구조 최적 설계에 대해서 (I, II)

Abstract

Although the external loads of most practical problems are dynamic in the real world, structural optimization generally uses static loads. A dynamic response optimization problem is usually converted to a static response optimization problem using the dynamic factor at critical times. However, it is difficult to define a proper dynamic factor and consider the variation of the critical time in optimization. The equivalent static loads (ESLs) method is an efficient method for dynamic response optimization. The equivalent static loads are defined as the loads for linear analysis, which generate the same response field as those of dynamic analysis. First, dynamic analysis is performed and displacements are evaluated at each time step. A static equivalent load set is made based on the dynamic displacements at each time step. The equivalent load sets are used as multiple loading conditions for linear static response optimization and the design is updated. The updated design is again used for dynamic analysis and the process proceeds in a cyclic manner. Therefore, dynamic (linear transient) response optimization is performed by a series of linear static response optimization. Several examples are solved by interfacing SOL 109 and linear static response optimization in SOL 200 of NASTRAN. NASTRAN 200 has the capability of linear transient response optimization. The results from ESLs are compared with the results of linear transient response optimization of SOL 200. In general, the results of the ESLs method show better performances.