The GATE Grind

GATE 2024 CE (CE2) – Question 29

Highway Pavements · Design of flexible and rigid pavements · 1 mark · Multiple choice

Various stresses in jointed plain concrete pavement with slab size of 3.5 m × 4.5 m are denoted as follows:
Wheel load stress at interior = $S_{wl}^i$; at edge = $S_{wl}^e$; at corner = $S_{wl}^c$
Warping stress at interior = $S_t^i$; at edge = $S_t^e$; at corner = $S_t^c$
Frictional stress between slab and supporting layer = $S_f$
The critical stress combination in the concrete slab during a summer midnight is

  1. $S_{wl}^c + S_t^c$
  2. $S_{wl}^e + S_t^e + S_f$
  3. $S_{wl}^e + S_t^e - S_f$
  4. $S_{wl}^c + S_t^c + S_f$

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Show answer and explanation

Correct answer: (A) $S_{wl}^c + S_t^c$

Explanation

At night the top of the slab is cooler than the bottom, so the slab edges and corners curl upward and lose contact with the base. A wheel load at the corner of such a lifted slab causes tension at the top. This is the corner stress with the warping stress at the corner, $S_{wl}^c + S_t^c$. The friction stress is not added in this combination.