Analysis of Box Girders with Diaphragms

Analyses based on thin-walled beam theory are presented for multicell box girders of deformable cross section. The influence of flexible interior diaphragms on stresses arising from deformation of the cross section is investigated for torsional loadings and box-cell properties appropriate for steel and reinforced concrete highway bridges. Stiffened plate elements and various end conditions are considered. Sample analyses show that warping stresses, transverse flexural stresses and shearing stresses are substantially affected by deformation of the cross section. Conventional flexural and torsional analyses do not reveal these effects. Interior diaphragms are shown to be effective in reducing deformation of the cross section and the associated stresses.