ENGINEERING COURSEWORK

Engineering coursework

Abstract

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 ?exural 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 ?nite 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 momentshear 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 ?nite 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, vi , the critical modes of failure in perforated sections under different moment-shear ratios may be readily assessed.

Effect of Section Shape on the Load Carrying Capacity of Beams

Introduction

Modern multistorey buildings always have a stringent requirement on headroom. In order to accommodate building services within the constructional depth of a ?oor, it is common practice to provide web openings in structural ?oor beams for passage of services. A large amount of research efforts on the structural behaviour of steel beams with web openings have been reported in the literature, primarily for steel beams with multiple hexagonal web openings, and also for composite beams with single rectangular web openings, both with or without reinforcement (Bernard, 1993, pp.2277-93). Rectangular web openings were often formed with aspect ratios ranging from 1.0 to 3.0 while the opening depth, do , was commonly restricted to about 50% of the overall section height, h. Circular web openings were also popular in commercial buildings with high speci?cations in building services due to easy installation of water pipes. In a perforated section under a global moment Mo,Sd and a global shear force Vo,Sd , three local actions are induced in the tee-sections above and below the web opening as shown in Fig. 1:

Axial force in the tee-section, NT, due to the global moment Mo,Sd.

Shear force in the tee-section, VT, due to the global shear ...