Analysis On The Influence Of Traffic Load On The Durability Of Concrete Wide Box Bridge Deck

The box section beam has a good mechanical performance and a strong torsional stiffness,and it is widely used in the long span bridges.Usually,all the structures work under the environment of vibration load,and bear the continuous disturbance(alternating)load caused by the repeated action of load-carrying vehicles for a long time,which has led to the crack disease of the box girder.The bridge deck slab is a structure that directly bears the load action of vehicle wheels,with the rapid development of the transportation industry,the impact pressure of the vehicles on the bridge deck slab increases day by day,and the existence of cracks in the concrete bridge deck slab itself has further reduced its durability.For this reason,based on the Hanjiadian No.1 super large bridge project,Guizhou completed in 2006,this paper has carried out a study on the fatigue durability of concrete bridge deck slab under the action of driving load:(1)The research on the local analysis method based on the ABAQUS sub-model combined with the user subroutine.The secondary development of ABAQUS is conducted by means of the Python language,the parametric modeling function of the variable section box girder and stirrup has been realized.The dynamic load of the vehicle wheel is simulated by use of the user subroutine of Dload,and the force bearing status of the bridge deck slab under the action of driving load is analyzed by combining with the sub-model technique,the validity of this method has been verified by the comparison.(2)The analysis for the influence of moving vehicle load on the crack tip stress intensity factor of bridge deck slab.The finite element model of the crack is created by combined with the testing results of the bridge on site.The stress intensity factor at the crack tip of bridge deck slab under the action of moving vehicle load is resolved by the method of interaction integration and subroutine.Based on the fracture toughness of concrete as the standard,the change conditions of the stress intensity factor at the crack tip of bridge deck slab under the different vehicle weight,different bumping position,different crack size and other working conditions have been investigated.(3)The fatigue propagation analysis of concrete bridge deck slab cracks under the impact action of overloaded vehicles.Based on the extended finite element of XFEM in the ABAQUS,the crack propagation test of three-point bent beams in the relevant literature has been simulated and calculated.The simulation results are in good agreement with the test results,and the accuracy of the method has been fully verified.On this basis,the propagation path of cracks in the lower edge of bridge deck slab under the action of cyclic impact load has been studied by combining with the improved Paris formula,and the fatigue propagation law of the longitudinal and transverse cracks under the action of cyclic load is preliminarily obtained.(4)The analysis on the influence of vehicle load action on the fatigue life of the crackfree and cracked concrete bridge deck slabs.According to the above analysis results,the fatigue check points are set up,and the bridge deck slab is loaded by the standard fatigue vehicle,the damage degree of the tensile reinforcement at each check point of the bridge deck slab without the cracks is obtained.Then,a box girder sub-model with the crack body has been established.Based on the typical vehicles and actual vehicle flow rate in the Guizhou highway section,the residual fatigue life of the cracked bridge deck slab has been estimated by combining the S-N curve of reinforcement bar and the Miner linear cumulative damage criterion,finally,the effects of the increase of actual vehicle flow rate and the change of overloaded rate on the fatigue life of bridge deck slab have been considered respectively.The analysis results have shown that the crack at the lower edge of the bridge deck slab has a significant effect on the stress amplitude of the tensile reinforcement,both the rise of vehicle flow rate and the increase of overloaded rate will shorten the service life of the bridge deck slab,and the passage of overloaded vehicles shall be strictly controlled during the operation of the bridge.