In-plane behaviour of composite floor slab diaphragm interfaces under high shear demand

Abstract

The different failure modes of composite floors subjected to in-plane shear forces have been determined by a number of researchers using pseudo-static testing. However, all previous experimental tests subjected the floors to a combination of shear and moment and did not represent the boundary conditions applying at the diaphragm interfaces with the seismic resisting system. This paper proposes a new experimental test setup in which the slabs being tested are subjected to near pure shear at the slab to supporting beam interface. Using the new experimental test setup, three composite floor slabs have been tested. In the first floor slab, the deck rib orientation is parallel to the supporting beam. For the second and third floor slab configurations, the deck rib orientation is perpendicular to the supporting beam. The second floor slab uses the standard end anchorage details adopted in New Zealand, involving a solid rib of concrete surrounding the shear studs along the secondary beam. The third floor slab uses the standard end anchorage detail adopted in Europe, in which the decking continues over the secondary beam and the shear studs are welded through the decking.It was found that all three slabs had similar strength and stiffness, albeit with different failure modes. The first slab exhibited the most brittle behaviour, whereas the second specimen exhibited a smoother post-peak behaviour and was the most ductile among these three details. A comparison between the test results and existing design equations has been made and a new equation is developed.