Expansion joints are often considered as one of the most vulnerable elements affecting the sustainability of traditional jointed bridges. Over the past several decades, a new type of integral abutment bridge (IAB) has been proposed, where the joints are eliminated at the abutments and/or along the length of the bridges. Although with wide acceptances, the IABs have not been largely applied in practice. Many arguments are unsettled and there are no national design guidelines currently. Among all, the thermal behavior is one of the most concerned issues, and that, to a large extent, limits the maximum length of IABs that can be constructed. Under this circumstance, a new type of fiber reinforced polymer (FRP) materials, with special material properties, are considered as an alternative to replace the traditional concrete and steel materials. However, the studies on the performances of both IABs and FRP bridges are not adequate. Therefore, an investigation on the thermal behaviors of IABs and FRP bridges is conducted. Then, an effort is made to analyze the responses by combining the FRPs with IABs, and to verify that such a configuration will help resolve the thermal issues of IABs. For FRP bridges, (1) the temperature distributions of a GFRP panel are discussed based on a field monitoring program conducted at the state of Kansas; (2) the influencing factors on the temperature distributions are studied, including the material property, environmental condition, and section hollowness; (3) the thermal gradients of the FRP panel bridges are proposed referring to the AASHTO LRFD design code; and (4) the jointed bridges performances, after replacing traditional slabs by FRP panels, are numerically analyzed. For IABs, (1) the thermal responses of the first full IAB in the state of Louisiana, Caminada Bay Bridge, are discussed based on a field monitoring program; (2) a parametric study is employed to analyze the effects of different parameters on the thermal performances, including the soil types, bent-pile connections, loading types, and support conditions; and (3) a numerical study is performed to verify the assumption that applying FRP panels on IABs will help resolve the thermal issues of IABs.

The serviceability and safety of buildings and bridges are expected to be maintained within a reasonable safety level throughout their lifetimes. However, the increase of the applied loads and degradation of structural performances reduce the safety of these structures over time. Therefore, the performance assessment of existing bridges with reliability theories is a worldwide problem in civil infrastructure systems. Theoretically, the bridge reliability, usually expressed by a reliability index, is quantified by comparing the structural capacity (R) with the load effects (Q), using the predefined limit state functions. A limit state function is a mathematical description of a boundary between the desired and undesired performance of a structure. The resistances of structures and live loads on the bridge are none stationary processes, where their statistic parameters, e.g., mean values and deviations, are time variant. Thus, traditional reliability analysis methods cannot be applied to the entire service life of bridges. In this research, the entire life cycle of bridges is treated as the sum of time series. During each time segment, both the load effect Q and the structural capacity R are assumed to be a stationary random process, and are expressed with a certain type of distribution. Thus, after obtaining the reliability probabilities for each time segments, the reliability probability for any length of mean recurrent intervals is obtained by the continued multiplication of the yearly reliability. The extreme structure response which reflects the extreme live load distribution for mean recurrence intervals is derived based on a short-term monitoring of a field bridge. The flexural capacity of bridge girders considering variation of concrete strength, corrosion of steel reinforcements in the concrete and steel components is discussed in details. The flexural capacity of bridge beams can be retrofitted with fiber reinforced polymers (FRP) materials. Finally, the flexural capacity of concrete bridge girders and steel girders strengthened with prestressed carbon fiber reinforced polymers (CFRP) are introduced. The time-variant reliability after the rehabilitation is calculated. The reliability of a bridge keeps decreasing all the time. There is a jump in the reliability when the bridge is strengthened. Rehabilitation of a bridge also slows down the rate of the performance degradation of the bridge.

