Design of Concrete Structures - II: Multiple Choice Questions (MCQ) & Answers
Unit 1: Staircases (Limit state method)
Multiple
Choice Questions
1.
The effective span of the staircase supported
at top and bottom risers by beams spanning in parallel with the riser is
A.
Clear distance between beams
B.
Distance between c/c of beams
C.
Clear distance between beams + d
D.
None of the above
ANS: B
2. 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. √(R2 +T2)
D.
R - T
ANS: C
3.
If T and R are
tread and rise respectively of a stair, then
A.
2R + T = 60
B.
R + 2T
= 60
C.
2R + T
= 30
D.
R +
2T= 30
ANS: A
4.
The minimum head room over a stair must be
A.
200 cm
B.
205 cm
C.
210 cm
D.
230 cm
ANS: C
5.
The
number of treads in a flight is equal to
A.
risers
in the flight
B.
risers
plus one
C.
risers minus one
D. None of the mentioned
ANS: C
6.
For
stairs spanning horizontally, the minimum waist provided is
A.
4 cm
B.
6 cm
C.
10 cm
D.
12 cm
ANS: D
7.
For
stairs spanning l metres longitudinally between supports at
the bottom and top of a flight carrying a load w per unit
horizontal area, the maximum bending moment per metre width, is
A. Wl2/4
B. Wl2/12
C. Wl2/10
D. Wl2/8
ANS: D
8.
The horizontal portion of a step in a staircase is known as
A.
Rise
B.
Flight
C.
Winder
D. Tread
ANS: D
9.
If
longitudinally spanning stairs are casted along with their landings, the maximum bending moment per meter width is taken as
A.
Wl2/8
B.
Wl2/4
C.
Wl2/12
D. Wl2/10
ANS: A
10.
The effective
span of stairs without stringer beams Where supported at the top and bottom risers
by beams spanning parallel with the risers, shall be taken as the distance
_________ between beams
A.
Centre-to-centre
B.
Clear distance
C.
centre-to-centre
+d
D. Clear distance + d
ANS: A
11.
In the case of
stairs with open wells, where spans partly crossing at right angles occur, the
load on areas common to any two such spans may be taken as ____ in each
direction
A.
2
B.
1/2
C.
1
D. 3/4
ANS: B
12.
In the case of
stairs where flights or landings are embedded into walls for a length of not
less than 110 mm and are designed to span in the direction of the flight, a
_____ mm strip may be deducted from the loaded area and the effective breadth
of the section increased by75 mm for purposes of design
A.
150
B.
120
C.
110
D. 100
ANS: A
13.
In the case of
stairs where spanning on to the edge of a landing slab, which spans parallel,
with the risers, a distance equal to the ___________ or one metre, whichever is
smaller.
A.
going of the stairs plus at each end
either half the width of the landing
B.
nosing of the
stairs plus at each end either half the width of the landing
C.
going of the
stairs plus at each end either full the width of the stair.
D. going of the stairs plus at each end either half the
width of the landing
ANS: A
14.
In the case of
stairs where the landing slab spans in the same direction as the stairs, they
shall be considered as acting together to form a single slab and the span determined
as the _______ of the supporting beams or walls
A.
distance inner
face-to-face
B.
distance center-to-center
C.
distance outer
face-to-face
D. distance centre - to - centre + d
ANS: B
15.
Self-weight of
step per m run will be
A.
R/2 *25
B.
T/2 *25
C.
R/2 *18
D. T/2 *18
ANS: A
Unit
2: Column Footings
A. Square
B.
Rectangular
C. Trapezoidal
D. Triangular
ANS: B
2. 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
3.
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
4.
Design a square footing for a short
axially loaded column of size 230 × 300 mm carrying 500 kN load. Use M20
concrete and fe415 steel. SBC of soil is 180 kN/m2
A.
2m × 2m
B.
2.5m x 2.5m
C.
1.67 m
x 1.67 m
D.
1 m x 1 m
ANS: C
5.
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
6.
For reinforcement in the short direction,
a central band equal to the width of the footing shall be
ANS: A
7.
