Deflection of simply supported box girder including effect of shear lag

The shear lag has been studied for many years. Nevertheless, most of the studies are related to the effect of the shear lag on stress distribution and very few have investigated the effect on deflection, although some design codes have formulas for the effect of the shear lag on deflection. In this conjunction, the present study carries out three-dimensional finite element analyses for various box girders to investigate the deflection at the mid-span. The multimesh extrapolation is employed to ensure the accuracy. The present study thus reveals the influence of the parameters that characterize the geometry of a box girder on the deflection. It is also shown that the formulas adopted in the design codes underestimate the deflection considerably. Based on the present numerical results, empirical formulas are proposed to compute the deflection magnification factors that account for the difference between the deflections due to the finite element analysis and the beam theory.