Dynamic Response Analysis Of Cable-stayed Bridge Considering The Pile-soil Interaction Under The Combined Action Of Wind-wavecurrent

With the release of the Outline of China’s National Comprehensive Three-dimensional Transportation Network Planning,the State Council has for the first time determined the requirements for the construction of the national medium and long-term transportation network at the central level.According to the planning,there will be more high-speed railway lines across the sea in the coastal area.As a control project in the line,the bridge will face many technical problems in the special oceanic environment.In terms of environmental loads,the long-span bridge in deep water bears random loads such as torpids,waves and winds.Under the condition of deep water,the wave-current load of the lower foundation even plays the dominant role.The coupling of the wind field of the upper structure and the wave-current field of the lower structure poses a major challenge to the driving comfort,structural safety and component fatigue of the long-span bridge.At present,the span of sea-crossing cable-stayed bridge is getting larger and larger,the seabed geological conditions are complex,which magnifies the influence of pile-soil interaction.However,there are few dynamic response analysis of the whole bridge considering the pile-soil interaction under the combined action of wind,wave and current.In this paper,the dynamic response of an sea-crossing long-span steel-truss cable-stayed bridge under the combined action of wind,wave and current is studied by numerical simulation and theoretical calculation.The main contents include:(1)A three-dimensional wave numerical flume model was established based on the standard k-ε turbulence model and the tru VOF method.The validity of numerical waves and wave force calculation results of the model obtained are compared with theoretical solutions and experimental results respectively,which verify the reliability of numerical waves generation of the wave numerical flume model established by the method in this paper and the accuracy of wave force calculation results of structures with different scales.(2)The combined action load of wind-wave-current considering a certain degree of coupling is calculated for an engineering example.Firstly,using the fitted six-parameter random wave spectrum and wave-current design parameters obtained from the measured data of the bridge site,the regular wave-current forces of the lower foundation composite structure and the random wave-current forces considering the effects of multiple physical fields on the wave frequency components are obtained according to the wave numerical flume established by the method in this paper.A 1:20 scale was used to simulate the flow field to obtain the static three-component force coefficient time history of the typical section of the bridge pylon.Based on the harmonic synthesis method,the wind field of the long-span cable-stayed bridge was simulated,and the wind load of the bridge pylon and the girder body were calculated by the quasi-steady aerodynamic theory considering the three-component force coefficient of the bridge pylon.(3)Based on ABAQUS,the full bridge finite element model of cable-stayed bridge in the completion stage is established,which fully considers the normal and tangential nonlinear behaviors of pile-soil interface.The effect of soil initial stress and soil initial water pressure on pile-soil interaction is considered.Compared with other models with simplified boundary conditions,the model considering the pile-soil interaction established in this paper can more accurately simulate the dynamic characteristics of the bridge.(4)Based on the time domain implicit dynamic analysis method,the dynamic response of a full bridge finite element model considering the characteristics of pile-soil interface under the combined action of wind-wave-current is calculated.The response differences of the model under the action of regular wave-current,wind action,regular wave-current and wind combined action,random wave-current and wind combined action were compared.The response results before and after considering the pile-soil interaction were compared.The spectral function considering the displacement response before and after the pile-soil interaction is obtained by using the Fast Fourier Transform.It is concluded that the dynamic response of pile-soil interaction to the combined action of wind,wave and current should be fully considered in the calculation of sea bridge.