Study On Shear Lag Of Steel-Concrete Composite Box Girder Considering Interface Slip Effect

Steel-Concrete Composite Box Beam is a new type of composite structure connecting steel beam and concrete slab through shear connector,which can jointly undertake the load.The interaction of the two can give full play to the advantages of the material,so it has the advantages of outstanding mechanical performance,obvious economic benefit and extensive use range.Under the vertical load,the shear lag effect is obvious in the composite box beam wing plate.In most cases,the shear connector can hardly be completely rigid.Thus,the interface slip phenomenon of the contact interface of the concrete plate and the steel beam in the composite box girder structure can not be avoided,so that the combination of the interface slip phenomenon is caused by the deformation of the concrete plate and the steel beam.The stress redistribution in the box girder is redistributed,so the study of the interface slip effect on the shear lag effect of the steel concrete composite box girder has a certain theoretical significance and application value.In this paper,the theoretical analysis of steel-concrete composite box girders is carried out.The main work and conclusions are as follows.(1)Using the energy variational method,the control differential equations are established by the displacement superposition method on the basis of the conversion section.The analytical expressions of stress and deflection under the double effects of interface slip and shear lag are derived according to the typical boundary conditions and load conditions.(2)The finite element analysis software ANSYS is used to establish the finite element analysis model of the simple supported composite box girder under the action of concentrated load and the cantilever beam under uniform load under the action of the concentrated load,and the simple supported composite box beam and the cantilever composite box girder are not considered under the specific load conditions.The finite element numerical solution of the longitudinal stress of the wing plate with the displacement effect and the slip effect shows that there is an obvious shear lag in the upper and lower wing plates of the composite box girder and the law of shear lag distribution,and the analytical solution is basically consistent with the numerical solution.It is proved that the calculation of the thrust guide does not consider slip andslip.The correctness and applicability of the analytical solution formula for shear lag effect of combined box girder under effect is discussed.(3)Combined with an example,the stress analytical values of concrete slabs and steel floors in composite box girders are coMPared and analyzed considering slip and no slip.The analysis shows that the maximum stress of the middle section of the concrete roof and the steel plate in the middle section of the simple supported composite box girder is reduced by 18.28% and 6.24% when the slip is considered,and the maximum stress of the concrete roof and the steel plate at the fixed end section of the cantilever composite box beam is reduced by 4.81% and 3.21% when the slip is considered.It can be seen that in the range of error allowed,the sliding effect of the composite box girder in a certain extent redistributes the internal stress to a certain extent,reducing the restraining effect between the steel web and the concrete plate,which leads to the reduction of the shear lag effect.