Arockiasamy, Madasamy

The finite element analyses of the concrete bridge system and single double-tee beams are carried out using both orthotropic and isotropic modeling including linear and nonlinear behavior. The orthotropic concrete double-tee bridge system is modeled to predict the deformational behavior of bridge deck under the AASHTO service loading conditions in the static regimes. The nonlinear analyses of reinforced and prestressed concrete rectangular beams are also carried out to verify the validity of modeling. Both the linear and nonlinear finite element analyses for single double-tee beams prestressed with FRP materials are carried out in this study. In this research, the MARC finite element software on the VAX frame is used as a tool to carry out the analyses.

This study evaluates the effectiveness of using externally bonded CFRP plates for repairing damaged prestressed concrete structures as an alternative to the metal sleeve splice. Currently the metal sleeve splice is the most often used method for the repair of damaged prestressed concrete bridges. The use of bonded CFRP plates could be a viable alternative to the use of steel in this type of repair because of their high strength and stiffness, resistance to corrosion and low weight. The bond strength of CFRP plates bonded to concrete was evaluated by the use of a peel test and correlated by a finite element analysis. The peel test showed that the structural system was not significantly adversely effected by harsh environmental conditions. The results of this study showed that the use of CFRP plates is a feasible alternative to steel in the metal sleeve splice repair with some limiting factors.

This study presents the experimental and theoretical studies on debond of steel bonded to concrete, which aids in understanding the mechanics of the repaired damaged prestressed concrete girders with externally bonded steel plates. The bond strength of bonded steel plate specimen is determined experimentally by the debond test. The initial crack is introduced in the specimens at three different locations, which include the steel/adhesive interface, adhesive through-thickness, and adhesive/concrete interface. Certain debond test specimens are exposed to freeze/thaw and tidal cycles to evaluate the degradation in bond strength resulting from the environmental conditions. The fracture toughness for debonding would be evaluated and expressed as the critical strain energy release rate. A finite element analysis was performed to evaluate the compliance and stress distribution in the debond test specimens. Also, stress distribution of repaired AASHTO prestressed concrete bridge girders with metal sleeve splice was also determined at the interface of steel and concrete.

Wheel load distribution on highway bridges is an important response parameter in determining structural member size and consequently the strength and serviceability of bridge members. It is, therefore, of critical importance in the design of new bridges and the evaluation of the load carrying capacity of existing bridges. The finite element method was used to carry out detailed analyses of different bridge types-solid slab bridges and slab-on-girder bridges with varying skew angles. The actual loads used in the bridge tests were modeled in the analysis. The available field test results for different skew bridges types viz., solid slab and slab-on-girder, were compared with the analytical values based on AASHTO, LRFD code and Finite Element Method. Important parameters such as beam spacing, span length, slab thickness, flexural rigidities of longitudinal and transverse girders, number of traffic lanes and total curb-to-curb deck width were identified in the load distribution of the skew bridges for varying skew angles.

The present study was mainly directed towards the analyses of comprehensive field test data, moment and shear load distribution of continuous slab-on-girder bridges, and effects of skew angle, diaphragms, and shoulders on the wheel load distribution factors. Analytical and field studies on the wheel load distribution of continuous slab-on-girder bridges are presented and compared with those based on the AASHTO and LRFD codes. The main parameters that affect moment and shear load distribution are compared for single and multiple span bridges. The study on moment and shear load distribution focuses on five main parameters: spacing between the girders, variation of skew angle, variation in the number of spans, ratio between adjacent two spans, and span length. The effect of diaphragms on wheel load distribution was first evaluated for a field test bridge and compared with a finite element model of the actual bridge. The diaphragm parameters that affect the wheel load distribution were studied to evaluate the effect of each parameter.

