ACI/PTI CODE-320-25: Post-Tensioned Structural Concrete—Code Requirements and Commentary

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Description

The “Post-Tensioned Structural Concrete—Code Requirements and Commentary” (“Code”) provides minimum requirements for the materials, design, and detailing of post-tensioned concrete buildings and, where applicable, nonbuilding structures. This Code was developed by using a consensus process and addresses structural concrete members and systems that contain post-tensioned tendons. The Technical Advisory Board Code Task Group of the Post-Tensioning Institute was instrumental in the development of code provisions and commentary for this Code and whose efforts are gratefully acknowledged. Among the subjects covered are: design and construction for strength, serviceability, and durability; one-way slabs; two-way slabs; beams; post-tensioning anchorages; construction document information; and field inspection and testing.

This Code adheres to the chapter and section numbering of ACI CODE-318-25 and either references or repeats applicable provisions from ACI CODE-318. Provisions that are identical to ACI CODE-318 and are repeated in this Code are denoted with an equal sign (“=”). Provisions that are applicable to post-tensioned concrete but are not repeated in the Code are denoted as “See ACI CODE-318.” The Code organization is such that all design and detailing requirements for structural systems or for individual members are presented in chapters devoted to those individual subjects, and the chapters are arranged in a manner that generally follows the process and chronology of design and construction. Information and procedures that are common to the design of multiple member types are located in utility chapters. Within chapters, the terms “out of scope” are used for numbered section headings from ACI CODE-318 that are not covered by this Code, while the term “intentionally left blank” is used as a place holder to maintain consistency with section numbering in situations where ACI CODE-318 includes a numbered provision that is not also in this Code.

Uses of the Code include adoption by reference in a general building code, and earlier editions have been widely used in this manner. The Code is written in a format that allows such reference without change to its language. Therefore, background details or suggestions for carrying out the requirements or intent of the Code provisions cannot be included within the Code itself. The Commentary is provided for this purpose. Some considerations of the committee in developing the Code are discussed in the Commentary, with emphasis given to the explanation of new or revised provisions. The commentary also provides explanations regarding situations where use of ACI CODE-318 and this Code are used. For instance, design of cast-in-place, nonprestressed concrete members or structures requires the use of ACI CODE-318 alone. Design of post-tensioned concrete structures requires the use of this Code and ACI CODE-318. Design of precast, post-tensioned concrete structures requires the use of applicable provisions of this Code, ACI CODE-318, and ACI-PTI CODE-319. For provisions that specifically address precast concrete and are generally not within the scope of post-tensioning, this code references either ACI CODE-318 or ACI-PTI CODE-319, where applicable.

Much of the research data referenced in preparing the Code is cited for the user desiring to study individual questions in greater detail. Other documents that provide suggestions for carrying out the requirements of the Code are also cited, including PTI design manuals, recommended practices, and reports.

Keywords:

anchorage; anchorage device; anchorage zone; beam-column frame; beams (supports); bonded tendon; combined stress; compressive strength; concrete; construction documents; continuity (structural); cover; deep beams; deflections; earthquake-resistant structures; elongation; flexural strength; floors; inspection; joints (junctions); loads (forces); modulus of elasticity; moments; post-tensioned concrete; prestressed concrete; prestressing steels; quality control; reinforcing steels; roofs; serviceability; shear strength; spans; splicing; strength analysis; stresses; stressing; structural analysis; structural design; structural integrity; structural walls; T-beams; torsion; unbonded tendon; walls.

Document Details

Author: Joint ACI-PTI Committee 320

Publication Year: 2025

Pages: 168

ISBN: 9781641953153

Formats: Printed Document or Protected PDF/Web View

Table of Contents

CHAPTER 1—General, p. 6

1.1—Scope of ACI/PTI CODE-320, p. 6

1.2—General, p. 6

1.3—Purpose, p. 7

1.4—Applicability, p. 7

1.5—Interpretation, p. 8

1.6—Building official, p. 9

1.7—Licensed design professional, p. 10

1.8—Construction documents and design records, p. 10

1.9—Testing and inspection, p. 10

1.10—Approval of specials systems of design, construction, or alternative construction materials, p. 11

