水工平面钢闸门主梁多失效模式相关的系统可靠度分析

System reliability analysis on main girder of plane gates considering multiple correlated failure modes

根据水工平面钢闸门主梁的破坏机理,确定了主梁受弯、受剪和弯剪复合破坏3种主要失效模式的极限状态方程,建立了考虑多失效模式相关的主梁系统可靠度分析的概率故障树模型。采用截尾正态分布主梁可靠度分析中的随机变量(闸门水荷载及主梁的腹板及翼缘的厚度等)。采用自适应重要性抽样方法计算了主梁多失效模式相关的系统可靠度,并与上下限法和层次分析法的结果进行了比较。结果表明,概率故障树模型能够有效地分析主梁多失效模式相关的系统可靠度问题,自适应重要抽样方法能够有效地计算主梁多失效模式相关的系统可靠度。忽略主梁失效模式间的相关性将会低估主梁的系统可靠度水平。主梁的抗力和静水压力的敏感性因子较大,它们对主梁可靠指标有非常明显的影响。建议将主梁系统的目标可靠指标取为:大中型闸门3.0,小型闸门2.0。

According to the failure mechanism of main girder of plane gates, the limit state functions are established for three failure modes, namely bending mode, shear mode and combination of bending and shear mode. A probabilistic fault tree is presented to simulate the system reliability of the main girders, with the correlated failure modes taken into account. The truncated normal distribution is used to describe the bounded random variables, such as the hydrostatic load, thickness of web and thickness of flange. The adaptive importance sampling method is adopted to calculate the system reliability of main girder with correlated failure, and the result is compared with the results of bounds method and analytical hierarchy process method. The result indicates that the probabilistic fault tree can effectively simulate the system reliability of main girders with correlated failure modes. The adaptive importance sampling method can effectively calculate the system reliability of main girder. The system reliability level will be underestimated if the correlations between different failure modes are not taken into account. The sensitivity analysis indicates that the resistance of main girders and hydrostatic load acting on gates may significantly affect the reliability index of main girder. Based on the analysis on the system reliability levels of main girder for different gates in current design code, the target system reliability indexes of main girder for different safety levels are suggested.