Mechanics, modeling and seismic behavior of a dual-core self-centering brace in series with a frictional gusset connection

Abstract

An all-steel dual-core self-centering brace (DC-SCB) has been developed to provide a self-centering and energy-dissipative response, which can reduce residual deformations of buildings in a large earthquake. The self-centering property of the brace is provided by elastic tensioning elements, but the surpassing yield strain of the tensioning elements under loading may decrease the elastic restoring force and increase the residual displacement of the brace. A high-performance DC-SCB that has a DC-SCB in series with a frictional gusset connection (FGC) is proposed to prevent the initial force of tensioning elements from decreasing by the FGC movement. The mechanics and the hysteretic response of the high-performance DC-SCB are first presented. The DC-SCBs with and without the FGC are modeled by a finite element program to verify the cyclic performance and the advantage of using the FGC. Then, a 5275 mm-long high-performance DC-SCB is tested for the verification; a full-scale one-story frame with a high-performance DC-SCB is also cyclically tested. Test results show that the local buckling of the beam occurred at 1.5% drift; the FGC activation and the beam lateral-torsional buckling (LTB) occurred at 2.3% drift. Moreover, three ten-story frames with and without the high-performance DC-SCB are analyzed to (1) validate the modeling scheme of the DC-SCB in series with the FGC, and (2) evaluate the seismic responses in earthquake motions. The high-performance DC-SCB is demonstrated to prevent the PT elements from exceeding the elastic deformation limit by using the additional FGC device in series at the brace end. However, an unexpected residual gap at the brace end after the FGC activation causes un-symmetric brace response in subsequent loading.