Development of a hybrid control algorithm for effective reduction of drift in multispan isolated bridges

Abstract This study aimed to develop a hybrid control algorithm for semiactive control devices to effectively control the drift caused by seismic loads in the superstructure of an isolated multispan bridge. First, bridge behavior was simulated using the Newmark method to select a semiactive control device that would be appropriate for the bridge structure. An optimal control force was selected to control the displacement and relative displacement of each superstructure element. Next, an equation of motion that employed a stochastic linearization capable of representing the nonlinearity beyond the structural linear limits was used. Further, a Bouc–Wen model was designed to simulate the nonlinearity of the structure model and the control device to configure the control logic. A hybrid control algorithm was developed to overcome the disadvantages of the clipped-optimal and Lyapunov control algorithms, which show excellent control effectiveness but experience problems during nonlinear control along with extreme manual control problems owing to their use of the Heaviside step function. The two control algorithms were used individually to make judgments, and the results of each were used to produce a three-stage signal (min., max., median). The performance of the proposed control method with the developed algorithm was verified through experimental tests. The developed hybrid control algorithm improved the performance of the two individual control algorithms and effectively controlled the behavior of multispan bridges.