GTU BE 8th Semester 2180612 Design of Prestressed Concrete Structures and Bridges(Departmental Elective – III) Summer 2018 Question Paper

1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE – SEMESTER ?VIII (NEW) – EXAMINATION ? SUMMER 2018
Subject Code: 2180612 Date: 02/05/2018
Subject Name: Design of Prestressed Concrete Structures &
Bridges(Departmental Elective – III)
Time: 10:30 AM to 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

MARKS
Q.1 (a) Define the terms: (1) Pretensioning (2) Tendon (3) Anchorage
03
(b) Write advantages and disadvantages of prestressed
concrete
04
(c) A rectangular concrete beam of cross-section 30cm deep
and 20cm wide is prestressed by means of 15 wires of
5mm diameter located 6.5 cm from the bottom of the beam
and 3 wires of diameter of 5mm, 2.5cm from the top.
Assuming the prestress in the steel as 840 N/mm
2
,
calculate the stressed at the extreme fibers of the mid span
sections when the beam is supporting its own weight over
a span of 6 m. If a uniformly distributed live load of 6
kN/m is imposed, evaluate the maximum working stress
in concrete. The density of concrete is 24 kN/m
3
07

Q.2 (a) Differentiate between Pretensioned and posttensioned
member
03
(b) Explain the differences of prestressed concrete over
reinforced concrete.
04
(c) A prestressed concrete beam with a rectangular section
120mm wide, 300mm deep supports a uniformly
distributed load of 4 kN/m, which includes the self-weight
of the beam. The effective span of the beam is 6 m. The
beam is concentrically prestressed by cable carrying a
force of 180 kN. Locate the position of the pressure line
in the beam.
07
OR
(c) A rectangular concrete bam 250 mm wide and 300 mm
deep is prestressed by a force of 540 kN at a constant
eccentricity of 60 mm. The beam supports a concentrated
load of 68kN at the centre span of 3 m. Determine the
location of the pressure line at the centre, quarter span and
support sections of the beam. Neglect the self-weight of
the beam.
07
Q.3 (a) Differentiate between short-term and long-term
deflections of prestressed concrete beams
03
(b) List the various types of tensioning device used in
prestressed concrete
04 1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE – SEMESTER ?VIII (NEW) – EXAMINATION ? SUMMER 2018
Subject Code: 2180612 Date: 02/05/2018
Subject Name: Design of Prestressed Concrete Structures &
Bridges(Departmental Elective – III)
Time: 10:30 AM to 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

MARKS
Q.1 (a) Define the terms: (1) Pretensioning (2) Tendon (3) Anchorage
03
(b) Write advantages and disadvantages of prestressed
concrete
04
(c) A rectangular concrete beam of cross-section 30cm deep
and 20cm wide is prestressed by means of 15 wires of
5mm diameter located 6.5 cm from the bottom of the beam
and 3 wires of diameter of 5mm, 2.5cm from the top.
Assuming the prestress in the steel as 840 N/mm
2
,
calculate the stressed at the extreme fibers of the mid span
sections when the beam is supporting its own weight over
a span of 6 m. If a uniformly distributed live load of 6
kN/m is imposed, evaluate the maximum working stress
in concrete. The density of concrete is 24 kN/m
3
07

Q.2 (a) Differentiate between Pretensioned and posttensioned
member
03
(b) Explain the differences of prestressed concrete over
reinforced concrete.
04
(c) A prestressed concrete beam with a rectangular section
120mm wide, 300mm deep supports a uniformly
distributed load of 4 kN/m, which includes the self-weight
of the beam. The effective span of the beam is 6 m. The
beam is concentrically prestressed by cable carrying a
force of 180 kN. Locate the position of the pressure line
in the beam.
07
OR
(c) A rectangular concrete bam 250 mm wide and 300 mm
deep is prestressed by a force of 540 kN at a constant
eccentricity of 60 mm. The beam supports a concentrated
load of 68kN at the centre span of 3 m. Determine the
location of the pressure line at the centre, quarter span and
support sections of the beam. Neglect the self-weight of
the beam.
07
Q.3 (a) Differentiate between short-term and long-term
deflections of prestressed concrete beams
03
(b) List the various types of tensioning device used in
prestressed concrete
04
2
(c) A beam of symmetrical I-section spanning 8 m has flange
width of 150 mm and flange thickness of 80 mm
respectively. The overall depth of the beam is 450 mm.
Thickness of web is 80 mm. The beam is prestressed by a
parabolic cable with an eccentricity of 150 mm at the
centre of the span and zero at the supports. The Live Load
on the beam is 2.5kN/m. (1) Determine the effective force in the cable for
balancing the Dead Load and Live Load on the
beams (2) Calculate the shift of the pressure line from the
tendon centre line.
07
OR
Q.3 (a) Explain the concept of load balancing in prestressed
concrete members
03
(b) Explain the principle of post tensioning 04
(c) A prestressed concrete beam 400mm X 600mm in section
has a span of 6m and is subjected to uniformly distributed
load of 16 kN/m including the self-weight of the beam.
The prestressing tendons are located at the lower third
point and provide an effective prestressing force of 960 N.
Determine the extreme fibre stresses in concrete at the mid
span section.
07
Q.4 (a) Write in brief investigation and planning to be carried out
for bridge design and construction
03
(b) Give classification of bridges based on various aspects 04
(c) Design a suitable section for the tie member of a truss to
support a maximum design tensile force of 600 kN. The
permissible compressive stress in concrete at the transfer
is 15 N/mm
2
and no tension is permitted under working
load. The loss ratio is 0.8. 7 mm diameter wires of ultimate
tensile strength of 1800 N/mm
2
with an initial stress of
1000 N/mm
2
may be used. The direct tensile strength of
concrete is 3 N/mm
2
. A load factor of 2 at the limit state
of collapse and 1.25 against cracking is required.
07
OR
Q.4 (a) Discuss the types of substructures for bridges 03
(b) Which are the preliminary data to be collected for the
design of bridges
04
(c) The deck slab of a road bridge of span 10 m is to be design
as a one-way prestressed concrete slab, with parallel post-
tensioned cable in each of which the force at transfer is
500 kN. If the deck slab is required to support a uniformly
distributed live load of 25 kN/m
2
, with the compressive
and tensile stress in concrete at any stage not exceeding 15
and zero N/mm
2
respectively, calculate the maximum
horizontal spacing of the cable and their position at the
mid span sections. Assume the loss ratio as 0.80
07
Q.5 (a) Enlist loads acting on bridges 03
(b) Briefly discuss the IS : 1343 code provisions regarding
bond and transmission length
04
(c) Describe the Grillage analogy 07

