The protection of civil engineering structures subjected to severe earthquake loading is a problem of widespread importance. Over the last two decades, a variety of control devices and algorithms have been proposed to reduce the impact of earthquakes on structures. Benchmark problems have been proposed to develop standardized methodologies for comparing various control systems. The first benchmark problem in structural control dealt with a laboratory scale structure equipped with an active mass driver that was subjected to seismic loads, and was proposed by Professor B.F. Spencer, Jr. from the University of Notre Dame. This problem was extremely useful for acquainting the structural control community with a variety of implementation issues.
This paper addresses the next generation benchmark problem in structural control for seismic protection , which focuses on the control of a full-scale 20-story building. Magnetorheological (MR) dampers are applied to reduce the structural responses of the next generation benchmark building. The MR damper is chosen for this study because it has quite attractive characteristics for these applications and has demonstrated a great deal of potential in previous investigations. Devices based on MR fluid technology are reliable, inexpensive, relatively insensitive to environmental factors, and require minimal power. In a recent experiment, a single MR damper used in conjunction with a clipped-optimal control algorithm was shown to be effective in reducing the responses of a multi-story test structure . Additionally, the performance of the semi-active control system surpassed that of comparable passive systems. Based on the results of these initial investigations, the MR appears to be quite promising for earthquake protection.
 B.F. Spencer, Jr., R.E. Christenson, and S.J. Dyke, "Next Generation Benchmark Control Problem for Seismically Excited Buildings," Proceedings of the Second World Conference on Structural Control, Kyoto, JAPAN, June 30 - July3, 1998.
 S.J. Dyke, B.F. Spencer Jr., M.K. Sain and J.D. Carlson, "An Experimental Study of MR Dampers for Seismic Protection," Smart Materials and Structures: Special Issue on Large Civil Structures, 1997 (in press).