Steel beams with large web openings of various shapes and sizes: Finite element investigation

Vierendeel mechanism is always critical in steel beams with single large web openings, where global shear force is transferred across the opening length, and the Vierendeel moment is resisted by the local moment resistances of the tee-sections above and below the web openings. At present, most of the current design methods recommend empirical interaction formulae on the moment resistances of the tee-sections to allow for the presence of local axial and shear forces. They ignore the true ultimate behaviour of the tee-sections under co-existing axial and shear forces and bending moment, and also the load redistribution within the perforated sections after yielding. A comprehensive finite element investigation on steel beams with web openings of various shapes and sizes is reported in this paper, and the primary structural characteristics of those steel beams are examined in detail. It is found that all steel beams with large web openings of various shapes behave similarly under a wide range of applied moments and shear forces. The failure modes are common in all beams, and the yield patterns of those perforated sections at failure are also similar to each other. Comparison on the global moment-shear interaction curves of those steel beams shows that they are similar to each other in shape, and thus, it is possible to derive empirical moment-shear interaction curves to assess the load capacities of all steel beams with web openings of various shapes and sizes. Furthermore, it is shown that for all web openings of various shapes and sizes considered in the present investigation, the most important parameter in assessing the structural behaviour of perforated sections is the length of the tee-sections above and below the web opening which controls the magnitude of local Vierendeel moments acting on the tee-sections. Based on the results of an extensive parametric study using finite element method, a simple empirical design method applicable for perforated sections with web openings of various shapes and sizes is developed. Details of the design method are fully presented in a complementary paper.