采用改进等价极值法的钢网架动力可靠性分析

Failure Probability Analysis on Truss Structure Using Improved Equivalent Extreme‑Value Method

为比较动力作用下航站楼钢网架结构可靠性的空间分布差异,基于等价极值原理中的极值(P),推导并改进了以逼近极值(ΔPi)为特征变量的结构失效概率计算方程。结合某机场航站楼钢网架优化案例,数值模拟分析了指廊钢屋盖在不同有效峰值加速度(effective peak acceleration,简称EPA)作用下的结构可靠性变化规律,总结了改进等价极值法在预测结构失效时的优越性。结果表明:利用改进等价极值法得到的结构失效概率上下界曲线能准确表征不同EPA作用下结构失效的“三阶段”变化趋势,且计算阈值区间随EPA增加而收敛,并在EPA大于0.22 g时趋于0;在结构设计优化指标满足规范要求时,改进等价极值法既能有效预测其可靠性变化趋势又具有较高预测精度;指廊结构区段内的支座节点失效概率与整体失效概率接近,EPA小于0.295 g时误差不超过4%,可通过监测代表节点实现结构整体可靠度监测。

In order to investigate the spatial distribution difference of the reliability about steel truss structure of terminal building under dynamic actions,the calculation equation of structural failure probability with approximate extreme-value(ΔPi)as characteristic variables are derived based on the extreme-value(P)at the principle of equivalent extreme-value.Combined with the optimization case of steel grid structure in an airport,the structural reliability laws of steel roof under different effective peak acceleration(EPA)are analyzed by numerical simulation,and the superiority of the improved equivalent extreme-value method in predicting structural failure is summarized.The results show that the upper and lower bound curves of structural failure probability obtained by the improved equivalent extreme-value method can accurately represent the variation trend of"three stages"of structural failure under different EPA,and the calculation threshold converges with the increase of EPA and approaches zero when EPA is greater than 0.22 g.When the optimization indexes of structural design satisfy the requirements of the code,the cantilever structure arrangement at the end of the corridor makes its dynamic reliability significantly weaker than that of the surrounding structures,which indicates that the improved equivalent extreme-value method can not only effectively predict the structural reliability trend,but also has higher prediction accuracy.In addition,the failure probability of support nodes in the corridor structure section is close to the overall failure probability,and the error is less than 4%when EPA is less than 0.295 g.Therefore,the overall reliability of the structure can be monitored by only supervising special nodes.