Experimental Study And Analysis On Composite Stress Performance Of Double Deck Concrete Box Girder

This paper is based on the National Natural Science Foundation of China "Research on the mechanism and design method of double deck traffic concrete box girder"(project approval number: 51378202),On the basis of the experimental study of the double deck traffic concrete box girder,the composite torsion torsion test and the whole process failure test were carried out,the ABAQUS finite element software is applied to simulate the composite mechanical performance test of double-layer traffic concrete box girder,On this basis,the influence of box girder model parameters on the torsion stiffness of box girder and the influence of different load conditions on the performance of box girder are analyzed.The main work of this paper is as follows:(1)The finite element analysis model is established for the test model of double deck concrete box girder.The whole process of the test box girder under the corresponding load condition is simulated.The analysis results are in good agreement with the test results.The reliability and accuracy of the model and simulation method established by ABAQUS software are verified.(2)On the basis of(1),the elastic finite element analysis is carried out on the open hole parameters of the double deck concrete box girder web,including the change curve of the box girder's torsional stiffness with the opening rate of the web,the torsion angle curve of the box girder,the rigidity of the box girder with the number of holes in the web,and the influence of the opening rate of the box girder,the shape of the web and the number of holes on the torsional stiffness of the box girder is obtained,based on this,a effective design method for web hole of box girder is put forward.(3)4 supports are placed at the end of the box girder to load the upper joints of the double-layer concrete box girder,and the elastic-plastic finite element analysis is carried out,including the load displacement curve and the strain distribution diagram of the concrete(steel)strain with the load.The failure mode of the box girder under this load condition is obtained.at the same time,the load and the upper and lower side nodes of the inner stiffener of the box girder are loaded and loaded with two load conditions at the same time.The concrete stress,damage diagram and the strain distribution map of the steel bar are compared under the three working conditions.It is found that the stress of concrete in box girder is not very different under the effect of three working conditions,and the stress of the lower side of the inner stiffener of the box girder is 4.9% more when the load is loaded than the upper side,so the bottom node under the three load conditions is loaded into the most unfavorable load condition.It is proved that the transfer performance between the upper and lower floors of the box girder stiffener is better,and the overall performance between the upper and lower beams of the box girder is strengthened.(4)4 supports are placed at the end of the box beam,and the elastic and plastic finite element analysis is carried out for two cases of the box girder with stiffening ring and inner diaphragm(stiffening ring closed).The stress distribution diagram of concrete and the width distribution curve of the deflection along the box beam are compared in the two cases.Through the analysis,on the basis of the test box beam model,the lateral force performance of the box girder and the local deformation of the box girder loading side box should be improved when the box girder is designed.Therefore,in order to improve the lateral force performance of the box beam,the stiffening ring of the box girder is thickened,when the volume of the stiffening ring thickens and the volume ratio of the lateral plate is more than 1.37,the ratio of the volume ratio of the stiffening ring is more than that of the diaphragm.The lateral force performance of box girder is effectively improved when the box girder is equipped with stiffening ring,which is basically equivalent to the internal partition board.The stiffening ring of the box beam effectively strengthens the lateral stiffness and the ability of the box chamber to resist distortion.