Civil Engineering - Concrete Structure
Exam Duration: 45 Mins Total Questions : 30
As the cube size increases, the strength of concrete
- (a)
decreases
- (b)
remains constant
- (c)
increases
- (d)
insufficient data
A concrete cube of 15 cm and a cylinder of 150 mm diameter and 300 mm height are tested for compressive strength, the strength of cube compared to cylinder will be
- (a)
higher
- (b)
lower
- (c)
equal
- (d)
difficult to assess
Modulus of rupture of concrete gives
- (a)
the direct tensile strength of concrete
- (b)
the direct compressive strength of concrete
- (c)
the tensile strength of concrete in bending
- (d)
the characteristic strength of concrete
The characteristic strength of the concrete is
- (a)
higher than the average cube strength
- (b)
lower than the average cube strength
- (c)
same as the average cube strength
- (d)
higher than 90% of the average cube strength
An RCC structure is subjected to following moments
dead load moment = 15 kN-m, live load moment = 19 kN-m wind load moment = 25 kN-m and seismic load moment=40kN-m.
The design. load moment (kN-m) for limit of collapse and for limit state of serviceability as per IS: 456-2000 are respectively
- (a)
71 and 62
- (b)
89 and 71
- (c)
89 and 62
- (d)
111 and 92
In LSM, of columns, the partial safety factors applied steel and concrete for serviceability limit states are
- (a)
1.5 for concrete and 1.15 for steel
- (b)
1.15 for concrete and 1.5 for steel
- (c)
1.5 for both steel and concrete
- (d)
1.0 for both steel and concrete
If the permissible stress in steel is 500 MPa, then working stress in bending compression would be taken
- (a)
167 MPa
- (b)
230 MPa
- (c)
240 MPa
- (d)
278 MPa
Modular ratio m for M30 grade concrete is
- (a)
3.11
- (b)
9.33
- (c)
12.44
- (d)
16.67
The depth of neutral axis is calculated from the known area of steel and it should be
- (a)
Less than 0.5 times the full depth of the beam
- (b)
more than 0.5 times the effective depth of the beam
- (c)
less than or equal to limiting value of neutral axis depth
- (d)
less than 0.43 times the effective depth of the beam
A under reinforced sections are
1. deeper
2. stiffer
3. can undergo large deflection at failure
Which of the following are correct?
- (a)
1, 2 and 3
- (b)
1 and 2
- (c)
1 and 3
- (d)
Only 2
The cross-section at mid span of a beam at the edge of a slab as shown the sketch. A portion of slab is considered as the effective flange width for the beam. The grades of concrete and reinforcing steel are in 25 and Fe 415 respectively. The total area of reinforcing bars (As ) is 400 mm2 . At the ultimate limit state Xu denotes the depth of the neutral axis from the top fibre. Treat ·the section as under reinforced and flanged (Xu > 100 mm)
The value of Xu (in mm) computed as per the limit state method of IS: 456-2000 is
- (a)
200.0
- (b)
223.3
- (c)
236.3
- (d)
273.6
A T-beam has following particulars
Thickness of slab=100m
Width of rib=300mm
Depth of beam=500mm
Centre to Centre distance ob beams-3.0m
Effective span of beams=6.0m
Distance between points of centre flexure=3.6m
What is the effective width of T-beam?
- (a)
3000 mm
- (b)
1900 mm
- (c)
1600 mm
- (d)
1500 mm
The minimum shear reinforcement in beams is provided in the forms of stirrups
- (a)
to resist extra shear force due to live load
- (b)
to resist the effect of shrinkage of concrete
- (c)
to resist the principal tension
- (d)
to resist shear cracks at the bottom of beams
Diagonal tension reinforcement is provided in a beam as
- (a)
longitudinal bars
- (b)
bent-up bars
- (c)
helical reinforcement
- (d)
900 bend at the bends of main bars
A column of 600 mm x 450 mm has unsupported length of 3 m. The deign criteria for the column as per IS: 456-2000 will be
- (a)
short column
- (b)
pedestal
- (c)
slender column
- (d)
cannot judge
What is the uplift at centre on release of wires form anchors due to pre-tensioning only for force P and eccentricity e for a pre-tensioned rectangular plank?
- (a)
\(\frac{PeL^2}{6EI}\)
- (b)
\(\frac{Pe^2L}{6EI}\)
- (c)
\(\frac{Pe^2L}{8EI}\)
- (d)
\(\frac{PeL^2}{8EI}\)
The modulus of rupture of concrete in terms of its characteristic cube compressive strength (fck) in MPa according to IS: 456-2000 is
- (a)
\(5000\sqrt f_{ck}\)
- (b)
0.7 fck
- (c)
5000 fck
- (d)
\(0.7 \sqrt{f_{ck}}\)
An isolated T-beam is used as a walkway. The beam is material supported with an effective span of 6m. The effective width of flange for the cross-section shown in figure, is
- (a)
900 mm
- (b)
1000 mm
- (c)
1259 mm
- (d)
2200 mm
Permissible bending tensile stress in high yield strength deformed bars of grade Fe 415 in a beam is
- (a)
190 N\mm2
- (b)
230 N\mm2
- (c)
140 N/mm2
- (d)
None of these
Consider the following statements
1. Modular ratio in working stress method depends upon the type of steel used
2. There is an upper limit on the nominal shear stress in beams (even with shear reinforcement) due to possibility of crushing of concrete in diagonal compression.
