18.0 - NOTATION fps = stress in prestressing steel at service loads less decompression stress, ksi 4/7/2019 Ce 572

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 4/7/2019 Ce 572

DECOMPRESSION STRESS fdc Strain 0.03 0.02 0.01 fdc fse fps Steel Stress at Service Load From Cracked Section Analysis 4/7/2019 Ce 572

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 4/7/2019 Ce 572

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 4/7/2019 Ce 572

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. 4/7/2019 Ce 572

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 ………………………… 4/7/2019 Ce 572

18.3.3 – NEW CLASS C Prestressed Flexural Members Are Classified as Follows: Condition Class Stress Condition Uncracked U Transition T Cracked C 4/7/2019 Ce 572

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 4/7/2019 Ce 572

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 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Assumed Behavior Prestressed Class U Uncracked Class T Transition Class C Cracked Nonprestressed 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Section Properties for Stress Calculations at Service Loads Prestressed Class U Gross Section (18.3.4) Class T Class C Cracked Section (18.3.4) Nonprestressed Not Required 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Tensile Stress at Service Loads Prestressed Class U Class T Class C No Limit Nonprestressed 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Deflection Calculation Basis Prestressed Class U Gross Section (9.5.4.1) Class T Cracked Section (9.5.4.2) Class C Nonprestressed Effective Moment of Inertia, Ieff 4/7/2019 Ce 572

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 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Crack Control Prestressed Class U Uncracked Class T No Requirement Class C 10.6.4 Modified by 18.4.4.1 Nonprestressed 10.6.4 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Computation of fps or fs for Crack Control Prestressed Class U Uncracked Class T No Requirement Class C Cracked Section Analysis Nonprestressed M/(As x Lever Arm), or 0.6fy 4/7/2019 Ce 572

TABLE R18.3.3 – SERVICEABILITY DESIGN REQUIREMENTS Side Skin Reinforcement Prestressed Class U No Requirement Class T Class C 10.6.7 Nonprestressed 4/7/2019 Ce 572

18.4.4 – SERVICEABILITY – CLASS C For structures subject to fatigue or exposed to corrosive environments, special investigations and precautions are required. 4/7/2019 Ce 572

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) 4/7/2019 Ce 572

18.4.4.1 – SPACING REQUIREMENT In 10.6.4 As Modified by 18.4.4 4/7/2019 Ce 572

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 4/7/2019 Ce 572

18.4.4.3 – STEEL STRESS fps Shall Not Exceed 36 ksi If fps  20 ksi, Spacing Limits Do Not Apply 4/7/2019 Ce 572

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 4/7/2019 Ce 572

18.8.1 – REINFORCEMENT LIMITS Previously in Appendix B of ’99 Code Limits Are Based on Net Tensile Strain, t 4/7/2019 Ce 572

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 4/7/2019 Ce 572 Ex. 24.3

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 4/7/2019 Ce 572

18.8.2 – MINIMUM REINFORCEMENT No Technical Change Was 18.8.3 in ’99 Code Total Reinforcement Must Satisfy:  Mn  1.2 Mcr 4/7/2019 Ce 572

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 4/7/2019 Ce 572

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. 4/7/2019 Ce 572

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 4/7/2019 Ce 572