A watershed-based modeling framework is developed in this dissertation for simulating temporal and spatial variations in DO in lowland rivers with organic-rich fine-grained sediment. The modeling framework is based on three major contributions/new models, including (1)VART-DO model for improved estimation of reaeration coefficient (K2) in natural streams, (2)VART-DOS model for simulation of temporal variations in DO in response to sediment resuspension, and (3)VART DO-3L model for simulation of spatial variations in DO. A major advantage of VART-DO model is the capability of simulating DO exchange across the water-sediment interface through the hyporheic exchange mechanism in addition to the air-water exchange. Simulation results from VART-DO model revealed that hyporheic exchange can reduce K2 by 30% while longitudinal dispersion increases K2 by 50%. VART-DOS model is developed for simulation of temporal variations in DO particularly due to sediment resuspension effect during high flow. Application results of VART-DOS model to the Amite River in Louisiana showed that 83% of DO consumption in water column in July 1990 was because of sediment resuspension. A novel feature of VART DO-3L model is that a fine-grained stream with the flocculent layer can be vertically modeled with three layers: overlying water column, an advection-dominated storage zone, and a diffusion-dominated storage zone in relatively consolidated stream bed-sediment. While the importance of flocculent layer to instream DO has been widely reported, VART-DO-3L model is the first modeling tool that incorporates the flocculent layer into DO modeling. This is a unique feature of VART-DO-3L model, making it possible for determining both longitudinal and vertical profiles of DO in streams. Results of VART-DO-3L for the Amite River indicated that the DO level decreases longitudinally from 7.9mg/L at the Denham Springs station to 2.89mg/L at the Port Vincent station. Vertically, DO level drops rapidly from overlying water column to the advection-dominated storage zone and further to the diffusive layer. The DO level in the advective layer is about 40% of that in water column. The thickness of the diffusive layer varies between 0-10mm, depending on effective diffusion coefficient. Developed models in this dissertation are also applicable to sandy/gravel rivers.

The Rolling Wheel Deflectometer (RWD) is capable of measuring pavement deflection at high speeds without traffic interruption or compromising safety along tested road segments. To optimize the use of RWD at the network level, an assessment tool is needed to incorporate RWD data into current Pavement Management System (PMS) and to identify pavements in need of maintenance or rehabilitation. The objective of this study is to present the development of a screening tool, referred to as the pavement assessment triangular model, to predict pavement overall conditions based on RWD deflection, roughness measurements, and surface conditions as described by the Pavement Condition Index (PCI). Formulation of the proposed tool and its application were based on data collected during evaluation and testing of RWD in Louisiana. The relationship among SN, deflections and pavement distresses were also investigated to better understand the screening tool. Based on the analysis presented in this study, the proposed pavement assessment triangular model may be used at the network level to identify deficient pavement sections.

In the wake of Hurricane Katrina, the U.S. Army Corps of Engineers (USACE) updated design methodologies and required factors of safety for hurricane and storm damage risk reduction system (HSDRRS) structures to incorporate lessons-learned from the system performance during Katrina and results of state-of-the-art research in storm surge modeling and foundation behavior. However, the criteria (USACE 2008) were not calibrated to a target reliability, which creates the need to understand the reliability provided by designs using those criteria, especially for pile-founded structures subject to global instability. This dissertation presents a methodology for quantifying the reliability of pile-founded structures that can be applied to hurricane risk reduction structures or more broadly to other types of pile-founded structures. The emphasis of this study is on a representative hurricane risk reduction structure designed using the new USACE criteria, for which the reliability is quantified for comparison to industry target reliabilities. A designer-friendly methodology for quantifying the reliability of hurricane risk reduction structures is presented, along with recommendations developed from a state-of-the-art review of geotechnical, hydraulic, and structural uncertainty data. This methodology utilizes commercial software and routine design methods for the development of inputs into an overarching framework that includes point estimate simulation models and event tree methods to quantify the structures system reliability. The methodology is used to illustrate differences in analysis results with and without accounting for variance reductions due to spatial correlation are also presented through stability and flowthrough limit states. Element reliabilities and overarching system reliabilities for a representative structure are quantified for hydrostatic hurricane storm surge loadings, soil loading, and dead loads. Wave loadings and impact loadings are not considered. The use of variance reductions on undrained shear strengths for point estimate simulations produced higher system reliability indices than the simulations not considering variance reductions for the stability and flowthrough limit states. Using the reduced variances, computed element and system reliabilities were above the industry target reliability indices presented in the literature.

