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Cyclic tests of all-steel web-restrained buckling-restrained brace subassemblages

Abstract:

In this study, cyclic tests of a buckling-restrained brace (BRB) subassemblage with an all-steel web-restrained brace (WRB) were conducted to investigate hysteretic behavior under combined axial and rotational demands. Four full-scale WRB frame subassemblages were subjected to the quasi-static displacement protocol used for BRB qualification described in the AISC 341–10 Seismic Provisions for Steel Buildings. Three different sizes of steel core plates were examined. One specimen used a nominal 7.9-mm thick by 152-mm wide plate, two WRB specimens used a nominal 12.7-mm thick by 152-mm wide plate, and one specimen used a nominal 12.7-mm thick by 229-mm wide plate. All specimens successfully completed the cyclic testing up to 2% story drift without experiencing brace instability, brace end connection failure, or rupture. Specimens with a 12.7-mm thick core plate survived additional cycles at 1.5% story drift before rupture. The test results also showed that the maximum compression forces were less than 1.3 times the maximum tension forces for each cycle corresponding to a deformation greater than the yield displacement, demonstrating that compression overstrength of the WRB was comparable with typical BRBs.