Assessment of shear strength of circular reinforced concrete beams

Reinforced concrete (RC) members with circular cross sections are sometimes preferred over rectangular cross sections in members such as columns, piers, and piles, because of their identical strength properties in all directions. In practice, the shear strength of a circular section is generally based on an equivalent rectangular section, using the formulation provided in ACI 318-14. This paper establishes the need to introduce an additional correction factor of 2/π to the shear strength estimation of circular stirrups, using the formulation applicable for rectangular stirrups. Use of this modified formula is validated in the experimental results of 30 tests on RC circular beams, reported in this paper, as well as 27 test results reported by Ang et al. (1989) and Jensen (2010). The theoretical predictions of shear strength have been based on ACI 318-14 and IS 456-2000.