Concrete Structure
Exam Duration: 45 Mins Total Questions : 30
Modular ratio m for M30 grade concrete is
- (a)
3.11
- (b)
9.33
- (c)
12.44
- (d)
16.67
If the value of \(\frac{X_u}{d}\) is less than the limiting value, then MR is given by
- (a)
0.87 fy Ast(d-0.446fck)
- (b)
\(\frac{0.78f_{ck}}{f_y}\)(d-0.446fck)
- (c)
0.87 fyAst(d-0.416Xu)
- (d)
0.362 fckbXu(d-0.416Xu)
If fcu and fy are the cube compressive strength of concrete and yield stress respectively and Es is the modulus of elasticity of steel for all grades of concrete. The ultimate flexural strain in concrete can be taken as
- (a)
0.002
- (b)
\(\frac{f_{cu}}{1000}\)
- (c)
0.0035
- (d)
0.002+\(\frac{f_{y}}{1.15E_s}\)
Nominal cover for longitudinal reinforcement in a beam with 30 mm bars and 8 mm stirrups should not be less than (take, CC=25mm)
- (a)
30 mm
- (b)
40 mm
- (c)
48 mm
- (d)
56 mm
A singly reinforced beam is reinforced with 3 bars of 16 mm diameter. Its dimensions are 300x550 mm. Material used are M 20 concrete and Fe 415 steel. It is to be designed as
- (a)
under reinforced
- (b)
balanced
- (c)
over reinforced
- (d)
doubly reinforced
A reinforced concrete beam, size 230 mm wide and 350 mm deep overall is simply supported over a span of 4 m. It is subjected to uniformly distributed w kN/m of increasing magnitude. Beam is reinforced with 3 HYSD bars of Fe 415 grade and 18 mm diameter placed at an effective cover of 40 mm on the bottom face. The characteristic compressive strength and the bending tensile strength of the concrete are 20 MPa and 3.1 MPa respectively.
The theoretical failure load for the attainment of limit state of collapse in flexure is
- (a)
54.03 kN/m
- (b)
27.01 kN/m
- (c)
7.27 kM/n
- (d)
6.52 kN/m
A doubly RCC beam is recommended when
- (a)
The depth of the beam is restricted
- (b)
The breath of the beam is restricted
- (c)
both depth and breath is restricted
- (d)
shear is very high
As the value of \(\frac{d'}{d}\) increases, the stress in compression steel for Fe 415 bars
- (a)
increase
- (b)
decrease
- (c)
remain same
- (d)
None of the above
If flange thickness larger than 0.2d and balanced neutral axis falls in the web the effective thickness of the flange yy is
- (a)
0.15 Xu ,max +0.65Df)⊁Df
- (b)
0.416X u ,max +0.65Df)⊁Df
- (c)
0.15 X u +0.65Df)⊁Df
- (d)
0.416X u +0.65Df)⊁Df
A bar of 20 mm diameter in a axially loaded short column is to be spliced with 16 mm diameter bar, the lap length required for proper transfer for the load in (mm) is (\(\tau_{bd}=1.2\) MPa and grade of steel Fe 415)
- (a)
752.18
- (b)
553.6
- (c)
576
- (d)
601.75
An RCC beam of size 400 x 900 mm, is subjected to a shear force of 100 kN, BM of 150 kN-m and twisting moment of 30 kN-m. longitudinal tension reinforcement shall be designed for a moment of
- (a)
280 kN-m
- (b)
250 kN-m
- (c)
207 kN-m
- (d)
180 kN-m
An RCC beam is of size 230 x 450 mm. It is subjected to factored SF=110 KN-m, BM=150 kN-m and twisting moment Tu=34 kN-m. Equivalent bending moment and equivalent shear force are respectively
- (a)
189, 350
- (b)
209, 346.5
- (c)
209, 290
- (d)
184, 144
The factored load carrying capacity of a column of 350 mm x 650 mm size with minimum percentage of steel is (column materials M20, Fe 415)
- (a)
2500 kN
- (b)
2312 kN
- (c)
1976 kN
- (d)
1536 kN
An RCC column of square cross-section (400mm x 400 mm) has its column load-moment interaction diagram as shown in given figure below
maximum uni-axial eccentricity for balanced failure of column shall be (Take fck = 25 MPa)
- (a)
400 mm
- (b)
567 mm
- (c)
667 mm
- (d)
750 mm
What is the net downward load to be considered for analysis of the pre-stressed concrete beam provided with a linear cable is shown in figure below?
