Punching shear strengthening of reinforced concrete flat plates using carbon fiber reinforced polymers

This research presents a strengthening technique for increasing punching shear resistance in reinforced concrete flat plates using carbon fiber reinforced polymers (CFRPs). This strengthening method employs CFRP strips in the vertical direction as shear reinforcement around the concentrated load area in a specified pattern. Experimental load deflection curves, strain measurements, and failure modes are reported for four strengthened specimens and two reference specimens tested for the research reported here. The results show that, by using a sufficient amount of CFRP strips in an efficient configuration, the failure surface can be shifted away from the column. The load carrying capacities of the strengthened reinforced concrete slabs are increased with increasing amount of vertical CFRP reinforcement used in a wider area. Punching shear strengths of test specimens are augmented up to 51 % relative to the control specimens. The pre- and postpunching behavior of the specimen with the highest increase in load carrying capacity is better than that of the reference specimen designed according to the current requirements of ACI 318-02. ACI 318-02 and CEB-FIP Model Code 90 requirements for punching shear design are critically examined in the light of current experimental findings.