Question

With regard to the shear design of RCC beams, which of the following statements is/are TRUE?

• A. Excessive shear reinforcement can lead to compression failure in concrete
• B. Beams without shear reinforcement, even if adequately designed for flexure, can have brittle failure
• C. The main (longitudinal) reinforcement plays no role in the shear resistance of beam
• D. As per IS456:2000, the nominal shear stress in the beams of varying depth depends on both the design shear force as well as the design bending moment

Hint:

In RCC beam design: shear failure is sudden and brittle, so shear reinforcement is critical. Excessive shear reinforcement shifts failure mode to concrete crushing, while IS 456 explicitly links nominal shear stress to both shear and bending effects.

Answer 1

The Correct Option is A, B, D

Statement (A): Excessive shear reinforcement increases the confinement of concrete and forces the beam to fail by crushing of concrete (compression failure) rather than shear cracking. Hence, this is TRUE.
Statement (B): If no shear reinforcement is provided, beams may suddenly fail in shear even when they are safe in flexure. This leads to a brittle failure without warning. Hence, this is TRUE.
Statement (C): The longitudinal reinforcement does play a role in shear resistance. It contributes through dowel action across cracks, enhancing shear strength. So, saying it plays no role is FALSE.
Statement (D): According to IS 456:2000, the nominal shear stress depends on the design shear force $V_u$ and the effective depth $d$ of the beam. For varying depth beams, both the shear force and bending moment influence the shear stress distribution. Hence, this is TRUE.
Conclusion: Statements (A), (B), and (D) are correct.
\[ \boxed{\text{Correct Statements: (A), (B), and (D)}} \]