Steel-concrete composite construction with precast concrete hollow core floor

Precast concrete hollow core floor units (hcu) are widely used in all types of multi-storey steel framed buildings where they bear onto the top flanges of universal beams. In the current UK market, hcu's account for about 50% of all floors used in steel framed buildings, with an annual production of about 4 million square metres worth pound 90m. The steel beam is normally designed in bending in isolation from the concrete slab and no account is taken of the composite beam action available with the precast units. A programme of combined experimental and numerical studies has been conducted, with the aim of deciding on a suitable approach for the design of composite steel beams that utilise precast concrete hollow core slabs. The results show that the precast slabs may be used compositely with the steel beams in order to increase both flexural strength and stiffness at virtually no extra cost, except for the headed shear studs. For typical geometry and serial sizes, the composite beams were found to be twice as strong and three times as stiff as the equivalent isolated steel beam. The failure mode was ductile. and may be controlled by the correct use of small quantities of tie steel and insitu infill concrete placed between the precast units.