Push-out tests on steel sections encased in steel fibre reinforced concrete

The configuration object of this study is a steel H-shaped profile encased in reinforced concrete where the shear connection is obtained by rebars passing through holes in the web of the steel profile. This configuration is common for different structural typologies such as filler beam decks, slim-floor beams, H-pile head, or beam-end anchorages. Experimental push-out tests were performed at the University of Luxembourg with the objective to investigate the impact of using steel fibre reinforced concrete as an addition to the traditional bar reinforcement. The geometrical configuration was representative of the intended final application as filler beam deck and three specimens were casted with normal concrete and three specimens with steel fibre concrete. The main contributors of the shear connection resistance are surface friction at lower load levels and the reinforced concrete dowels through the web holes for higher load levels. Though a robust rebar reinforcement was foreseen, results showed a considerable enhancement of the structural performance thanks to the presence of steel fibres even for a moderate volumetric ratio. The enhanced tensile properties highly contribute to the shear resistance of the concrete matrix, ensuring higher resistance levels before the activation of shear failure surfaces. Steel fibres also confer a higher ductility to the concrete matrix particularly useful at steel-concrete contact interfaces where high local pressures take place.