Strengthening of concrete slab-column connections using CFRP strips

This paper presents experimental data and results on the effect of externally bonded carbon fiber-reinforced polymer (CFRP) strips on the punching shear of interior slab-column connections. A total of six square slabs with a concentric column were constructed with overall dimensions of 1220 mm by 1220 mm and 100 mm thick slab and 150 × 150 mm column. The test variables were the configuration and amount of CFRP strips externally bonded to the tension face of the slab. The specimens were simply supported along their edges and tested in punching with vertical load applied through the central column. The test results clearly showed that CFRP strengthening leads to significant improvements in the structural behaviour of slab-column connections. The increase in punching capacity of strengthened slabs was up to 29%, while the increase in stiffness was up to 80% compared to the unstrengthened slab. Punching capacities of the test specimens were evaluated using a recently developed model that accounts for both configuration and amount of CFRP strips. The predicted punching capacities using the analytical model were compared with the experimental results, and good agreement was found.