Load-carrying performance and design of BRBs confined with longitudinal shuttle-shaped-trusses

Abstract

This paper presents load-carrying performance and design method for a Shuttle-Shaped Truss-Confined Buckling-Restrained Brace (SSTC-BRB). Such external restraining system (ERS) innovation through adopting longitudinally variable cross-sectional trusses in the BRB significantly enhances axial load-carrying efficiency of SSTC-BRB that could carry very large axial applied load for over long BRB design when used on exposed purpose externally. Firstly, the elastic buckling performance of the SSTC-BRB is comprehensively investigated by adopting a beam element Finite Element (FE) model, and this leads to an explicit expression of the elastic buckling load of the SSTC-BRB that is adopted to define the restraining ratio of the SSTC-BRB for its strength and stiffness design. Consequently, the load resistance of SSTC-BRBs under monotonic axial compression is numerically analyzed. Accordingly, the lower limit of restraining ratio of the SSTC-BRBs subjected to monotonic axial load is recommended for their load resistance design, where the core could be fully yielded with the plastic strain amplitude reaches 2% without global instability of the SSTC-BRBs. Finally, the hysteretic responses of SSTC-BRBs subjected to axial compressive-tensile cyclic loads are studied numerically, and the corresponding lower limit of restraining ratio of SSTC-BRBs is proposed for their energy-dissipation design. Those two lower limits of restraining ratios of the SSTC-BRBs obtained in this study provide fundamentals for preliminary static and seismic designs of SSTC-BRBs.