## RCC STRUCTURES DESIGN Questions and Answers

Q-NO: 1
An R.C.C. beam of 6 m span is 30 cm wide and has a lever arm of 55 cm. If it carries a U.D.L. of 12 t per m and allowable shear stress is 5 kg/cm2, the beam
A. Is safe in shear
B. Is safe with stirrups
C. Is safe with stirrups and inclined bars
D. Needs revision of section
ANS: D

Q-NO: 2

According to I.S. : 456, slabs which span in two directions with corners held down, are assumed to be divided in each direction into middle strips and edge strips such that the width of the middle strip, is
A. Half of the width of the slab
B. Two -third of the width of the slab
C. Three-fourth of the width of the slab
D. Four-fifth of the width of the slab
ANS: C

Q-NO: 3
The load stress of a section can be reduced by
A. Decreasing the lever arm
B. Increasing the total perimeter of bars
C. Replacing larger bars by greater number of small bars
D. Replacing smaller bars by greater number of greater bars
ANS: C

Q-NO: 4
the column head support a flat slab, is generally kept The diameter of
A. 0.25 times the span length
B. 0.25 times the diameter of the column
C. 4.0 cm larger than the diameter of the column
D. 5.0 cm larger than the diameter of the column
ANS: A

Q-NO: 5 fixed at its ends, the
If is the uniformly distributed load on a circular slab of radius maximum positive radial moment at its centre, is
A. 3WR²/16
B. 2WR²/16
C. WR²/16
D. None of these
ANS: C

Q-NO: 6
The maximum ratio of span to depth of a slab simply supported and spanning in one direction, is
A. 35
B. 25
C. 30
D. 20
ANS: C

Q-NO: 7
If the width of the foundation for two equal columns is restricted, the shape of the footing generally adopted, is
A. Square
B. Rectangular
C. Trapezoidal
D. Triangular
ANS: B

Q-NO: 8
The floor slab of a building is supported on reinforced cement floor beams. The ratio of the end and intermediate spans is kept
A. 0.7
B. 0.8
C. 0.9
D. 0.6
ANS: C

Q-NO: 9
Pick up the correct statement from the following:
A. Lateral reinforcement in R.C.C. columns is provided to prevent the longitudinal reinforcement from buckling
B. Lateral reinforcement prevents the shearing of concrete on diagonal plane
C. Lateral reinforcement stops breaking away of concrete cover, due to buckling
D. All the above
ANS: D

Q-NO: 10
In case the factor of safety against sliding is less than 1.5, a portion of slab is constructed downwards at the end of the heel slab, which is known as
A. A key
B. A cut-off wall
C. A rib
D. All the above
ANS: D

Q-NO: 11
Lapped splices in tensile reinforcement are generally not used for bars of size larger than
A. 18 mm diameter
B. 24 mm diameter
C. 30 mm diameter
D. 36 mm diameter
ANS: D

Q-NO: 12
Minimum spacing between horizontal parallel reinforcement of the same size should not be less than
A. One diameter
B. 2.5 diameters
C. 3 diameters
D. 3.5 diameters
ANS: A

Q-NO: 13
For a ribbed slab
A. Clear spacing between ribs shall not be greater than 4.5 cm
B. Width of the rib shall not be less than 7.5 cm
C. Overall depth of the slab shall not exceed four times the breadth of the rib
D. All the above
ANS: D

Q-NO: 14
A very comfortable type of stairs is
A. Straight
B. Dog legged
C. Geometrical
D. Open newel
ANS: D

Q-NO: 15
Columns may be made of plain concrete if their unsupported lengths do not exceed their least lateral dimension
A. Two times
B. Three times
C. Four times
D. Five times
ANS: C

Q-NO: 16
The width of the flange of a L-beam, should be less than
A. One- sixth of the effective span
B. Breadth of the rib + four times thickness of the slab
C. Breadth of the rib + half clear distance between ribs
D. Least of the above
ANS: D

Q-NO: 17
A pre-stressed concrete member is preferred because
A. Its dimensions are not decided from the diagonal tensile stress
B. Large size of long beams carrying large shear force need not be adopted
C. Removal of cracks in the members due to shrinkage
D. All the above
ANS: D