CHAPTER 2—Notation and Terminology, p. 12

2.1—Scope, p. 12

2.2—Notation, p. 12

2.3—Terminology, p. 17

CHAPTER 3—Referenced Standards, p. 29

3.1—Scope, p. 29

3.2—Referenced standards, p. 29

Chapter 4—Structural System Requirements, p. 30

4.1—Scope, p. 30

4.2—Materials, p. 30

4.3—Design loads, p. 30

4.4—Structural system and load paths, p. 30

4.5—Structural analysis, p. 34

4.6—Strength, p. 34

4.7—Serviceability, p. 35

4.8—Durability, p. 35

4.9—Sustainability, p. 35

4.10—Structural integrity, p. 36

4.11—Fire resistance, p. 36

4.12—Requirements for specific types of construction, p. 36

4.13—Construction and inspection, p. 38

4.14—Strength evaluation of existing structures, p. 38

Chapter 5—Loads, p. 39

5.1—Scope, p. 39

5.2—General - See ACI CODE-318, p. 39

5.3—Load factors and combinations, p. 39

ChAPTER 6—Structural Analysis, p. 40

6.1—Scope, p. 40

6.2—General, p. 40

6.3—Modeling assumptions, p. 40

6.4—Arrangement of live load, p. 40

6.5—Simplified method of analysis for nonprestressed continuous beams and one-way slabs - See ACI CODE-318, p. 41

6.6—Linear elastic first-order analysis, p. 41

6.7—Linear elastic second-order analysis - See ACI CODE-318, p. 43

6.8—Inelastic analysis - See ACI CODE-318, p. 43

6.9—Acceptability of finite element analysis - See ACI CODE-318, p. 43

Chapter 7—One-Way Slabs, p. 44

7.1—Scope, p. 44

7.2—General, p. 44

7.3—Design limits, p. 44

7.4—Required strength, p. 45

7.5—Design strength, p. 45

7.6—Reinforcement limits, p. 46

7.7—Reinforcement detailing, p. 49

Chapter 8—Two-Way Slabs, p. 52

8.1—Scope, p. 52

8.2—General, p. 52

8.3—Design limits, p. 53

8.4—Required strength, p. 54

8.5—Design strength, p. 58

8.6—Reinforcement limits, p. 59

8.7—Reinforcement detailing, p. 61

8.8—Nonprestressed two-way joist systems - Out of Scope, p. 71

8.9—Lift-slab construction, p. 71

Chapter 9—Beams, p. 72

9.1—Scope, p. 72

9.2—General, p. 72

9.3—Design limits, p. 73

9.4—Required strength, p. 74

9.5—Design strength, p. 76

9.6—Reinforcement limits, p. 78

9.7—Reinforcement detailing, p. 80

9.8—Nonprestressed one-way joist systems - Out of Scope, p. 85

9.9—Deep beams - See ACI CODE-318, p. 85

CHAPTER 10—Columns, p. 86

10.1—Scope, p. 86

10.2—General - See ACI CODE-318, p. 86

10.3—Design limits - See ACI CODE-318, p. 86

10.4—Required strength - See ACI CODE-318, p. 86

10.5—Design strength - See ACI CODE-318, p. 86

10.6—Reinforcement limits, p. 86

10.7—Reinforcement detailing, p. 86

CHAPTER 11—Walls, p. 88

11.1—Scope, p. 88

Chapter 12—Diaphragms, p. 89

12.1—Scope, p. 89

12.2—General - See ACI CODE-318, p. 90

12.3—Design limits - See ACI CODE-318, p. 90

12.4—Required strength - See ACI CODE-318, p. 90

12.5—Design strength, p. 90

12.6—Reinforcement limits - See ACI CODE-318, p. 92

12.7—Reinforcement detailing - See ACI CODE-318, p. 92

Chapter 13—Foundations, p. 93

13.1—Scope, p. 93

Chapter 14—Plain Concrete (out of scope), p. 93

Chapter 15—Cast-in-Place Joints, p. 93

15.1—Scope, p. 93

Chapter 16—Connections between Members, p. 93

16.1—Scope, p. 93

Chapter 17—Anchoring to Concrete, p. 93

17.1—Scope, p. 93

Chapter 18—Earthquake-Resistant Structures, p. 94

18.1—Scope, p. 94

18.2—General - See ACI CODE-318, p. 95

18.3—Ordinary moment frames - See ACI CODE-318, p. 95

18.4—Intermediate moment frames, p. 95

18.5—Intermediate precast structural walls - Out of scope, p. 96

18.6—Beams of special moment frames, p. 96

18.7—Columns of special moment frames - See ACI CODE-318, p. 97

18.8—Joints of special moment frames - See ACI CODE-318, p. 97

18.9—Special moment frames constructed using precast concrete - See ACI/PCI-CODE 319, p. 97

