基于评估使用年限的既有结构可靠度评定实用方法

A Practical Method for Reliability Assessment of Existing Structures Based on Assessed Working Life

在分析国内外关于考虑抗力和荷载效应时变性的结构可靠度研究成果的基础上,提出了既有结构基于评估使用年限的可靠度评定实用方法。分析表明,不考虑设计使用年限内的抗力退化时,结构累积失效概率与服役年数成正比。结构抗力随机过程模型采用服役起始点随机变量乘以一个确定的抗力衰减函数表示,则结构抗力随机过程可退化为随机变量。同时考虑结构在评估使用年限内的抗力退化和评估使用年限缩短引起的抗力需求调整,建立了既有结构基于评估使用年限的累积失效概率和可靠指标条件方程。为便于工程应用,用抗力平均退化系数和抗力需求折减系数表示可靠指标的动态变化,建立了既有结构评估的抗力-需求比实用表达式,并提出了不同评估使用年限下的抗力需求折减系数建议值。

After analyzing domestic and abroad research on structural reliability considering the time-variation of resistance and load effect,a practical method was proposed for reliability assessment of existing structures based on the assessed service life.Analysis showed that the cumulative failure probability of a structure was proportional to the number of service years,when the resistance degradation in the design working life was not considered.The random process model of structural resistance was expressed using a random variable at the service starting point multiplied by a determined resistance attenuation function.Then the structural resistance random process degraded into a random variable.Taking into account the resistance degradation and the resistance demand adjustment caused by the shortened assessed working life,the conditional equations of cumulative failure probability and reliability index were established based on the assessed working life of existing structures.For engineering applications,the dynamic change of reliability index was expressed by the resistance demand discount coefficient and the average of resistance degradation coefficient.The practical expression for the resistance-demand ratio in the assessment of existing structures was established,and the recommended value of resistance demand discount coefficient under different assessed working lives was proposed.