A comparative study on minimum shear reinforcement provisions in codes of practice for reinforced concrete beams

The Australian Concrete Code (AS 3600) went through a number of significant changes to the shear provisions in the last decade through the introduction of the modified compression field theory. However, there were some discrepancies identified, specially related to the minimum shear reinforcement provisions. This paper investigates the parameters which affect the reserve strength of shear reinforcement using a database of shear tests of beams with minimum shear reinforcement. The current minimum shear reinforcement provisions in Australian concrete code (AS 3600-2018), Australian bridge design code (AS 5100-2017) and American concrete institute code (ACI 318-19) were reviewed using a database of 1237 shear tests of beams without shear reinforcement. According to the requirements for providing shear reinforcement, AS 3600-2018 demonstrated 50 % lower safety margin compared to ACI 318-19 and AS 5100-2017. Thus, in recent amendment 2 of the AS 3600 (released for public discussion) proposed a secondary factor, ks, to increase the safety of the requirement of shear reinforcement. In this study, effectiveness of the ks factor and an author defined constant factor, 0.75 were evaluated against the shear tests database. The conclusions based on the statistical analysis confirms that 0.75 factor is more efficient in increasing the safety margin compared to the ks factor.