Dynamic Analysis Of Vessel-Train-Bridge Coupling System Considering Pile-Soil Interaction

With the development of China's shipping system,vessel collision accidents have become more and more frequent in recent years.However,bridges are widely used in the construction of high-speed railway lines.If the vessel collision happens on a highspeed railway bridge,it will inevitably threaten the running safety of the train on the bridge.Therefore,it's an important reference for high-speed railway bridge design to establish a reasonable train-bridge dynamic interaction model and evaluate the trainbridge coupling dynamic response subjected to vessel collision.It has important theoretical significance and practical value to carry out the research on the vesseltrain-bridge coupling dynamic characteristics.Pile-soil interaction was rarely considered in the past research of vessel-bridge collision.In order to assess the influence of vessel collision on the dynamic system of train-bridge more accurately,a vessel-train-bridge coupling dynamic model considering pile-soil interaction is established in this paper,based on the assumption of the Winkler foundation beam.The main contents and results are as follows:(1)Adopting the closed contact model of wheel-rail,a vehicle vibration model with 15 degrees of freedom is established by self-programming in Matlab.Based on the low interference spectrum of the German high-speed railway,the inverse Fourier transform method is used to obtain the random track irregularity in time domain.(2)Based on the assumption of Winkler foundation beam,the linear elastic and nonlinear pile-soil interaction models are established by using "m method" and "P-Y curve method".By applying horizontal static load to the beam models of Winkler foundation,it is found that with the increase of horizontal load,the difference of displacements at pier top between elastic and nonlinear pile-soil models is also increasing,and the working performance of the models are consistent with the expectation.(3)The modal analysis of the finite element models with or without pile-soil interaction is carried out.It is clearly seen that after considering the pile-soil effect,the stiffness of the full bridge model is reduced,the natural vibration period becomes longer,and each vibration mode shape exhibits different characteristic differences.When analyzing the dynamic characteristics of train-bridge coupling system,the influence of pile-soil interaction should be fully considered.(4)Dynamic calculations are carried out towards the bridge models considering the fixed,elastic and nonlinear pile-soil interaction,respectively.The result shows that: the lateral and vertical dynamic responses of the bridge will be increased at different levels if the pile-soil interaction is included.(5)The dynamic responses of the train-bridge system subjected to vessel collision are calculated,and five variables including speed of train,peak collision force,collision position,layout of pile foundation,and type of colliding vessel,are selected to study their influence on vessel-train-bridge coupling system.Research shows: 1)The train speed has a significant positive correlation influence on the dynamic responses,especially for the most sensitive three indices including lateral acceleration,lateral wheel-rail force and derailment coefficient of the car body.2)The higher the peak of collision force is,the greater the lateral acceleration,lateral wheelrail force and derailment coefficient are.3)The closer the collision is to the pier top,the greater its influence on vehicles' running safety.4)For the pier vulnerable to lateral vessel collision,it is helpful to change the layout type of pile foundation and increase the number of piles along the collision direction to reduce the influence of collision.5)The collision forces produced by different kinds of vessels are quite different.When the duration and peak of collision force are equal,the bulbous-bow cargo ship exerts greater influence on the dynamic responses of train-bridge coupling system than flat-bow barge.(6)Subjected to strong force,the pile body is assumed to be broken at the position where stress reaches to the maxima under extreme condition.The influence of pile breaking effect on trains' running safety is preliminarily explored.The result indicates that: the maximum value of each lateral dynamic responses of the trainbridge system increases after the pile breaking accident,which greatly reduces the running safety of the train.