Full scale uniaxial and subassemblage tests on the seismic behavior of all-steel buckling-resistant brace

Full-scale uniaxial and subassemblage tests are conducted to study the property and proper configuration of all-steel BRB with cruciform cross section encased in a square steel tube, which is to be installed in a six-floor office building in Beijing. The first BRB specimen was designed according to the client's requirement, and tested without gusset plates under uniaxial quasi-static cyclic loading by using MTS actuator. The top end bent during the loading process because of the initial eccentricity caused by machining error of the end part. The design is then improved and another BRB specimen is fabricated according to the test results of the first one. Under uniaxial cyclic loading, its core plates are fractured at the weld spots, indicating that there should be no additional weld on the yielding part of the core except the necessary connection between the core plates. For the specimen in the subassemblage test, which includes BRB and gusset plates, thickness of the portion of the rectangle reinforcing ribs outside of the outer tube are increased to restrain the slippage of the tube. No rupture is observed during the subassemblage test, and numerous hysteretic loops are obtained. The compression strength amplification factor and the cumulative inelastic ductility factor satisfy the standard of the SEAOC-AISC recommended provisions. The results show that the improved all-steel BRB with cruciform cross section encased in a square steel tube presents large ductility and high energy dissipation capacity.