ENHANCED SHEAR RESISTANCE OF REINFORCED CONCRETE BEAMS WITHOUT STIRRUPS

The concept of “adjusted” reinforcement, i.e. of beams with an optimised reinforcement layout that follows the principal tensile stress trajectories, was suggested recently to improve shear resistance in a reinforced concrete beam without stirrups. It has been known for a long time that the influence of av/d ratio has a significant effect on the load capacity of a reinforced concrete beam. A series of experiments was conducted at Queen’s University of Belfast to investigate the behaviour and ultimate shear strength of beams with “adjusted” reinforcement with loads applied at different value of av/d. In this paper, some results obtained from the preliminary studies conducted with av/d  2.0 are presented. Truss models were used as an analytical tool to analyze the internal forces and also to explain the internal force action of adjusted reinforcement contributes to the beam’s shear resistance. The results from this study showed that adjusted reinforcement can provide sufficient shear resistance for av/d ratios of up to 4, if properly detailed. This appears to be of particular importance since all previous beams with adjusted reinforcement had a comparatively small span/depth ratio.