Influence of shear lag effect on deflection of box girder
Received:February 10, 2011  Revised:August 15, 2011
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KeyWord:thin-walled box girder  shear lag effect  energy variation method  deflection  twin-cell box girder
张元海 兰州交通大学 土木工程学院, 兰州
林丽霞 兰州交通大学 土木工程学院, 兰州
刘勇 兰州交通大学 土木工程学院, 兰州
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      The warping displacement function for shear lag of twin-cell box girder is chosen upon the axial equilibrium of the relevant warping stress.Through defining the moment and product of inertia corresponding to the shear lag warping,the governing differential equations for shear lag analysis of thin-walled box girder are established by applying the energy variation method.The deflection formulas for simply supported and cantilever box girders under concentrated and uniform loads respectively and the finite segment element stiffness matrix are derived through solving the governing differential equations.Model test and ANSYS shell element results validate the formulas derived.The increase of deflection due to shear lag effect of simply supported,cantilever,and continuous box girders is numerically studied.It is shown that,the increase of deflection for simply supported box girder due to shear lag is remarkable under both concentrated and uniform loads.The increase of deflection for continuous box girder can reach 14% under concentrated loads.For a simply supported box girder with span-width ratio 4.0~6.0,the mid-span deflection calculated by elementary beam theory can be multiplied by 1.05~1.11.The influence of shear lag effect on the deflection of cantilever box girder can be generally ignored.