Shear Lag in Box Girders

An initial approximate method is presented to evaluate the shear lag phenomenon in reinforced concrete single-box girder bridges. Assuming an ideal cross-section and considering a symmetrical deformation of the top and bottom slabs, but preserving continuity conditions at the web-slab intersection points, a fourth order non-homogeneous differential equation with constant coefficients was obtained. Making further simplifications, quick results are obtained for uniformly distributed loads. In spite of all the simplifications these results were in good agreement with the German specifications for shear lag provided that midspan reduction factors are desired. the factors are the most important anyway, because they are valid practically almost for the whole span length.