Bottom
bars under the columns are extended into the interior of the footing slab to a
distance greater than
A. 42 f from the center of the
column
B. 42 f from the inner edge of
the column
C.
42 f from the outer edge of
the column
D.
24 f from the center of the column
ANS: C
8.
The
weight of a foundation is assumed as
A.
5% of
wall weight
B.
10% of wall weight
C.
12% of
wall weight
D. 15% of wall weight
ANS: B
9.
According
to I.S.: 456, 1978 the thickness of reinforced concrete footing on piles at its
edges, is kept less than
A.
200 mm
B.
300 mm
C.
450 mm
D. 750 mm
ANS: A
10.
A
foundation is called shallow if its depth, is
A.
one-fourth of its width
B.
half
of its width
C.
three-fourth
of its width
D.
equal to its width
ANS: D
11.
According
to I.S.: 456, 1978 the thickness of reinforced concrete footing on piles at its
edges, is kept less than
A.
5 cm
B.
10 cm
C.
15 cm
D. 25 cm
ANS: C
12.
If p is
the net upward pressure on a square footing of side b for a square column of side a, 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(c-a)2/8
D. B.M. = pb(b+a)/8
ANS: C
13.
The combined footing is required in
following situations
A.
If loaded footing of columns overlap
B.
Columns may be near to property line
C.
S. B. C. of soil being less
D.
All a), b) and c)
ANS: D
14.
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
15.
The unit weights of various materials used
for building construction are given in _____
A.
IS:456-2000
B.
IS:875 (Part-I) – 1987
C.
IS:12119-1987
D. IS:
5816-1999
ANS: B
Unit
3: Analysis
and design of cantilever and counterfort retaining walls
1. The stability of a retaining wall is checked for which of the following condition
A. Overturning about toeB. Overturning about heal
C. Both of above
D. None of the above
ANS: A
A. Ultimate load
B. Characteristic load
C. Working load
D. None of the above
ANS: A
I. Simply supported retaining wall
II. Counterfort retaining wall
III. Cantilever retaining wall
A. I and II only
B. II and III only
C. I and III only
D. I, II and III
ANS: B
4.
In Cantilever retaining wall stem, heal
slab and toe slab are all acting as cantilever due to pressure from
A.
Backfill only
B.
Soil pressure only
C.
Both a
and b
D.
Neither a nor b
ANS: C
5.
The
toe projection of foundation slabs is taken as ____
A.
as one-third of the base
B.
as one
sixth of the overall height of the wall
C.
equal
to heel slab
D. below ground surface.
ANS: A
6.
In reinforced & plain concrete
footings, the thickness at the edge shall not be less than __________ mm for
footing on soil
A.
100 mm
B.
200 mm
C.
150
mm
D.
230 mm
ANS: C
7.
Cantilever
retaining walls can be safely used for height, not more than ___.
A. 3 m
B. 4 m
C. 5 m
D. 6 m
ANS: D
8.
The
design of a retaining wall assumes that the retained earth is _______
A.
dry
B.
is
free from moisture
C.
is not
cohesive
D.
consists
of granular particles
E.
all the above
ANS: E
9.
The thickness of the base slab of a retaining wall generally provided, is -______
A.
one
half of the width of the stem at the bottom
B.
one-third
of the width of the stem at the bottom
C.
one-fourth of the width of the steam at the bottom
D.
width of the stem at the bottom
E. twice the width of the
steam at the bottom.
ANS: D
10.
Pick
up the incorrect statement from the following:
A.
In the stem of a retaining wall, reinforcement is provided near the earthside
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
11.
To
have pressure wholly compressive under the base of a retaining wall of
width b, the resultant of the weight of the wall and the pressure exerted
by the retained earth should have eccentricity not more than ____
A.
b/3
B.
b/4
C.
b/6
D. b/8
ANS: C
12.
Total
pressure on the vertical face of a retaining wall of height h acts
parallel to the free surface and from the base at a distance of ____
A.
h/4
B.
h/3
C.
h/2
D. 2h/3
ANS: B
13.
