Cardiff theory: Web panel aspect ratio limits and their relation with inclination angle of membrane tensile yield strength

Abstract

Theoretical predictions of the ultimate shear resistance of slender-plate girders are broadly based on either Cardiff theory or Hoglund’s theory. Cardiff theory assumes an equilibrium stress field (tension field) in the girder, which satisfies the theoretical conditions for a lower-bound strength prediction, provided the material possesses sufficient ductility for the stress field to be developed. Previous investigators did not determine the limits of web panel aspect ratio (b/d) or its relation to inclination angle of membrane tensile yielding strength (IAMTYS), which are important parameters in Cardiff theory. This paper presents a theoretical analysis to identify the limits of b/d that can be applied to Cardiff theory and their relation with c/b, the ratio of the distance where the plastic hinges form in the flanges (c) to the panel width (b). This analysis is based on previously published experimental results of ninety six steel plate girders subjected to shear. We make recommendations regarding (1) the optimum limits of panel aspect ratio for a given IAMTYS, and (2) the range of c/b values that can be used to predict the ultimate shear resistance using Cardiff theory.