GATE 2023 CE (CE2) – Question 27
With regard to the shear design of RCC beams, which of the following statements is/are TRUE?
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Correct answer: (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; (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
Explanation
Check each statement against shear behaviour in reinforced concrete beams.
- **A. Excessive shear reinforcement can cause concrete compression failure.** True. With too many stirrups, the diagonal concrete struts crush before the stirrups yield, which is a brittle failure. ✓
- **B. A beam without shear reinforcement can fail in a brittle way even if flexure is adequate.** True. Diagonal tension cracking happens suddenly, with little warning. ✓
- **C. Longitudinal steel plays no role in shear resistance.** False. It provides dowel action, restrains crack width and, through the steel percentage, affects the shear strength of the concrete ($\tau_c$ depends on $100A_s/bd$).
- **D. In IS 456 the nominal shear stress in beams of varying depth depends on both the design shear force and the design bending moment.** True. The formula is $\tau_v=\dfrac{V_u\pm(M_u/d)\tan\beta}{bd}$. ✓
Correct: **A, B and D**.