Vibration Response Analysis Of Long Span Suspension Bridge Under The Action Of Heavy Vehicles

In the existing vehicle-bridge coupling vibration analysis,most vehicle models are modeled as mass-spring-damping multi degree of freedom vibration models,which usually simplify the wheel as point or equivalent line surface contact.However,these models can not accurately simulate the vehicle dynamic characteristics and the influence of flexible tire on the vehicle-bridge coupling vibration.Based on the LS-DYNA program,taking a long-span suspension bridge as the engineering research background,fine three-dimensional vehicle model and bridge model are constructed.The vehicle sub model and the bridge sub model are coupled by means of the surface to surface contact method,and the bridge response analysis is carried out.The main research contents and corresponding achievements are as follows:1.Based on LS-DYNA program,the linear elastic rubber material is used to simulate the tire,and five axle heavy haul truck is taken as reference.Then,the tire pressure is defined,and the dynamic characteristics of truck suspension system are simulated by spring damping element,beam and shell element combined with the structural parameters of common heavy-duty five axle vehicle.Finally,a fine three-dimensional vehicle model is established,and its effectiveness is verified.2.The single beam model and equivalent plate shell model of the suspension bridge are constructed by means of ANSYS.The dynamic characteristics of the two models are compared to verify the rationality of the equivalent plate shell model.Through the contact algorithm built in explicit solution program LS-DYNA,the vehicle subsystem and bridge subsystem are coupled to form the displayed vehicle bridge coupling vibration analysis model.The characteristic responses of the suspension bridge are compared and analyzed under various vehicle load cases.3.The influence of the number of vehicles on the bridge vibration is analyzed under two load cases.The calculation results show:the growth value of each characteristic response is not monotonous linear with the change of the number of vehicles.For example,when the number of vehicles increases from one to two,the maximum dynamic displacement of the main beam increases from 114.69mm to 216.58mm,which is 1.89 times;the increase of suspender stress increases from 10.62MPa to 20.24MPa,which is 1.906 times.4.In order to analyze the influence of "bump" on bridge vibration,50 mm high obstacles are set on the bridge deck of 1/4 span,1/2 span and 3/4 span of main girder to compare the influence of obstacles on bridge system vibration.The results show:the increase of stress amplitude of suspender,top plate and bottom plate at 1/4 span of main girder is the largest.The stress amplitude of suspender,top plate and bottom plate increased by 35.38%,22.55%and 20.36%,respectively.For example,under the barrier free and barrier free conditions,the stress growth value of suspender increases from 10.30MPa to 15.94MPa,the stress growth value of local position of top plate increases from 6.63MPa to 8.56MPa,and the stress growth value of local position of bottom plate increases from 8.76MPa to 11.00MPa.