Seismic Performance and Failure Mechanism of Megabraced Frame-Core Tube Structures with Different Brace Patterns

Abstract

The effect of mega braces on structural stiffness has been comprehensively discussed for various megabraced frame-core tube structures. However, few studies have considered how mega braces affect the failure mechanism of mega structures exposed to seismic action, which is a nonlinear process. To address this issue, we present a study on the effects of different brace patterns on the failure mechanism and seismic performance of megabraced frame-core tube structures. Specifically, the yield order of components, the distribution of plasticity, the distribution of internal forces, the degradation of structural nonlinear stiffness, and the behavior factor have been investigated. This study reveals that the yield of mega braces will change the deformation mode of adjacent mega columns and thus affect the plasticity distribution of adjacent substructures. The enhancement of mega braces improves the exterior tubes (thereby increasing their capacity to serve as the second line of seismic defence), mitigates the rate at which system stiffness degrades, and improves the overstrength of the structural systems. In addition, after the yield of mega braces, the maintenance of a higher-amplitude axial force changes the proportion of internal force components in mega columns, reducing their ductility and further affecting the overall ductility of the structural system.