Optimal design of a base isolated system for a high-rise steel structure

In a previous study (Kaplan H, Seireg A., Int. J. Comput. Appl. Technol., 2 000; 13(1/2): 25-41), the authors proposed a base isolation system for eart hquake protection of structures. The system incorporates spherical supports for the base, a specially designed spring-cam system to keep the base rigi dly supported under normal conditions and to allow it to move for the durat ion of the earthquake under the constraint of a spring with optimized stiff ness characteristics. A single-degree-of-freedom structure was considered t o investigate the feasibility of the concept. The simulation of the system response shows a 20 times reduction of the transmitted force as a result of using the proposed design in the considered case. This paper extends the p revious study to the case of a 40-storey steel structure subjected to the T aft as well as El Centro earthquakes. A 7.5 and 6 times reduction of the ma ximum transmitted force was achieved for the considered disturbances, respe ctively, without any adverse effects due to the tilting moment which is inh erent in this type of base isolation. Copyright (C) 2001 John Wiley & Sons, Ltd.