Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 8th Sem New 2180612 Design Of Prestressed Concrete Structures And Bridges Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VIII(NEW) EXAMINATION ? SUMMER 2019
Subject Code:2180612 Date:13/05/2019
Subject Name:Design Of Prestressed Concrete Structures & Bridges
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.
4. Use of code IS: 1343 (2012) is permitted.
Q.1 (a) Define (1) Post-tensioning (2) Bonded Prestressed Concrete
(3) Degree of Prestressing.
03
(b) What are different principles of post tensioning and applications of post
tensioning?
04
(c) A live load of 2kN/m is imposed on an unsymmetrical I section beam with
300mm wide and 60 mm thick top flange, 100mm wide and 60mm thick bottom
flange and 80 mm thick and 280 mm long web. The effective prestressing force
of 100kN is located at 50mm from the bottom of the beam and at the center of
the span. Consider length of span as 7m.Calculate the stresses at the center of
the span section of the beam for the following load conditions:
a) Prestress + self-weight.
b) Prestress +self-weight +live load.
07
Q.2 (a) What are different types of losses of prestress in pretensioning and post-
tensioning?
03
(b) Explain the concept of thrust line and how it is located. 04
(c) A rectangular concrete beam 120 mm wide and 300 mm deep is used over an
effective span of 6m to support a uniformly distributed load of 4kN/m including
the self-weight of the beam. It is prestressed by a straight cable carrying a force
of 180kN and located at an eccentricity of 50mm. determine the location of
thrust line in the beam and plot its position at quarter and central span sections.
07
OR
(c) A rectangular beam 300mm wide and 800mm deep supports two concentrated
loads of 20kN each at the third point of span of 9m.if the eccentricity of the
trapezoidal cable profile is 100mm for the middle third portion of the beam,
calculate the prestressing force required to balance the bending effect of the
concentrated load neglecting the self-weight of the beam. If the resultant stress
due to self-weight, imposed loads and prestressing force is zero at bottom fibre
of the mid span section, calculate the effective force in the cable. Consider same
cable profile and density of concrete as 24kN/m
2
07
Q.3 (a) Define transmission length and how can we calculate it? 03
(b) How straight and trapezoidal tendon profiles affect deflections? 04
(c) A pretensioned T section has a flange 1200mm wide and 150mm thick. The
width and depth of the rib are 300mm and 1500mm respectively. The high
tensile steel has an area of 4700mm
2
and is located at an effective depth of
1600mm.calculate the flexural strength of T section. ( Assume fck = 40N/mm
2
,
fp = 1600N/mm
2
and use IS Code method)
07
OR
Q.3 (a) Enlist different types of flexural failure and explain any one. 03
(b) Briefly discuss IS 1343 recommendations for design of prestressed members
subjected to shear, torsion and bending.
04
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VIII(NEW) EXAMINATION ? SUMMER 2019
Subject Code:2180612 Date:13/05/2019
Subject Name:Design Of Prestressed Concrete Structures & Bridges
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.
4. Use of code IS: 1343 (2012) is permitted.
Q.1 (a) Define (1) Post-tensioning (2) Bonded Prestressed Concrete
(3) Degree of Prestressing.
03
(b) What are different principles of post tensioning and applications of post
tensioning?
04
(c) A live load of 2kN/m is imposed on an unsymmetrical I section beam with
300mm wide and 60 mm thick top flange, 100mm wide and 60mm thick bottom
flange and 80 mm thick and 280 mm long web. The effective prestressing force
of 100kN is located at 50mm from the bottom of the beam and at the center of
the span. Consider length of span as 7m.Calculate the stresses at the center of
the span section of the beam for the following load conditions:
a) Prestress + self-weight.
b) Prestress +self-weight +live load.
07
Q.2 (a) What are different types of losses of prestress in pretensioning and post-
tensioning?
03
(b) Explain the concept of thrust line and how it is located. 04
(c) A rectangular concrete beam 120 mm wide and 300 mm deep is used over an
effective span of 6m to support a uniformly distributed load of 4kN/m including
the self-weight of the beam. It is prestressed by a straight cable carrying a force
of 180kN and located at an eccentricity of 50mm. determine the location of
thrust line in the beam and plot its position at quarter and central span sections.
07
OR
(c) A rectangular beam 300mm wide and 800mm deep supports two concentrated
loads of 20kN each at the third point of span of 9m.if the eccentricity of the
trapezoidal cable profile is 100mm for the middle third portion of the beam,
calculate the prestressing force required to balance the bending effect of the
concentrated load neglecting the self-weight of the beam. If the resultant stress
due to self-weight, imposed loads and prestressing force is zero at bottom fibre
of the mid span section, calculate the effective force in the cable. Consider same
cable profile and density of concrete as 24kN/m
2
07
Q.3 (a) Define transmission length and how can we calculate it? 03
(b) How straight and trapezoidal tendon profiles affect deflections? 04
(c) A pretensioned T section has a flange 1200mm wide and 150mm thick. The
width and depth of the rib are 300mm and 1500mm respectively. The high
tensile steel has an area of 4700mm
2
and is located at an effective depth of
1600mm.calculate the flexural strength of T section. ( Assume fck = 40N/mm
2
,
fp = 1600N/mm
2
and use IS Code method)
07
OR
Q.3 (a) Enlist different types of flexural failure and explain any one. 03
(b) Briefly discuss IS 1343 recommendations for design of prestressed members
subjected to shear, torsion and bending.
04
(c) A prestressed concrete pile, 250 mm square,contains 60 pre-tensioned wires,
each of 2 mm diameter uniformly distributed over the section. the wires are
initially tensioned on the prestressing bed with a total force of 300kN.Calculate
the final stress in concrete and the percentage loss of stress in steel after all
losses,Given the following data Es=210kN/mm2,Ec=32kN/mm
2
,Shortening
due to creep=30X10
-6
mm/mm per N/mm
2
of stress, total shrinkage=200X10
-6
per unit length, Relaxation of steel stress=5% of initial stress.
07
Q.4 (a) Explain in details the Live load specification for road bridge as per IRC. 03
(b) What is strain compatibility method? 04
(c) The deck slab of a road bridge of span 10m is to be designed as a one way
prestressed concrete slab,with parallel post-tensioned cables 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 compressive and tensile stress in
concrete at any stage not exceeding 15 and zero N/mm2 respectively, calculate
the maximum horizontal spacing of the cables and their positions at the mid-
span section. assume the loss ratio as 0.80.
.07
OR
Q.4 (a) Write in brief investigation and planning to be carried out for bridge design and
construction
03
(b) How do you Compute the loss of stress due to elastic deformation of concrete? 04
(c) What are the salient design features of prestressed concrete one way and two
way slab panels?
07
Q.5 (a) Explain Courbon?s Method for Load distribution on bridge deck. 03
(b) Give classification of bridges based on various aspects. 04
(c) Explain role of pier as a substructure part of Bridges. Also enlist the loads and
forces to be considered while designing pier
07
OR
Q.5 (a) Enlist loads acting on bridges. 03
(b) Give classification of bridges based on various aspects. 04
(c) Which are the preliminary data to be collected for the design of bridges? 07
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This post was last modified on 20 February 2020