Probabilistic economic seismic loss estimation of steel braced frames incorporating emerging self-centering technologies

Abstract

This paper presents a comprehensive economic seismic loss assessment of emerging steel frames incorporating different types of self-centering braces. Particular focus is on failure mechanism of the braces and accurate modelling of the possible failure modes, especially fracture of the PT tendons and failure of energy dissipation devices. Moreover, the damage state, component fragility, and repair cost of the considered braces are developed in a more rigorous manner, aided by professional judgment and market research with reduced subjective decision. System-level analysis shows that tendon fracture indeed happens in the braces with FRP tendons under the maximum considered earthquake (MCE), which compromises the self-centering capability of the structures. Shape memory alloy (SMA)-viscoelastic hybrid braces are shown to effectively reduce the deformation and floor acceleration demands, and leads to the lowest probability of collapse. By examining the vulnerability functions and expected losses of the structures, a single-core SCB configuration with FRP tendons leads to the worst economic performance due to the limited brace ductility. A dual-core configuration can significantly improve the brace ductility and hence reduce the economic loss. The SMA-viscoelastic hybrid brace results in the best economic performance with the lowest expected loss. A subsequent sensitivity analysis shows that the vulnerability curves of the structures exhibit mild sensitivity to the residual inter-story drift threshold, but the modelling assumption has a more remarkable influence on the economic loss estimation results. Employing idealized numerical models without considering brace failure in the analysis could underestimate the seismic loss of self-centering braced frames by more than 30%.