Research On Influence Of Variation Of Reinforced Pile Foundation Parameters On Existing Bridge Seismic Response

As one of the most important buildings on the transportation channel,the bridge has always attracted people's attention on its disaster research.With the developing of research,the research on the impact of bridges on disasters also extends from considering single disaster factor to considering multiple disaster factors at the same time.Among them,it is an important aspect of this kind of research to consider the impact of the pile foundation on the seismic response of the bridge structure during the river bed is scoured.The ground motion transfers the seismic effect to the structure through the foundation,and the riverbed scouring causes the environment change of the bridge foundation,which changes the boundary constraints and thus affects the seismic response of the bridge.In view of this kind of problem of considering erosion and earthquake at the same time,this paper studies the influence of different pile foundation design parameters on the seismic response of the bridge structure in consideration of the erosion of the river bed to study the new pile foundation reinforcement design with exposed damage of the pile foundation.The following work has been done:1.The hazards of earthquakes and scouring disasters on bridges are introduced.The research status of considering both earthquakes and scouring factors in multi-hazard design.The characteristics and applicable scope of commonly used seismic analysis methods for bridges,as well as the pile-soil interaction.2.Taking the project of a double-column bridge pier highway bridge caused by erosion of the river bed as a result of the erosion of the pile foundation,the project of adding a "pile foundation + bearing platform" for reinforcement is used as the engineering background.The Midas / civil 2019 finite element software is used to establish finite element models with different pile foundation parameters.The influence of the number of pile foundations,diameters of pile foundations and pile foundation spacing on the natural frequency and seismic response of bridges under the condition of river bed scouring was studied.3.The multiple Ritz vector method is used to analyze the dynamic characteristics of the finite element models of each research program,and the results of the former 10 order modal natural frequencies of all models are studied.Considering the erosion of the river bed,the paper analyzes the influence of number of piles,pile diameters and pile distance of additional reinforced pile foundations on the natural frequency of the bridge.4.Based on the results of natural frequency analysis,the response spectrum analysis method is used to study the E1 and E2 seismic effects in the transverse and forward directions to the bridge model.Four key sections were selected on the bridge pier and pile foundation,and the influence of the number of piles and diameters of the reinforced pile foundation on the internal force and displacement of the bridge was analyzed with condition of river bed scour.5.The time-history analysis method was made to earthquake response of the bridge.According to the results,the influence of different number and diameters of the reinforced pile foundation on the internal force and displacement of the bridge is analyzed with river bed erosion.Comparing the results of the time history analysis with the response spectrum analysis,it is found that the results of the time history analysis are basically consistent with the results of the response spectrum method,but the value of the seismic response is much larger.The time-history analysis should not be ignored.6.The research results of the paper show that for the works of pile foundation reinforcement bridge with double-column piers,the additional "pile foundation + cap" reinforcement scheme is appliable.Among the influence factors,the number of new-added piles is most important,then the pile diameter.If this type of reinforcement design is adopted,it is recommended to give priority to structural solutions with a large number of piles,the same pile diameter and a relatively small pile diameter,and to avoid the designs with different pile diameters.In addition,it is necessary to improve the ability of resisting the transvers moment at the top of piles.