随机结构系统基于可靠性的优化设计

提出了以梁板（薄板）为基体的随机结构系统（即结构元件的面积、长度、弹性模量和强度等均为随机变量）在随机载荷作用下，基于可靠性的优化设计方法．给出了随机结构系统安全余量和系统可靠性指标的敏度表达式；给出最佳矢量型算法．首先是用改进的一次二阶矩和随机有限元法求出安全余量的可靠性指标的表达式，然后用概率网络估算(PNET)法求出系统失效概率的公式，对该式两边求导得出了系统可靠性指标的敏度表达式，进而用最佳矢量型算法进行优化设计．在优化迭代过程中，采用梯度步和最佳矢量步相结合的方法进行计算．最后给出了一个算例，说明该方法计算效率高，收敛稳定，适合工程应用．

Optimum Design Based on Reliability in Stochastic Structure Systems

The optimum design method based on the reliability is presented to the stochastic structure systems(i.e.the sectional area,length,elastic module and strength of the structural member are random variables)under the random loads.The sensitivity expression of system reliability index and the safety margins were presented in the stochastic structure systems.The optimum vector method was given.First,the expressions of the reliability index of the safety margins with the improved first-order second-moment and the stochastic finite element method were deduced,and then the expressions of the systemic failure probability by probabilistic network evaluation technique(PNET) method were obtained,after derivation calculus,the expressions of the sensitivity analysis for the system reliability were obtained.Moreover,the optimum design with the optimum vector algorithm was undertaken.In the optimum iterative procedure,the gradient step and the optimum vector step were adopted to calculate.At the last,a numerical example was provided to illustrate that the method is efficient in the calculation,stably converges and fits the application in engineering.