Study On Shear Lag Effects In Steel-concrete Composite Box Girder

Steel-concrete composite box girder is developed rapidly because of its simple cross section,high carrying capacity and significant economic benefit,etc.Shear lag effect is one of the defining characteristics of box girder structures,it is difficult to reflect shear lag effect in composite box girder with partial shear connection.The article focus on the research of shear lag effects in the simple supported steel-concrete composite box girder with single cell,including the analytical theory and numerical simulation of shear lag effects in composite box girder.Based on bending theory of thin wall box beam,given the axial self-equilibrium condition for longitudinal stress,a new warping displacement function for steel-concrete composite box beam is introduced.According to the principle of minimum potential energy,the governing differential equations and boundary conditions are established.The shear lag effect formulas of simply supported steel-concrete composite box girder under concentrated load and distributed load are deduced.According to elastic theory,the governing differential equations of interface shearing force are established.In terms of plane stress problem,the equilibrium equations,boundary conditions and the equation of compatibility are derived.Separation variable method was applied to solve differential equations.The effectiveness of this algorithm was verified by the sample application.Based on the analytical theory,the finite element analysis method of composite box girder is proposed,and the three-dimensional finite element model of steel-concrete composite box girder is established by commercial software ANSYS.The correctness and reliability of shear lag effect analysis of steel-concrete composite box girder are verified and the influence of section geometric parameters on the shear lag effect is revealed.The research results can describe the bending characteristics of the composite box girder and provide a reference for the structural design of the steel-concrete composite box girder.