| With the proposal of China's "Marine Power" strategy,the construction of deep-water long-span bridges plays a vital role in improving our transportation network and transportation efficiency,promoting the economic development of coastal cities and regional cultural exchange.The marine environment of deep water bridge foundation is very complex.In the service period,it bears the wave load that changes with space and time.There are significant differences in the stress characteristics and response of the deep water bridge foundation under the action of wave force in different structural forms.At present,the research on the wave response of the deep water bridge foundation is rare at home and abroad,and the research on the foundation structure of deep water bridge under wave loading has not been reported.Therefore,based on the foundation engineering of a long span bridge under construction,the wave force response of foundation under different pile foundation design is studied.Based on the linear wave theory,the wave forces acting on deep water bridge foundations(piles and caps)are calculated respectively.By establishing the finite element model of the foundation of the deep water bridge,the dynamic characteristics of the structure are analyzed,and the dynamic response of the wave force is calculated,and the indexes which can be used to evaluate the response of the deep water foundation wave force are screened.The influence of the pile height and the relative position of the pile cap to the static water surface on the response of the structure wave force is studied.The difference of the wave force response of the deep water bridge foundation is compared with the different structure forms(different pile diameter,pile foundation number and distribution),and the stress characteristics and the applicable scope of the deep water foundation with different structure forms are summarized.At last,from the angle of reducing the free length of pile foundation,three new group pile foundation structures are proposed,which are double bearing foundation,separated three platform foundation and joint pile foundation,and the response problem under wave load is solved.The following conclusions are drawn.Firstly,the deep water bridge foundation is subjected to forced vibration under the action of wave force.The structural response can be stabilized at short time excitation,and the dynamic magnification effect is not significant.The displacement of pile cap,the moment and the shear force at the bottom of piles can be used as an index to evaluate the wave force response of the structure.Secondly,for the deep water bridge foundation with different heights,the wave force response of the structure will reach the maximum when the top height of the foundation is near the static water surface.Thirdly,for the foundation structure with different pile diameters and different pile numbers,increasing the diameter of pile foundation can effectively reduce the displacement response of pile top and cap,and it has a strong effect on the optimization of the mechanical performance of the foundation structure.But,increasing the number of pile foundations cannot significantly reduce the displacement response of pile caps,and it has limited effect on the mechanical performance of structures.Fourthly,the increase of the lower cap,such as the double bearing foundation and the separated three platform foundation,can significantly improve the overall stiffness of the structure,reduce the response of the wave force and displacement of the structure and the response of the moment of the pile bottom.By setting up the joint pile group,such as the joint pile foundation,the response of the wave force and displacement of the structure can be reduced to a certain extent and the bending moment response of the pile bottom can also be reduced,under the condition that the shear force of the pile bottom is basically unchanged.Finally,the conclusions of this paper can provide a reference for the selection of deep-water bridge foundation structure. |
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