Download VTU BE 2020 Jan ECE Question Paper 15 Scheme 8th Sem 15CV82 Design of Prestressed Concrete Elements

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Time: 3 hrs. Max. Marks: 80
Note: I. Answer any FIVE full questions, choosing ONE full question from each module.
2. Use of IS 1343-1980 is permitted.
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a%
Module-1
c 1 I a. Explain the need for High Strength conc and higher grade steel for PSC member. (04 Marks)
.a
,

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b. Define Pre-stressed Concrete. Explain the different types of Pre-stressed Concrete.
co
b
y (04 Marks)
4.) ..,

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c. A PSC inverted T beam section web 300x900mm. Flange 300x600mm simply supported
Y ,.;
over a span of 15m. The beam is tensioned by 3 cables each containing 12 wires of 7 mm
g o diameter placed at 150mm from soffit at midspan. If the initial prestress is 1000 N/mm
-

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oi) ii
calculate the max UDL the beam can carry maximum compressive stress is limited to
c 0 0
' E ,-
1

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. z
i 15 MPa and tensile stress is limited to 1 MPa. Assume 15% loss of pre stress. (08 Marks)
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t-
E
? . OR
.c
c.. - ?,::

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2 a. Explain Load Balancing Concept. (02 Marks)
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41
b. Explain post tensioning anchorages devices and explain any one in details. (06 Marks)
? 0

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c c
? c. A rectangular beam 200x300mm is pre-stressed by 15 wires of 5 mm diameter located at
2
6
1

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1 65mm from bottom and 3 wires of 5mm diameter at 25mm from top initial pre-stress is
o 4
,

To

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-
O
840 N/mm
2
. Calculate stress at midspan. (08 Marks)

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c ---
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toc
c c
,-. Module-2

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g i 3 a. Define loss of pre-stress. Explain different loss of pre-stress with suitable example.
45 74
(06 Marks)
ir.
o b. A post tensioned concrete beam 100x300mm span 10m is pre-stressed successively,

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0 ?
-.- .. co
tensioned and anchored by 3 cables each having C/S area 200 mm
2
. Initial pre stress is

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8 . .
g c '
9
' .
1200 N/mm

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2
. First cable is parabolic with e = 50mm at mid span and e = 50mm above NA at

52
.

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.... =
support. Second cable is parabolic with e = 50 at midspan and zero at support. Third cable is
d ,
3 t
straight cable with 50mm eccentricity. Find the loss of pre-stress due to elastic deformation.

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...0.
c ?
Take m = 6.
co .?
(10 Marks)

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8
6-
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ot
.

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0 r
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1
>
O 2

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OR
4 a. Derive the expression for deflection for a beam of length / subjected to point load at mid

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span, UDL. Two point load symmetrically placed at middle third point. Prestress P applied
on a straight cable with e as eccentricity and a parabolic cable with e = 0 at support and e at
mid span. (06 Marks)
b. A simply supported beam having span 6m is post tensioned by 2 cable both having
e = 50mm at mid span. First cable is parabolic and anchored 100mm above CG at support.

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Second cable is straight. C/s of each cable is 200mm
2
and initial prestress is 1200 N/mm
2
.

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O
Area of cone 2x10
4
mm
2

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radius of gyration 120mm. The beam support a two point load each
20 kN at middle third point Ec 38 kN/mm
2
. Calculate (i) Short term deflection (ii) Long
term deflection .Take 4 = 2, Loss of prestress 20%. (10 Marks)

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1 of 2
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USN
15CV82
C.

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Eighth Semester B.E. Degree Examination, De n.2020
Design of Prestressed Concrete Elements
Time: 3 hrs. Max. Marks: 80
Note: I. Answer any FIVE full questions, choosing ONE full question from each module.
2. Use of IS 1343-1980 is permitted.

--- Content provided by​ FirstRanker.com ---

}
-
a%
Module-1
c 1 I a. Explain the need for High Strength conc and higher grade steel for PSC member. (04 Marks)

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.a
,
b. Define Pre-stressed Concrete. Explain the different types of Pre-stressed Concrete.
co
b

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y (04 Marks)
4.) ..,
c. A PSC inverted T beam section web 300x900mm. Flange 300x600mm simply supported
Y ,.;
over a span of 15m. The beam is tensioned by 3 cables each containing 12 wires of 7 mm

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g o diameter placed at 150mm from soffit at midspan. If the initial prestress is 1000 N/mm
-
oi) ii
calculate the max UDL the beam can carry maximum compressive stress is limited to
c 0 0

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' E ,-
1
. z
i 15 MPa and tensile stress is limited to 1 MPa. Assume 15% loss of pre stress. (08 Marks)
.

