Probabilistic seismic performance and loss evaluation of a multi-story steel building equipped with butterfly-shaped fuses

Abstract

Shear fuses are structural elements that protect surrounding members from damages by undergoing substantial yielding, and then are easily replaced after a major earthquake event. Butterfly-shaped shear fuse is a promising type of structural system, which can effectively align member's flexural capacity to the imposed moment demand due to its unique geometry. Although recent studies suggest that butterfly-shaped fuses exhibit substantial ductility and energy dissipation, their impact on the global performance of multi-story buildings requires further investigation. This study presents a comprehensive risk-based evaluation of a six-story eccentrically braced steel frame retrofitted with butterfly-shaped fuses. Two nonlinear finite element models of the original prototype building and retrofitted building with butterfly-shaped fuses are developed in OpenSees and incremental dynamic analysis is conducted. The results are used to derive global and story-based fragility and seismic demand hazard curves. Furthermore, earthquake-induced losses associated with structural and non-structural assemblies are quantified and the impact of butterfly-shaped fuses on the distribution of story acceleration and drift demands are evaluated.The results show that butterfly-shaped fuses significantly improve the structure's performance in terms of all drift-related damage states and the improvement is more pronounced at severe damage states. In particular, the risk of exceeding complete damage state in the retrofitted building's lifetime is reduced to approximately one-fourth of the original building's values. Furthermore, shear fuses effectively mitigate weak story formation at lower stories due to their large energy dissipation and ductility. The improved drift-related performance reduces the drift-induced loss of structural and non-structural assemblies, resulting in 44.64% smaller total annual loss for the studied building. In addition, although butterfly-shaped fuses reduce the probability of exceeding slight damage state for the floor acceleration, their impact is negligible at higher acceleration-related damage states.