Design of Pre-Tensioned Cable-Stayed Buckling-Restrained Braces Considering Interrelationship between Bracing Strength and Stiffness Requirements

Abstract

The conventional restraining ratio approach is not suitable for a straightforward design of the pre-tensioned cable-stayed buckling-restrained brace (PCS-BRB) because of its complicated buckling-restrained system. This study uses an adequate bracing approach to establish a more rigorous design procedure for the PCS-BRB by analyzing and designing the PCS-BRB as a braced system; a simplified midspan braced column with translational and rotational springs. Based on the results from an elastic buckling analysis, the influences of the midspan translational and rotational spring stiffnesses on the buckling axial loads associated with symmetric and antisymmetric buckling modes, respectively, are discussed. In a second-order analysis, the solution for the column differential equation of equilibrium is derived considering both symmetric and antisymmetric initial imperfections. The inverse interrelationship between the bracing strength and stiffness requirements is investigated. Then, using the results from these analyses for the midspan braced column, the adequate bracing approach is followed for the design of the PCS-BRB. The strength limits of the cable-stayed system are formulated for its effectiveness, and its adequate stiffness requirements are determined based on examination of these strength limits. A detailed design procedure and an elementary design example are presented.