Theory of Structures

31. A two hinged parabolic arch of span l and rise h carries a load varying from zero at the left end to thrust is

  1. ω2/4h
  2. ω2/8h
  3. ω2/12h
  4. ω2/16h

Correct answer: (D)
ω2/16h

32. For permissible shear stress fs, the torque transmitted by a thin tube of mean diameter D and wall thickness t, is

  1. (πD2/2) t fs
  2. (πD/2) t fs
  3. πD2t fs
  4. (πD2t2/4) fs

Correct answer: (A)
(πD2/2) t fs

33. The area of the core of a column of cross sectional area A, is

  1. (1/3) A
  2. (1/6) A
  3. (1/12) A
  4. (1/18) A

Correct answer: (D)
(1/18) A

34. Keeping the depth d constant, the width of a cantilever of length l of uniform strength loaded with a uniformly distributed load w varies from zero at the free end and

  1. (2w/σd2) × l2 at the fixed end
  2. (3w/σd) × l2 at the fixed end
  3. (3w/σd2) × l2 at the fixed end
  4. (5w/σd) × l2 at the fixed end

Correct answer: (C)
(3w/σd2) × l2 at the fixed end

35. If Ix and Iy are the moments of inertia of a section about X and Y axes, the polar moment of inertia of the section, is

  1. (Ix + Iy)/2
  2. (Ix - Iy)/2
  3. Ix + Iy
  4. (Ix/Iy)

Correct answer: (C)
Ix + Iy

36. A shaft rotating N.R.M. under a torque T, transmits a power

  1. /30 Newton metres/sec
  2. /30 Newton metres/min
  3. /60 Newton metres/min
  4. /60 Newton metres/sec

Correct answer: (A)
/30 Newton metres/sec

37. A lift of weight W is lifted by a rope with an acceleration f. If the area of cross-section of the rope is A, the stress in the rope is

  1. [W (1 + f/G)]/A
  2. (1 - g/f)/A
  3. [W (2 + f/G)]/A
  4. [W (2 + g/f)]/A

Correct answer: (A)
[W (1 + f/G)]/A

38. There are two hinged semicircular arches A, B and C of radii 5 m, 7.5 m and 10 m respectively and each carries a concentrated load W at their crowns. The horizontal thrust at their supports will be in the ratio of

  1. 1 : 1½ : 2
  2. 2 : 1½ : 1
  3. 4.24%
  4. None of these

Correct answer: (C)
4.24%

39. A steel rod 1 metre long having square cross section is pulled under a tensile load of 8 tonnes. The extension in the rod was 1 mm only. If Esteel = 2 × 106 kg/cm2, the side of the rod, is

  1. 1 cm
  2. 1.5 cm
  3. 2 cm
  4. 2.5 cm

Correct answer: (C)
2 cm

40. The shape factor of standard rolled beam section varies from

  1. 1.10 to 1.20
  2. 1.20 to 1.30
  3. 1.30 to 1.40
  4. 1.40 to 1.50

Correct answer: (A)
1.10 to 1.20

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