<title>Seismic response control of nonlinear base-isolated structures using variable fluid dampers</title>

Abstract

In this study, the seismic response of a base-isolated three-story test structure is investigated. At the isolation level, the structure is equipped with a fluid damper having adaptive characteristics. Since the isolation system is strongly nonlinear, a nonlinear feedback control algorithm is utilized to determine the appropriate level of damping in the isolation system. This paper focuses on the development of an intelligent controller that can effectively suppress vibrations of the nonlinear structural system due to various excitations. Specifically, numerical simulations are performed using several historical earthquakes to evaluate the dynamic response of the test structure and isolation system when different damping mechanisms (passive, semi-active (variable), or active) are incorporated within the isolation system. The numerical simulations demonstrate that variable damping is effective in simultaneously controlling the response of the structure and the isolation system. Such control is particularly important for structures subjected to disparate ground motions such as frequent, weak earthquakes versus rare, strong earthquakes or far-field versus near-field earthquakes.