Dynamic Response Of Deep-water Foundation Of Cross-sea Bridge Subjected To Earthquake And Wave Loads

Nowadays,with the construction of bridges crossing large rivers,some long-span bridge projects have been started,such as Hong Kong-Zhuhai-Macao bridge and Qiongzhou Strait Bridge.Cross-sea bridges are usually constructed in vast sea.It's inevitable to being tested not only by deep water,torrent and complicated geographic condition,but also by severe marine environment,which including typhoon,surge,violent earthquake and ship collision and so on.The technical difficult and costs of deep water foundation of large-scale bridge is fairly high in the process of design,construction and maintenance.However,deep water foundation is the bearing part of bridges,and playing a critical role in the whole structure.Exploring the dynamic response characteristics of it has a great significance.In this paper,the deep water foundation is taken as the research object.Firstly,types of deep water foundation are summarized.Aimed at the issue of dynamic response subjected to complex environment loads,the seismic load and wave force are simulated and analyzed.Through finite element method,the dynamic response characteristics of deep water foundation has been contrasted and analyzed.There are several types of deep water foundation.And each one has its own characteristic,which is suitable for specific sea area.For choosing appropriate type of deep water foundation,natural environment,loads and construction conditions and other factors should be considered.With the increase of water depth,it is inevitable facing a series of engineering problems,including several environment,disaster loads,and constructional difficulties.And problems contain all links of the construction period,such as geological survey,structural design,site construction and operation maintenance.Considering the complex ocean and geological environment,the design of deep water foundation should think over the effect of seismic load,wave force and their joint effect.Taking the characteristics of geologic and history seismic of Qiongzhou Strait into account,two levels of synthetic seismic waves have synthesized.Based on FLOW-3D software,three-dimensional numerical flume has been established,and wave force of the structure has obtained by using numerical simulation method.Through Newmark dynamic time history analysis,the law of dynamic response of open caisson foundation is explored under the effect of seismic load,wave force and their joint effect.Results show that the constraint function of deep soft soil is limited.And the joint action of two loads has an obvious amplification effect on dynamic response of structure.The shear effect of open caisson foundation is remarkable.Taking the deep water foundation of Qiongzhou Strait Bridge as the research object,and disastrous factors such as seismic load and ship impact load are considered.Based on finite element method,characteristics of static and dynamic response of deep water foundation are analyzed.The results show that it's inappropriate to simplifying the seismic load to static equivalent load.At the same time,the shear,extrusion and torsion effect of the structure is significantly subjected to huge horizontal load.In this case,the wake position locates at the top of pile group foundation.It is necessary to ensure the smooth transition of inertial force of the structure by using rigid pile caps or other structural measures.