Seismic risk assessment of partially self-centering braced frames designed with multiple-objective-based method

Partially self-centering building structures are promising seismic resilient systems by balancing the reduction of residual deformations, nonstructural loss, and initial construction costs. This research seeks to establish a multiple-objective-design (MOD) approach for partially self-centering buckling restrained braced frames (PSBRBFs) and explore the risks associated with collapse, demolition, and nonstructural damage in PSBRBFs designed using the MOD approach. The peak displacement is set as an objective for achieving the desired collapse-prevention performance while the residual displacement is set as another objective to ensure the expected post-earthquake repairability. To this end, the step-by-step procedures of the MOD method are introduced based on the prediction models of peak and residual displacements of PSBRBFs. 6 building cases are designed with the MOD method. The dynamic results demonstrate that analyzed PSBRBFs can simultaneously achieve the targeted peak and residual displacements, validating the effectiveness of the MOD method. Seismic fragility assessments are conducted utilizing incremental dynamic analyses (IDAs) to investigate the influence of different performance objectives (i.e., different target peak and residual displacements) on the collapse, demolition, and nonstructural damage probabilities of PSBRBFs. And seismic risks of the designed PSBRBFs are investigated with the consideration of earthquake hazard risks. Results indicate that the demolition risks of the designed PSBRBFs are all larger than the corresponding collapse risks. Based on the analysis results, high PID and low RID design targets were recommended for practical applications to achieve excellent performance against demolition and comparable performance in avoiding collapse and nonstructural damage.