离散变量框架结构的可靠性优化

以框架结构系统的可靠性分析为基础,给出离散变量框架结构可靠性优化的相对差商方法及迭代格式,并用算例证明了该法的有效性及实用性。

RELIABILITY-BASED ON OPTIMIZATION FOR FRAME STRUCTURES WITH DISCRETE VARIABLES

Based on the requirement of engineering practice, a structure is designed by the determinism method according to economic and safety criteria, this is the aim of traditional structural design. It is more practical to understand the structural safety sense from the probability point of view. Based upon this idea people find a reasonable method to design the optimum structural member size, this is the reliability-based on structural optimization method. The traditional optimization procedure is to make the objective function to be maximum or minimum, subjected to a set of constraint conditions, and no matter whether the objective function or constarint conditions are all unconcerned with the reliability concept. Therefore it is inevitable that the traditional optimal structure design exists two defects: the first is that the optimum structure obtained by the traditional optimum design method can't be guaranteed having the necessary reliability level, the second is that in the traditional optimum design the randomnes of the parameters of material's mechanical behaviours and member's geometric properties are neglected, so the safety index is indefinite. Therefore the requirement of reliability should be added in the mathematic model of optimum design. The optimum structure obtained by this model is called reliability-based on optimization. In this paper, the relative difference quotient method is used to the reliability-based on optimization for frame structures with discrete variables, and an iteration scheme to find the optimum solution is presented. Some examples show that the method is effective and practical.