18.10—Special structural walls - See ACI CODE-318, p. 97

18.11—Special structural walls constructed using precast concrete - See ACI/PCI CODE-319, p. 97

18.12—Diaphragms and trusses, p. 97

18.13—Foundations - See ACI CODE-318, p. 97

18.14—Members not designated as part of the seismic-force-resisting system, p. 97

Chapter 19—Concrete: Design and Durability Requirements, p. 100

19.1—Scope, p. 100

19.2—Concrete design properties - See ACI CODE-318, p. 100

19.3—Concrete durability requirements - See ACI CODE-318, p. 100

19.4—Grout durability requirements, p. 100

Chapter 20—Steel Reinforcement Properties, Durability, and Embedments, p. 101

20.1—Scope, p. 101

20.2—Nonprestressed bars and wires - See ACI CODE-318, p. 101

20.3—Prestressing strands, wires, and bars, p. 101

20.4—Headed shear stud reinforcement, p. 104

20.5—Provisions for durability of steel reinforcement, p. 105

20.6—Embedments - See ACI CODE-318, p. 108

Chapter 21—Strength Reduction Factors, p. 109

21.1—Scope, p. 109

21.2—Strength reduction factors for structural concrete members and connections, p. 109

CHAPTER 22—Sectional Strength, p. 110

22.1—Scope, p. 110

22.2—Design assumptions for moment and axial strength, p. 110

22.3—Flexural strength, p. 111

22.4—Axial strength or combined flexural and axial strength, p. 111

22.5—One-way shear strength, p. 112

22.6—Two-way shear strength, p. 119

22.7—Torsional strength, p. 127

22.8—Bearing - See ACI CODE-318, p. 133

22.9—Shear friction - See ACI CODE-318, p. 133

Chapter 23—Strut-and-Tie Method, p. 134

23.1—Scope, p. 134

Chapter 24—Serviceability, p. 135

24.1—Scope, p. 135

24.2—Deflections due to service-level gravity loads, p. 135

24.3—Distribution of flexural reinforcement in one-way slabs and beams, p. 138

24.4—Shrinkage and temperature reinforcement, p. 140

24.5—Permissible stresses in prestressed concrete flexural members, p. 141

Chapter 25—Reinforcement Details, p. 144

25.1—Scope, p. 144

25.2—Minimum spacing of reinforcement - See ACI CODE-318, p. 144

25.3—Standard hooks, seismic hooks, crossties, and minimum inside bend diameters - See ACI CODE-318, p. 144

25.4—Development and anchorage of reinforcement - See ACI CODE-318, p. 144

25.5—Splices - See ACI CODE-318, p. 144

25.6—Bundled reinforcement - See ACI CODE-318, p. 144

25.7—Transverse reinforcement - See ACI CODE-318, p. 144

25.8—Post-tensioning anchorages and couplers, p. 144

25.9—Anchorage zones for post-tensioned tendons, p. 145

CHapter 26—Construction Documents and Inspection, p. 156

26.1—Scope, p. 156

26.2—Design criteria - See ACI CODE-318, p. 157

26.3—Member information - See ACI CODE-318, p. 157

26.4—Concrete materials, mixture requirements, and grouts - ACI CODE-318, p. 157

26.5—Concrete production and construction - See ACI CODE-318, p. 157

26.6—Reinforcement materials and construction requirements - See ACI CODE-318, p. 157

26.7—Anchoring to concrete - See ACI CODE-318, p. 157

26.8—Embedments - See ACI CODE-318, p. 157

26.9—Additional requirements for precast concrete - See ACI/PCI CODE-319, p. 157

26.10—Additional requirements for post-tensioned concrete, p. 157

26.11—Formwork - See ACI CODE-318, p. 159

26.12—Evaluation and acceptance of hardened concrete - See ACI CODE-318, p. 159

26.13—Inspection - See ACI CODE-318, p. 159

Chapter 27—Strength Evaluation of Existing Structures, p. 160

27.1—Scope, p. 160

Commentary References, p. 161

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