Experimental and Analytical Study on a Nonlinear Isolated Bridge under Semiactive Control

Abstract eng:
The semiactive control system applied to a nonlinear isolated bridge with a magneto-rheological (MR) damper controlled by an improved sliding mode control algorithm is successfully implemented and evaluated through a series of shaking table tests. In the past researches, numerical simulations revealed that structural control systems are effective in mitigating seismic responses for isolated bridges which exhibit nonlinear responses under near-field ground motions. This paper is aimed to show the practical implementation of the semiactive control system to a nonlinear isolated bridge. A two-story shear-type structure model made of steel plates is designed to imitate the nonlinear dynamic behavior of an isolated bridge. In particular, since the column plates are replaceable, next nonlinear test can be continued using the same model by only changing the steel plates. Compared to the control methods based on feedback of displacements and velocities, the used improved sliding mode control based on feedback of velocities and accelerations shows more practical application into real structures, because it is easier to measure acceleration than displacement during earthquakes. Through comparison between analytical and experimental results, the MR damper satisfactorily traces the demanded control force by the control algorithm and the response time histories agreed to each other well. The results verify the feasibility of semiactive control system for a nonlinear structure in practical implementation. Since the results also present that the semiactive control system has outstanding performance, the semiactive control system provides a valuable control method for mitigating seismic responses of nonlinear isolated bridges.

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