RCC Structures Design Questions and Answers Section-3

RCC – Structures Design

QUESTION –  101

If longitudinally spanning stairs are casted along with their landings, the maximum bending moment per metre width, is taken as

A. wl²/4

B. wl²/8

C. wl²/10

D. wl²/12

ANS: B

QUESTION –  102

If P kg/m2 is the upward pressure on the slab of a plain concrete footing whose projection on either side of the wall is a cm, the depth of foundation D is given by

A. D = 0.00775 aP

B. D = 0.0775 aP

C. D = 0.07775 aP

D. D = 0.775 Pa

ANS: A

QUESTION –  103

If the shear stress in a R.C.C. beam is

A. Equal or less than 5 kg/cm2, no shear reinforcement is provided

B. Greater than 4 kg/cm2, but less than 20 kg/cm2, shear reinforcement is provided

C. Greater than 20 kg/cm2, the size of the section is changed

D. All the above

ANS: D

QUESTION –  104

For a continuous floor slab supported on beams, the ratio of end span length and intermediate span length, is

A. 0.6

B. 0.7

C. 0.8

D. 0.9

ANS: D

QUESTION –  105

In a singly reinforced beam

A. Compression is borne entirely by concrete

B. Steel possesses initial stresses when embedded in concrete

C. Plane sections transverse to the centre line of the beam before bending remain plane after bending

D. Elastic moduli for concrete and steel have different values within the limits of deformation of the beam

ANS: C

QUESTION –  106

RCC Structures Design Questions and Answers

The ratio of the breadth to effective depth of a beam is kept

A. 0.25

B. 0.50

C. 0.70

D. 0.75

ANS: B

QUESTION –  107

In a cantilever retaining wall without a heel slab

A. Thickness of the stem is kept same throughout

B. Base slab is made 10 cm thicker than the stem

C. Width of the base slab is kept 0.7 time the total height of the wall

D. All the above

ANS: D

QUESTION –  108
is the pre-stressed force applied to the tendon of a rectangular pre-stressed beam whose area
of cross section is and sectional modulus is . The maximum stress in 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

QUESTION –  109

A T-beam behaves as a rectangular beam of a width equal to its flange if its neutral axis

A. Remains within the flange

B. Remains below the slab

C. Coincides the geometrical centre of the beam

D. None of these

ANS: A

QUESTION –  110

For the design of a simply supported T-beam the ratio of the effective span to the overall depth of the beam is limited to

A. 10

B. 15

C. 20

D. 25

ANS: C

QUESTION –  111

A reinforced concrete cantilever beam is 3.6 m long, 25 cm wide and has its lever arm 40 cm. It carries a load of 1200 kg at its free end and vertical stirrups can carry 1800 kg. Assuming concrete to carry one-third of the diagonal tension and ignoring the weight of the beam, the number of shear stirrups required, is
A. 30

B. 35

C. 40

D. 45

ANS: C

QUESTION –  112

The width of the rib of a T-beam, is generally kept between

A. 1/7 to 1/3 of rib depth

B. 1/3 to 1/2 of rib depth

C. 1/2 to 3/4 of rib depth

D. 1/3 to 2/3 of rib depth

ANS: D

QUESTION –  113

A ribbed slab is provided for

A. A plain ceiling

B. Thermal insulation

C. Acoustic insulation

D. All the above

ANS: D

QUESTION –  114

To ensure that the hogging bending moment at two points of suspension of a pile of

length L equals the sagging moment at its centre, the distances of the points of suspension from either end, is

A. 0.107 L

B. 0.207 L

C. 0.307 L

D. 0.407 L

ANS: B

QUESTION –  115

The stresses developed in concrete and steel in reinforced concrete beam 25 cm width and 70 cm effective depth, are 62.5 kg/cm2 and 250 kg/cm 2 respectively. If m = 15, the depth of its neutral axis is

A. 20 cm

B. 25 cm

C. 30 cm

D. 35 cm

ANS: C

QUESTION –  116

If the depth of actual neutral axis of a doubly reinforced beam

A. Is greater than the depth of critical neutral axis, the concrete attains its maximum stress earlier

B. Is less than the depth of critical neutral axis, the steel in the tensile zone attains its maximum stress earlier

C. Is equal to the depth of critical neutral axis; the concrete and steel attain their maximum stresses simultaneously

D. All the above

ANS: D

QUESTION –  117

If the modular ratio is , steel ratio is and overall depth of a beam is , the depth of the critical neutral axis of the beam, is

