Carbon Fibre Reinforced Polymer Strengthened Slabs Effect on Punching Shear

Abstract

This thesis presents an experimental study on the punching strengthening of reinforced concrete slabs using CFRP plates. Six specimens with two different reinforcement ratios-two series each of three specimens- were prepared for this study. All specimens are two-way square slabs with a central column stub. For each series one specimen was left un-strengthened, the control specimen, the second specimen was strengthened with CFRP plates placed at the middle of the first expected punching shear zone in the four directions and the third specimen was strengthened with two plates- placed side by side- bonded to the slab at the face of the central column stub in the four directions. All laminates were extended for the full length of the slab to reduce the risk of deboning failure. The failure for all the strengthened slabs was due to debonding of the laminates which led to premature failure of the slabs; without increase in the ultimate load compare with the un-strengthened slabs. The strengthened slabs showed a remarkable improvement in the service conditiondeflection and cracking- but a brittle mode of failure. Depending on the experimental results the use of CFRP plates for punching shear strengthening for slabs requires reliable means of preventing debonding.