SUMMARYOne of the key limit states of buckling-restrained braces (BRBs) is global flexural buckling including the effects of the connections. The authors have previously proposed a unified explicit equation set for controlling the out-of-plane stability of BRBs based on bending-moment transfer capacity at the restrainer ends. The proposed equation set is capable of estimating BRB stability for various connection stiffnesses, including initial out-of-plane drift effects. However, it is only valid for symmetrical end conditions, limiting application to the single diagonal configuration. In the chevron configuration, the out-of-plane stiffness in the two ends differs because of the rotation of the attached beam. In this study, the equation set is extended to BRBs with asymmetric end conditions, such as the chevron configuration. Cyclic loading tests of the chevron configuration with initial out-of-plane drifts are conducted, and the results are compared with the proposed equation set, which is formulated as a function of the normalized stiffness of the attached beam.
One of the key limits of buckling-restrained braces (BRBs) is overall flexural buckling caused by connection failure, and they are required to exhibit stable hysteresis under cyclic axial loading with initial outof-plane drifts simulating the bi-directional effects of a ground motion. In this paper, a series of cyclic loading tests with initial out-of-plane drifts for built-up type BRB is carried out, and the stability performance including various connection conditions and initial out-of-plane drifts are researched. These results are compared with the stability evaluation equations proposed by the authors, and the validity and accuracy of these equations are discussed.
Global out-of-plane stability of buckling-restrained braces is often governed by yielding of the neck. The authors previously proposed a method 9) to evaluate this buckling mechanism, including the gusset rotational stiffness, connection length and neck -restrainer flexural continuity. While the proposed method has shown good agreement with experimental and numerical studies, this paper revisits a key assumption in the derivation, where the neck is modelled as an elasto-perfectly plastic hinge. Detailed FEM studies of a chevron BRB experiment with a range of gusset and framing boundary conditions are conducted, and an inelastic buckling model inspired by Shanley's theory introduced.
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