A numerical study on linear bifurcation web buckling of steel I-beams in the sidesway mode

Sidesway web buckling is a limit state that needs to be considered during the design of steel I-beams subjected to transverse concentrated loads. Sidesway web buckling capacity equations presented by design codes offer estimates which are conservative to varying degrees. In this paper, the sidesway web buckling equations used by the AISC-LRFD specification are revisited. A parametric study based on finite element analysis has been conducted to identify the parameters that influence the web buckling of simply supported beams subjected to concentrated loads. The effects of coexistent bending stresses on the buckling capacity have been explored. A new set of design equations has been developed by complementing the results of the parametric study with the fundamentals of plate buckling theory. In addition, beams having negative end moments have been analyzed under concentrated loads. A lateral buckling type of instability which precedes sidesway web buckling has been identified for beams with negative end moments. Design equations have been developed for beams with end rotational restraints in the light of findings from the numerical analyses.