通用设计表达式灵敏度系数优化方法

AN OPTIMIZATION OF SENSITIVITY FACTORS FOR GENERAL DESIGN FORMULA

作用随机过程组合方法和设计值法相结合得到的地震组合时的通用设计表达式,目的是提高设计的灵活性。由于地震作用的变异性很大,国际标准提出的标准灵敏度系数不再适用,若变量变异性发生较大变化,为提高可靠度控制精度,标准灵敏度系数必须重新取值,而枚举优化法目的性差。通过建立定性优化方向函数,给出每个基本变量标准灵敏度系数所取数值对可靠指标计算值与目标可靠指标差值的贡献,用于标准灵敏度系数的初取值和优化环节,使在作用效应比例对下整体最优。将优化结果用于不同设计使用年限和不同目标可靠指标的情况下得到的相对误差说明,优化方法可以用于设计使用年限50年及一个合适的目标可靠指标情况。

General design formula in seismic combination can be obtained by associating combination of actions based on stochastic processes with design value method.It aims at improving flexibility of design.Due to the large variability of seismic action,the sensitivity factors recommended by international standard are not suitable.If the variability of variables changed greatly,in order to improve the control precision of reliability,standardized sensitivity factor values must be re-valued.Enumeration optimization method is lack of purpose.A function that can give a qualitative optimization direction is proposed.It can give the contribution to the difference between calculated and target value of reliability index caused by the sensitivity factor value of each variable.The function can be used in choosing initial value process and optimizing process,overall optimal result can be obtained under all proportion pairs.The standardized sensitivity factors are used for different design working life and different target reliability index,the errors show that optimization link can use 50-year design working life and a suitable target reliability index.