TIME-DEPENDENT RELIABILITY OF EXISTING BRIDGES CONSIDERING NON-STATIONARY LOAD PROCESS

A large number of new bridges have been built in China during the past decades, and now many of them are suffering greater risk of serviceability from ever-increasing traffic loads. In previous studies, when evaluating structural reliability for existing bridges, the loading process is assumed as a stationary Poisson process and all loads follow the same distribution. However, significant tendency of increasing is observed from recorded traffic data of our country in the past years, thus the existing methodology is not valid when load change occurs. In this paper, an improved method is proposed to calculate the time-dependent reliability with non-stationary load process. Illustrative examples demonstrate the accuracy and effectiveness of the proposed method. The existing method is a special case of the proposed one. By means of the proposed method, the sensitivity of structural reliability is investigated to the parameters of stochastic traffic load process. It is shown that the traffic load change has great impact on structural reliability; the increment of mean load by 1.1% per year, or the increment of standard deviation of load by 1.3% per year results in a twice failure probability in a service period of 20 years.