Experimental Performance of Multi-Story X-Braced Frame Systems

摘要

The engineering properties of Concentrically Braced Frame (CBF) systems have the potential to meet multiple performance objectives. However, previous research has shown that current design can lead to soft stories, unexpected failure modes or premature brace failure. A NEES small group research project entitled "International Hybrid Simulation of Tomorrow's Braced Frames" aims to enhance the performance of braced frames by developing innovative seismic design techniques considering the interaction of the brace-frame components and the system as a whole. Tomorrow's Concentric Braced Frame 1 (TCBF-1) is the first of a series of tests to be developed and tested at the NCREE laboratory in Taiwan. TCBF-1 is a two story, single bay frame with X-bracing. The X-brace configuration of TCBF-1 has been chosen to provide a first experimental evaluation of this type of system and of the middle gusset plate connection. This test will serve as a basis for calibrating nonlinear analytical models of braced frame behavior under development as part of the research. Through analytical and experimental methods carried out at the University of Washington (UW), a balanced design approach has been developed that permits development of inelastic deformation from multiple yield mechanisms including gusset plate and framing elements. TCBF-1 provides a confirmation study for this past research and the corner gusset plate connections researched at the UW. The initial test program consisted of three separate phases which used different brace sections and gusset plate geometries. TCBF-1 HSS-R was designed with high strength HSS tube sections, thin gusset plates, and modified geometric requirements. TCBF-1 WF-R was designed using the same methods but wide-flange brace sections were used. TCBF-1 HSS-T has been designed from a modified version of the current design procedure using high strength HSS tube brace sections and tapered gusset plates.rnThis paper outlines the design approach for the first specimen, TCBF-1 HSS-R, and summarizes the experimental performance for all three test phases. Details, data and photos of the test frames during construction, preparation and testing can be found on the NCREE website.