Behavior and design method of fixed-fixed buckling-restrained braces.

The buckling-restrained braces (BRBs) are often connected to the frame structures by fixed joints in practice, and the cores usually have complicated details near the ends, namely unsupported yielding segments and/or strengthened segments. Based on theoretical and numerical analysis, this paper presents the influence of complicated boundary constraints on the behaviors of the BRBs. It is revealed that the fixed joints can effectively prevent the core unsupported segments from bending too much, and BRBs with fixed ends usually perform better than those with pinned joints, and the advantage exists even when the ends of BRBs rotate with frame joints in the structures. Based on theoretical and FEA results, a simplified model is proposed to simulate the core segments near the BRB's ends. Using an iterative algorithm cooperatively, the simplified model can approximately determine the unfavorable additional eccentricities at the ends of restraining part. In the frame structures the rotations at two ends of the BRB are unequal, and the two different eccentricities can be equivalent to the same eccentricity by equivalent eccentricity coefficient. Finally, by taking the equivalent additive eccentricities obtained into account, a design procedure for the fixed-fixed BRBs is achieved. [ABSTRACT FROM AUTHOR]