The total pressure on the vertical face of a retaining wall of height h exerted
by the retained earth weighing w per unit volume having an
angle of surcharge ฮฑ°, is:
A. 0.3 H
B. 0.4 H
C. 0.6 H
D. 0.7 H
ANS: D
15.
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 meter are 30° and 2000
kg respectively, the effective width of the stem at the bottom, is
A.
51.5
B.
53.5
C.
52.5
D. 55.5
ANS: B
16. Choose the correct statement from the following:
A. In the stem of a retaining wall, reinforcement is provided near the earthside
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. All of these.
ANS: D
=============================== ++++ ===============================
Unit 4: WATER TANK
1.
In case of water tank permissible stress
for concrete in direct tension for grade of concrete M 25 is ___________ N/mm2
A.
1.3
B.
0.9
C. 1.4
D. 1.5
ANS: A
2. The
permissible tensile stress in H.Y.S.D bars on face away from liquid if
thickness of member greater than 225 mm is _______N/mm2
A. 150
B. 115
C.
130
D. 190
ANS: D
3.
The permissible tensile stress in M.S.
bars on liquid retaining face is ___________ N/mm2.
A. 125
B.
100
C. 115
D. 150
ANS: C
4.
For thickness of slab upto 100 mm in case
of water tank the minimum percentage of reinforcement should be ___________
A.
0.1
B.
0.2
C.
0.3
D.
0.4
ANS: C
5.
In case of water tank for concrete
permissible stress in bending tension for grade of M25 concrete is ___________
N/mm2.
A.
1.8
B. 2.5
C. 2.8
D.
2.7
ANS: A
6.
In case of water tanks the permissible
tensile stress in shear reinforcement (M.S. bars) for members having thickness
less than 225 mm is ___________ N/mm2.
A. 175
B. 125
C.
115
D.
190
ANS: C
7.
The permissible tensile stress in M.S.
bars on liquid retaining face is ___________ N/mm2.
A.
115
B.
100
C.
125
D. 150
ANS: A
8.
In water tanks the compressive
(permissible) stress in column subjected to direct load is _________ N/mm2
for HYSD bars.
A.
115
B.
125
C.
175
D. 150
ANS: C
9.
The tanks situated underground, the walls
of the tanks are to be generally designed for
A.
Earth pressure only
B.
Water pressure only
C.
Both Earth and water pressure
D.
All of
these
ANS: D
10.
The floor of the underground water tanks
is designed for _________ pressure, for the empty tank condition.
A.
Uplift
B.
Water
C.
Earth
D.
All of
these
ANS: D
11.
For design of water tanks the permissible
stress in bending tension in HYSD bars is for is ____________ N/mm2
less than 225 mm.
A.
115
B.
140
C.
150
D. 230
ANS: C
12.
In case of water tanks the permissible
shear stress for M20 grade concrete is _______ N/mm2
A.
1
B.
1.2
C.
1.25
D.
1.7
ANS: D
13.
The permissible tensile stress in M.S.
bars on liquid retaining face is _____ N/mm2.
A.
115
B. 110
C. 125
D. 150
ANS: A
14. For design of water tanks the permissible stress in bending tension in
M.S. bars on face away from liquid is for thickness more than 225 mm. is
____________ N/mm2.
a)
115
b)
140
c)
125
d)
190
Answer: C
15. The minimum reinforcement in walls, floors and roofs in each of two
directions at right angles, within each surface zone shall not be less than _____
of the surface zone, for HYSD bars.
a) 0.25 %
b)
0.35 %
c) 0.45 %
d) 0.15 %
Answer: B
16. The minimum reinforcement in walls, floors and roofs in each of two
directions at right angles, within each surface zone shall not be less than ____
for mild steel reinforcement bars.
a) 0.65 %
b)
0.64 %
c) 0.46 %
d) 0.35 %
Answer: B
Unit 5 Introduction to Pre-stressed concrete
1.