3. A rectangular slap whose length is equal to its width may not be a two-way slab for some support conditions
The true statements are
- (a)
1 and 2
- (b)
2 and 3
- (c)
1 and 3
- (d)
1, 2 and 3
A rectangular column section of 250 mm x 400 mm is reinforced with five steel bars of grade Fe 500 each of 20 mm diameter. Concrete mix is M 30. Axial load in the column section with minimum eccentricity as per IS: 456-2000 using limit state method can be applied up to
- (a)
1707.37
- (b)
1805.30
- (c)
1806.40
- (d)
1903.70
An RCC square footing of side length 2 m ad uniform effective depth 200 mm is provided for a 300 mm x 300 mm column. The line of action of the vertical compressive load passes through the centroid of the footing as well as of the column. If the magnitude of the load is 320 kN, the nominal transerve (one way) shear stress in the fotting is
- (a)
0.26N/ mm2
- (b)
0.30N/ mm2
- (c)
0.34N/ mm2
- (d)
0.75N/ mm2
A concrete column carries an axial load of 450 Kn and a bending moment of kN-m at its base. An isolated footing of size 2m x 3 m side along the plane of bending moment, is provided under the column. Centres of gravity of column and footing coincide. The net maximum and minimum pressures in kN/m 2 on soil under the footing are respectively.
- (a)
95 and 55
- (b)
95 and 75
- (c)
75 and 55
- (d)
75 and 75
A rectangular pre-stressed beam 150 mm x 300 mm size is used over an effective span of 10 m. The cable with zero eccentricity at the supports, and linearly varying to 50 mm at the centre, carries an effective pre-stressing force of 500 kN. Find the magnitude of the concentrated load Q located at the centre of span for the following conditions at the centre of span section.
When the load counteracts the bending effect of pre-stressing force (neglect self-weight)
- (a)
10 kN
- (b)
20 kN
- (c)
25 kN
- (d)
45 kN
A RCC beam of the rectangular cross-section of width 230 mm and effective depth 400 mm is subjected to a maximum factored shear force of 120 kN. The grades of concrete, main steel and stirrup steel are M20, Fe 415 ann Fe 250 respectively. For the area of main steel provided, the design shear strength \(\tau_c\) as per IS: 456 is 0.48 N/mm2 .The beam is designed for collapse limit state.
The spacing (mm) of 2-legged 8 mm stirrups to be provided is
- (a)
40
- (b)
115
- (c)
250
- (d)
400
A singly RCC rectangular beam has a width of 150 mm and an effective depth of 330 mm. The characteristics compressive strength of concrete is 20 MPa and the characteristic tensile strength of strength of steel 415 Mpa. Adopt the stress blocks for concrete as given in IS: 456-2000 and take limiting value of neutral axis depth as 0.48 times the effective depth of the beam.
The limiting are of tension steel in mm2 is,
- (a)
473.9
- (b)
412.3
- (c)
373.9
- (d)
312.3
At the limit state of collapse, an RCC beam is subjected to flexural moment 200 kN-m, shear force of 20 kN and torque 9 kN-m. The beam is 300 mm wide and has a gross depth of 425 mm with an effective cover of 25 mm. The equivalent nominal shear stress ( \(\tau_{ve}\)) as calculated by using the design code terms out to be lesser than the design shear strength (\(\tau_{c}\)) of the concrete.
The equivalent shear force \(V_{c}\) is
- (a)
20 kN
- (b)
54 kN
- (c)
56 kN
- (d)
68 kN
A rectangular pre-stressed beam 150 mm x 300 mm size is used over an effective span of 10 m. The cable with zero eccentricity at the supports, and linearly varying to 50 mm at the centre, carries an effective pre-stressing force of 500 kN. Find the magnitude of the concentrated load Q located at the centre of span for the following conditions at the centre of span section.
If the pressure line passes through the upper kern point under the action of pre-stress, self weight and external load
- (a)
10 kN
- (b)
15 kN
- (c)
20 kN
- (d)
45 kN
A simply supported beam of 4.5 m effective span length is carrying a total factored dead load and live load of intensity 41 kN/m. Size of beam is (220 mm x 350 mm), beam is designed as doubly reinforced use material M 20 grade of concrete and Fe 415 steel.
Total tension steel reinforcement provided is
- (a)
1296 mm2
- (b)
1122 mm2
- (c)
1092 mm2
- (d)
1002 mm2
A pre-stressed beam with a cross-section 300 mm width and 600 mm depth is 12 m long. It carries a live load of 12 kN/m in addition to its self-weight. It is pre-stressed with 2000 mm2 high tensile steel located at 175 mm from soffit. The cable profile is straight for full length of beam and is stressed to a level of 800 N/rnm2. It is bonded to concrete.
The correct pressure line diagram is given by figure
- (a)
-q.png)
- (b)
-q.png)
- (c)
-q.png)
- (d)
-q.png)
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1654060942.png)
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