Pole assignment using PSO-SA hybrid algorithm for sliding mode control on isolated bridges with columns of irregular height

Bridge structures may be complicated due to various terrain, route alignment, ramps, interchanges, etc. If columns of a bridge are of irregular height but of identical cross section, the induced seismic forces and responses of each column are varied because of the different stiffness of each column. The isolation system has been extensively adopted in bridges to mitigate the induced seismic force. However, the deck displacements of isolated bridges maybe become excessively large under extreme ground motions. Structural control has been shown to effectively mitigate the seismic responses of isolated bridges in the past studies. So far there is no study on the structural control of isolated bridges with columns of irregular height. This research is aimed to study the effectiveness of the sliding mode control for the isolated bridge with the columns of irregular height. It is noted that the sliding surface of the sliding mode control dominates the dynamic behavior of structures. A four-span isolated bridge with columns of irregular height, which is designed based on the balancing-member-stiffness method, is analyzed in this study. Since the target bridge has to be idealized as at least a four-degree-of-freedom system for sufficiently understanding the dynamic behavior, it is needed to determine at least five poles of the sliding surface. Although it is possible to find out an optimal sliding surface by parametric study, the work is tedious and troublesome. The PSO-SA hybrid searching algorithm is adopted to explore the optimum sliding surface of the sliding mode control in this study. Through numerical simulation, the results demonstrate that the sliding mode control with the optimum sliding surface obtained by using the PSO-SA hybrid search method can more effectively decrease the seismic responses of the target bridge than by using the parametric study method.