Seismic Analysis of a Self-Centering Braced Frame in Pseudodynamic Tests: Response Characteristics, Brace Contribution, and Damage Evolution

Abstract

This study investigated the seismic performance and self-centering behavior of a three-story steel frame equipped with self-centering brace (SCBs) using pseudodynamic tests aided by OpenSees version 2.5.7 and OpenFresco version 2.7.0. The three-story self-centering braced frame (SCBF) was simplified to a three-story shear building model, and a generic experimental element with three nodes with horizontal degrees of freedom was used to establish a two-dimensional (2D) numerical model. The input ground motions were scaled to a service level earthquake (SLE), design basis earthquake (DBE), maximum considered earthquake (MCE), and a very rare earthquake (VRE) with 63%, 10%, 2%, and 0.5% probability of exceedance in 50 years, respectively. The test results demonstrated the excellent seismic performance and self-centering behavior of the SCBF. The maximum story drift ratio and maximum residual story drift ratio of the SCBF under a VRE were 1.91% and 0.119%, respectively, below the thresholds of 2.0% and 0.5%. The SCBs provided more than 90% of the initial lateral stiffness of the SCBF and dissipated approximately 55% of the seismic input energy. The seismic performance of the SCBF satisfied the no-damage criterion under an SLE and DBE. Although the columns in Story 1 yielded under an MCE and VRE, no visible residual deformation of the column flanges was detected in Story 1 after the tests. In addition, the maximum residual drift ratio of Story 1 was only 0.066%. Therefore, the columns in Story 1 only required simple and quick reinforcements before being usable. Unexpected factors, such as the fit-up tolerances around the pins, out-of-sync activation of the SCBs in the same story, residual deformation of the SCBs, and the out-of-sync activation of the two groups of disc springs in the same SCB, did not affect the seismic performance and self-centering capacity of the SCBF.