Reliability Analysis of Bridge Structures for Earthquake Excitations

In this paper, a numerical approach to the reliability analysis of prestressed reinforced concrete long span bridges is presented. A bridge is modeled by finite element software and the analysis is performed in time domain by considering the bridge material nonlinearity. The considered random variables are: Specific strength of concrete, yield stress of steel bars, yield stress of prestressed bars, all sectional dimensions, structural damping ratio, effective depth of steel bars aiid the magnitude and PGA of earthquake. In this study, the reliability of a bridge structure is evaluated under earthquake excitations. For this purpose, the First-Order Second-Moment (FOSM) method is used. In this method, the mean value and standard deviation of the random variables are considered for evaluating structural reliability. The proposed procedure is applied to evaluate the reliability of an existing prestressed arch concrete bridge located in Bandar-e-Anzali in Iran. Bandar-e-Anzali is a very high-risk earthquake zone. The results of the study show that the structural da.rn.ping ratio, magnitude and PGA of earthquakes have a significant effect on the variation of reliability in the structure, while variations in the dimensions of the structure have little effect on the reliability index.