A novel methodology for structural robustness assessment of offshore platforms in progressive collapse

Abstract Accidental events may cause a chain of local damages of offshore platforms and eventually result in an overall collapse of platform structures, which exposes the structural vulnerability in resisting non-proportional failure. In addition, due to the redundancy of structure and the uncertainty of failure response, there may exist a series of different potential failure paths for offshore platforms. Therefore, this paper proposes a novel methodology for structural robustness assessment considering multi-failure paths to quantify the robustness of offshore platforms. By using the generalized bearing-capacity-ratio method combined with the incremental-loading method, all possible failure paths could be sought out and the most possible failure sequence be identified. Based on failure paths analysis, three novel robustness indices are established from different perspectives, respectively: (1) path-dependent & state-dependent robustness index RI, (2) overall dynamic robustness index RP, (3) and comprehensive robustness index RW for structural pre-evaluation. Also, by introducing the maintenance reinforcement into the structural robustness simulation, the effects of the whole reinforcement and the critical path reinforcement on structural robustness are studied. Robustness analysis results show that the differences of robustness of different failure paths are significant, although the accidental events occur in small probability path, its impact on the structural robustness is serious so it should be paid more attention. Besides, strengthening the critical path could significantly improve the structural robustness and achieve the goal of robustness control.