Novel design equations for shear strength of local web-post buckling in cellular beams

Abstract

To complement available design methods, this study develops a practical and economical approach to estimate shear strength of non-composite symmetric and asymmetric cellular beams, based on failure by local web-post buckling. Influence of geometric web-post parameters on the buckling strength and mechanism, such as section size, opening depth ratio, spacing ratio and tee depth, are investigated with a validated finite element (FE) web-post model. The validation is against 13 cases reported in the literature, and 390 parametric web-post models are analyzed. Tee depth is found to be the key parameter distinguishing failure modes between buckling and Vierendeel bending. The buckling design equation is adopted based on a simple strut model. The observed stress distributions from simulations suggest half the web-post width for the effective strut width and half the length of a line segment tangent to neighboring openings as the strut length. Based on the simulation study, an effective length is proposed to incorporate the effects of restraint due to the tee section and the stress variation around the opening. The strut models of the upper and lower parts of the web-post are separately computed for their buckling shear strength according to BS EN 1993-1-1 and ANSI/AISC 360-10. The shear strength of each part is related to the web-post shear strength through the vertical shear area of the tee section. Accuracy of the proposed model is validated against existing experiments or their FE models. The new design equations facilitate safe and cost-effective design of cellular beams.