A Study on the Displacement Control of an Isolated Bridge with Rocking Response of Spread Foundations

In practical bridge design, the bridges with isolators are generally employed to mitigate the induced seismicforces. The bridges in hard soil site are generally designed with spread foundations. A number of researchershave proposed the concept of rocking isolation of spread foundations, and studied the effect of the rockingisolation for the bridges with rigid bearings. However, the bridges in hard soil site may be designed by usingboth isolators and spread foundations. In literature, there are no researches regarding the isolated bridgeswith consideration of rocking of spread foundation. According to the past study, the isolated bridge withrocking response results in extensive large displacement of superstructures as the same as the traditionalisolated structures. Such a large displacement may cause the pounding of decks even the fracture of isolators.In this study, structural control technology will be employed to decrease the displacement response,including passive control and semiactive control. Since such a bridge exhibits highly complicated nonlinearbehavior, the modified sliding mode control which is suitable for nonlinear structures, will be adopted tocalculate the required control force. The optimum control parameters will be obtained by using the PSO-SAhybrid optimum searching algorithm. A new search loop of the PSO-SA searching algorithm will beproposed to decrease the searching time. Besides, a shaking table test with passive control will be conductedby using the existing bridge model and linear viscous dampers to verify the feasibility of the practicalapplication of structural control.