Collapse of Square PSC Slabs with Corner Restraint

Three simply-supported 1.5 m (60 in.) square, 60 mm (2.4 in.) thick under-reinforced prestressed concrete slabs, with corners held down, have been tested to failure under centrally applied concentrated loading. Prestressing was applied eccentrically in both directions by straight bonded 7 mm (0.24 in.) or 5 mm (0.20 in.) diam wires. The concrete cube strength 50N/mm2—7,500lb/in.2) and diam of the loading platen (152 mm-6 in.) were kept constant while steel ratio was varied. Measurements of concrete strains, steel strains, slab deflections and corner reactions were taken during the tests. Final failure of each slab was by punching either along, or at a distance from the perimeter of the platen after the development of the yield-line mechanism. It is shown that the collapse load can be predicted reasonably by the load required for fan mechanism development. For a slab with corners held down, but without corner-lever reinforcement, it is shown that the yield load can only be predicted and distinguished from a similar one with corners allowed to lift, by taking into consideration the flexural strength of concrete across the corner lever.