Membrane forces acting on thin-walled box girders considering shear lag effect

A new method for the determination of membrane forces acting on box girder bridges considering shear lag effect is proposed in this paper. A box girder is divided into four thin plate elements: top plate, bottom plate, cantilever and web. Using the equilibrium conditions of the plates, the membrane force equation for each plate element is established. The analytical formulas for calculating the membrane normal, transverse and shear forces of each plate element considering shear lag effect are derived. The proposed method is easy to implement in the design of thin-walled box girders considering shear lag effect. h examples using the high order finite strip element method and the experiment, the results obtained by the proposed method are examined and the accuracy of the proposed method is verified. The discussions on the shear lag effect on the membrane forces acting on cantilever box girders are given considering the variations of span to width ratio, width to height ratio and various loading conditions.