1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE – SEMESTER ?VIII (NEW) – EXAMINATION ? SUMMER 2018
Subject Code: 2180612 Date: 02/05/2018
Subject Name: Design of Prestressed Concrete Structures &
Bridges(Departmental Elective – III)
Time: 10:30 AM to 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

MARKS
Q.1 (a) Define the terms: (1) Pretensioning (2) Tendon (3) Anchorage
03
(b) Write advantages and disadvantages of prestressed
concrete
04
(c) A rectangular concrete beam of cross-section 30cm deep
and 20cm wide is prestressed by means of 15 wires of
5mm diameter located 6.5 cm from the bottom of the beam
and 3 wires of diameter of 5mm, 2.5cm from the top.
Assuming the prestress in the steel as 840 N/mm
2
,
calculate the stressed at the extreme fibers of the mid span
sections when the beam is supporting its own weight over
a span of 6 m. If a uniformly distributed live load of 6
kN/m is imposed, evaluate the maximum working stress
in concrete. The density of concrete is 24 kN/m
3
07

Q.2 (a) Differentiate between Pretensioned and posttensioned
member
03
(b) Explain the differences of prestressed concrete over
reinforced concrete.
04
(c) A prestressed concrete beam with a rectangular section
120mm wide, 300mm deep supports a uniformly
distributed load of 4 kN/m, which includes the self-weight
of the beam. The effective span of the beam is 6 m. The
beam is concentrically prestressed by cable carrying a
force of 180 kN. Locate the position of the pressure line
in the beam.
07
OR
(c) A rectangular concrete bam 250 mm wide and 300 mm
deep is prestressed by a force of 540 kN at a constant
eccentricity of 60 mm. The beam supports a concentrated
load of 68kN at the centre span of 3 m. Determine the
location of the pressure line at the centre, quarter span and
support sections of the beam. Neglect the self-weight of
the beam.
07
Q.3 (a) Differentiate between short-term and long-term
deflections of prestressed concrete beams
03
(b) List the various types of tensioning device used in
prestressed concrete
04
2
(c) A beam of symmetrical I-section spanning 8 m has flange
width of 150 mm and flange thickness of 80 mm
respectively. The overall depth of the beam is 450 mm.
Thickness of web is 80 mm. The beam is prestressed by a
parabolic cable with an eccentricity of 150 mm at the
centre of the span and zero at the supports. The Live Load
on the beam is 2.5kN/m. (1) Determine the effective force in the cable for
balancing the Dead Load and Live Load on the
beams (2) Calculate the shift of the pressure line from the
tendon centre line.
07
OR
Q.3 (a) Explain the concept of load balancing in prestressed
concrete members
03
(b) Explain the principle of post tensioning 04
(c) A prestressed concrete beam 400mm X 600mm in section
has a span of 6m and is subjected to uniformly distributed
load of 16 kN/m including the self-weight of the beam.
The prestressing tendons are located at the lower third
point and provide an effective prestressing force of 960 N.
Determine the extreme fibre stresses in concrete at the mid
span section.
07
Q.4 (a) Write in brief investigation and planning to be carried out
for bridge design and construction
03
(b) Give classification of bridges based on various aspects 04
(c) Design a suitable section for the tie member of a truss to
support a maximum design tensile force of 600 kN. The
permissible compressive stress in concrete at the transfer
is 15 N/mm
2
and no tension is permitted under working
load. The loss ratio is 0.8. 7 mm diameter wires of ultimate
tensile strength of 1800 N/mm
2
with an initial stress of
1000 N/mm
2
may be used. The direct tensile strength of
concrete is 3 N/mm
2
. A load factor of 2 at the limit state
of collapse and 1.25 against cracking is required.
07
OR
Q.4 (a) Discuss the types of substructures for bridges 03
(b) Which are the preliminary data to be collected for the
design of bridges
04
(c) The deck slab of a road bridge of span 10 m is to be design
as a one-way prestressed concrete slab, with parallel post-
tensioned cable in each of which the force at transfer is
500 kN. If the deck slab is required to support a uniformly
distributed live load of 25 kN/m
2
, with the compressive
and tensile stress in concrete at any stage not exceeding 15
and zero N/mm
2
respectively, calculate the maximum
horizontal spacing of the cable and their position at the
mid span sections. Assume the loss ratio as 0.80
07
Q.5 (a) Enlist loads acting on bridges 03
(b) Briefly discuss the IS : 1343 code provisions regarding
bond and transmission length
04
(c) Describe the Grillage analogy 07

3

OR
Q.5 (a) Explain the criteria for selection of type of bridge. 03
(b) Write the design principles for pre-tensioned prestressed
bridge decks
04
(c) Explain forces acting on bearing. Write points are to be
consider for design of bearing
07
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