Bending Deformation of the Steel Core of Buckling-Restrained Braces

Installation of buckling-restrained braces (BRBs) is an effective means to improve the seismic performance of building structures. The authors have developed a new variation of BRBs that use steel-and-mortar planks for the buckling-restraining system. A large number of laboratory test results, suggest that these BRBs exhibit excellent performance on par with widely used commercialized BRB products. Using the new BRBs, an experimental study was conducted to examine how bending deformation of the steel core affects the cyclic loading performance of the BRB. Four BRB specimens were fabricated in the laboratory. The specimens combined a flat-plate steel core with a relatively small width-to-thickness ratio of six, and a very stiff buckling-restraining system whose Euler buckling load was six times the yield strength of the steel core. Two specimens placed longitudinal round bars in the mortar-free gaps adjacent to the side of steel core. Two specimens kept the gaps empty by intension. The test results suggest that placement of round bars in the mortar-free gaps is an effective method to control major-axis bending deformation of the steel core.