This report presents the experimental and theoretical studies on the feasibility of using CFRP laminates for strengthening damaged reinforced concrete beams in cold environment. Experimental work includes investigation on fatigue strength, ultimate capacity and failure modes of repaired reinforced concrete beams in cold environment and room temperature. The repaired concrete beams subjected to fatigue in cold environment exhibit fewer number of cracks than those observed in beams at room temperature. The crack propagation and resulting damage were faster in beams tested in room temperature than those at cold temperatures. The study also includes investigation of thermal response of repaired plain concrete beams with CFRP laminates subjected to thermal cycles. Analytical studies on the distributed shear forces and peeling forces of repaired reinforced concrete beams were carried out to analyze the interaction between the laminate and the concrete interface. The temperature distribution and strains developed by the temperature differential are determined in the repaired plain concrete beams subjected to thermal cycles and the analytical results compared with the measured values.

Four concrete piles prestressed with Carbon Fiber Reinforced Plastics were cast, in which two piles were fabricated with CFRP transverse reinforcement. The remaining two were provided with transverse steel spiral reinforcement. The piles were designed according to Florida Department of Transportation (FDOT) guidelines. The Pile Driving Analyzer (PDA) was chosen as the primary data acquisition system for the pile driving due to its mobility, reliability and robustness based on the high frequency excitation. The Pre-driving analysis consisted of several stages. The estimated static bearing capacity of the experimental piles was first calculated followed by SPT sampling at the pile driving site to obtain the soil conditions. The percent skin and toe friction, ultimate capacities, driving system parameters, maximum displacements, energy, integrity, tensions and static capacity were determined prior to pile driving. The piles were then driven and the data from the pile driving compared with the analysis.

In a highly corrosive environment, corrosion is the main factor leading to deterioration and eventual failure of conventional reinforced or prestressed concrete structures. Carbon Fiber Reinforced Plastics (CFRP) are considered as an alternative to steel reinforcement due to its excellent corrosion resistance. This investigation was conducted to establish the feasibility of using CFRP cables as reinforcing elements in reinforced concrete columns. Besides investigating durability of CFRP cables in adverse environments (alkali and sea water) experimental and theoretical studies were carried out to study the behavior of CFRP reinforced concrete slender columns under combined axial load and bending moment. Exposure to air, sea water and alkali environments with alternating wet/dry cycles had no adverse effect on the strength of the CFRP cables. The CFRP reinforced concrete columns subjected to eccentric loads exhibited excellent ultimate load capacity. Feasibility of using CFRP cables in the reinforced concrete columns is assessed based on deflections, strains, curvatures, crack distributions, first crack loads and ultimate loads.

Carbon Fiber Reinforced Plastics has recently has been recognized as an alternative to conventional steel reinforcement in concrete due to its excellent resistance to corrosion. Four rectangular concrete beams and four concrete columns reinforced with CFRP bars were cast for the study of the long term behavior under uniform sustained loading. The beams were simply supported and subjected to uniform sustained loading. The columns were arranged in a steel reaction framework. The beams and columns were instrumented and monitored to observe the change in the behavior due to the creep and shrinkage of concrete. An analytical method is developed to predict the long term behavior of CFRP reinforced concrete members. The calculated deformations compare reasonably with the experimental values. A modified equation for the calculation of the long term deflection is proposed for CFRP reinforced concrete beams. A simplified equation for the calculation of the creep coefficient is also proposed.

The Knowledge Based System CARAT is developed to rate any existing steel truss bridge. CARAT is capable of rating statically determinate and indeterminate truss bridges. Corrosion, temperature effects and the remaining fatigue life of the truss members can be evaluated using CARAT. The other expert system SKEWRAT is developed to determine the strength of skew bridges. Skew AASHTO girder and slab bridges can be analyzed using SKEWRAT. The architecture of both CARAT and SKEWRAT are based on production system model and set of IF-THEN rules are developed using EXSYS Professional Shell editor. The inference mechanism fire rules according to the built-in reasoning process. The suggestions given by Bakht and Jaeger (8) are incorporated to determine the strength characteristics of skewed AASHTO girder and slab bridges. Programming Languages FORTRAN and C are used extensively for the software development. The validity of both the softwares are verified and illustrated in detail with four examples.