Under the action of earthquakes, the dynamic responses of cross-sea bridges are greatly influenced by the dynamic interaction between each pier and the surrounding water. Based on Morison equation, this paper mainly explores the responses of a continuous girder cross-sea bridge in uncontrolled and semi-active control modes, under the combined effect of earthquake and hydrodynamic pressure. First, a simplified two-degree-of-freedom (2DOF) analysis model was constructed for the bridge: the combined stiffness was proposed to reflect the effects of the bending and shear deformation features of the pier; the pier mass was aggregated on the top of the pier as the additional pier mass, using the shape function of linear deformation; the hydrodynamic pressure distributed on the pier was calculated by the Morison equation, converted into the equivalent node load on the top of the pier, and further transformed into the additional hydrodynamic mass. Then, a magnetorheological (MR) damper was added between the pier and the girder. The semi-active algorithm of the MR damper was designed based on the clipped-optimal control algorithm. The control force of the MR damper was optimized by the H2/LQG active control method. The results show that the hydrodynamic pressure changes the dynamic features of the bridge and increases the seismic responses of the bridge, calling for a stronger control force for semi-active control; the impact of hydrodynamic pressure must be considered in the seismic design of cross-sea bridges; the MR semi-active control can effectively suppress the dynamic responses of cross-sea bridges, enhancing the seismic safety of the bridge. The research results provide new insights into the vibration control of cross-sea bridges.
Under the action of earthquake, the dynamic interaction between the bridge pier and the surrounding water has a great impact on the dynamic response of the bridge structure. With a continuous sea-crossing beam bridge as an example, this paper studied the stochastic optimization of the parameters of nonlinear viscous damper and its damping performance under the fluid-solid coupling effect of waves and piers. In this study, a 2-degree-offreedom bridge analysis model considering the fluid-solid coupling effect was constructed, and a nonlinear viscous damper was set in the model and subject to equivalent linearization according to the equivalent energy consumption criterion. Then on this basis, with minimizing the variance of the displacement of pier top as the target, this study applied the Lyapunov method to optimize the parameters of the damper, and explored its impact on the seismic response of the bridge and the damping performance considering the fluid-solid coupling effect. The research results showed that the fluid-solid coupling effect changed the dynamic characteristics of the bridge and increased its seismic response, and the viscous damper can effectively reduce the seismic response of the sea-crossing bridge and improve its damping performance.
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