Further Insights into Postbuckling of Web Panels. I: Review of Flange Anchoring Mechanism

Abstract

This study revisits the anchoring mechanism believed to be the source of the postbuckling strength of plate girder web panels. In classical tension field theories, it has been implicitly assumed that a tension field cannot develop in the web panel without recourse to the anchoring mechanism of the flanges and/or adjacent panels. The contribution of the flange anchoring mechanism in practical plate girders differs from theory to theory. It has been found during this study that the anchoring mechanism hardly develops, no matter how heavy the flanges are, without transverse stiffeners that have sufficient axial stiffness necessary to keep the flanges from moving the web panel inwards during the anchoring action. In practical plate girders, the contribution of the flange anchoring mechanism to the postbuckling strength is negligibly small not because the flanges are too flexible to function as anchors but because the transverse stiffeners are axially too flexible to support the flanges. Taking advantage of the flange anchoring mechanism in practical designs is beyond the realm of possibility because it requires an inconceivably high axial stiffness of the transverse stiffeners.