Load resistance and hysteretic response of shuttle-shaped truss-confined BRBs

Abstract

This paper presents a Shuttle-Shaped Truss-Confined Buckling-Restrained Brace (SSTC-BRB) that is simply composed of a single steel tube core and a number of shuttle-shaped truss frames sharing a single external restraining tube. The SSTC-BRB, as an innovation in the external restraining system of the BRB, significantly improves the material utilization, and is particularly exposed externally to enhance the architectural aesthetics. The in-plane elastic buckling, load resistance and hysteretic responses of the SSTC-BRBs are investigated through Finite Element Model (FEM) that has been validated previously by using the test results of Truss-Confined Buckling-Restrained Brace (TC-BRB). Firstly, the elastic buckling performance of the SSTC-BRB is investigated and the obtained results indicate that there exist two possible elastic buckling modes for SSTC-BRBs, namely single-wave buckling and double-wave buckling modes. Secondly, the load resistance of SSTC-BRBs under monotonic axial compression is numerically analyzed, where the combined initial imperfections of SSTC-BRBs are involved particularly in the analysis. As a result, a lower limit of restraining ratio of SSTC-BRBs as a load-carrying type of BRBs is recommended, where the core could be fully yielded with its axial compressive strain reaches 0.02 without global instability of the SSTC-BRBs. Finally, the hysteretic performance of SSTC-BRBs subjected to axial compressive-tensile cyclic loads is studied numerically, and the corresponding lower limit of restraining ratio of SSTC-BRBs is proposed for them to be energy-dissipating types of BRBs. Those two lower limits of restraining ratios of the SSTC-BRBs corresponding to load-carrying and energy-dissipating types of BRBs could provide fundamental guidance for preliminary design of SSTC-BRBs.