Analysis Of Shear Lag And Slip Effect Of Steel-Concrete Composite Box Girder

The steel-concrete composite box girder develops rapidly because of its advantages such as superior mechanical properties,excellent economic benefits and effectiveness,and suitable for traditional construction methods,the steel-concrete composite box girder develops rapidly.The shear lag effect is the uneven distribution of stress broadways of concrete roof and steel box girder bottom plate under the external load;The ignorance of the shear lag effect will cause an unsafe structure;For steel-concrete composite box girder,the relative slide of the joint surface of the concrete slab and steel box girder should not be ignored.The relative slide effect increases the deformation of the composite girder and re-distributes the stress inside the composite girder.So it is necessary to analyze the shear lag and slip effect of steel-concrete composite box girder.Based on the Rayleigh-Ritz energy principle,theoretical analysis is done on the shear lag effect of steel-concrete composite box girder with and without the consideration of joint surface sliding in this paper;the following work is completed:Firstly,the governing differential equation of the shear lag effect of steel-concrete composite box girder without the consideration of the joint surface sliding is established,and the stress analytical solution of concrete slabs and steel bottom plates under several typical boundary conditions are derived.The results show that,there is a shear lag with the direct stress of both the upper and lower wing plate of the composite box girder,and the shear lag complies with the rules of shear lag distribution;After the comparison between the analytical solution in this paper and the finite element solution,the results were approximately matching.Secondly,the governing differential equation of the shear lag effect of steel-concrete composite box girder with the consideration of the double effects of joint surface sliding and shear lag effect is established;the deflection and stress analytical solution of composite box girder under typical boundary conditions is derived.Compared with the shear lag effect analytical solution without the consideration of sliding,the results show that,the joint surface sliding of composite box girder weakens the shear lag effect;furthermore,the sliding will increase the deformation deflection of the composite girder.In the end,finite element models with and without the consideration of sliding are established via ANSYS.After the comparison between the analytical solution in this paper and the finite element solution,the results show that there is a coupling relationship between slip effect and shear lag effect of composite box girder and the existence of the sliding will weaken the shear lag effect of the concrete slab and the steel floor;The finite element deflection values of a simply supported composite box girder and a cantilever composite box girder under vertical loads are compared.The deflection values of the sliding finite element are larger than those without sliding.Slip will increase the deflection of composite beams.