This paper examines the ASCE first generation benchmark problem for a seismically excited cable-stayed bridge, and proposes a new semiactive control strategy focusing on inclusion of effects of control-structure interaction. The subject of the ASCE benchmark problem is a cable-stayed bridge in Cape Girardeau, Missouri, for which construction is expected to be completed in 2003. The goal of the benchmark study is to provide a restbed structure on which researchers can systematically compare and evaluate the relative merits of proposed structural protection for cable stayed-bridges. In this paper, magnetorheological (MR) fluid dampers, which belong to the class of controllable fluid dampers, are proposed for use in a control strategy for protecting the bridge. A clipped-optimal control algorithm, shown to perform well in previous studies involving MR fluid dampers, is employed. A comprehensive study of the adequacy of various types of dynamic models for MR fluid dampers, such as a Bingham model, a Bouc-Wen model, and a modified Bouc-Wen model, is provided. In contrast to previous studies, models considered in this study are based on experimental data for a full-scale MR fluid damper. Because the MR fluid damper is a controllable energy-dissipation device that cannot add mechanical energy to the structural system, the proposed control strategy is fail-safe in that bounded-input, bounded-output stability of the controlled structure is guaranteed. Numerical simulation results considering several historical earthquakes scaled to various magnitudes show that the proposed semiactive control strategy using MR fluid dampers is the promising one of the applicable control methods to reduce seismic responses of cable-stayed bridges.
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