Structural system reliability-based design optimization considering fatigue limit state

Abstract

The fatigue -induced sequential failure of a structure having structural redundancy requires system -level analysis to account for stress redistribution. System reliability -based design optimization (SRBDO) for preventing fatigue -initiated structural failure is numerically costly owing to the inclusion of probabilistic constraints. This study incorporates the Branchand -Bound method employing system reliability Bounds (termed the B 3 method), a failure -path structural system reliability analysis approach, with a metaheuristic optimization algorithm, namely grey wolf optimization (GWO), to obtain the optimal design of structures under fatigue -induced system failure. To further improve the efficiency of this new optimization framework, an additional bounding rule is proposed in the context of SRBDO against fatigue using the B 3 method. To demonstrate the proposed method, it is applied to complex problems, a multilayer Daniels system and a three-dimensional tripod jacket structure. The system failure probability of the optimal design is confirmed to be below the target threshold and verified using Monte Carlo simulation. At earlier stages of the optimization, a smaller number of limit -state function evaluation is required, which increases the efficiency. In addition, the proposed method can allocate limited materials throughout the structure optimally so that the optimally -designed structure has a relatively large number of failure paths with similar failure probability.