An experimental investigation of the effects of imperfections on the strength of steel box girders

As part of a major study, an experimental box girder having nominally identical cantilever sections was constructed to model the geometry of a pier girder of the Hunt Club–Rideau Bridge structure in Ottawa. The one-fourth scale model did not, however, replicate the varying depth of the prototype. The objective was to determine whether a deliberate reduction in the gross heat input for welds attaching longitudinal stiffeners to the flange plates for one end of the girder (and hence would incur reduced plate distortions and residual stresses) could augment the carrying capacity of a statically loaded box girder. In fact, the results from the two tests are such as to suggest that inward bent transverse stiffeners may account for a greater reduction in strength than do the imperfections of local plate panels of compression flanges. Key words: box girders, bridges, experiments, geometric imperfections, residual stresses, strength, structural steel.