A new approach to pendulum base isolation

Abstract

A new approach to base isolation for reducing the destructive effect of earthquake is proposed. In this method mushroom-shaped (pendulum-like) basements are used under structures as base isolation. These basements have spherical surfaces and are located on the foundations. Basements have pinned arms that are connected to structure columns. When the length of the arm is less than the radius of spherical surface, their action is similar to a spring. In other words, when a displacement in a structure happens, a returning force is applied to the structure and the stability of the structure is guaranteed. The characteristic of these springs is that their stiffness can easily be set. As the stiffness is settable therefore the stiffness can be set in a way that, first, the force applied to the structure will be acceptable, and second the maximum displacement will not exceed the allowable limit. In this research the basements together with the structure were modeled as a one-degree-of-freedom system of mass, spring and damper. A FORTRAN program was written to determine the response of system against earthquake acceleration. Three different earthquakes were considered. The results show that the proposed method is very effective in reducing the action of earthquake on structure. Copyright © 2005 John Wiley & Sons, Ltd.