Abstract: In this paper for a composite structural system a method of optimum design based on reliability is developed and multi-level optimization technique is adopted. For system level optimizaiton, the minimal structural weight is taken as the design objective and the reliability requirement of composite structural system is taken as constraint condition. For member level optimization, maximal reliability of member is taken as the design objective and keeping member weight unvarying is taken as the constraint. The optimal criteria and iterative formulae are derived. The method is quite efficient and can be extended to large scale composite structures.

Key words: reliability, composite structural system一。ntimum design based on reliability