SUMMARY This paper presents a new type of electromagnetic damper with rotating inertial mass that has been developed to control the vibrations of structures subjected to earthquakes. The electromagnetic inertial mass damper (EIMD) consists of a ball screw that converts axial oscillation of the rod end into rotational motion of the internal flywheel and an electric generator that is turned by the rotation of the inner rod. The EIMD is able to generate a large inertial force created by the rotating flywheel and a variable damping force developed by the electric generator. Device performance tests of reduced‐scale and full‐scale EIMDs were undertaken to verify the basic characteristics of the damper and the validity of the derived theoretical formulae. Shaking table tests of a three‐story structure with EIMDs and earthquake response analyses of a building with EIMDs were conducted to demonstrate the seismic response control performance of the EIMD. The EIMD is able to reduce story drifts as well as accelerations and surpasses conventional types of dampers in reducing acceleration responses. Copyright © 2013 John Wiley & Sons, Ltd.

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We propose a semi-active control of civil structures based on a one-step-ahead prediction of the seismic response. The vibration control device (VCD), which has been developed by authors, generates two types of resistance forces, i.e., a damping force proportional to the relative velocity and an inertial force proportional to the relative acceleration between two stories. The damping coefficient of the VCD can be changed with a command signal to an electric circuit connected to the VCD. In the present paper the command signal for changing the damping coefficient of each VCD is assumed to take two values, i.e., the command to take the maximum or minimum damping coefficient. The optimal command signal is selected from all candidates of command signals so that the Euclidean norm of the one-step-ahead predicted seismic response, calculated by a numerical integration, is minimized. As an example a semi-active control of a fifteen-story building with three VCDs is considered. The simulation results show that the proposed semi-active control achieves superior performance on vibration suppression compared with a passive control case where the damping coefficient of each VCD is fixed at its maximum value.

SUMMARY Various semi‐active control methods have been proposed for vibration control of civil structures. In contrast to active vibration control systems, all semi‐active control systems are essentially asymptotically stable because of the stability of general structural systems with structural damping and the energy dissipative nature of the semi‐active control itself. In this study, by utilizing the aforementioned property on the stability of semi‐active control systems, a structural model for the semi‐active control design and a model‐based semi‐active control law are simultaneously designed so that the control performance of the resulting semi‐active control system becomes good. The model for the control system design is assumed to be a linear parameter varying model with adjustable structural design parameters. The semi‐active control law is based on the one step ahead prediction of the structural response of the designed model for the control system design. A genetic algorithm is adopted to obtain design parameters in the model for the control system design and the semi‐active control law. Those design parameters are optimized so that the closed‐loop system with the detailed dynamic model that accurately approximates the dynamic behavior of the real structural system and the semi‐active control law obtained with the model for the control system design. The effectiveness of the present approach is shown with a simulation study. Copyright © 2013 John Wiley & Sons, Ltd.

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