Design of Box Girder Bridges by Nonlinear Theory

by Ahmad Salahuddin, (M.ASCE), Univ of Zimbabwe, Harare, Zimbabwe,

Document Type: Proceeding Paper

Part of: Structures Congress XII


A modified design procedure applicable to a large number of conventional box girder bridges with longitudinally-stiffened flanges has been presented in this paper. It determines the ultimate load carrying capacity of box girders subjected to flexural loads and has outlined some broad guidelines for studying the effects of such important factors as imperfections and shear lag effects on the stability of box girders. This method, based on the nonlinear theory of plate buckling, incorporates the following main factors: (1) the geometrical non-linearities representing the change of geometry effect on the post-buckling strength of box girders; (2) the non-linearity of the material due to yielding of certain portions of the girder considered along with its deformation and plastic yielding; (3) the interaction between the walls comprising the periphery of the box girder; and (4) the large number of longitudinal stiffeners attached to the compression flanges of box girders. This procedure can be essentially characterized as a limit-state-design approach which lends itself easily to any type of load factor. The author recommends that the ultimate collapse load determined by the nonlinear rather than the linear theory of buckling should be used as a design criterion for proportioning box girders.

Subject Headings: Girder bridges | Box girders | Failure loads | Load bearing capacity | Nonlinear analysis | Bridge design | Ultimate loads

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