考虑抗力非平稳劣化和荷载相关性的桥梁可靠性分析

BRIDGE RELIABILITY ANALYSIS CONSIDERING NON-STATIONARY DEGRADATION OF RESISTANCE AND LOAD DEPENDENCY

桥梁结构在服役期间受到环境侵蚀和均值增大的相关荷载作用,承载力降低,安全状况不容乐观。为了准确评估服役桥梁在剩余使用寿命内的安全性能,需要考虑结构抗力劣化的非平稳特性以及荷载的时间相关性。该文基于时变可靠度理论,采用Gamma分布描述结构抗力的非平稳劣化过程,并用二维联合分布函数表示相邻荷载的相关性,基于贝叶斯原理,提出了计算公式,并采用蒙特卡洛模拟(MCS)对计算结果进行了验证。对四川省某钢筋混凝土简支梁桥的时变可靠度分析结果表明:在单次条件概率分子的二重积分结果大于0.7时,公式计算结果与MCS结果接近,证明了其正确性;Gamma劣化过程的尺度参数越大,荷载的时间相关性越弱,结构失效概率越大;当作用于结构的车辆荷载年均增长率超过2%时,桥梁在30年内失效的概率较大,需要对结构进行定期监测、养护和维修。

The bridge structure is subjected to environmental erosion and increasing correlated load impacts during its service life.These factors cause bridge resistance deterioration and make its safety performance less optimistic.To accurately evaluate bridge safety performance in its remaining service life,it is essential to consider the non-stationary characteristics of structural resistance degradation and the time correlativity of load effects.Under the framework of time-dependent reliability,a reliability equation based on Bayesian theory is proposed by using Gamma distribution to describe the non-stationary degradation of bridge resistance while adopting twodimensional joint distribution function of adjacent loads to express their time correlativity.Monte Carlo simulation is then used to verify the results.The analysis to a simply supported RC bridge in Sichuan province shows that:the results of the equation are close to numerical solutions of MCS when the double integral of molecule of a single conditional probability is greater than 0.7,which proves its correctness;the larger scale parameter of Gamma degradation process and the weaker time-correlativity of load effects will lead to greater structural time-dependent failure probability;when the annual growth rate of vehicle load intensity is higher than 2%,the bridge failure probability within 30 years is relatively large,where regular inspection,maintenance and repair are required.