PUNCHING SHEAR IMPROVEMENT OF FLAT SLABS USING STEEL FIBERS AND SHEAR STUDS

Punching shear is a conspicuous phenomenon of fracture mechanism in R.C Flat slab. To meet high shear and flexural demand at critical shear zones of column supports or point loads of flats slabs, the design codes proposed to construct Column heads (capital) and Slab drops against punching shear failure. But this may lead to decrease head clearance and increase of construction cost. To optimise the slab geometry at critical sections of punching shear zones, an experimental programme conducted on three full scale R.C flat plate slabs (NSF, WSF1, WSF2) constituted with different shear resistant elements(steel fibres and headed shear studs) used in punching shear zone. The flat slabs configurated by NSF is “Flat slab using conventional shear reinforcement bars, and WSF1 is “Flat slab using steel fibre concrete in shear zone and the rest of slab with conventional reinforcement” and WSF2 is “Flat slab with combination of steel fibre reinforcement and shear studs used in punching shear zone only and the rest of slab with conventional reinforcement. Random oriented hooked steel fibres of 1.5% volume fraction used for implicit strengthening of concrete at critical punching shear zone. The test parameters considered in this study are shear performance, load capacity, stiffness degradation, energy dissipation, and crack pattern. The test results indicated that, use of steel fibres and shear studs in critical punching shear zone of flat slab is significantly improves punching resistance mechanism, and load carrying capacity of flat slab (WSF2). Further the punching shear failure at ultimate load was observed by ductile mode with good energy dissipation.