Investigation of punching shear behavior of flat slabs with different types and arrangements of shear reinforcement

Punching shear behavior is experimentally investigated through testing a total of thirteen reinforced concrete flat slabs. Four different types of punching shear reinforcement configurations are examined, namely, ordinary closed rectangular stirrups (ST group), rectangular spiral stirrups (RSP group), advanced rectangular spiral stirrups (ARSP group), and circular spiral stirrups (SP group). Each configuration included three different spacings of 100, 150 and 200 mm. In addition, a reference slab specimen is cast without any punching shear reinforcement. The test results indicated that the circular spiral reinforcement scheme has the highest enhancement with regard to the punching shear capacity compared to the other reinforcement schemes. The percentage of enhancement of the SP group compared to the reference specimen ranges between 23% and 30%. For the other three different rectangular schemes, the enhancement of the punching shear strength for the RSP group and the ARSP group is in the range of 15–23% and 16–25%, respectively. Finally, the punching shear capacity of the ST group increased by 9–13% compared to the reference specimen. The shear carrying capacity of the specimens is also calculated using the ACI 318-19 code and Eurocode 2 equations. The results showed that both codes are capable of predicting the shear carrying capacity for all the schemes. Also, although both codes are conservative, the Eurocode 2 gives a better estimate of the shear carrying capacity than the ACI 318-19 code.