Categories: 8th Semester

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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