Exam Details
| Subject | Prestressed Concrete | |
| Paper | ||
| Exam / Course | Diploma in Civil Engineering (DCLE - G) | |
| Department | School of Engineering & Technology (SOET) | |
| Organization | indira gandhi national open university | |
| Position | ||
| Exam Date | December, 2016 | |
| City, State | new delhi, |
Question Paper
No. of Printeld Pages: 4 IBCEE..ooll DIPLOMA IN CML ENGINEERlNG DCLE(G) Term-End Examination UOB42 Decetnber, 2016
$Ct:E-061 PRESTRESSEO CONCRETE
. Time: 2 hours Maximum Marks: 10
Note: Question no. 1 is compulsory. Attempt any four questions from the remaining questions. Use of scientific calculator is allowed. Assume required data suitably, if found missing.
1. Choose the most appropriate answer from the given options: 7x2=14
The value of shrinkage strain for concrete in post-tensioned structures
increases with age of member at transfer
decreases with age of member at transfer
depends on type of anchorage system
remains constant
Splices are used for
stretching tendons
positioning anchorages
holding tendons with correct profile
joining tendons
As compared to an R.C.C. Beam for the same span and loading, the size in prestressed concrete structure is
less
more
equal
None of the above
In prestressed concrete structures, the steel used is
Mild steel bars
HYSD bars
High tensile strength wire
All of the above
The minimum grade of concrete used in pre-tensioned concrete structures is
M-25
M-30
M-35
M-40
Tensile strength of concrete may be calculated from the relation
0.7
Which of the following losses occurs only in post-tensioning?
Shrinkage of concrete
Elastic shortening of concrete
Loss due to friction
Creep of concrete
2. Discuss the advantages of preatressed concrete members as compared to reinforced concrete members. 7
Discuss the reasons to provide high strength steel and high strength concrete for prestressed concrete structures. 7
3. A pre-tensioned concrete beam of size 150 mm x 350 mm is carrying prestressing force of 400kN. Calculate the loss of prestress due to elastic deformation if this beam has constant eccentricity of prestressing force as 60 mm. Assume Es 210 kN/mm2 and E=35 kN/mm2. 7
Explain the loss of prestress due to friction in a post-tensioned concrete beam. 7
4. Discuss, briefly, the Load Balancing concept for prestressed concrete beam. 7
Discuss thermo-electric prestressing in brief. 7
5. Explain Hoyer's long line system of pre-tensioning in brief. 7
Discuss the steps to design a prestressed concrete rectangular beam. 7
6. Calculate the stresses at mid span of a prestressed CQncrete beam in top and bottom fibres. The beam has a simple supported span of 6.5 m and carries an imposed load of 12 kN/m. The cross-section of the beam is 200 mm x 450 mm (depth) and a prestressing force of 450 kN is applied concentrically. Assume density of concrete as 25 kN/m3. 7
Write down briefly the applications of prestressed concrete members. 7
7. Write short notes On any two of the following: 2x7=14
Salient Codal Provisions of serviceability for prestressed concrete members
Prestressed concrete pipes and poles
Secondary stresses due to tendon curvature
$Ct:E-061 PRESTRESSEO CONCRETE
. Time: 2 hours Maximum Marks: 10
Note: Question no. 1 is compulsory. Attempt any four questions from the remaining questions. Use of scientific calculator is allowed. Assume required data suitably, if found missing.
1. Choose the most appropriate answer from the given options: 7x2=14
The value of shrinkage strain for concrete in post-tensioned structures
increases with age of member at transfer
decreases with age of member at transfer
depends on type of anchorage system
remains constant
Splices are used for
stretching tendons
positioning anchorages
holding tendons with correct profile
joining tendons
As compared to an R.C.C. Beam for the same span and loading, the size in prestressed concrete structure is
less
more
equal
None of the above
In prestressed concrete structures, the steel used is
Mild steel bars
HYSD bars
High tensile strength wire
All of the above
The minimum grade of concrete used in pre-tensioned concrete structures is
M-25
M-30
M-35
M-40
Tensile strength of concrete may be calculated from the relation
0.7
Which of the following losses occurs only in post-tensioning?
Shrinkage of concrete
Elastic shortening of concrete
Loss due to friction
Creep of concrete
2. Discuss the advantages of preatressed concrete members as compared to reinforced concrete members. 7
Discuss the reasons to provide high strength steel and high strength concrete for prestressed concrete structures. 7
3. A pre-tensioned concrete beam of size 150 mm x 350 mm is carrying prestressing force of 400kN. Calculate the loss of prestress due to elastic deformation if this beam has constant eccentricity of prestressing force as 60 mm. Assume Es 210 kN/mm2 and E=35 kN/mm2. 7
Explain the loss of prestress due to friction in a post-tensioned concrete beam. 7
4. Discuss, briefly, the Load Balancing concept for prestressed concrete beam. 7
Discuss thermo-electric prestressing in brief. 7
5. Explain Hoyer's long line system of pre-tensioning in brief. 7
Discuss the steps to design a prestressed concrete rectangular beam. 7
6. Calculate the stresses at mid span of a prestressed CQncrete beam in top and bottom fibres. The beam has a simple supported span of 6.5 m and carries an imposed load of 12 kN/m. The cross-section of the beam is 200 mm x 450 mm (depth) and a prestressing force of 450 kN is applied concentrically. Assume density of concrete as 25 kN/m3. 7
Write down briefly the applications of prestressed concrete members. 7
7. Write short notes On any two of the following: 2x7=14
Salient Codal Provisions of serviceability for prestressed concrete members
Prestressed concrete pipes and poles
Secondary stresses due to tendon curvature
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Subjects
- Construction Equipment
- Construction Management
- Construction Supervision and Building Maintenance
- Irrigation Engineering
- Prestressed Concrete
- Soil Mechanics and Foundation Engineering
- Technical Documentation
- Transportation Engineering