Punching shear strengthening of flat-slabs with CFRP dowels

An economical and easy-to-install strengthening method to enhance the punching shear capacity of slab-column connections in existing deficient flat-plate structures is presented in this study. Seven specimens representing typical interior slab-column connections were tested and experimental results are reported in detail. The strengthening scheme employs the use of in-house fabricated carbon fibre reinforced polymer (CFRP) dowels placed around the column stubs in different numbers and arrangements as vertical shear reinforcement. The test results indicated that the ultimate punching shear capacity of the strengthened specimens improved up to 1.33 times that of the specimen without any strengthening. The experimental punching shear capacities and observed failure modes of the specimens were compared with the estimations of strength and failure modes given by the punching shear strength provisions of three different concrete design codes.