全尺寸兩層鋼構架之夾型挫屈束制斜撐穩定性研究

Abstract

This work presents testing and finite element analysis of a two-story, buckling-restrained braced frame (BRBF) with X bracing, called X-BRBF. The BRB in this work is composed of a core plate sandwiched by a pair of restraining members, called a sandwiched buckling restrained brace (SBRB). The weak axis of the SBRB core was transverse to the dual-gusset plate connection and the in-plane movement of the frame to eliminate its weak axis buckling. The objectives of two-phase tests were to evaluate: (1) the seismic performance of SBRBs with a small width-to-thickness ratio of the core plate (=3), (2) the effects of free-edge stiffeners on the gusset and SBRB stability, and (3) the SBRB stability associated with beam buckling. All gusset connections had free-edge stiffeners in the Phase 1 test, and free-edge stiffeners were removed from half of the gusset connections in the Phase 2 test. The X-BRBF in the Phase 1 test exhibited good performance up to a second-floor drift of 1.6%, but in Phase 2 test the second-floor SBRB, caused by the lateral-torsional buckling (LTB) of the beam, experienced asymmetric buckling about the strong axis of the core at 1.6% second-floor drift. The other SBRB with no beam LTB showed one-side buckling about the strong axis at a 2% drift. However, the strength degradation of the specimen was not observed during the strong axis instability of SBRBs, indicating acceptable orientation for excluding the weak axis buckling of SBRBs. The strong axis instability of SBRBs in the Phase 2 test could be evaluated by using the stability concept with the measured out-of-plane deformation of gusset plates. Non-linear finite element analysis was also conducted on the specimen for further investigation of SBRB instability.