In a load-balanced prestressed concrete
beam under self-load the cross-section is subjected to
B. Bending stress
C. Axial and bending stress
D. Axial and shear stress
ANS: A
2. A pre-stressed concrete
member
A. is made of concrete
B. is made of reinforced
concrete
C.
is stressed after casting
D.
possesses internal stresses.
ANS: D
3.
The prestressed concrete beam is suitable
for ___________
A.
Large
spans
B. Short
spans
C. Both
large and short spans
D. None of
these
ANS: A
4.
In pre stressed concrete section the
______________ section is effective.
a)
Above N.A.
b)
Below N.A.
c)
Partially above and below
d)
Entire section
ANS: D
5.
High
strength concrete is used in the prestressed 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)
to overcome cracks due to shrinkage
e)
all the
above.
ANS: E
6.
The concept used for the analysis of a prestressed concrete section is
A. Stress concept
B. Strength concept
C. Load balancing concept
D. All above
ANS: D
7.
High strength of concrete is required for
prestressed concrete work because _____
A.
Large
prestressing force is applied
B.
High
bond stress is required
C.
Bursting
stress is more
D.
All of above
ANS: D
8.
In prestressed concrete section
_______section is effective.
A.
Above
N.A.
B.
Partially
above and below
C.
Below
N.A.
D.
Entire
ANS: D
9.
In design of rectangular P.S.C. beam the
eccentricity of tendons is given by________
A.
(2 Md + Ml)/2p
B.
(Md + 2Ml)/2p
C.
2 Md + 2MI/p
D. None of these
ANS: A
10.
In design of rectangular P.S.C. beam the
eccentricity of tendons is given by________
A.
2 Md + Ml/2p
B.
Md + 2Ml/2p
C.
2 Md + 2MI/p
D. None of
these
ANS: D
11.
How is the deflection in RC beam
controlled as per IS 456?
A.
By using large aspect ratio
B.
By using small modular ratio
C.
By
controlling span to depth ratio
D.
By moderating water cement ratio Water
12. If the loading on a prestressed rectangular beam, is uniformly distributed, the tendon to be provided should be
A. straight below the centroidal axis
B. parabolic with convexity downward
C. parabolic with convexity upward
D. straight above the centroidal axis
ANS: B
13. In a prestressed 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
E. high strength concrete but low tensile steel
ANS: D
14. 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
15. The cable profile in prestressed concrete beam to resist UDL throughout the span shall be preferably
A. Along NA
B. Parallel to NA
C. Triangular
D. Parabolic
ANS: D
16. Minimum grade of concrete used for prestressed work should have a cube strength of ___________ N/mm2 for post tensioned.
a) 25
b) 30
c) 35
d) 40
Answer: B
17. For pre-tensioned prestressed concrete, the grade of concrete shall be not less than M ___.
a) 30
b) 35
c) 40
d) 45
Answer: C
Unit 6: Analysis of Symmetrical and unsymmetrical
sections
1.
The profile of cable in prestressed
concrete beam is usually similar to ___________
A. Shear
force diagram
B.
Bending moment diagram
C. None of
a and b
D. T. M.
diagram
ANS: B
2. The
cable profile in prestressed concrete beam to resist u.d.1 throughout the span
shall be preferably.
A.
Along
NA
B. Parallel to NA
C. Triangular
D.
Parabolic
ANS: D
3.
In C.C.L. standard system____________
number of wires is tensioned at a time.
A. 2
B. 4
C.
6
D. 12
ANS: C
4.
Safe stress in concrete at service is
________ fck.
a) 0.3
b) 0.4
c) 0.6
d) 0.5
ANS: B
5.
Safe stress in concrete at transfer is
________ fck.
a) 0.3
b) 0.4
c) 0.6
d) 0.5
ANS: D
6.
The permissible tensile stress in concrete
is _______ √fck
A. 0.125
B. 0.129
C. 0.126
D. 0.127
ANS: B
7.
If a rectangular prestressed 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
A.
5 cm
B.
10 cm
C.
15 cm
D. 20 cm
ANS: B
8.
