Self-centering tension brace for seismic damage mitigation: From real-time hybrid simulation test to performance-based seismic retrofit design

Abstract

Various self-centering tension braces (SCTBs) have been proposed to enhance the seismic resilience of existing buildings. However, studies validating their seismic retrofit efficacy under dynamic seismic excitations remain limited, and performance-based retrofit design methodologies using SCTBs are still absent, hindering their practical applications in earthquake engineering. This paper first conducts a real-time hybrid simulation test on a reinforced concrete (RC) frame installed with two SCTB specimens to verify the SCTBs’ retrofit efficacy. Subsequently, a multi-step performance-based seismic retrofit method is proposed, utilizing SCTBs to retrofit two RC frames with varying numbers of stories and retrofit objectives. Finally, seismic fragility assessment using Latin hypercube sampling and incremental dynamic analysis are conducted for the retrofitted frames, considering uncertainties in both structural attributes and ground motion inputs. The real-time hybrid simulation test demonstrates that SCTB has excellent retrofit efficacy under seismic excitations, with 17 % and 84 % reductions in the mean values of the maximum and residual story drifts, respectively. Also, both the deterministic analyses and fragility assessment demonstrate that the proposed performance-based seismic retrofit design method achieves the preassigned performance objectives without the need for repeated iterations. The retrofitted structures exhibit needed resilience against structural collapse under maximum considered earthquakes and prompt post-earthquake recovery under design basis earthquakes.