Robustness assessment of RC structures designed for progressive collapse under multiple hazards

The goal of robustness assessment is to enable stakeholders to obtain efficient information, for reducing potential adverse effects of hazards before a natural disaster occurs, to obtain more realistic evaluation results and retrofit alternatives. A series of tests were carried out to investigate the effect of secondary beam on resisting progressive collapse. To further estimate the structural performance, a risk-based fuzzy conditional robustness assessment approach is established. The developed framework is applied to three various design RC structures subjected to multiple hazards, which is simulated by OpenSEEsPy. In this framework, the effect of the dependence configuration and the epistemic uncertainty on the vulnerability curves, loss-PGA curves, and the robustness index are studied by introducing the Vine-Copula and fuzzy theories. Results show that the effect of epistemic uncertainty on the hazard consequence becomes more pronounced with the increasing of PGA, and the lack of such consideration causes incurring additional retrofit costs for the stakeholders. Moreover, the fuzzy conditional robustness index of the models indicated that the installation of secondary beam showed a superior performance, compared with another reinforcement strategy of additional steel ratio. Finally, a method of survival probability-based robustness assessment is built on the developed assessment procedure and verified.