Question

Shear resistance of concrete in a reinforcement beam is dependent on

• A. Tension reinforcement in the beam
• B. Compression reinforcement in the beam
• C. Shear reinforcement in the beam
• D. None of the reinforcement in the beam

Answer 1

The correct option is A Tension reinforcement in the beam

(a)
In a reinforced concrete beam external shear is resisted by

1. Shear resistance ${}^{\prime }{V}_{cz}^{\prime }$ of the uncracked portion of concrete
2. Vertical component ${}^{\prime }{V}_{ay}^{\prime }$ of the 'interface shear' (aggregate interlock) force $V_a$
3. Dowel force $V_d$ in the tension reinforcement (due to dowel action); and
4. Shear resistance $V_s$ carried by the shear (transvers) reinforcement. if any.

The presence of increased longitudinal reinforcement in the flexural tension zone not only contributes to enhanced dowel action $V_d$, but also serves to control the propagation of flexural cracks and contributes to increasing the depth of the neutral axis, and thereby the depth of the uncracked concrete in compression; this enhances the contributions of $V_a$ and $V_{cz}$. Thus, the higher the percentage tension reinforcement, the greater the shear resistance in the concrete upto a limit