P is the prestressed force applied to the tendon of a rectangular prestressed beam whose area of cross-section is A and
sectional modulus is Z. The maximum stress f in
the beam, subjected to a maximum bending moment M, is
ANS: C
9.
If A is
the sectional area of a prestressed rectangular beam provided with a tendon
prestressed by a force P through its centroidal
longitudinal axis, the compressive stress in concrete, is
A.
P/A
B.
2P/A
C.
A/P
D.
P/2A
ANS: A
10. If Md and Mt are
the maximum bending moments due to dead load and live load respectively and F is
the total effective pressure, for a balanced design of a prestressed concrete
beam of steel, is
A. e = (Md/F+Mt/2F)
B. e = (Md/2F+Ml/F)
C. e = (Md/2F+Ml/3F)
D. e = (Ml/3F+Ml/2F)
ANS: B
11. If the tendon is placed
at an eccentricity e below the centroidal axis of the longitudinal axis of a rectangular beam (sectional modulus Z and
stressed load P in the tendon) the stress at the extreme top edge
A.
is
increased by PZ/e
B.
is
increased by Pe/Z
C.
is decreased
by PZ/e
D.
is decreased
by Pe/Z
E.
Remains unchanged
ANS: C
12. If the loading on a
prestressed rectangular beam is uniformly distributed, the tendon to be
provided should be
A.
straight
below centroidal axis
B.
parabolic with convexity downward
C.
parabolic
with convexity upward
D. straight above
centroidal axis
ANS: B
13. In a prestressed 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
E. high strength concrete
but low tensile steel
ANS: D
14. 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
15. For pre-tensioned prestressed concrete, the grade of concrete shall be
not less than M ___.
a) 30
b) 35
c)
40
d) 45
Answer: C
Unit 7: Losses in prestress
(Note Q 6 & 7 carries 5 Marks each)
1.
If C
is creep coefficient, f is original prestress in concrete, m is the 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
2. In case
of pre-tensioned RC beam.
A.
Shrinkage
of concrete is of order 3 x 104
B. Relaxation of steel can
be ignored
C. Only one wire can be
stretched at a time
D.
Even mild steel can be
used for prestressing.
ANS: D
3. Relaxation losses for
prestressing steel at 1000 Hrs and at 27°C for internal stress 0.7fp
is ___
A. 0 N/mm2
B. 35 N/mm2
C. 70 N/mm2
D. 90 N/mm2
ANS: C
4. Relaxation losses for
prestressing steel at 1000 Hrs and at 27°C for internal stress 0.6fp
is ___
A. 0 N/mm2
B. 35 N/mm2
C. 70 N/mm2
D. 90 N/mm2
ANS: B
5.
For
straight or moderately curved structures, with curved or straight cables, the
value of prestressing force P, at a distance x meters from the tensioning end
and acting in the direction of the tangent to the curve of the cable shall be
calculated as below:
A.
Px = Po e-(ยต
ฮฑ + kx)
B.
Px = Po e-(ยตฮฑ
- kx)
C.
Px = Po (1 - ยตฮฑ
- kx)
D.
Px = Po e (
ยตฮฑ +
kx)
ANS: A
6. A
Post-tensioned concrete beam 250 mm wide & 360 mm deep has a span of 12 m.
the beam is prestressed by steel wires of area 350 mm2 provided with
a parabolic profile ACEDB with eccentricity at midspan of 60 mm with an initial
prestress of 1250 N/mm2. The percentage loss of prestress in the
wires due to friction only, at midspan will be_______. If ยต = 0.30 and k =
0.0015 per meter.
A. 3.4%
B. 1.5%
C. 4.4%
D. 5.6%
ANS: B
7. A Prestressed concrete beam is provided with a tendon with
parabolic profile with ฦ = 0.06o, the tendon is being tensioned from end A. Calculate the percentage loss of
prestress due to friction, from end A to the end B. Take ยต = 0.30 and k =
0.0015 per meter. Stress in tendon at A = 1050 N/mm2.
A. 3.4%
B. 1.5%
C. 5.4%
D. 5.6%
ANS: C
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