New strategy for controlling structures collapse against earthquakes

Abstract

A control strategy for structures subjected to earthquake actions is investigated. The strategy is inspired from the human beings reaction when they are attack by earthquake excitation. Humans realize the earthquake excitation by the neurons, sent this information to the brain, a decision is taken there and by neuron system the decision is sent it back to the muscles for suitable action. In similar way the 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 earthquake signal. The algorithm transforms the earthquake signal and structure into a complex plane and, depending on their relative positions, the equivalent forces that should be applied to the structure by the control devices, which are installed on the building, are calculated. From the numerical results it is shown that the above control procedure is efficient in reducing the response of building structures subjected to earthquake loading, with small amount of required control forces. The influence of time delay and saturation capacity is taken into account. Characteristic buildings controlled by pole placement algorithm and subjected to earthquake excitation are analyzed for a range of levels of time delay and saturation capacity of the control devices. The response reduction surfaces for the combined influence of time delay and force saturation of the controlled buildings are obtained. Conclusions regarding the choice of the control system and the desired properties of the control devices are drawn.