Abstract
In order to solve the instabilities, fracture failures, and difficult repairs of welded gusset plates in buckling-restrained braced frames (BRBFs) under severe earthquakes, the idea of a full-length outer restraint BRB (FLBRB) is introduced. This new brace consists of a cross-section core, two end-weakened connectors, and a full-length outer restraint. In this paper, three FLBRBs with different parameters were designed, and their mechanical behaviors were evaluated through quasi-static testing, including failure mode, stress distribution and hysteretic behavior. Besides, the refined FE models were established and compared with the test. And the simplified bilinear load-displacement model and hysteretic rule considering the degradation of unloading stiffness are proposed based on the experimental investigation and FE simulation, the simplified bilinear load-displacement model and hysteretic rule considering the degradation of unloading stiffness are proposed, as well as the formulas for calculating the stiffness of either loading or unloading. The results demonstrate that the FLBRB has good hysteresis performance as it can confine the plastic to the weakened connectors and the BRB. Furthermore, the simplified restoring force model was verified by comparing it with the experiment, indicating that the load–displacement curve of the FLBRB could be accurately predicted by the suggested theoretical formula and model. These research results can be adopted to provide theoretical foundation for the engineering application of the FLBRB.
Publisher
The Hong Kong Institute of Steel Construction