Oluwafemi Samson Afolabi

Abstract

This study experimentally investigated the shear behavior of high-strength reinforced concrete deep beams, comparing the performance of Self-Compacting Concrete (SCC) and Vibrated Concrete (VC) with varying transverse reinforcement configurations. A total of four deep beam specimens, designed for a target compressive strength of 60 MPa and a shear span-to-depth ratio (a/d) of 0.75, were subjected to four-point bending tests. Material characterization of the reinforcing steel revealed ultimate stresses ranging from approximately 17 N/mm² to 28 N/mm², with ultimate strains extending up to 12%, confirming the ductile nature of the reinforcement. The force-deflection responses of the deep beams demonstrated significant variations in load-carrying capacity and ductility. Peak loads observed ranged from approximately 65 kN to 195 kN, with corresponding deflections at peak load varying from 3.2 mm to 26 mm. Notably, some specimens exhibited highly ductile post-peak behavior, sustaining substantial loads even at deflections exceeding 20 mm. Analysis of failure modes indicated a complex interaction between concrete type and transverse reinforcement spacing. Beam B9 (SCC with 50 mm stirrup spacing) and Beam B12 (VC with 100 mm stirrup spacing) experienced brittle shear compression failures. In contrast, Beam B10 (SCC with 100 mm stirrup spacing) and Beam B11 (VC with 50 mm stirrup spacing) exhibited ductile flexural failures. These findings suggest that SCC, even with wider stirrup spacing, can promote ductile flexural failure, potentially due to its superior compaction and bond characteristics, while VC beams required denser reinforcement to achieve similar ductile behavior. The research provides valuable quantitative data for understanding the influence of concrete type and transverse reinforcement on the shear performance of deep beams, contributing to the refinement of design models for modern concrete applications.