Effect of Width and Effective Length on Shear Strength of RC Slender Beams without Shear Reinforcement

This paper investigates the influence of beam width-to-depth ratio (b/d) and effective length-to-depth ratio (leff/d) on the shear strength of reinforced concrete beams without shear reinforcement by using experimental testing and finite-element analysis. Six rectangular beams, each 250-mm deep with a shear span-to-depth ratio of 2.74, were subjected to testing: three having fixed length of 2,000 mm and varying width-to-depth ratio (b/d), and three having fixed width of 150 mm and varying effective length-to-depth ratio (leff/d), under a four-point loading configuration. This study investigates the impact of these parameters on beam behavior and assesses the predictive capabilities of four building codes. Experimental results showed a significant increase in shear capacity (up to 40%) as b/d increased from 0.46 to 0.91. However, when leff/d increased from 5.46 to 10.05, the shear capacity reduced by 20%. Moreover, finite-element (FE) analysis results indicated an 85% enhancement in shear capacity when b/d increased from 0.46 to 4.56, and a 26% reduction in shear capacity when leff/d increased from 5.46 to 31.05. The analyzed building codes predicted an increase in shear strength with increasing b/d, although with varying rates of increment. However, experimental and FE results indicated decreased shear strength, whereas codes predicted constant shear strength with increasing length. To address these inconsistencies, one code’s prediction equation has been modified to include b/d and leff/d, and new equations have been proposed. In addition, for the modified equation, validation using experimental results from previous literature and sensitivity analysis to study the impact of parameters have been conducted. This paper emphasizes the importance of considering both beam b/d and leff/d for accurately predicting the shear capacity of RC beams and highlights the need for refined prediction models in building codes.