| The objective of this dissertation is the development of time-dependent corrosion models for evaluation of concrete bridges. Four computer programs were developed: (1) Finite element program for prediction of diffusion of chloride ions for a general corrosion model, (2) Finite element program for prediction of diffusion of hydrogen atoms with crack propagation in wires of tendons, for a stress-corrosion cracking (SCC) model, (3) Nonlinear section analysis program for the calculation of the ultimate resistance of concrete bridges, and (4) Integrated pre- and post-processor program for evaluation of time-varying reliability for corroded concrete bridges.; Using the programs, the analysis was performed to determine the relationship between the corrosion damage and system reliability of concrete bridges. The considered random variables include rebars and prestressing tendons, strength of rebars and tendons, bond strength, dimensions, loads, water to cement ratio, and correlation coefficient for corrosion in rebars and tendons. The developed programs were applied to evaluate the bending resistance of the girders, the maximum crack width, and crack propagation in concrete and steel. The analysis was performed for the selected prestressed and partially prestressed concrete girder bridges.; It is suggested to improve crack width control equation in the current AASHTO LRFD Code by including the effect of water to cement ratio and the importance factor. The latter depends on the maximum allowable crack widths in various environmental conditions. Because the proposed equations are based on the strain compatibility of the considered sections, they can be applied to crack control by stress levels in prestressed and nonprestressed reinforcements in a unified manner. Crack width prediction by the suggested equation is compared well with experimental results, and better than the current crack prediction equation of the CEB-FIP specifications.; A decoupling technique has been developed for evaluation of the crack propagation in a wire section, driven by the hydrogen diffusion. A 3-dimensional crack propagation can be modeled effectively using two 2-dimensional finite element models, one for fracture analysis of a round bar in a longitudinal section, and the other one for hydrogen diffusion analysis in a transverse section. The obtained analytical results show a good agreement with the available test results. |
