The Influence of Shear Effects on the Deflections of Steel Box Girder Bridges

Abstract

It is already well known that the shear lag phenomenon, generated by shear deformations in the flanges of box girders, can result in a very non-uniform distribution, across the flange width, of longitudinal normal stresses, and consequently can then influence girder deflections. The shear lag effects become even more pronounced in cases where flange width increases in relation to girder span. However, in box girders, where the cross-sectional area of webs usually represents a fraction of the total cross sectional area, also shear deformations of webs can significantly affect the magnitudes of girder deflections. Both these phenomena – the shear lag in the flanges and the shear deformations in the webs – become particularly manifest in box girders subjected to considerable shear forces. Such a situation occurs when a box girder bridge is under the action of usual deal and live loads.