Study On Coupling Analysis Of Wave Force-seismic And Seismic Control Of Cross-sea Continuous Girder Bridge

The effects of waves of the piers of cross-sea bridges mainly include incident wave forces excited by waves,amplitude wave forces,and radiation wave forces generated by water-pier interaction.Under seismic actions,large cross-sea bridges influenced by earthquakes and waves simultaneously,the load environment is extremely complex.With the increase in the span of sea-crossing bridges,the superstructure becomes lighter,resulting in the rigidity of structures becoming smaller,damping becoming lower,and the structure becoming more and more sensitive to environmental dynamic loads.Once a cross-sea bridge is damaged,the repair cost and difficulty are extremely high,and the bridge piers below the sea surface cannot even be repaired.To avoid the ductility damage to the pier caused by the earthquake,the use of damping control technology is the best choice to ensure its safety.Therefore,it is necessary to carry out research on the seismic response to sea-crossing bridges and the corresponding seismic control research under the coupling action of earthquake and wave.The main research contents of this paper are as follows:(1)Based on the theory of radiation waves,the calculation formulas for the internal and external dynamic water pressure of the circular cross-section hollow piers of the cross-sea bridge are derived,and the bridge ground motion equations for the internal and external dynamic water pressure are established.Combined with the radiation wave theory,the velocity potential function of hydrodynamic added mass in the inner region deduced from this paper is applied to Chopra formula,and a new formula for calculating the added mass of hydrodynamic water in the inner region of hollow pier is established.The derived hydrodynamic pressure formula was verified by the computational fluid dynamics(CFD)method,and on this basis,the distribution law of hydrodynamic pressure on the submerged water depth,diameter and other parameters of the bridge pier were studied,it can provide relevant theories about the accurate and simplified calculation of the project support.(2)Based on the distributed parameter model with concentrated parameters and Euler beam theory,the "pier mass" analysis model of deep-water sea crossing seismic isolation continuous girder bridge is proposed.The corresponding frequency equation,pier distribution parameters and damping motion equation of pier top concentrated parameters are derived.The motion equations are decoupled by orthogonal conditions,and an improved mode superposition method of seismic response analysis is proposed.The correctness of the method is verified by comparing with the calculated results of SAP2000.On this basis,the influence of dynamic water pressures and water depth change in the seismic performance of Bridges is studied,which provides a new way for the simplified calculation of seismic isolation from deep-water cross-sea continuous girder Bridges.(3)According to the size of the water-facing surface of the pier,Morison equation and the amplitude waves theory are used to establish the dynamic response analysis model of the cross-sea bridge under wave action.Taking a non-navigable continuous beam(3×85m)of a sea-crossing bridge as an example,a finite element analysis model of the bridge structure considering the coupling effect of wave forces and earthquake is established,and the corresponding plane structures analysis program is compiled using MATLAB software.On this basis,the coupling characteristics of earthquake wave interaction are studied,which are different from the superposition of single earthquake and wave action.At the same time,the dynamic response law of bridge structure of the combined action of wave,earthquake and wave is studied.(4)Aiming at the seismic control of the sea-crossing continuous girder bridge,the motion equation of the bridge structure with fluid viscous dampers and the state spaces equation of it combined with wave forces and earthquake are established.In order to improve the efficiency of parameter optimization of fluid viscous dampers,a stochastic optimization method of viscous damper parameters is proposed by the formula of equivalent linearization for fluid viscous dampers and Clough-Penzien spectral filtering state equation,the Lyapunov equation which can directly solve the random response is proposed to minimize the variance in the pier top displacement.The proposed method is used to optimize the damper parameters of the actual project,and the parameter sensitivity analysis method is used for comparison and verification.On this basis,according to the optimized damper parameters,the viscous damping performance of the bridge structure under the combined action of wave force and earthquakes is studied.The results show that the optimization results obtained by the stochastic optimization method and the parameter sensitivity analysis method is in good agreement.In addition,in the seismic mitigation design of cross-sea bridges,it is necessary to consider wave-seismic coupling.