High strength steel frames with curved knee braces: Performance-based damage-control design framework

Abstract

High strength steel frames with curved knee braces (HSSFs-CKBs) are typical seismic resilient structural systems. Previous experimental research showed that an HSSF-CKBs specimen could be readily repaired after an earthquake by replacing damaged curved knee braces (CKBs) which serve as energy dissipating devices, as long as high strength steel components stay essentially elastic to shake down post-earthquake residual deformations. To provide a practical tool for engineers in seismic resilience design, this paper developed a performance-based damage-control design framework for low-to-medium rise HSSFs-CKBs. A multi-storey HSSF-CKBs was first interlinked with an equivalent bilinear single-degree-of-freedom (SDOF) system. Then, the seismic input energy demand of the HSSF-CKBs was determined based on the seismic energy balance of the equivalent SDOF system, which was further distributed to different storeys to design structural components. To facilitate the design, a stepwise design procedure was proposed. A three-storey low-rise HSSF-CKBs and a six-storey medium-rise HSSF-CKBs were designed following the procedure. The seismic response of the designed structures was examined by pushover analyses and nonlinear time-history analyses using numerical models verified by shaking table test data. The analysis results showed that the designed structures exhibited the expected behaviour, and the maximum interstorey drifts were controlled below the design target, which verified the effectiveness of the proposed design framework.