Computational Study Modelling the Experimental Work Conducted on the Shear Capacity of Perforated Concrete- Steel Ultra Shallow Floor Beams (USFB)

Abstract

In modern building construction floor spans are becoming longer and one way of achieving this is to use composite beams. In order to minimize the structural depth of the composite sections, and to produce lighter members for economy reasons, steel perforated beams are designed to act compositely with the floor slab in an Ultra Shallow Floor Beam (USFB). In the USFB the concrete slab lies within the steel flanges and is connected through the web opening, providing enhanced longitudinal and vertical shear resistance. There is an additional benefit in increased fire resistance. The aim of this project is to investigate, through finite element simulations and suitable tests, the contribution of concrete in composite cellular beams in resisting vertical shear when the concrete slab lies between the flanges of the steel section. The concrete between the flanges provides the load path to transfer the shear force. For the computational approach to the problem, a three-dimensional Finite Element (FE) model was created, in which contact elements were implemented at the interface of the concrete and steel. In an earlier experimental study, four specimens of composite beams of similar concrete strength were tested under monotonic loading in order to produce reliable results. One specimen was from a lower grade of concrete and was tested in order to calibrate the shear resistance and the failure mode. One bare steel perforated section with web openings was also tested as a comparison. The comparison between the experimental and the computational results leads to useful conclusions. The results for the composite beams show a significant increase in shear resistance. The shear enhancement demonstrated in this study can now be used in design practice.