Study On Structural Load Transfer Performance Of Bridge Plate Connection In Expressway Reconstruction And Expansion

In recent years,with the rapid development of our economy,the traffic flow of the early built freeway is becoming more and more saturated,restricting the traffic capacity of the road and affecting the safe operation.Therefore,it has become the new mode of expressway construction to improve the traffic capacity and service level of existing expressway.In this paper,prefabricated hollow slab Bridges commonly used in expressways are selected from existing solid hollow slabs for expressways reconstruction and expansion,and the load transfer performance of different connection structures of old and new girder plates is systematically studied by means of material performance test,beam plate loading test and finite element simulation verification,respectively.The main research contents are as follows:(1)This paper systematically introduces the widening methods commonly used in expressway reconstruction and expansion of existing Bridges,and analyzes their advantages and disadvantages.On this basis,the adaptability of each widening method is expounded,and the material properties of bridge in medium and long term service are accurately judged.It is concluded that the strength of existing bridge concrete and steel meets the original design strength grade requirements.It can provide reliable material reserve for the long-term service of existing Bridges,and provide accurate material properties for finite element modeling.Systematic tests on different existing Bridges were carried out to accurately obtain the mechanical properties of existing beams and plates,which provided theoretical support for reasonable width.(2)Unconnected,wet connected,rigid connected,diaphragm joint and wet +diaphragm joint were used to carry out beam and plate splicing tests.The failure mechanism of each joint structure was understood through the test phenomenon.The results show that the failure mechanism of each joint structure has obvious directionality,and the largest cracks are in the contact surface with the old and new beam and plate.The failure mode of the connecting structure is mainly shear failure.The failure of diaphragm is accompanied by obvious stress concentration phenomenon,and the stress concentration failure at the bottom of beam body is the most obvious.The stress concentration can be alleviated by the combination of wet joint and diaphragm.No matter what kind of connection structure,the overall deformation trend of beam and plate is the same,but the different load transfer performance and structural cracking load lead to great differences in beam and plate deflection.According to the initial displacement ratio,the average displacement ratio before cracking and the cracking load of the connecting structure,the comprehensive performance of the connecting structure is determined,and according to the comprehensive performance of the connecting structure and the actual condition of the expressway reconstruction and expansion,the reasonable application scheme of the connecting structure is given.(3)Finite element simulation of ABAQUS and introduction of Concrete Damage Plasticity(concept of plastic damage of concrete)were performed comparative analysis of plasticity tests in a state closest to reality.The errors of various kinds between the simulated test results and the actual test results remained within 10%,and the simulated data were highly consistent with the experimental results.It can provide an accurate model for subsequent similar splicing force analysis.(4)The finite element model was used to analyze the influence of the dimension difference of the joint structure on the load transfer performance.The main conclusions are as follows: the thickness of the pavement layer,the width of the transverse section and the number of diaphragms have significant effects on the structural performance,and the performance is improved with the increase of the pavement layer thickness.There is a linear relationship between the beam spacing and the load transfer performance of the connected structure(increasing the spacing decreases the load transfer performance).The number of baffle plates has the greatest influence on the transfer performance(increasing the number,improving the transfer performance)and it is nonlinear.The number of diaphragmers has little influence on the transfer performance of wet + diaphragmers.