Seismic Resilience Study of Steel Concentrically Braced Frame Structure with Dual Viscous and Metallic Hysteretic Damper

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Steel concentrically braced frames(CBF)are popular seismic resistant structural systems widely used all over the world due to their high elastic stiffness and moderate ductility for many decades. However, conventional CBFs are subject to soft-story damage pattern which may lead to collapse caused by overly large drift concentrated in one story in strong earthquakes; measures to enhance the seismic resilience of CBFs is thus desirable. This study looks into quantifying the seismic resilience of CBFs with and without dual-action damping devices by following the newly released 2018 ed. FEMA P58 procedure. The dual-action damping device includes a viscous damper and metallic hysteretic dampers which are activated at different timing: viscous damper always active and effective in controlling story drift during small and moderate earthquakes, while metallic hysteretic dampers are activated only when the story drift exceeds a pre-specified value during strong earthquakes. A six-story steel CBF and a three-story steel CBF buildings designed by SAC Steel Project research (1999) are adopted as prototype building to demonstrate the effectiveness of dual-action damping device in enhancing the seismic resilience of CBFs. Nonlinear static analyses as well as nonlinear time-history analysis are performed to obtain the Engineering Demand Perimeters (EDP) required for seismic resilience evaluation. Collapse Fragility is developed based on incremental dynamic analysis (IDA) by SPO2IDA Tool. The distribution function of Decision Variables (DV), including Repair cost, Repair time, Casualties etc., is obtained through Monte-Carlo simulation of prior nonlinear time-history analysis EDP by Performance Assessment Calculation Tool (PACT). It is found from this study that the Collapse Risk and the Potential Loss of the prototype structure with dampers have been significantly reduced, suggesting the dual-action damping device provides a beneficial alternative for enhancing the seismic resilience of CBFs.