Bridge design should take into account not only safety and functionality, but also the cost effectiveness of investments throughout a bridge life-cycle. This work presents a probabilistic approach to compute the life-cycle cost (LCC) of corroding reinforced concrete (RC) bridges in earthquake prone regions. The approach is developed by combining cumulative seismic damage and damage associated to corrosion due to environmental conditions. Cumulative seismic damage is obtained from a low-cycle fatigue analysis. Chloride-induced corrosion of steel reinforcement is computed based on Fick’s second law of diffusion. The proposed methodology accounts for the uncertainties in the ground motion parameters, the distance from source, the seismic demand on the bridge, and the corrosion initiation time. The statistics of the accumulated damage and the cost of repairs throughout the bridge life-cycle are obtained by Monte-Carlo simulation. As an illustration of the proposed approach, the effect of design parameters on the life-cycle cost of an example RC bridge is studied. The results are shown to be valuable in better estimating the condition of existing bridges (i.e., total accumulated damage at any given time) and, therefore, can help schedule inspection and maintenance programs. In addition, by taking into consideration the deterioration process over a bridge life-cycle, it is possible to make an estimate of the optimum design parameters by minimizing, for example, the expected cost throughout the life of the structure.

Box-girder bridges supported by single reinforced concrete (RC) columns are expected to sustain seismic shocks with minor structural damages in seismically active regions where transportation is substantially required for rescuing and evacuating tasks. Such viaducts are vulnerable to damage when they are subjected to strong ground motions and acceleration pulse records, especially when responding in a flexural mode or having relatively low core confinement. Using a nonlinear dynamic solver that applies the fibre element method, global and local damage curves are computed based on the dissipated energy under hysteretic curves and based on constitutive curves, respectively. The RC bridge with seismic isolation bearing is used as an alternative system to control the damage, and modelled using linkage elements between the substructure and super structure. It was found that seismic isolation can be controlled to dissipate partial seismic energy so that the RC column gains the least possible minor damage. Using a MatLab program, a fibre element nonlinear model was built using a simplified iterative process and simplified constitutive relations. The number of fibres and elements under the dynamic loading was found to be affecting the final results of the analysis. Using crack growth modelling based on fracture mechanics, the combined discrete element/finite element explicit-Elfen code was applied to investigate the crack growth in 3D dynamically loaded RC columns. Despite its excessive computational cost and time, this code provides reliable information about local damage in the RC column core. Earthquake records with the pulse acceleration phenomenon have a severe damage potential on the structure. The difference in damage intensities was detected by crack growth modelling for the same problem using different loading rates. Critically stressed zones can be investigated independently by using the relative response technique, in which responses from the numerically analysed structure are re-used as applied loads onto a small-scale crack model for the critical member. Two general conclusions can be obtained; bridges with single RC columns designed by the demand/capacity criterion could suffer severe damage and possible collapse when subjected to strong ground motions. Secondly; hysteresis-based methods provide a global damage evaluation based on strength and ductility only regardless of the damage growth inside the concrete core and the buckling of bars, which could lead to progressive collapse.

There has been increasing interest in evaluating the performance of existing reinforced concrete (RC) bridges just after natural disasters or man-made events especially when the defects are invisible, or in quantifying the improvement after rehabilitations. In order to obtain an accurate assessment of the reliability of a RC bridge, it is critical to incorporate information about its current structural properties, which reflects the possible aging and deterioration. This dissertation proposes to develop an adaptive reliability analysis of RC bridges incorporating the damage detection information obtained from nondestructive testing (NDT). In this study, seismic fragility is used to describe the reliability of a structure withstanding future seismic demand. It is defined as the conditional probability that a seismic demand quantity attains or exceeds a specified capacity level for given values of earthquake intensity. The dissertation first develops a probabilistic capacity model for RC columns and the capacity model can be used when the flexural stiffness decays nonuniformly over a column height. Then, a general methodology to construct probabilistic seismic demand models for RC highway bridges with one single-column bent is presented. Next, a combination of global and local NDT methods is proposed to identify in-place structural properties. The global NDT uses the dynamic responses of a structure to assess its global/equivalent structural properties and detect potential damage locations. The local NDT uses local measurements to identify the local characteristics of the structure. Measurement and modeling errors are considered in the application of the NDT methods and the analysis of the NDT data. Then, the information obtained from NDT is used in the probabilistic capacity and demand models to estimate the seismic fragility of the bridge. As an illustration, the proposed probabilistic framework is applied to a reinforced concrete bridge with a one-column bent. The result of the illustration shows that the proposed framework can successfully provide the up-to-date structural properties and accurate fragility estimates.