Research On Structures Time-varying Reliability Analysis Optimization And Sensitivity Analysis Method

Structural reliability analysis,sensitivity analysis and optimization design are very advantageous design methods in modern engineering structure design.It can consider the widespread uncertainty in structure size,material properties and so on.However,the following two problems are seldom considered in the current structural reliability analysis,optimization design and sensitivity analysis:(1)Time-varying reliability problem caused by structural parameters changing with time.(2)The influence of structural multi-model on structural reliability.In this paper,reliability analysis,optimization and sensitivity research are carried out around these two problems.The main contents include:(1)To solve the problem of time-varying reliability,a weighted stochastic simulation strategy based on the extremum method is proposed.The proposed method only needs one conventional reliability analysis simulation to obtain the results of time-varying failure probability function with time,so as to avoid the computational cost caused by the conventional method requiring multiple reliability analysis.Finally,examples are given to verify the proposed method.The results show that the weighted method can greatly reduce the calculation amount and improve the efficiency of time-varying reliability calculation on the premise of ensuring the accuracy.(2)Based on the weighted stochastic simulation strategy,the time-varying reliability sensitivity analysis methods of weighted Monte Carlo method and weighted important sampling method are proposed respectively.Similarly,the index value of time-varying reliability sensitivity can be obtained by calculating the sample points only once.(3)To solve the problem of time-varying reliability optimization.This paper presents a time varying reliability decoupling optimization method based on weighted stochastic simulation.The proposed method first uses the weighted strategy to obtain the functional estimation of the structural failure probability with time and design variables through a reliability analysis,without the need for multiple reliability analysis.Then the approximate failure probability function estimation can be used to transform the reliability optimization problem into a regular deterministic optimization problem,which greatly improves the efficiency of reliability optimization.(4)For the structural multi-model problem,the methods of analysis of variance sensitivity and moment independent sensitivity index are proposed.Based on the results of sensitivity analysis of the example,it is concluded that,for the composite model,one of the influencing factors is the weight value,and the other is the randomness of the model itself(modeling mode,model parameters,etc.)which also has an important influence on the composite model.(5)The software for structural time-varying reliability and structural sensitivity analysis is design and develop.The software can obtain the structural time-varying reliability index and the structural sensitivity index,and the software can link ANSYS,ABAQUS and other third-party commercial finite element software,to maximize the convenience of processing the actual structure analysis.