Steel beams with large web openings of various shapes and sizes: an empirical design method using a generalised moment-shear interaction curve

摘要

Vierendeel mechanism is always critical in steel beams with single large web openings. While the depth of web openings controls both the shear and the flexural failures of the perforated sections, it is the length of the web openings that governs the 'Vierendeel' mechanism which in turn depends on the local shear and moment capacities of the tee sections above and below the web opening. A comprehensive finite element investigation on steel beams with web openings of various shapes and sizes was reported in a complementary paper, and the primary structural characteristics of those steel beams were presented in detail. 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 develop a generalised moment-shear interaction curve to assess the load capacities of all steel beams with web openings of various shapes and sizes. As the global shear forces cause both shear failure and 'Vierendeel' mechanism in perforated sections, the effect of local 'Vierendeel' moments acting onto the tee-sections above and below the web openings may be incorporated through a reduction to the global shear capacities of the perforated sections. A global coupled shear capacity is thus established and its values for web openings of various shapes and sizes are obtained directly from the finite element investigation. Details of the design method are fully presented in this paper. Moreover, an indicative parameter, the 'Vierendeel' parameter, is established to assess the performance of 'Vierendeel' mechanism in perforated sections. Through comparison among the moment and the shear utilisation ratios, m and v, and the 'Vierendeel' parameter, v_i , the critical modes of failure in perforated sections under different moment-shear ratios may be readily assessed.