退化结构时变可靠度分析

Time-dependent reliability analysis of deteriorating structures

退化结构的检修问题都涉及时变结构可靠度的计算。对退化结构的时变可靠度,抗力必须表为随机过程。该文考虑退化结构功能函数随机过程,并考虑活载为连续随机过程、Poisson过程以及Bernoulli过程,由之导出一个时段内的时变可靠度公式。以混凝土碳化引起的主筋锈蚀的公路桥T型梁为例,计算了这3种活载过程下的时变可靠度。算例表明,对相同的初始抗力,退化结构在设计使用年限的时变可靠度明显低于目标时不变可靠度。用作用和抗力的均值和方差在t时刻的瞬时值代入Cornell可靠度指标而计算的"时变可靠度指标"不反映可靠度。

Inspection and repair of deteriorating structures is scheduled based on assessments of the time-varying structural reliability. The resistance of deteriorating structures is a non-stationary stochastic process. This analysis uses a stochastic analysis of the performance function of deteriorating bridge structures assuming continuous, Poisson, Bernoulli vehicle loading processes to analyze the time-varying reliability. The analysis is based on a T-shape girder of a highway bridge with corroded reinforcement bars due to concrete carbonification. The analysis shows how the time-varying reliability decreases to much lower than the target reliability during the design lifetime and that the Cornell reliability index calculated from values of the mean and the variance of the action effect and resistance at time t does not accurately represent the reliability.