-D solid models. The results from the parametric studies indicated that several parameters such as skew, span length, spacing, stiffness of diaphragm and girder have different levels of influence on the effectiveness of diaphragms in live load distribution for bridges. Correction factors were developed which could quantify the ID influence on load distribution. Results from various studies indicated that a steel diaphragm section can possibly replace the RC steel diaphragms.