18.0 - NOTATION

1. 18.0 - NOTATION fps = stress in prestressing steel at service loads less decompression stress, ksi Ce 572

2. 18.0 - NOTATION fdc = decompression stress. Stress in the prestressing steel when stress is zero in the concrete at the same level as the centroid of the tendons, ksi Ce 572

3. Stress Steel Stress at Service Load From Cracked Section Analysis fdc fps fse 0 0.01 0.02 0.03 Strain DECOMPRESSION STRESS fdc Ce 572

4. DECOMPRESSION STRESS fdc • fdc = fse + fc x Eps/Ec where fc is the Concrete Stress at Level of Steel Under Dead Load and Prestress • fdc May Be Conservatively Taken as fse Ce 572

5. 18.0 - NOTATION s = center-to-center spacing of flexural tension steel near the extreme tension face, in. Where there is only one bar or tendon near the extreme tension face, s is the width of extreme tension face Ce 572

6. 18.1.3 – CODE SECTIONS EXCLUDED FROM CHAPTER 18 18.1.3 - The following provisions of this code shall not apply to prestressed concrete, except as specifically noted: Sections 7.6.5, 8.4, 8.10.2, 8.10.3, 8.10.4, 8.11, 10.3.2, 10.3.3, 10.5, 10.6, 10.9.1, and 10.9.2; Chapter 13; and Sections 14.3, 14.5, and 14.6, except that certain sections of 10.6 apply as noted in 18.4.4. Ce 572

7. 18.4.2 – PERMISSIBLE STRESSES (’99) (c) Extreme fiber stress in tension in precompressed tensile zone … (d) Extreme fiber stress in tension in precompressed tensile zone … based on transformed cracked sections ………………………… Ce 572

8. 18.3.3 – NEW CLASS C Ce 572

9. 18.3.3 – PRESTRESSED FLEXURAL MEMBERS • Classes U, T, and C Are Based on the Computed Extreme Fiber Stress ft at Service Loads in the Precompressed Tensile Zone • Precompressed Tensile Zone is that Portion of the Member Cross Section in Which Flexural Tension Occurs Under Dead and Live Loads Ce 572

10. 18.3.3 – PRESTRESSED FLEXURAL MEMBERS • New Class C Permits Design Using Any Combination of Prestressing Steel and Nonprestressed Reinf. • Classes U, T, and C Apply to Both Bonded and Unbonded Members, Except … • Prestressed Two-Way Slab Systems Must Be Designed as Class U Ce 572

11. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

12. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

13. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

14. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

15. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS • Prestressed Concrete Members with Tension Not Exceeding Are Class U, and a Cracked Section Deflection Analysis is Not Required • In ’99 Code, a Cracked Section Deflection Analysis Was Required for Members With Tension Exceeding , but the Section Was Not Assumed to be Cracked Unless the Tension Exceeded Ce 572

16. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

17. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

18. TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Ce 572

19. 18.4.4 – SERVICEABILITY – CLASS C • For structures subject to fatigue or exposed to corrosive environments, special investigations and precautions are required. Ce 572

20. 18.4.4 – SERVICEABILITY – CLASS C Use 10.6.4 and Eq. (10-4) to Compute Spacing s (for Crack Control), Except: • For Tendons, Use 2/3 of Spacing “s” Required by Eq. (10-4) • With Combination of Nonprestressed Reinf. And Tendons, Use 5/6 of Spacing “s” Required by Eq. (10-4) (3) Use fps in place of fs in Eq. (10-4) Ce 572

21. 18.4.4.1 – SPACING REQUIREMENT • In 10.6.4 • As Modified by 18.4.4 Ce 572

22. 18.4.4.2 – STEEL STRESS • fps = Stress in Tendon at Service Load Less Decompression Stress fdc • Stress at Service Load is Based on a Cracked Section Analysis • fdc May Be Conservatively Taken as the Effective Prestress fse Ce 572

23. 18.4.4.3 – STEEL STRESS • fps Shall Not Exceed 36 ksi • If fps  20 ksi, Spacing Limits Do Not Apply Ce 572

24. 18.4.4.4 – SKIN REINFORCEMENT • If Effective Depth > 36 in., Skin Reinforcement Must Satisfy 10.6.7 • Area of Skin Reinforcement, Ask, Includes Both Nonprestressed Reinforcement and Tendons Ce 572

25. 18.8.1 – REINFORCEMENT LIMITS • Previously in Appendix B of ’99 Code • Limits Are Based on Net Tensile Strain, t Ce 572

26. 18.8.1 – REINFORCEMENT LIMITS • Per 10.3.3 and 10.3.4, Prestressed Concrete Sections Are Classified as: • Tension Controlled • Transition, or • Compression Controlled •  Factors Given in 9.3.2 Ce 572 Ex. 24.3

27. R18.8.1 – REINFORCEMENT LIMITS • Net tensile strain limits for tension-controlled sections given in 10.3.4 may also be stated in terms of p as defined in the 1999 and earlier editions of the code • The net tensile strain limit of 0.005 corresponds to p = 0.32b1 for prestressed rectangular sections Ce 572

28. 18.8.2 – MINIMUM REINFORCEMENT • No Technical Change • Was 18.8.3 in ’99 Code • Total Reinforcement Must Satisfy:  Mn 1.2 Mcr Ce 572

29. 18.8.3 – FLEXURAL MEMBERS • Place Part or All of the Bonded Reinforcement Close to Extreme Tension Fiber Reason: Control Cracking Under Full Service Loads or Overloads • See 18.9 for Members with Unbonded Tendons Ce 572

30. 18.9 – MINIMUM BONDED REINF. 18.9.3 — For two-way flat plate slab systems, minimum area and distribution of bonded reinforcement shall be as required in 18.9.3.1, 18.9.3.2, and 18.9.3.3. Ce 572

31. 18.10.4 - MOMENT REDISTRIBUTION • Moment Redistribution Permitted If Bonded Reinforcement Is Provided At Supports • Redistribution Per 8.4 Applies Equally to Prestressed and Nonprestressed Concrete Ce 572