Analysis Of Seismic Response Of Continuous Bridge Under Non-uniform Seismic Excitations

At present,the influence of the seismic spatial on the structural response is mainly concentrated in large span bridges,such as cable-stayed bridges and long-span continuous girder bridges,and there is very few studies on small-span bridges.The existing geological data has been confirmed,even in the 50 m range,the vibration amplitude and phase of different foundation may also be very different.Continuous girder bridge has become an important part of urban traffic because of its economy and practicability.Therefore,it is necessary to study the effect of ground motion on the continuous girder bridge with small span,which can provide reference for the seismic design of small span continuous beam bridge.The spatial of ground motion is mainly composed of three aspects: traveling wave effect,coherence effect and local site effect.In this paper,we first use Matlab to compile the program to generate the seismic wave according to the random vibration theory.The finite element model of the continuous girder bridge is established by using ANSYS software.The bridge is analyzed by multiple working conditions,including analysis under the uniform excitation,considering the traveling wave effect and the coherence effect,considering the traveling wave effect,the coherence effect and the local site effect by using multi-point input method "Code for Design of Ground Base and Foundation of Highway Bridge and Culverts"(JTG D63-2007)proposed “m” method to consider the pile-soil interaction.After taken the pile-soil interaction into consideration,the traveling wave effect,the coherence effect and the local site effect is also taken into account.In contrast to the uniform excitation,analyze the influence of the traveling wave effect,the coherence effect and the local site effect on the response of bridge such as bending moment,bearing displacement and top displacement of bridge pier.Compare the bridge structural response with considering pile-soil interaction and without considering pile-soil interaction,analyze the influence of the pile-soil interaction effect.The ground motion does not change obviously for the bridge span is small after considering the traveling wave effect and the coherence effect.The ground motion changes obviously after considering the traveling wave effect,the coherence effect and the local site effect.And the peak value of the soft soil site increases obviously followed by sand site,while the changes of the peak value of ground motion of hard soil site is the most unobvious.Compared with the uniform excitation,part of the bridge response get increased,while other partial response decreases,and the same response of different parts performs as different rules,after considering the traveling wave effect and coherence effect,which can not simply say the traveling wave effect and the coherence effect on the structure is helpful or harmful.The influence of traveling wave effect and coherence effect on the shear and bending moment of the structure is larger than that on the bearing displacement and the displacement at the top of pier.On the basis of traveling wave effect and coherence effect,the effect of soft soil site on the structural response is obvious,and the effect of hard soil site is unobvious.When considering the effect of pile-soil interaction,the shearing force and bending moment of the structure is obviously reduced,while several of the bearing displacement is and displace at top pier is obviously increased.In general,the effect of pile-soil interaction is helpful for the bending moment and the shearing force,and enlarge the bearing displacement and displacement at the top of pier.