A practical design formulation for perforated beams with openings strengthened with ring type stiffeners subject to Vierendeel actions

In this paper, the effect of ring type stiffeners on the Vierendeel mechanism of perforated beams with various opening shapes is investigated. Vierendeel mechanism causes beams to fail with four plastic hinges that occur in the vicinity of large and usually isolated web openings. The practical ring type stiffeners are used in this study to increase the mechanical strength of perforated beams. The effects of stiffener thickness and stiffener height are analyzed for different stiffener thickness to web opening diameter and stiffener height to web thickness ratios. A beam profile of UB457 × 152 × 52 and of steel grade S275 is employed. Finite element analysis is conducted with both geometric and material non-linearities to obtain the failure loads for different cases of perforated beams. Shear/moment interaction diagrams are also obtained so that they can be directly used by practicing engineers. Such interaction curves are plotted for various opening shapes with stiffeners to demonstrate the effect of stiffeners on the Vierendeel mechanism. Yield patterns of various beams with different web opening shapes and ring type stiffeners are also presented. Moreover, a design formulation is derived for direct use by engineers. This study has ultimately shown that, the stiffener's thickness and height has different shear and moment effects on the performance of perforated beams depending on the opening type and web opening diameter.