A. [m/(m – r)] d

B. [m/(m + r)] d

C. [(m + r)/ m] d

D. [(r – m)/m] d

ANS: B

QUESTION –  118

The maximum diameter of a bar used in a ribbed slab, is

A. 12 mm

B. 6 mm

C. 20 mm

D. 22 mm ANS: D

QUESTION –  119

A column is regarded as long column if the ratio of its effective length and lateral dimension, exceeds

A. 10

B. 15

C. 20

D. 25

ANS: B

QUESTION –  120

According to the steel beam theory of doubly reinforced beams

A. Tension is resisted by tension steel

B. Compression is resisted by compression steel

C. Stress in tension steel equals the stress in compression steel

D. All the above

ANS: D

QUESTION –  121

The breadth of a ribbed slab containing two bars must be between

A. 6 cm to 7.5 cm

B. 8 cm to 10 cm

C. 10 cm to 12 cm

D. 12 cm to 15 cm

ANS: B

QUESTION –  122

The stem of a cantilever retaining wall which retains earth level with top is 6 m. If the angle of repose and weight of the soil per cubic metre are 30° and 2000 kg respectively, the effective width of the stem at the bottom, is

A. 51.5

B. 52.5

C. 53.5

D. 54.5

ANS: C

QUESTION –  123

If the diameter of the main reinforcement in a slab is 16 mm, the concrete cover to main bars is

A. 10 mm

B. 12 mm

C. 14 mm

D. 16 mm

ANS: D

QUESTION –  124

Minimum spacing between horizontal parallel reinforcement of different sizes, should not be less than

A. One diameter of thinner bar

B. One diameter of thicker bar

C. Twice the diameter of thinner bar

D. None of these

ANS: B

QUESTION –  125

For a number of columns constructed in a rcjw, the type of foundation provided, is

A. Footing

B. Raft

C. Strap

D. Strip

ANS: D

QUESTION –  126

A singly reinforced concrete beam of 25 cm width and 70 cm effective depth is provided with 18.75 cm2 steel. If the modular ratio (m) is 15, the depth of the neutral axis, is

A. 20 cm

B. 25 cm

C. 30 cm

D. 35 cm

ANS: C

QUESTION –  127

In testing a pile by load test, pile platform is loaded with one and half times the design load and a maximum settlement is noted. The load is gradually removed and the consequent rebound is measured. For a safe pile, the net settlement (i.e. total settlement minus rebound) per tonne of test load should not exceed

A. 10 mm

B. 15 mm

C. 20 mm

D. 25 mm

ANS: D

RCC Structures Design Questions and Answers

QUESTION –  128

The diameter of main bars in R.C.C. columns, shall not be less than

A. 6 mm

B. 8 mm

C. 10 mm

D. 12 mm

ANS: D

QUESTION –  129

If d is the diameter of a bar, ft is allowable tensile stress and fb, is allowable bond stress, the bond length is given by

A. ft .d/4fb

B. ( /4). (ft .d/fb)

C. ft .d²/fb

D. ( /4). (f .d3/f )

ANS:t Ab

QUESTION –  130

An intermediate T-beam reinforced with two layers of tensile steel with clear cover 13 cm encasted with the floor of a hall 12 metres by 7 metres, is spaced at 3 metres from adjoining beams and if the width of the beam is 20 cm, the breadth of the flange is

A. 300 cm

B. 233 cm

C. 176 cm

D. 236 cm

ANS: C

QUESTION –  131

The length of lap in tension reinforcement should not be less than the bar diameter × (actual tension / four times the permissible average bond stress) if it is more than

A. 18 bar diameters

B. 24 bar diameters

C. 30 bar diameters

D. 36 bar diameters

ANS: C

QUESTION –  132

As the percentage of steel increases

A. Depth of neutral axis decreases

B. Depth of neutral axis increases

C. Lever arm increases

D. Lever arm decreases

ANS: B

QUESTION –  133

The effective width of a column strip of a flat slab, is

A. One-fourth the width of the panel

B. Half the width of the panel

C. Radius of the column

D. Diameter of the column

ANS: B

QUESTION –  134

As per IS : 1343, total shrinkage for a pre-tensioned beam, is

A. 3.0 × 10-2

B. 3.0 × 10-3

C. 3.0 × 10-5

D. 3.5 × 10-5

ANS: D

QUESTION –  135

Dimensions of a beam need be changed if the shear stress is more than

A. 10 kg/cm2

B. 15 kg/cm2

C. 20 kg/cm2

D. 25 kg/cm2

ANS: C

QUESTION –  136

Based on punching shear consideration, the overall depth of a combined footing under a column A, is