Recently, congestion pricing emerged as a cost-effective and efficient strategy to mitigate the congestion problem on freeways. This study develops a feedback-control based dynamic toll approach to formulate and solve for optimal tolls. The study compares the performance of the proposed methodology to that of the current strategy deployed on Interstate 95 express lanes. Two objectives are studied: one is to maximize the toll revenue while maintaining a minimum level of service on the managed lanes and the other is to maximize both revenue and throughput on the managed lanes while keeping a minimum level of service. The impact of drivers value of time based on their income level is also examined. Three values ranging from 60% to 120% of the mean hourly income are used. The results show that for high demand, an increase in the probability of choosing managed lanes is obvious, with the highest increase observed for the case of 120%. Besides, the effects of distributions of drivers value of time among drivers are addressed. Two numerical examples are provided to explain how the proposed strategy works under three driver groups and forty-four driver groups, and an external module is developed to execute the strategy in real time during VISSIM runtime. When compared to the currently adopted toll pricing strategy on I-95, the proposed strategy with both objectives produce steadier toll rate profiles, while keeping the speeds at 45 mph or more. The objective of revenue maximization produces larger toll revenue and objective of both revenue and throughput maximization produces higher throughput on the managed lanes.

The Northern coast of the Gulf of Mexico is threatened by storm surge and waves from tropical storms. It has been long known that marsh vegetation attenuates storm surge and waves and is vital for sustaining marsh edges. However, little is known about the relationship between plant properties and the amount of storm surge and wave reduction the plants provide. In order to better understand the stiffness properties and physical dimensions of saltmarsh vegetation, which are directly related to their ability to attenuate waves and storm surge, this study has been conducted. Stiffness of salt marsh vegetation was determined through direct bending and through board drop testing at several locations along the Southeast Louisiana Gulf Coast from August 13, 2009 to September 15, 2011. Biomechanical properties of salt marshes, including plant dimension and bending stiffness modulus, were measured on coastal marshlands on the Southeast gulf coast of Louisiana, and are correlated with plant total height, stem height, stem diameter, plant stem density, and seasonal variations and botanical behavior. Two methods were employed, including direct stem bending and indirect board drop tests. The dataset is analyzed in depth to develop empirical equations of plant stiffness and compared with those found in the literature based on vegetation on river floodplains. These wave and surge measurements along with vegetation data are applicable to calibrating wave models that incorporate the reduction of energy due to wetland vegetation. The mitigation of wave energy and storm surge is critical to the survival of Louisianas wetlands and coastline. Salt marsh vegetation has the ability to mitigate the potential damage caused by storm surges and large waves. This study will improve our understanding of the role of vegetation in attenuating waves and storm surge and the accuracy of the parameterization of the vegetation effects in the-state-of-the-art wave models. The successful quantification of wave and surge attenuation by salt marshes will be a positive contribution to Louisianas hurricane protection and coastal restoration efforts.

Global as well as local behavior of prestressed girder bridges made continuous by adding continuity diaphragms with a recently proposed positive moment continuity detail were investigated in this study. The focus of the investigation is on the positive moment caused by temperature gradients, time dependent effects such as creep and shrinkage, and some live load positions, and on the force transfer mechanisms through the diaphragm. The study utilized different approaches including analytical models for temperature evaluations and finite element models for structural assessments. Field data from a bridge using the new detail were used to validate the developed models. The temperature field of the bridge at different times of the year was estimated using an analytical method. The computed temperature profiles, actual recorded temperatures at the bridge site, and AASHTO specified design gradients are presented and compared. Primary as well as secondary thermal stresses were calculated and restraint moment caused by temperature gradient was quantified. A 3-D finite element model capable of predicting the long term behavior of prestressed girder bridges is presented. A temperature independent creep model was adopted and calibrated using early age data. Construction sequence was considered in the analysis. The FE restraint moment predictions were compared to results obtained from other commonly used analytical method. A parametric study was conducted using the analytical method to investigate the creep coefficient values. Performance of the continuity detail under live load effects was investigated. A live load test was carried out at the bridge site using two loaded trucks. A full bridge 3-D finite element model was also developed and validated with the field data. The validated FE model was also used to investigate the efficiency of the continuity detail. A more detailed 3-D FE model that zooms in on the joint was also built accounting for critical behavioral aspects of the continuity details under service conditions. Contact between cast-in-place concrete and precast concrete, transfer length of prestressing strands, and actual 180º-hook hairpin bar detail were included in the detailed model. Force transfer mechanism, stress distribution and the effective gross moment of inertia at end of girder were investigated.

