Steel braced frames with dual-core SCBs and sandwiched BRBs: Mechanics, modeling and seismic demands

Abstract

A new steel dual-core self-centering brace (DC-SCB) is developed to have a flag-shaped re-centering hysteretic response under cyclic loads. Axial deformation capacity of the brace is doubled by serial deformations of two sets of tensioning elements arranged in parallel. In this paper, the mechanics of the new brace is first explained by considering a fabrication error of the member length, followed by testing one DC-SCB to evaluate its cyclic performance. The member length fabrication error, which is even 1/3000 times the brace length, significantly decreases the initial axial stiffness of the brace but does not affect the overall hysteretic behavior. Finite element analysis is conducted on the specimen to verify the mechanics and hysteretic responses observed in the test. Finite element analyses are also performed on other 16 DC-SCBs to evaluate how tensioning element types, initial post-tensioned force, and friction force affect the cyclic performance of the brace. Additionally, three braced frames of varying heights are designed using two bracing members, DC-SCBs and sandwiched buckling-restrained braces (BRBs). Nonlinear time history analyses are conducted on these braced frames to obtain seismic demands under both design and maximum considerable levels of earthquake motions and near-field motions. Self-centering braced frames generally exhibit smaller peak interstory drifts and residual drifts than buckling-restrained braced frames.