Keywords: semi-active control, tuned mass damper, electromagnetic transduction.

The performance of tuned mass dampers (TMDs), widely used in civil engineering, depends on their state parameters. Therefore the evolution of the controlled structure and the evolution of the type of excitation may pull down the efficiency of this kind of device. Active tuned mass dampers (ATMDs) have been widely explored for damping the dynamic response of bridges under construction and submitted to various types of external excitations such as wind. However with respect to the permanent control of bridges under operating conditions, active devices suffer from several drawbacks such as the necessity of an important source of external energy that must always be available.

In this paper a new type of semi-active control system based on an electromechanical device is presented. This semi-active tool consists of a pendulum coupled to an alternator. The alternator converts the mechanical energy of the oscillating pendulum into electrical energy to be dissipated through an exterior resistor via the Joule effect. Given an optimal design of a reference pendulum TMD for the structure in its current configuration, the semi-active control consists of changing the resistor in real-time in such a way to lock the apparent stiffness and damping of the real TMD at their desired optimal values at each construction step and for each type of external excitation. Detailed experimental studies on a small-scale bridge mock-up show the effectiveness of this semi-active control device and validates the capability of the semi-active control law to make the performance of the actuator independent of the structural evolution and of the type of the external excitation.

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