Mechanics of Web Panel Postbuckling Behavior in Shear

This paper revisits a fundamental assumption used in most classical failure theories for postbuckled web plates under shear, namely that the compressive stresses that develop in the direction perpendicular to the tension diagonal do not increase any further once elastic buckling has taken place. This assumption naturally led to a well-known theory that tension field action in plate girders with transverse stiffeners must be anchored by flanges and stiffeners in order for the webs to develop their full postbuckling strength. However, a careful examination of the results of the nonlinear finite-element analyses carried out for this study reveals that the diagonal compression continuously increases in close proximity to the edges after buckling, thereby producing in the web panel a self-equilibrating force system that does not depend on the flanges and stiffeners. These findings provide a fuller understanding of the actual mechanics of tension field action.