In this study, the synthesis process, composition, and microstructure as well as mechanical properties of geopolymers generated by 3 different kinds of raw materials (i.e., metakaolin, mixture of red mud and fly ash, mixture of red mud and rice husk ash) was explored. For geopolymers from identical raw materials, variable parameters involved in the synthesis were examined to investigate the extent and degree of geopolymerization. Uniaxial compression testing was used to examine the mechanical properties (i.e. compressive strength, stiffness, and failure strain). Then the composition and microstructure were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) as well as energy-dispersive X-ray spectroscopy (EDXS). The results demonstrates that the geopolymeric products are not pure geopolymer binders, but geopolymeric composites, which generally comprise pure geopolymer binder as the major matrix, a small amount of unreacted source materials and nonreactive crystalline phases (e.g., quartz, anhydrite, and hematite) from parent materials as inactive fillers. Moreover, the study also shows that geopolymeric products can be used as a cementitious material to replace Portland cement in certain engineering applications, such as roadway construction, which brings environmental and economic benefits. Owing to the consistent properties of metakolin-based geopolymers, they were selected to be examined as smart adhesives for the infrastructure health monitoring. A distributed geopolymer-fiber optic sensing (G-FOS) system was proposed, where metakaolin-based geopolymers are used as smart adhesives to affix optical fibers to existing in-service structures to form the integrated G-FOS sensor for infrastructure health monitoring. The concept of such a G-FOS system was explained, and laboratory experiments as well as prototype testing were conducted to validate the concept and its feasibility. The results showed that varying the geopolymer composition (e.g., SiO2/Al2O3 ratio) and adding sand filler can both alter the tensile cracking strain for tailored sensing applications for both steel and concrete structures. Further prototype testing on steel and concrete demonstrated the feasibility of the proposed G-FOS system that can be used to monitor tensile strain and crack width for steel and concrete structures, respectively.

With the current demand for Portland cement concrete (PCC) sustainability, supplementary cementitious materials (SCMs) are used in concrete mixtures. The SCMs positively impact the environmental and economic aspects of concrete mixtures and improve the mixture properties in both fresh and hardened concrete. In this research, one control and twenty-four ternary mixtures, with various combinations of fly ashes (Class C and F), slags (Grade 100 and 120), and Portland cement were fabricated. The thermal properties (coefficient of thermal expansion (CTE), thermal conductivity, and heat capacity) and mechanical properties of the selected ternary mixtures were measured at various ages. Temperature gradients were measured using a concrete pavement (10-in. thick) to characterize daily and seasonal temperature variations through the slab thickness. The correlation between air temperature and surface temperature, as well as air temperature and temperature difference of the slab thickness, were established based on the measured temperature gradients in the concrete pavement. The enhanced integrated climatic model (EICM) analysis was conducted, using measured material properties and climatic conditions. A local calibration of EICM was performed by comparing EICM-predicted temperature gradients to field measurement. It was concluded that the surface temperature is suitable to accurately predict temperature gradients in EICM. A thermal stress analysis of the ternary mixtures was conducted to calculate the critical tensile stress on the PCC pavements by means of the measured mechanical properties, nonlinear temperature gradients obtained from EICM, and CTE gradients throughout the slab thickness. The ratios of tensile stress-to-strength at the critical state of concrete pavements were estimated as well, in order to investigate the vulnerability of ternary mixtures to tensile stress. The ratio of tensile stress-to-strength shows that all the ternary mixtures, inclusive of the replacement of 30 % slag with 20 % fly ashes, 30 % slag with 30 % fly ashes, and 50 % slag with 20 % fly ashes (both Class C and F), do not exceed 100 % tensile stress-to-strength ratio at all ages. These combinations may be considered as the limitation of ternary mixture replacement with slags and fly ashes.