Q-NO: 18
If the ratio of the span to the overall depth does not exceed 10, the stiffness of the beam will
ordinarily be satisfactory in case of a
A. Simply supported beam
B. Continuous beam
C. Cantilever beam
D. None of these
ANS: C

Q-NO: 19
carrying a uniformly distributed load per metre length is suspended at two A pile of length points, the maximum, B.M. at the centre of the pile or at the points of suspension, is
A. WL/8
B. WL²/24
C. WL²/47
D. WL²/16
ANS: C

Q-NO: 20
If is the net upward pressure on a square footing of side for a square column of side , the maximum bending moment is given by
A. B.M = pb (c – a)/4
B. B.M = pb (b – a)²/4
C. B.M = pb (b – a)²/8
D. B.M = pb (b + a)/8
ANS: C

Q-NO: 21
To ensure uniform pressure distribution, the thickness of the foundation, is
A. Kept uniform throughout
B. Increased gradually towards the edge
C. Decreased gradually towards the edge
D. Kept zero at the edge
ANS: C

Q-NO: 22
longitudinal bars and lateral stirrups, is
A. Stress in concrete × area of concrete
B. Stress in steel × area of steel
C. Stress in concrete × area of concrete + Stress in steel × area of steel
D. None of these
ANS: C

Q-NO: 23
mutually perpendicular principal stresses acting on a soil mass, the normal stress If p1 and p2 are
A. [(p – p p p to the principal plane carrying the principal stress p1, is: sin 2
B. [(p – p p p cos 2
C. [(p p p – p cos 2
D. [(p p p – p /2] sin 2
ANS: C

Q-NO: 24
The maximum permissible size of aggregates to be used in casting the ribs of a slab, is
A. 5 mm
B. 7.5 mm
C. 10 mm
D. 15 mm
ANS: C

Q-NO: 25
Pick up the incorrect statement from the following: Tensile reinforcement bars of a rectangular beam
A. Are curtailed if not required to resist the bending moment
B. Are bent up at suitable places to serve as shear reinforcement
C. Are bent down at suitable places to serve as shear reinforcement
D. Are maintained at bottom to provide at least local bond stress
ANS: C

Q-NO: 26
Steel bars are generally connected together to get greater length than the standard length by providing
A. Straight bar splice
B. Hooked splice
C. Dowel splice
D. All the above
ANS: D

Q-NO: 27
The minimum thickness of the cover at the end of a reinforcing bar should not be less than twice the diameter of the bar subject to a minimum of
A. 10 mm
B. 15 mm
C. 20 mm
D. 25 mm
ANS: D

Q-NO: 28
Top bars are extended to the projecting parts of the combined footing of two columns Ldistance apart for a distance of
A. 0.1 L from the outer edge of column
B. 0.1 L from the centre edge of column
C. Half the distance of projection
D. One -fourth the distance of projection
ANS: B

Q-NO: 29
For M 150 grade concrete (1:2:4) the moment of resistance factor is
A. 0.87
B. 8.50
C. 7.50
D. 5.80
ANS: B

Q-NO: 30
is the pre- stressed force applied to tendon of a rectangular pre-stressed beam whose area of cross section is and sectional modulus is . The minimum stress on the beam subjected to a maximum bending moment is
A. f = (P/A) – (Z/M)
B. f = (A/P) – (M/Z)
C. f = (P/A) – (M/Z)
D. f = (P/A) – (M/6Z)
ANS: C

Q-NO: 31
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:
A. (1 – C) mf – eE
B. (C – 1)mf + eE
C. (C – 1)mf – eE
D. (1 – C)mf + eE
ANS: B

Q-NO: 32
In a pre-stressed member it is advisable to use
A. Low strength concrete only
B. High strength concrete only
C. Low strength concrete but high tensile steel
D. High strength concrete and high tensile steel
ANS: D

Q-NO: 33
An R.C.C. lintel is spanning an opening of 2 m span in a brick wall. The height of the roof is 2.9 m above the floor level and that of the opening is 2.1 m above the floor level. The lintel is to be designed for self weight plus
A. Triangular load of the wall
B. UDL of wall
C. UDL of wall + load from the roof
D. Triangular load + load from the roof
ANS: C

Q-NO: 34
The minimum clear cover for R.C.C. columns shall be
A. Greater of 40 mm or diameter
B. Smaller of 40 mm or diameter
C. Greater of 25 mm or diameter
D. Smaller of 25 mm or diameter
ANS: C

