Composite behaviour of half castellated beam with concrete top slab

This paper presents both experimental and numerical studies of composite half castellated beams. Six specimens of two different sizes with 1000 mm by 120 mm concrete top slab were fabricated. Different number of openings makes length of specimens varies from 2.9 m to 5.7 m. They were tested to failure as simply supported beams under the application of two concentrated loads. The first observed failure pattern is cracking of the concrete slab in tile longitudinal axis of the beam. It was followed by transverse cracking of the slab near the supports. Final failure occurred when the first web post (the one near support) of the steel section buckled. The nonlinear behaviour and corresponding failure load and mode were then compared with those obtained through numerical modeling. A FEM software was used to model the composite beam in which load imperfection was introduced to simulate the real behaviour. Good agreement between the numerical and experimental results is observed. For comparison purpose, a half-castellated steel beam without concrete top slab was also tested. It was found that the beam failed in lateral torsional buckling which shows that the addition of a concrete top slab greatly enhances the beam capacity.