RCC Structures Design

71. If 'A' is the sectional area of a pre-stressed rectangular beam provided with a tendon pre-stressed by a force 'P' through its centroidal longitudinal axis, the compressive stress in concrete, is

1. P/A
2. A/P
3. P/2A
4. 2A/P

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72. If a rectangular pre-stressed beam of an effective span of 5 meters and carrying a total load 3840 kg/m, is designed by the load balancing method, the central dip of the parabolic tendon should be

1. 5 cm
2. 10 cm
3. 15 cm
4. 20 cm

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73. If A_c, A_sc and A are areas of concrete, longitudinal steel and section of a R.C.C. column and m and c are the modular ratio and maximum stress in the configuration of concrete, the strength of column is

1. σ_cA_c + m σ_cA_sc
2. σ_c(A - A_sc) + m σ_cA_sc
3. σ_c[A + (m - 1)A_sc]
4. All the above

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74. If C is creep coefficient, f is original pre-stress in concrete, m is modular ratio, E is Young's modulus of steel and e is shrinkage strain, the combined effect of creep and shrinkage is:

1. (1 - C)mf - eE
2. (C - 1)mf + eE
3. (C - 1)mf - eE
4. (1 - C)mf + eE

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75. If d and n are the effective depth and depth of the neutral axis respectively of a singly reinforced beam, the lever arm of the beam, is

1. d
2. n
3. d + n/3
4. d - n/3

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76. If d is the diameter of a bar, f_t is allowable tensile stress and f_b, is allowable bond stress, the bond length is given by

1. f_t.d/4f_b
2. (π/4). (f_t.d/f_b)
3. πf_t .d²/f_b
4. (π/4). (f_t.d³/f_b)

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77. If depth of slab is 10 cm, width of web 30 cm, depth of web 50 cm, centre to centre distance of beams 3 m, effective span of beams 6 m, the effective flange width of the beam, is

1. 200 cm
2. 300 cm
3. 150 cm
4. 100 cm

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78. If diameter of a reinforcement bar is d, the anchorage value of the hook is

1. 4d
2. 8d
3. 12d
4. 16d

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79. If is the load on a circular slab of radius , the maximum radial moment at the centre of the slab, is

1. WR²/16
2. 2WR²/16
3. 3WR²/16
4. 5WR²/16

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80. If is the net upward pressure on a square footing of side '' for a square column of side 'a', the maximum bending moment is given by

1. B.M = pb (c - a)/4
2. B.M = pb (b - a)²/4
3. B.M = pb (b - a)²/8
4. B.M = pb (b + a)/8

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