Study on the overturning resistance of a new staggered story isolated structure

Abstract

The isolated bearings of high-rise base isolated structures are prone to buckling instability under tensile and compressive stresses, leading to structural overturning. This limits the height of base isolated structures, while a new staggered story isolated structure is suitable for high-rise isolated buildings. Its overall structure resembles the "mortise and tenon" commonly used in traditional Chinese architecture. On one hand, the core tube is embedded in the substructure, which lowers the center of gravity of the superstructure and reduces the overturning moment. On the other hand, the interlocking of the superstructure and substructure provides advantages for the overturning resistance of the structures. In this study, a calculation formula was derived for the overturning resistance ratio of the new staggered story isolated structure. Five models with a height of 106.4 m were established using ETABS. The effects of changing the position of the frame isolated layer and adding viscous fluid dampers on the overturning resistance were analyzed. The results indicate that the new staggered story isolated structure has a lower risk of overturning compared to both the non-isolated structure and the base isolated structure under rare earthquakes. It effectively mitigates excessive tensile stress on the isolated bearings and minimizes the number of isolated bearings experiencing tensile stress. Additionally, it reduces the risk of overturning of the superstructure in high-rise buildings under rare earthquakes, thus compensating for the height limitations of base isolated buildings. As the position of the frame isolated layer in the new staggered story isolated structure is raised, the overturning resistance ratio of the superstructure increases while that of the substructure decreases. Therefore, it is necessary to reinforce the substructure. Placing viscous fluid dampers between the substructure and the core tube can enhance the overturning resistance ratio of the substructure and the overall structure. The new staggered story isolated structure effectively reduces the number of plastic hinges in the superstructure and minimizes damage to the core tube between the frame and the core tube isolated layers. Moreover, the addition of viscous fluid dampers makes the hysteresis curves of corner column isolated bearings in the frame isolated layer fuller.