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Fo
. ,
t-
E
? . OR

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.c
c.. - ?,::
2 a. Explain Load Balancing Concept. (02 Marks)
o
41

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b. Explain post tensioning anchorages devices and explain any one in details. (06 Marks)
? 0
c c
? c. A rectangular beam 200x300mm is pre-stressed by 15 wires of 5 mm diameter located at
2

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6
1
1 65mm from bottom and 3 wires of 5mm diameter at 25mm from top initial pre-stress is
o 4
,

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To
-
O
840 N/mm

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2
. Calculate stress at midspan. (08 Marks)
c ---
o -0
toc

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c c
,-. Module-2
g i 3 a. Define loss of pre-stress. Explain different loss of pre-stress with suitable example.
45 74
(06 Marks)

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ir.
o b. A post tensioned concrete beam 100x300mm span 10m is pre-stressed successively,
0 ?
-.- .. co
tensioned and anchored by 3 cables each having C/S area 200 mm

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2
. Initial pre stress is
8 . .
g c '
9

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' .
1200 N/mm
2
. First cable is parabolic with e = 50mm at mid span and e = 50mm above NA at

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52
.
.... =
support. Second cable is parabolic with e = 50 at midspan and zero at support. Third cable is
d ,

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3 t
straight cable with 50mm eccentricity. Find the loss of pre-stress due to elastic deformation.
...0.
c ?
Take m = 6.

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co .?
(10 Marks)
8
6-
..1

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ot
.
0 r
E '
1

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>
O 2
U > ,
O
,_: rsi

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OR
4 a. Derive the expression for deflection for a beam of length / subjected to point load at mid
span, UDL. Two point load symmetrically placed at middle third point. Prestress P applied
on a straight cable with e as eccentricity and a parabolic cable with e = 0 at support and e at
mid span. (06 Marks)

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b. A simply supported beam having span 6m is post tensioned by 2 cable both having
e = 50mm at mid span. First cable is parabolic and anchored 100mm above CG at support.
Second cable is straight. C/s of each cable is 200mm
2
and initial prestress is 1200 N/mm

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2
.
O
Area of cone 2x10
4

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mm
2
radius of gyration 120mm. The beam support a two point load each
20 kN at middle third point Ec 38 kN/mm
2

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. Calculate (i) Short term deflection (ii) Long
term deflection .Take 4 = 2, Loss of prestress 20%. (10 Marks)
1 of 2
cA

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College
15CV82
Module-3
5 An unsymmetrical I section having top flange 750x200mm bottom flange 450x250mm
thickness of web 150mm overall depth 1000mm. If permissible tensile and compressive

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stress at transfer and working load are not to exceed zero in tension 15 N/mm
2
in
compression. Determine P and e to resist self weight and applied moment 1012 kNm and
450 kNm. Assume loss of pre stress 15%. (16 Marks)

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OR
6 Design a post tensioned girder which is spaced 2.4 m c/c and has an effective span of 9m.
Live load 15 kN/m
2
, DL(3 kN/m

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2
+ Self weight). Compressive stress at transfer and working
load are 14 Nimm
2
and 12 N/mm

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2
tension is 1 N/mm
2
at all stages of loading loss Ratio 0.8.
Determine number of 7mm diameter wires required if permissible tension is 1000 N/mm

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2
.
Assume cover as 100 mm. (16 Marks)
Module-4
7 a. Explain types of shear cracks. (04 Marks)

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b. A' PSC beam 250mm wide 150mm deep is subjected to SF 900 kN fiber stress under
working load is 4 N/mm
2
effective pre-stress is 1000 N/mm
2

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and area of cable is 1500 min
-
.
Design shear reinforcement slope of cable at support is (1/6). (12 Marks)
OR

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8 A pre-stressed concrete beam of span 10m, cross section 120mm x 300mm is prestressed by
a cable carrying a force of 180 kN the beam support a UDL 5 kN/m including self weight
compare the magnitude of principal tension with and without axial pre-stress. Estimate the
reduction in principal stress. Also find % reduction if a parabolic cable used with e = 50 mm
at mid span and zero at support. (16 Marks)

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Module-5
9 a. Explain stress distribution in End Block. (04 Marks)
b. Explain Indian Standard Code IS-1343 method for calculation of Burstire force. (04 Marks)
c. The end block of a post tensioned pre-stressed concrete beam 300mm x 300mm is subjected
to a pre-stressing force 832.8 kN. Anchorage area 11720 mm

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2
. Design suitable anchorage
reinforcement. (08 Marks)
OR
10 a. Explain composite construction in PSC members. (06 Marks)

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b. A composite T beam is made up of pre tensioned web 100mm wide 200mm deep and a cast
insitu slab 400mm wide 40mm thick having a modulus of elasticity 28 kN/mm
2
. If the
differential shrinkage is 100x 1 V' units determined shrinkage stresses developed in the

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precast and cast insitu units.
(10 Marks)
of
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