Effect of asymmetric flexural reinforcement ratios on punching shear resistance

The impact of varying flexural reinforcement ratios in the orthogonal directions ([Formula: see text] and [Formula: see text]) on the punching shear resistance (PSR) of flat slabs was experimentally investigated. Six slabs, measuring 1.5 m × 1.5 m × 0.15 m, were tested, with a constant average reinforcement ratio ([Formula: see text]) of 0.3% and [Formula: see text] ratios ranging from 1.2 to 3.0. The results indicated an insignificant effect on punching resistance for [Formula: see text]≤ 2.5. Increasing [Formula: see text] led to wider, more dispersed cracks and enhanced ductility. Comparisons of various codes (BS 8110-1:1997, ACI 318-19, the first and second generations of Eurocode 2 (EC2-2004 and EC2-2023, respectively) and fib Model Code 2010 (MC2010)) revealed that BS 8110-1:1997 provided conservative predictions except for [Formula: see text]= 3.0, while ACI 318-19 consistently overestimated the punching resistance. MC2010 (level of approximation IV) accounted for the reduction in PSR at higher [Formula: see text] ratios. Tests from the literature with [Formula: see text] up to 4.4 exhibited further strength reduction. Comparisons of EC2-2004 and EC2-2023 showed that EC2-2004 gave conservative estimates, with diminishing accuracy as [Formula: see text] increased, while EC2-2023 accurately predicted the punching resistance for [Formula: see text] ≤ 2.5, but overestimated it for higher ratios. This study highlights the limitations of current codes in addressing reinforcement asymmetry effects, and recommends incorporating a reduction factor in EC2-2023 for [Formula: see text] > 2.5 to account for reduced PSR.