Control strategy for mitigating the response of structures subjected to earthquake actions

On-line control strategy for structures subjected to earthquake actions is investigated. The general control strategy consists of monitoring the incoming signal, analyzing it and recognizing its dynamic characteristics, applying the control algorithm for the calculation of the required action, and finally applying this action. Thus, the way in which the structure is controlled, and the algorithm that is used, are based on the dynamic characteristics and the frequency content of the applied dynamic signal. The procedure of selection of poles of the controlled structure, which is critical for the success of the algorithm, is proposed in this paper. The proposed methodology transforms each consecutive part of the signal, as well as the uncontrolled structure, to the complex plane and, depending on their relative positions, and following specific rules, the desired poles of the controlled structure are calculated and adjusted during the earthquake. According to those locations of poles, and using the pole placement algorithm, the feedback matrix is estimated, and then the equivalent forces that should be applied to the structure by the control devices, which are installed on the building, are calculated. Parametric simulations for different dynamic loads and seismic actions are performed, for both single and multi degree of freedom systems. From the numerical results it is shown that the above control procedure is efficient in reducing the response of building structures, with a small amount of required control forces.