A. (Area of the column A × Safe punching stress)/Load on column A

B. (Perimeter of column A × Safe punching stress)/(Load on column A + Upward pressure × Area of the column)

C. (Perimeter of column A × Safe punching stress)/(Load on column A × Upward pressure × Area of the column)

D. None of these

ANS: B

QUESTION –  137

Pick up the correct statement from the following:

A. A pile is a slender member which transfers the load through its lower end on a strong strata B. A pile is a slender member which transfers its load to the surrounding soil C. A pile is a slender member which transfers its load by friction

D. A pile is a cylindrical body of concrete which transfers the load at a depth greater than its width

ANS: B

QUESTION –  138

In a combined footing if shear stress exceeds 5 kg/cm2, the nominal stirrups provided are:

A. 6 legged

B. 8 legged

C. 10 legged

D. 12 legged

ANS: D

QUESTION –  139

The weight of reinforced concrete, is generally taken as

A. 2200 kg/m3

B. 2300 kg/m3

C. 2400 kg/m3

D. 2500 kg/m3

ANS: C

QUESTION –  140
If W is the load on a circular slab of radius R, the maximum circumferential moment at the centre
of the slab, is
A. WR²/16
B. 2WR²/16
C. 3WR²/16
D. Zero
ANS: C
QUESTION –  141
a retaining wall and is the horizontal earth pressure, the factor of safety
If is weight of
against sliding, is
A. 1.0
B. 1.25
C. 1.5
D. 2.0
ANS: C

QUESTION –  142

The effective span of a simply supported slab, is

A. Distance between the centres of the bearings

B. Clear distance between the inner faces of the walls plus twice the thickness of the wall

C. Clear span plus effective depth of the slab

D. None of these

ANS: B

QUESTION –  143

In a beam the local bond stress Sb, is equal to

A. Shear force/(Leaver arm × Total perimeter of reinforcement)

B. Total perimeter of reinforcement/(Leaver arm × Shear force)

C. Leaver arm/(Shear force × Total perimeter of reinforcement)

D. Leaver arm/(Bending moment × Total perimeter of reinforcement)

ANS: A

QUESTION –  144

A continuous beam shall be deemed to be a deep beam if the ratio of effective span to overall depth, is

A. 2.5

B. 2.0

C. Less than 2

D. Less than 2.5 ANS: A

QUESTION –  145

With usual notations the depth of the neutral axis of a balanced section, is given by

A. mc/t = (d – n)/n

B. t/mc = (d – n)/n

C. t/mc = (d + n)/n

D. mc/t = n/ (d – n)

ANS: D

QUESTION –  146

Pick up the true statement from the following:

A. Plain ceiling provides the best property diffusing light

B. In the absence of beams, it is easier to install piping

C. In the absence of beams, it is easier to paint

D. All the above

ANS: D

QUESTION –  147

If the maximum shear stress at the end of a simply supported R.C.C. beam of 16 m effective span is 10 kg/cm2, the length of the beam having nominal reinforcement, is

A. 8 cm

B. 6 m

C. 8 m

D. 10 m

ANS: C

QUESTION –  148

If the length of a wall on either side of a lintel opening is at least half of its effective span L, the load W carried by the lintel is equivalent to the weight of brickwork contained in an equilateral triangle, producing a maximum bending moment

A. WL/2

B. WL/4

C. WL/6

D. WL/8

ANS: C

QUESTION –  149

The section of a reinforced beam where most distant concrete fibre in compression and tension in steel attains permissible stresses simultaneously, is called

A. Balanced section

B. Economic section

C. Critical section

D. All the above ANS: D

The length of the lap in a compression member is kept greater than bar diameter x (Permissible stress in bar / Five times the bond stress) or

A. 12 bar diameters

B. 18 bar diameters

C. 24 bar diameters

D. 30 bar diameters

ANS: C

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