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GATE 2016 CE (CE1) – Question 17

Concrete Structures · Design and detailing of beams and slabs · 1 mark · Multiple choice

In shear design of an RC beam, IS 456:2000 specifies allowable concrete shear strength $\tau_c$ and a maximum permissible shear stress $\tau_{c,max}$. The latter check takes care of ______.

  1. additional shear resistance from reinforcing steel
  2. additional shear stress that comes from accidental loading
  3. possibility of failure of concrete by diagonal tension
  4. possibility of crushing of concrete by diagonal compression

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Show answer and explanation

Correct answer: (D) possibility of crushing of concrete by diagonal compression

Explanation

The maximum allowable nominal shear stress limits crushing of the concrete compression struts in the web. Additional shear reinforcement cannot prevent this diagonal compression failure once the concrete limit is exceeded. Therefore the mechanism is **diagonal compression, D**, rather than yielding of longitudinal reinforcement.