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2. By Dr. Attaullah Shah Swedish College of Engineering and Technology Wah Cantt. CE-407 Lec-02 Structural Engineering

3. The net stress in the prestressed section The resultant stress due to the combined effect of applied loads and pre- stress force is given as: At the ends of the beam where there is no moment the MC/I =0, the stress becomes

4. Example

5. Solution

6. The kern of a section is the region in which a compressive point load may be applied without producing any tensile stress on the cross section.

7. Shapes of pre-stressed sections: −Rectangular shape: Simple and easy to pour −I-Section and T-section: Economical −Channels and Boxes

8. Prestress losses −The initial prestress becomes smaller with time due to following reasons: A lump sum value has been recommended by ACI Code

9. Elastic Shortening

11. Losses due to shrinkage

12. Relaxation of creep in the tendons

13. Slippage in post tension and anchorage system

14. Friction along the duct

15. Ultimate Stress of pre-stressed section

22. Assignment No.1