This document discusses prestressed concrete design and provides information on: 1) Cold working and stress relieving processes used to strengthen steel wires for prestressing. This includes rolling bars through dies to reduce diameter and tempering to improve properties. 2) The differences between cold working, stress relieving, and strain tempering and how each improves the steel. 3) Examples of initial superstructures for bridges like box girders and the Zuari Bridge in Goa.

1. CE 337/CE 568 : Prestressed
Concrete Design
Prof. Sasankasekhar Mandal
BE (Jadavpur Univ., Kolkata, 1993), ME (UOR, Roorkee, 1996), PhD (IIT, Roorkee, 2001)
Department of Civil Engineering
IIT (BHU), Varanasi, UP 221 005

2. IS 1343 – 2012 specifications on materials
(aggregates)

3. Influence of maximum size of aggregate on compressive
strength of concrete, AM Neville (2011)

4. Cold working followed by stress relieving
• Cold working: rolling the bars through a series of dies
The high carbon steel ingots are hot rolled into rods and cold drawn through
series of dies to reduce the diameter and increase tensile strength.
Note that this process decreases durability of the wires. So, the cold drawn
wires are subsequently tempered to improve their properties.
Tempering is also known as Ageing/ stress relieving.
• Stress relieving: heating the strand to about 350°C (range 150 – 4200C) and
cooling slowly. Improves plastic deformation of steel and improves the tensile
strength.
• Strain tempering for low relaxation: heating the strand to about 350°C while it is
under tension.
• Improves the stress- strain behaviour of steel. Also the relaxation loss is reduced.

5. Cold working versus stress relieving
• Cold working: rolling the bars through a series of dyes.
• Stress relieving: heating the strand to about 350°C and cooling slowly.
Improves plastic deformation of steel.
• Strain tempering for low relaxation: heating the strand to about 350°C
while it is under tension.
• Improves the stress- strain behaviour of steel. Also the relaxation loss
is reduced.

6. Examples of initial super structures

7. Examples of initial super structures

8. Evolution of box girder bridges

9. Typical box girder cross section of a flyover
bridge

10. Examples of initial super structures

11. Zuari bridge 807m long Goa

12. Properties of cold drawn stress relieved wires (IS 1785)

13. Properties of High tensile indented wire (IS 6003)

14. Sheathing

15. Comparative Properties of different types of wire

16. Terminology IS 1343 -2012

17. Anchorage devices

18. Anchorage devices

19. Terminology IS 1343 -2012

20. Terminology IS 1343 -2012

21. Terminology IS 1343 -2012

22. Pre-tensioned pre-stressed concrete

23. Post-tensioned pre-stressed concrete

24. Terminology IS 1343 -2012

25. Sheathing

26. Sheathing : Corrugated HDPE ducts

27. Sheathing : Corrugated HDPE ducts

28. Terminology IS 1343 -2012

29. Typical diagram of transmission length

30. Typical diagram of transmission length