Buckling mechanism of steel core of buckling-restrained braces

• Buckling mechanism of steel core of BRBs is revealed.
• Analytical expression of the maximum contact force is derived.
• The maximum bending moment of restraining member is obtained.

This paper investigates the buckling mechanism of the steel core of buckling-restrained braces. The development of buckling mode is revealed with increasing axial load. The formulae of the maximum contact force and the maximum bending moment of the restraining member are obtained. The analytical results are validated by the finite element analysis. Compared to the results by conventional analysis, the number of contact points or buckling waves is much less; for hinged ends, the contact force for the lower mode is the identical while the contact force for higher modes is 1/4 lower; for fixed ends, the contact force is half of the conventional method.