Over the last few years. the use of fiber reinforced plastic (FRP) for strengthening of concrete structures has been investigated by many researchers. Most of these researchers studied the repair and strengthening of reinforced concrete beams and columns using FRP. The use of FRP in strengthening concrete slabs is in flexure, by bonding it to the tension face of these slabs. The use of FRP in strengthening flat plates in punching shear is a new application. This research shows the experimental results obtained from an experiment investigation of 26 half scale two-way slab column interior connection. The program includes twenty specimens strengthened with either glass fiber reinforced plastics (GFRP) or carbon fiber reinforced plastics (CFRP) as external stirrups. The remaining six specimens include two specimens without shear reinforcement as a reference ones, and four specimen reinforced with steel stirrups for comparison. The parameters investigated were, the shape of FRP and steel stirrups (four shapes for FRP and two shapes for steel), the number of stirrups rows and the spacing between these rows, and of course the type of FRP (Glass, Carbon). The test results showed an effective increase in punching shear strength for specimens strengthened with FRP compared with the punching shear strength for reference specimens. The results showed also an increase of flexure stiffness at ultimate for the strengthened specimens compared with the reference specimens. The strengthening using FRP showed also an enhancement in ductility. A theoretical calculation for punching shear strength of the tested specimens was made. |
