이산공간에서 등가정하중을 이용한 비선형동적응답 구조물의 강건최적설계

Abstract

The equivalent static loads method is an optimization technique that can handle nonlinear dynamic response structural optimization. The equivalent static loads (ESLs) are defined as the linear static load sets which generate the same response field in linear static analysis as that from nonlinear dynamic analysis The ESLs are made from the results of nonlinear dynamic analysis and used as external forces in linear static response optimization. Although deterministic values are considered in optimization, there are tolerances and various variations in dimensions when designing or producing products. Robust optimization is employed to reduce the variation of responses. The Taguchi method has been modified for robust optimization of structures in the discrete space. That is, the design variables can have some discrete values. The inner array and outer array are used to evaluate the average and variation of the functions. In this research, the value of the inner array is evaluated by nonlinear dynamic analysis and ESLs are made at each point of the inner array. An outer array is set up by using the variations of the design variables for each row of the inner array and the functions of the outer array are calculated by linear analysis with ESLs. Therefore, the expensive process for evaluation of the response variation is replaced by low-cost linear analysis. Various structural examples are selected to verify the proposed method. A simple three-bar truss is chosen to compare the proposed method with the method that uses nonlinear dynamic analyses. A large scale automobile crash problem is solved including some small scale problems.