Optimum Allocation of Reliability in Redundant Truss Structure

Many studies have been made on optimum structural design based on the reliability concept. However, they are limited to a simple type of structures. This may be attributable to the difficulty of reliability analysis and the lack of efficient algorithm to obtain optimum solutions for optimum design problems. Murotsu et al. developed an effective method of reliability analysis for redundant truss structures, using a Matrix method. As for an efficient algorithm, Murotsu et al. also proposed a basic idea of an optimum design procedure. This paper extends the proposed design procedure to the optimum allocation of reliability for large-scale redundant truss structures, combined with the method of reliability analysis. The problem treated in this paper is to allocate reliability to each member of a structure so that the structural weight is minimized under a constraint on the reliability of the structure. Optimum allocation of reliabilities to the members is attained by iterating the following two steps until optimality conditions are satisfied. The first step is to adjust the allocated reliabilities of the members such that the structural weight may be minimized under a fixed structural reliability. The strategy for the adjustment is determined by considering the sensitivity of the structural weight to the variation in the assigned reliabilities of the members. The second step is to determine the design variables corresponding to the specified reliabilities of the members. The proposed optimum design procedure is applicable to the cases of normal and non-normal distributions. The design examples were provided for statically indeterminate plane and space truss structures, and the validity of the proposed method was demonstrated. (Received May 26, 1981) キー・ワー ド: 信頼性, 構造設計, 破損確率, 最適配分