Finite strip evaluation of effective flange width of bridge girders: Discussion

Abstract

The authors are commended for doing a useful study on the effective widths of flanges in beam and slab and box-girder bridges. The fact that the effective flange widths increase with the level of load in the zone of nonlinear behaviour is confirmed by several research workers. Dowling et al. (1977), after testing models of steel box girders, concluded that shear lag has little weakening effect on the flange strength. Maisel et al. (1973) , made similar remarks about concrete box girders. Consideration of the shear-lag effects can be important for working loads but at ultimate loads the usefulness of such consideration tends to diminish. In Fig. 1 the authors have shown BE to be measured from the edges of the beam flange for beam-slab bridges, from the centre line of webs for multispine box-girder bridges and from the face of webs for multicell box-girder bridges. Considering that the actual flange width of AASHTO and steel wide-flange girders was not directly considered in the idealization, why do these differences in determining 2B and BE exist? It might be appropriate to measure BE and 2B from the centre line of the webs in all cases. Such a simplification would make the use of Fig. 7 a and b even simpler. For serviceability limit states the Ontario highway bridge design code requires one-lane loaded conditions to be considered for all bridges. The empirical effective-width charts appear to have been developed for all design lane loaded conditions. Will the charts be still applicable if only one of the design lanes is loaded ? The authors clearly state that the purpose of the exercise was to determine effective widths of com-