Performance‐based seismic design of the outrigger of a high‐rise overrun building with asymmetric vertical setback in a strong earthquake area

Abstract

SummaryOutriggers, which should be systematically analyzed and designed based on seismic performance methods in the different seismic level actions, can improve the lateral stiffness of irregular high‐rise structures. In this paper, a concrete‐filled steel frame‐core tube‐outrigger structural system is adopted for a practical overrun high‐rise building with an obviously asymmetrical vertical setback in a high‐intensity seismic region. To ensure the seismic safety of irregular high‐rise building structures, the members of the outrigger are designed based on the seismic performance analysis method, and the complex joint region and slab of the outrigger floor are also refined and analyzed. In addition, the effect of outrigger on the damage states of the structural and member is evaluated using the elastic–plastic analysis method in the rare earthquake action. Finally, the seismic mitigation efficiency of the high‐rise structure with the viscous dampers installed on the outrigger floor is analyzed. The results indicate that the member size of the outrigger should be determined based on the performance objectives of the moderate earthquake action rather than the frequent earthquake action. The shear force distribution ratio of the outer frame located at the outrigger floor is obviously amplified, which shows that the cooperative bearing ability of the outer frame and the core tube is improved because of the outrigger action. The stress in the complex joint region of the outrigger, which satisfies the material strength requirement, is analyzed by the refined finite element analysis method. The slab of the outrigger floor, which should be strengthened to effectively transfer larger horizontal seismic shear force, has obvious damage in the rare earthquake action. The region of the structure with an outrigger that experiences significant damage in the rare earthquake action is located at the outrigger floor and adjacent upper domains rather than the bottom domains, which is different from that of a structure without an outrigger. The internal force of the outrigger member can be reduced by considering viscous damper action, but the seismic mitigation efficiency is not significant because of the limited number of dampers.