Study On The Damage Behavior Of Pile Foundation Of The High Pile-cap Continuous Beam Bridge Under Barge Collision

With the rapid development of traffic construction,bridge structures in riverintensive coastal areas is commom these days.Meanwhile,the pile foundation of highpiled caps has large free lengths of pile foundation above riverbed and thus weak stiffness of single pile itself,so that the pile foundation is vulnerable under the impact of barges.Therefore,the research on bridge damage is particularly important.However,there are few domestic studies focusing on the damage behavior of piles under the impact of inland barges on bridge structures.This essay carries out an experimental research on barge impacting single pile foundation model,explores the influence of different factors on the dynamic response and damage of single pile foundation structure,and further studies the dynamic response of pile foundation structure under inland river 500 DWT barge impacting high pile cap continuous beam bridge system.Specific research contents and relevant conclusions are listed as follows:(1)Using self-designed pendulum hammer impact device to carry out multi-angle impact pile foundation tests,and using similarity theory to verify the finite element model.Results show that under impact,the acceleration response and displacement response of pile foundation structure have a obvious lag,in which the earliest and largest response was found at the pile top.(2)Effects of reinforcement ratio,axial compression ratio,integral cast-in-place type and assembly type on lateral bearing capacity and dynamic response of single pile structure are studied.Results show that the reinforcement ratio has a great influence on the dynamic response of the structure itself,and the axial compression ratio restricts the deformation ability of the structure,which makes the compression failure easy to occur;the self-recovery ability of the structure is greatly improved by the rebound deformation of the pre-stressed steel bar in the assembled specimens,and the impact force of structures can be reduced and the duration of the impact can be prolonged.(3)By developing the finite element model of ship collision of continuous girder bridge with high pile cap,the dynamic response characteristics of pile foundation structure when barges collide with the pier,cap and pile foundation at different positions under three common pile foundation arrangements are compared and analyzed,and the effective time of impact and the proportion of shear force distribution on pile top are used to study the pile foundation mechanical performance.Results show that there is a certain time difference in the propagation of stress wave,and there is a lag between bending moments and shear force;under the conditions of impacting piers and caps,the front row piles in the direction of impacting have larger force than the the back row piles,and the force of the same row of piles is basically the same;the impacting pile foundation shows the characteristics of single pile in the side of impacting,and the transmission performance of the cross beam is better than that of the caps.The change of impact angle and pile foundation layout will affect the load distribution among the piles.