- (a)
25 kN
- (b)
50 kN
- (c)
75 kN
- (d)
Zero
What is the distance between the kerns for the section given below?
- (a)
100
- (b)
<100
- (c)
>100 and <150
- (d)
>150
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 a bar of diameter D embedded in a large concrete block as shown in adjoining figure, with a pullout force f being applied. Let σb and σ st be the bond strength and the tensile strength of bar respectively. If the block is held in position and it is assumed that the material of the block does not fail, which of the following option represents the maximum value P?
- (a)
Maximum of \(\frac{\pi}{4}D^2\sigma_b\) and \((\sigma DL)\sigma_{st}\)
- (b)
Maximum of \(\frac{\pi}{4}D^2\sigma_{st}\) and \((\sigma DL)\sigma_{b}\)
- (c)
Maximum of \(\frac{\pi}{4}D^2\sigma_b\) and \((\sigma DL)\sigma_{st}\)
- (d)
Maximum of \(\frac{\pi}{4}D^2\sigma_{st}\) and \((\sigma DL)\sigma_{b}\)
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 short column with 300 mm x 300 mm square cross-section is made of m 20-grade concrete and has 4 numbers, 20 mm diameter longitudinal bars of Fe 415 steel. It is under the action of concentric axial compressive load. Ignoring the reduction in the area of concrete due to steel bars the ultimate axial load carrying capacity of the column is
- (a)
1659 kN
- (b)
1548 kN
- (c)
1198 kN
- (d)
1069 kN
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 pre-stressed concrete beam supports an live load of 4 kN/m over an effective span of 10 m. The beam has a rectangular section with a width of 200 mm and overall depth of 600 mm. The pre-stressing cable has parabolic profile with an eccentricity of 100 mm at the centre and zero at the ends.
What is the effective pre-stressing force if bending effect of pre-stressing force is nullified by the live load for the mid-span section. (Ignore self-weight)
- (a)
250 kN
- (b)
400 kN
- (c)
500 kN
- (d)
650 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 flexural moment \(M_{ev}\) for designing the longitudinal tensioned steel is
- (a)
187 kN-m
- (b)
200 kN-m
- (c)
209 kN-m
- (d)
2013 kN-m
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
An RCC beam is of 230 mm width, 370 mm overall depth effective cover to compression steel and tension steel is 40 mm. Compression reinforcement consists of 2 numbers of 16 mm diameter bars and tension steel consists of 2 numbers of 25 mm diameter bars. This doubly reinforced beam is made of M 20 concrete and Fe 415 steel.
Stress in compression reinforcement (MPa)
Steel grade Fe 415 | ||||
---|---|---|---|---|
d'/d | 0.05 | 0.10 | 0.01 | 0.20 |
fsc | 355 | 353 | 342 | 326 |
The compressive stress fsc (in MPa) in the compression steel is
- (a)
353.0
- (b)
350.2
- (c)
348.6
- (d)
342.0
An RCC beam is of 230 mm width, 370 mm overall depth effective cover to compression steel and tension steel is 40 mm. Compression reinforcement consists of 2 numbers of 16 mm diameter bars and tension steel consists of 2 numbers of 25 mm diameter bars. This doubly reinforced beam is made of M 20 concrete and Fe 415 steel.
Stress in compression reinforcement (MPa)
Steel grade Fe 415 | ||||
---|---|---|---|---|
d'/d | 0.05 | 0.10 | 0.01 | 0.20 |
fsc | 355 | 353 | 342 | 326 |
Moment of resistance of the beam is given as
- (a)
193.5 kN-m
- (b)
185.2 kN-m
- (c)
180.2 kN-m
- (d)
132.2 kN-m
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 location of thrust line from the CG at mid span is
- (a)
40 mm
- (b)
30 mm
- (c)
20 mm
- (d)
10 mm