Experimental behavior of truss‐confined buckling‐restrained braces

Abstract

Buckling‐restrained braces (BRBs) can effectively improve the stiffness, strength, and energy dissipation capacity of building structures. The key feature of the proposed truss‐confined BRB (TC‐BRB) is an additional truss confining system attached outside the central steel casing. The truss system is composed of several steel open‐web truss frames, thereby providing the required restraining rigidity and reducing the central casing section size and infilled mortar. The overall self‐weight is decreased compared with a conventional BRB, especially in cases of long‐span and large force capacity BRB applications. This research program was conducted to investigate the hysteresis behavior of the TC‐BRBs in terms of truss member response, buckling resisting ability, and cumulative deformation capacity. Six one‐third‐scale TC‐BRB specimens, each 6.3 m long and with different yield capacities, truss frame shapes and sizes, were tested using cyclically increasing loads with or without an out‐of‐plane end drift. The six specimens eventually failed either from global flexural buckling of the entire restraining system or a tensile fracture of the steel core at a very large axial strain. The experimental results demonstrated that the TC‐BRBs can be designed and fabricated to have a very stable and highly repeatable hysteretic response, meeting the American Institute of Steel Construction acceptance criteria. It provides a valuable database to support the further development of design guidelines for the engineering application of the proposed TC‐BRBs.