A compression model for ultimate postbuckling shear strength

Tension field theory has traditionally been used to determine the ultimate postbuckling shear strength of steel plates. More than a dozen theories have been proposed in the last nine decades to describe and predict this phenomenon, and all are based on the tensile response of the web plate, referred to as tension field action. Alternatively, in this paper a compression approach for determining the ultimate postbuckling shear strength is studied. First, an experimentally-validated finite element model is used to examine the mechanics of plate shear buckling. The response is shown to be similar to axially compressed plates, but in this case the axial compression is acting on a diagonal. Then a physical model and formulation based on the compressive strength of the plate is developed for predicting the ultimate postbuckling shear strength of a plate. For common design parameters of most bridge and building structures, this compression approach produces strengths that are closer to experimental and finite element results than the best and commonly accepted formulation based on tension field action. Overall, the results of this study show that a compression approach to predicting the postbuckling shear capacity of plates is an honest representation of shear buckling mechanics and has good correlation to extensive experimental results, where in many cases improved correlation is seen compared to formulations based on tension field action.