Q-NO: 35
The minimum thickness of a flat slab is taken
A. L/32 for end panels without drops
B. L/36 for end panels without drops
C. L/36 for interior panels without drop
D. All the above
ANS: D

Q-NO: 36
The design of heel slab of a retaining wall is based on the maximum bending moment due to:
A. Its own weight
B. Weight of the soil above it
C. Load of the surcharge, if any
D. All the above
ANS: D

Q-NO: 37
An R.C.C beam of 25 cm width has a clear span of 5 metres and carries a U.D.L. of 2000 kg/m inclusive of its self weight. If the lever arm of the section is 45 cm., the beam is
A. Safe in shear
B. Is safe with stirrups
C. Is safe with stirrups and inclined members
D. Needs revision of the section
ANS: A

Q-NO: 38
The neutral axis of a T-beam exists
A. Within the flange
B. At the bottom edge of the slab
C. Below the slab
D. All the above
ANS: D

Q-NO: 39
A pre-cast pile generally used, is
A. Circular
B. Square
C. Octagonal
D. Square with corners chamfered
ANS: D

Q-NO: 40
The spacing of transverse reinforcement of column is decided by the following consideration.
A. The least lateral dimension of the column
B. Sixteen times the diameter of the smallest longitudinal reinforcing rods in the column
C. Forty-eight times the diameter of transverse reinforcement
D. All the above
ANS: D

Q-NO: 41
The self-weight of the footing, is
A. Not considered for calculating the upward pressure on footing
B. Also considered for calculating the upward pressure on footing
C. Not considered for calculating the area of the footing
D. Both B. and C.
ANS: A

Q-NO: 42
Pick up the incorrect statement from the following:
A. In the stem of a retaining wall, reinforcement is provided near the earth side
B. In the toe slab of a retaining wall, reinforcement is provided at the bottom of the slab
C. In the heel slab of a retaining wall, reinforcement is provided at the top of the slab
D. None of these
ANS: D

Q-NO: 43
If the bearing capacity of soil is 10 tonnes/cm2 and the projection of plain concrete footing from walls, is a cm, the depth D of footing is
A. D = 0.0775 a
B. D = 0.775 a
C. D = 0.775 a
D. D = 0.775 a2
ANS: B

Q-NO: 44
After pre-stressing process is completed, a loss of stress is due to
A. Shrinkage of concrete
B. Elastic shortening of concrete
C. Creep of concrete
D. All the above
ANS: D

Q-NO: 45
In a simply supported slab, alternate bars are curtailed at
A. 1/4th of the span
B. 1/5th of the span
C. 1/6th of the span
D. 1/7th of the span
ANS: D

Q-NO: 46
If R and T are rise and tread of a stair spanning horizontally, the steps are supported by a wall on one side and by a stringer beam on the other side, the steps are designed as beams of width
A. R + T
B. T – R
C. 2 + T2)
D. R – T
ANS: C

Q-NO: 47
If p1 and P2 are effective lateral loadings at the bottom and top exerted by a level earth subjected to a super-load on the vertical face of height h of a retaining wall, the horizontal pressure p per unit length of the wall, is
A. [( – )/2] h
B. [( + )/4] h
C. [( + )/2] h
D. ( – h ANS: C

Q-NO: 48
In the zone of R.C.C. beam where shear stress is less than 5 kg/cm2, nominal reinforcement is provided at a pitch of
A. One -half lever arm of the section
B. One-third lever arm of the section
C. Lever arm of the section
D. One and half lever arm of the section
ANS: C

Q-NO: 49
The transverse reinforcements provided at right angles to the main reinforcement
A. Distribute the load
B. Resist the temperature stresses
C. Resist the shrinkage stress
D. All the above
ANS: D

Q-NO: 50
Long and short spans of a two way slab are l and l and load on the slab acting on strips parallel to lx and ly be wx and wy respectively. Accordingy to xRankine Grashoff theory
A. (wx/wy) = (ly/lx)
B. (wx/wy) = (ly/lx)²
C. (wx/wy) = (ly/lx)4
D. None of these
ANS: C

Q-NO: 51
The pitch of the main bars in a simply supported slab, should not exceed its effective depth by
A. Three times
B. Four times
C. Five times
D. Six times
ANS: D

