Global stability design method of buckling-restrained braces considering end bending moment transfer: Discussion on pinned connections with collars

The negative effect of end bending moment on the global stability of pin-connected buckling-restrained braces (BRBs) with end collars was validated in the authors’ prior testing. Although this is a common issue for all types of BRBs, the corresponding effect has not yet been considered in the traditional design method. In this paper, the analytical models are first proposed based on the configurations of one of the commonly used pin-connected BRBs. The in-plane flexural demands on the casing and brace end rotational demands are then derived theoretically considering the effect of end bending moment transfer in the casing. The global stability design criterion that considers both in-plane bending effects and frictional force is proposed and validated by prior test results. The effect of key BRB parameters on the global stability is also examined by parametric study. A moment amplification factor method is presented, based on the configuration of pin-connected BRBs with end collars, to further simplify the proposed method. Several future research needs for the global stability design of the BRBs with the other types of connections are presented finally.