Shear Capacity- Rotational Relationship of the Normal Reinforced Concrete Beams

Abstract

This study investigated the shear-rotation relationship of concrete beams under static loading. Nine cantilever beams with section dimensions of (200×300) mm and an effective depth of 266 mm were tested until failure. The study focuses on the effects of varying shear span-to-effective depth ratios (a/d) and spacing between stirrups on the beam’s behavior. The (a/d) ratio varied from 2.44 to 4.511, and the shear reinforcement spacing was (75, 100, and 150) mm. The key results included three modes of failure: shear, combined, and flexural failures. The shear failure occurred at an (a/d) ratio of 2.443, combined failure occurred at an a/d ratio of 3 and 3.571, and flexural failure occurred at an a/d ratio of 3.57 and 4.511. The ultimate load capacity of the beams decreased from 11.43% to 35.28% as the a/d ratio increased from 2.443 to 4.51. Curvature ductility increased significantly with high a/d ratios, rising to 174.95% as the (a/d) ratio increased from 2.44 to 3. Also, curvature ductility increased by 183.65% as the (a/d) ratio increased from 2.443 to 4.511. However, it decreased up to 25.98% with larger stirrup spacing, i.e., 150 mm. The shear-rotation demonstrated a significant increase with increasing (a/d) ratio from 2.443 to 3.571, i.e., 92%. However, this increase was accompanied by an increase in the rotation by 81.42% as (a/d) changed from 2.443 to 3.571, and increased to 84.84% as (a/d) changed from 2.443 to 4.511. The shear-plastic rotation relationship indicated that increasing the (a/d) ratio significantly improved ductility and the beam's ability to absorb energy. Increasing the spacing between stirrups adversely affected these properties, leading to reduced ductility, curvature, and load resistance.