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结合现行规范及钢管混凝土拱桥的受力特点,给出钢管混凝土拱桥安全-中介-失效三级工作模式的确定准则.据此计算结构的损伤概率与失效概率及对应的可靠度指标,建立可靠度指标与三级工作模式的直接关系.基于三级工作模式,提出评估在役桥梁结构可靠度的有限元-神经网络-蒙特卡罗(FNM)法.根据时变可靠度理论,将结构继续服役期离散化,随机抽样生成蒙特卡罗法所需的最少样本,由随机有限元法计算训练样本,用神经网络扩展训练样本,最后通过蒙特卡罗法计算失效概率和损伤概率,得到结构时变可靠度,判断其工作状态.运用该方法对一座建成10年,主跨83.6m的钢管混凝土拱桥进行分析,结果表明,该桥主拱处于安全状态,这一结论与实际情况相符.说明FNM法对于评价在役桥梁的可靠性是可行的.
According to the existing rules and the mechanical characteristics of CFST arch bridge, the criteria for determining the three-stage safety-mediation-failure mode of CFST arch bridge are given, and the damage probability, failure probability and corresponding reliability index of the structure are calculated to establish the reliability Index and the three-level working mode.Based on the three-level working mode, the finite element neural network-Monte Carlo method (FNM) is proposed to evaluate the reliability of the existing bridge structure.According to the theory of time-varying reliability, the structure will continue to serve Periodic discretization, the random sample to generate the minimum sample required by Monte Carlo method, calculate the training samples by stochastic finite element method, extend the training samples by neural network, and finally calculate the failure probability and the damage probability by Monte Carlo method, Reliability and determine its working status.This method is used to analyze a 10-year-old CFST arch bridge with a main span of 83.6m.The results show that the main arch of the bridge is in a safe state, which is consistent with the actual situation.Finally, It is feasible to evaluate the reliability of the bridge in service.