Semiactive Fuzzy Control of the Seismic Response of Building Frames

A methodology for semiactive control of building frames using multiple semiactive hydraulic dampers (SHDs) driven by fuzzy controllers is presented. The SHDs are installed in combination with steel bracings and are placed at different floor levels. The fuzzy controller is designed for the bottom-most SHD. Other controllers are assumed to provide control command for the variable damping coefficient of an SHD in certain proportion to that obtained for the bottom-most controller. Different proportions giving different distributions of the semiactive control force along the height of the frame are tried in order to arrive at the best distribution for obtaining the maximum control of a response quantity of interest. The methodology is developed in the MATLAB environment using the SIMULINK and FUZZY tool boxes. As an illustrative example, a five-storied steel frame is selected from the literature. The control of the responses of the frame under the El Centro earthquake record is obtained for a specified set of the frame, steel bracings, and SHD properties. An extensive parametric study is conducted to investigate the effectiveness of the control scheme under variation of the important parameters. The control strategy with the optimum values of parameters designed for the El Centro earthquake is tested for three synthetically generated earthquakes. The results of the study show that an efficient semiactive control strategy can be developed using a fuzzy rule base. Further, optimum combinations of parameters for maximum control are different for different response quantities of interest.