Behaviour of Strengthened Flat Slab with Opening at Edge Column under Punching Shear Strength

Flat slab system is widely used because of its architectural flexibility Punching is one of the major and critical problems in flat slab especially for the edge column. There are many traditional ways to increase the punching shear strength of concrete slabs like increasing the slab thickness or column dimensions which is against the architectural desire Using FRP strengthening for the flat slabs against punching shear can be considered as a new application. Sometimes an opening is needed to be punched through existing slabs to install cables, elevators and ventilation systems, etc. This causes weakening due to the cutting of concrete and reinforcing steel and also increases the punching problems especially if the opening beside the edge columns. This research is aimed to evaluate the effects of strengthening with Glass Fiber Reinforced Polymer (GFRP) on the punching shear behaviour of flat slab with an opening varying in location with respect to the edge column. Bearing capacity, deflection, ductility, energy absorption and stiffness obtained from the tested slabs are compared to the control specimen, which was without opening and strengthening. It is observed that, the punching shear capacities of the strengthened specimens significantly increased compared to control specimen. Creating openings in flat slab beside the edge column should be approached with great caution and avoided if possible because of its bad effects. In case of openings are of extreme necessity, it is recommended to be created in the front of the edge column not in the side.