Time-dependent reliability analysis for in-service bridge considering correlated non-stationary stochastic process

Non-stationary characteristics of correlated loads and resistance degradation of in-service bridge structure should be considered in time-dependent reliability analysis. This paper proposes a reliability model to assess safety performance of in-service bridges by using Monte Carlo Simulation based on Copula theory for correlated loads subjected to normal distribution and Extreme Type I distribution, where an empirical equation is obtained based on resistance degradation described by a Gamma process for simplified reliability calculation of correlated adjacent loads following Extreme Type I distribution. The results indicate that load correlativity decreases bridge failure probability, which is advantageous for the safety performance assessment in its subsequent service life; larger scale parameter of Gamma process will slightly increase time-dependent failure probability since it brings higher possibility of steep decrease of resistance in a short time.