Q-NO: 52
High strength concrete is used in pre-stressed member
A. To overcome high bearing stresses developed at the ends
B. To overcome bursting stresses at the ends
C. To provide high bond stresses
D. All the above
ANS: D

Q-NO: 53
on a circular slab of radius , the maximum radial moment at the centre of the If is the load slab, is WR²/16
A. 1WR²/16
B. 2WR²/16
C. 3WR²/16
D. 5WR²/16
ANS: C

Q-NO: 54

If A is the area of the foundation of a retaining wall carrying a load W and retaining earth of
weight w per unit volume, the minimum depth (h) of the foundation from the free surface of the
earth, is )/(1 + sin )]
A. h = (W/Aw) [(1 –
B. h = (W/Aw) [(1 + )/(1 + sin )]
C. h = (W/Aw) [(1 – )/(1 + sin )]²
D. h W/Aw) [(1 – )/(1 + sin )]²
ANS: C

Q-NO: 55

If the permissible compressive and tensile stresses in a singly reinforced beam are 50 kg/cm2 and 1400 kg/cm2 respectively and the modular ratio is 18, the percentage area At of the steel required for an economic section, is
A. 0.496 %
B. 0.596 %
C. 0.696 %
D. 0.796 %
ANS: C

Q-NO: 56
The modular ratio m of a concrete whose permissible compressive stress is C, may be obtained from the equation.
A. m = 700/3C
B. m = 1400/3C
C. m = 2800/3C
D. m = 3500/3C
ANS: C

Q-NO: 57
Enlarged head of a supporting column of a flat slab is technically known as
A. Supporting end of the column
B. Top of the column
C. Capital
D. Drop panel

ANS: C

Q-NO: 58
Thickened part of a flat slab over its supporting column, is technically known as
A. Drop panel
C. None of these
ANS: A

Q-NO: 59
If is the sectional area of a pre-stressed rectangular beam provided with a tendon pre -stressed by a force through its centroidal longitudinal axis, the compressive stress in concrete, is
A. P/A
B. A/P
C. P/2A
D. 2A/P
ANS: A

Q-NO: 60
Side face reinforcement shall be provided in the beam when depth of the web in a beam exceeds
A. 50 cm
B. 75 cm
C. 100 cm
D. 120 cm
ANS: B

Q-NO: 61
A pre-stressed rectangular beam which carries two concentrated loads W at L/3 from either end, is provided with a bent tendon with tension P such that central one-third portion of the tendon remains parallel to the longitudinal axis, the maximum dip h is
A. WL/P
B. WL/2P
C. WL/3P
D. WL/4P
ANS: C

Q-NO: 62
The minimum head room over a stair must be
A. 200 cm
B. 205 cm
C. 210 cm
D. 230 cm
ANS: C

Q-NO: 63
If q is the punching shear resistance per unit area a, is the side of a square footing for a column of side b, carrying a weight W including the weight of the footing, the depth D. of the footing from punching shear consideration, is
A. D = W (a – b)/4a²bq
B. D = W (a² – b²)/4a²bq
C. D = W (a² – b²)/8a²bq
D. D = W (a² – b²)/4abq
ANS: B

Q-NO: 64
For initial estimate for a beam design, the width is assumed
A. 1/15th of span
B. 1/20th of span
C. 1/25th of span
D. 1/30th of span
ANS: D

Q-NO: 65
In a slab, the pitch of the main reinforcement should not exceed its effective depth
A. Three times
B. Four times
C. Five times
D. Two times
ANS:

Q-NO: 66
If the length of a combined footing for two columns l metres apart is L and the projection on the left side of the exterior column is x, then the projection y on the right side of the exterior column, in order to have a uniformly distributed load, is (where is the distance of centre of gravity of column loads) .
A. y = L – (l – ) )
B. y = L/2 + (l –
C. y = L/2 – (l + )
D. y = L/2 – (l – )
ANS: D

Q-NO: 67
Total pressure on the vertical face of a retaining wall of height h acts parallel to free surface and from the base at a distance of
A. h /4
B. h/3
C. h/2
D. 2h/3
ANS: B

Q-NO: 68
If the tendon is placed at an rectangular beam (sectional top edge
A. Is increased by PZ/e
B. Is increased by Pe/Z
C. Is decreased by Pe/Z
D. Remains unchanged
ANS: C