Life-cycle benefits estimation for hybrid seismic-resistant self-centering braced frames

The hybrid self-centering braced frames (HSBFs) with shape memory alloy-based braces (SMABs) and viscous dampers (VDs) are an emerging structural system developed for improving the seismic resilience of traditional braced frames (e.g., buckling restrained braced frames [BRBFs]) and self-centering braced frames (SCBFs) by reducing residual inter-story drifts (RIDs) and floor acceleration responses simultaneously. Nevertheless, the excellent performance of HSBFs is captured by introducing high initial construction costs. This paper aims to highlight the benefits of HSBFs compared with BRBFs and SCBFs by investigating the earthquake-induced life-cycle costs. To this end, 6-story BRBF, SCBF, and HSBF are designed separately to achieve the same maximum inter-story drifts under design basis earthquakes (DBE) for a fair comparison. The advanced numerical models of the considered systems were developed, and nonlinear dynamic analyses were conducted to obtain the structural seismic responses under various intensities. Monte Carlo simulation (MCS) was adopted for considering the modeling uncertainty. The life-cycle costs were subsequently estimated based on the revised HAZUS loss estimation method. The influence of RIDs, initial construction costs of SMABs and VDs, and values of contents inside buildings were comprehensively investigated. It has been found that HSBF can achieve better performance in reducing seismic loss than BRBF and SCBF due to its excellent capability of controlling structural and nonstructural damage. SCBF may show higher seismic loss than BRBFs, given high RID limits for demolition or high building contents' value, highlighting the importance of controlling floor acceleration responses of SCBFs. The life-cycle benefits of BRBFs, SCBFs, and HSBFs are highly influenced by the RIDs, initial construction costs of SMABs and VDs, building contents' values, and building's lifetime. HSBFs show better life-cycle benefits than SCBFs when the building's lifetime is not lower than 50 years. Compared to BRBF, the life-cycle cost effectiveness of SCBF can be only achieved when the initial cost of SMABs is lower than 1.21 times that of BRBs for the building with 50 years' lifetime; the life-cycle cost effectiveness of HSBF6 can be only achieved when the initial cost of SMABs or VDs is lower than 1.84 times that of BRBs for the building with 50 years' lifetime. It has been concluded that reducing the initial costs of SMABs and VDs is critical and essential for increasing the life-cycle economic benefits of SCBFs and HSBFs and promoting their real-world applications.