Buckling of Web Posts in Perforated Beams

The buckling of the web post is investigated for steel I-beams containing adjacent rectangular web openings, and a method is presented for determining the buckling moment. An expression is derived for the effective buckling length of a web post, and its validity is demonstrated by means of tests on scale models. The elastic buckling moment of the post could then be found from elastic buckling theory, and it is used to obtain the actual buckling moment from an inelastic buckling analysis due to Nethercot and Trahair. Analysis of practial beams shows that web post buckling can affect the ultimate flexural strength of perforated plate girders, but it is not significant for rolled sections.