Seismic Performance and Storey-Based Stability of Suspended Buildings

Abstract

Buildings designed with floors suspended on mega supporting structures (core tubes/frames) are referred to as suspended buildings. Such buildings can meet some practical requirements such as the gaining of large open spaces. Some aspects, including seismic performance and structural stability, however, are not completely understood by the engineering community. This motivated an investigation into the performance of suspended buildings subjected to gravity and ground earthquake motion. The stability of suspended floors and their mega supporting structures is discussed in relation to P-delta effect. A suspended-floor section is able to gain stiffness from gravity, but the stability of its mega supporting structure may be a problem due to the up-shifted gravity. This leads to a discussion of the storey-based stability method for assessing the critical load multipliers to be applied to the supporting frames. In view of the pros and cons of suspended buildings, a passive control system with three-performance levels is presented using pendulum floors and connection dampers to dissipate energy and avoid pounding. Optimal control system parameters were studied in order to help with the selection of connection stiffnesses and damping coefficients during the design of suspended buildings. Initial results show that, as opposed to a pendulum TMD, the large suspended-floor masses themselves play a key role in reducing the seismic response, and buildings are able to be designed as types of suspended systems which are effective against strong earthquake motion combined with gravity.