Experimental Bending Tests on Encased Steel-Concrete Composite Beams with SFRC

The paper describes full scale structural beam tests investigating the use of steel fiber reinforced concrete (SFRC) for steel-concrete composite structures. Steel profiles encased in reinforced concrete used for composite filler beam decks have been enhanced by high-strength steel fibres in the concrete matrix in addition to the conventional reinforcement bars. The obtained experimental evidence confirms that SFRC is advantageous for this specific application by improving the structural behavior both at Ultimate Limit State (ULS) as well as at Serviceability Limit State (SLS), therefore permitting a reduction of material consumption compared to the traditional solution to ensure a given design level. In fact, the enhanced compressive properties of SFRC, and namely the increased ductility compared to normal reinforced concrete, are relevant for encased steel-concrete sections as they allow to reach the complete yielding of the steel component also in compression. This ensures a higher bending moment resistance useful for ULS design. On the other side, the improved tensile properties of SFRC allow for a reduced cracking phenomena which permits to rely on an increased bending stiffness at SLS load levels compared to the use of normal concrete. This becomes relevant when deformation limits or vibration control becomes design decisive.