Study On Shear Lag Effect Of Steel And Concrete Composite Box Girder

Prestressed composite steel and concrete box girder is a new structure composed by concrete slab and steel box girder connected by shear connectors.Its advantages such as saving material small,cross-section size,high capacity,high stiffness and good dynamic performance.At present,the research on the mechanical properties of the prestressed composite steel and concrete box girder at home and abroad is mainly aimed at the internal force,deformation and interface slip,etc.Most of previous studies on steel and concrete composite box girder did not take the shear lag effect into consideration,so this paper will focus on analyzing the shear lag effect of steel and concrete composite box girder.The main components of the work are illustrated as follows:Considering the slip effect and shear deformation,this paper used the minimum potential energy principle to establish the basic differential formula of linear prestressed steel and concrete composite box girder shear lag effect.It established deflection and stress calculation formula of shear lag effect of simply supported composite box beam composite box beam under the concentrated load and uniformly distributed load,and the correctness of the formula is verified by experiment and finite element.The calculation result show that the secondary and three parabolic function for shear lag warping displacement function is closer to the measured values.The results show that the span-width ratio is the most important factor to affect the shear lag effect of composite box girder,but the thickness of concrete and bond stiffness have less influence.Considering the slip effect,this paper established the differential formula of curved composite beam with corrugated steel web which taken the torsion,bending,and shear lag effect into consideration through energy principle.Several solution such as trigonometric series method and finite difference numerical method was given.Through the relationship between deformation and internal force,the expression of deflection.turn angle and longitudinal displacement function was obtained.The results show that the inside normal stress of curved composite box girder under uniform load,is larger than the outside,and the normal strain distribution on the cross section is more uniform with the increase of curvature.According to the structure characteristics of the prestressed composite steel and concrete beams,the calculation model is established by using ABAQUS finite element analysis program,and the correctness of the finite element calculation model is verified by experiment.Nonlinear characteristic of prestressed composite box girder are analyzed,and the calculation results show that the shear lag effect of composite box girder cross section reduce under the action of the prestress.