System reliability-based topology optimization considering failure dependence based on D-vine copula model

Purpose – This study aims to develop a system reliability-based topology optimization framework for structural layout design problems involving multiple, dependent failure modes. The goal is to enhance structural safety while efficiently addressing the influence of failure dependence. Design/methodology/approach – A D-vine copula model is employed to characterize complex statistical dependencies among limit state functions. To overcome computational challenges arising from evolving topologies and nonlinear performance functions, a quantile-based decoupling strategy is proposed, along with an adaptive reliability allocation method. Findings – The proposed methodology is validated through two numerical examples: a planar bridge and a simplified turbine disk. Comparative studies are conducted among deterministic, component-level, system-level and independent reliability-based topology optimization formulations. Results demonstrate that accounting for failure dependence leads to more rational and safer designs. Neglecting such dependence can result in overly conservative or unsafe structural layouts. Originality/value – This work provides a novel system reliability-based design framework that integrates failure dependence modeling using D-vine copula model into topology optimization. Although limited to two representative case studies, the findings offer meaningful insights into the trade-offs among different RBTO strategies and emphasize the importance of capturing failure dependence in system-level reliability design.