Buckling-restrained brace with multiple steel bar cores using SHS outer tube

Abstract

To overcome the limited maximum strength of buckling-restrained braces (BRBs) using single roll-threaded processed core bars, a BRB with multiple steel bar cores was proposed in a recent study. Its mechanical behavior was revealed by experimental studies; however, improvements are required in the structure of the BRB owing to its complexity and heavy weight. This study proposes an improved BRB with multiple steel bar cores in which the dual buckling-restraining member consists of a square hollow section (SHS) outer tube and two sets of circular hollow section (CHS) inner tubes. The outer tube is used to improve the flexural stiffness and solve the weight issues associated with the previous type. Three full-scale specimens were tested to determine their mechanical behaviors, such as the hysteresis behavior and internal force variation of the restraining members. The test results indicate that the proposed BRB can exhibit a stable hysteresis response and satisfactory energy dissipation if it fulfills the requirements of restraining members stipulated in the design method. Furthermore, finite element analysis (FEA) was used to determine the cyclic behavior of the proposed BRB. Based on the analysis results, the inner tube failure mode, core buckling response, and variation in the core strain distribution are presented to complement the observations obtained from the tests.