318 14 building code requirements for structural concrete and commentary

CONCRETE DESIGN

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4 Building Code Requirements for Structural Concrete (ACI 318M-14) and Commentary (ACI 318RM-14) Reported by ACI Committee 318

An ACI Standard

Building Code Requirements for Structural Concrete (ACI 318M-14)

An ACI Standard

Commentary on Building Code Requirements for Structural Concrete (ACI 318RM-14)

An ACI Report

Reported by ACI Committee 318

Randall W. Poston, Chair Basile G. Rabbat, Secretary

VOTING MAIN COMMITTEE MEMBERS

Neal S. Anderson Florian G. Barth Roger J. Becker

Kenneth B. Bondy Dean A. Browning James R. Cagley Ned M. Cleland

W. Gene Corley* Ronald A. Cook

Charles W. Dolan

Anthony E. Fiorato Catherine E. French

Robert J. Frosch Luis E. Garcia

Brian C. Gerber S. K. Ghosh

David P. Gustafson James R. Harris

Terence C. Holland Shyh-Jiann Hwang

James O. Jirsa Dominic J. Kelly

Gary J. Klein Ronald Klemencic Cary Kopczynski

Colin L. Lobo Paul F. Mlakar Jack P. Moehle

Lawrence C. Novak Gustavo J. Parra-Montesinos

David M. Rogowsky David H. Sanders Guillermo Santana

Thomas C. Schaeffer Stephen J. Seguirant Andrew W. Taylor

James K. Wight Sharon L. Wood

Loring A. Wyllie Jr.

VOTING SUBCOMMITTEE MEMBERS

Raul D. Bertero Allan P. Bommer John F. Bonacci Patricio Bonelli Sergio F. Breña

JoAnn P. Browning Nicholas J. Carino

David Darwin Jeffrey J. Dragovich Kenneth J. Elwood Lisa R. Feldman

Harry A. Gleich H. R. Trey Hamilton

R. Doug Hooton Kenneth C. Hover

Steven H. Kosmatka Michael E. Kreger

Jason J. Krohn Daniel A. Kuchma

Andres Lepage Raymond Lui LeRoy A. Lutz

Joe Maffei Donald F. Meinheit

Fred Meyer Suzanne Dow Nakaki

Theodore L. Neff Viral B. Patel

Conrad Paulson Jose A. Pincheira

Carin L. Roberts-Wollmann Mario E. Rodríguez

Bruce W. Russell

M. Saiid Saiidi Andrea J. Schokker

John F. Silva John F. Stanton Roberto Stark

Bruce A. Suprenant John W. Wallace W. Jason Weiss

Fernando V. Yáñez

INTERNATIONAL LIAISON MEMBERS

F. Michael Bartlett Mathias Brewer Josef Farbiarz

Luis B. Fargier-Gabaldon Alberto Giovambattista

Hector Hernandez

Angel E. Herrera Hector Monzon-Despang

Enrique Pasquel

Patricio A. Placencia Oscar M. Ramirez

Fernando Reboucas Stucchi

CONSULTING MEMBERS

Sergio M. Alcocer John E. Breen

Neil M. Hawkins H. S. Lew

James G. MacGregor Robert F. Mast

Julio A. Ramirez Charles G. Salmon*

ACI 318M-14 supersedes ACI 318M-11, and published March 2015. Copyright © 2015, American Concrete Institute.

All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduc- tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.

1

*Deceased.

First Printing March 2015

ISBN: 978-1-942727-11-8

Building Code Requirements for Structural Concrete and Commentary

Copyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. This material may not be reproduced or copied, in whole or part, in any printed, mechanical, electronic, film, or other distribution and storage media, without the written consent of ACI.

The technical committees responsible for ACI committee reports and standards strive to avoid ambiguities, omissions, and errors in these documents. In spite of these efforts, the users of ACI documents occasionally find information or requirements that may be subject to more than one interpretation or may be incomplete or incorrect. Users who have suggestions for the improvement of ACI documents are requested to contact ACI via the errata website at http://concrete.org/Publications/ DocumentErrata.aspx. Proper use of this document includes periodically checking for errata for the most up-to-date revisions.

ACI committee documents are intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the material it contains. Individuals who use this publication in any way assume all risk and accept total responsibility for the application and use of this information.

All information in this publication is provided “as is” without warranty of any kind, either express or implied, including but not limited to, the implied warranties of merchantability, fitness for a particular purpose or non-infringement.

ACI and its members disclaim liability for damages of any kind, including any special, indirect, incidental, or consequential damages, including without limitation, lost revenues or lost profits, which may result from the use of this publication.

It is the responsibility of the user of this document to establish health and safety practices appropriate to the specific circumstances involved with its use. ACI does not make any representations with regard to health and safety issues and the use of this document. The user must determine the applicability of all regulatory limitations before applying the document and must comply with all applicable laws and regulations, including but not limited to, United States Occupational Safety and Health Administration (OSHA) health and safety standards.

Participation by governmental representatives in the work of the American Concrete Institute and in the development of Institute standards does not constitute governmental endorsement of ACI or the standards that it develops.

Order information: ACI documents are available in print, by download, on CD-ROM, through electronic subscription, or reprint and may be obtained by contacting ACI.

Most ACI standards and committee reports are gathered together in the annually revised ACI Manual of Concrete Practice (MCP).

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PREFACE TO ACI 318M-14 The “Building Code Requirements for Structural Concrete” (“Code”) provides minimum requirements for the materials,

design, and detailing of structural concrete buildings and, where applicable, nonbuilding structures. This Code addresses struc- tural systems, members, and connections, including cast-in-place, precast, plain, nonprestressed, prestressed, and composite construction. Among the subjects covered are: design and construction for strength, serviceability, and durability; load combi- nations, load factors, and strength reduction factors; structural analysis methods; deflection limits; mechanical and adhesive anchoring to concrete; development and splicing of reinforcement; construction document information; field inspection and testing; and methods to evaluate the strength of existing structures. “Building Code Requirements for Concrete Thin Shells” (ACI 318.2) is adopted by reference in this Code.

The Code user will find that ACI 318-14 has been substantially reorganized and reformatted from previous editions. The principal objectives of this reorganization are to present all design and detailing requirements for structural systems or for indi- vidual members in chapters devoted to those individual subjects, and to arrange the chapters in a manner that generally follows the process and chronology of design and construction. Information and procedures that are common to the design of members are located in utility chapters.

The quality and testing of materials used in construction are covered by reference to the appropriate ASTM standard speci- fications. Welding of reinforcement is covered by reference to the appropriate American Welding Society (AWS) standard.

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 of the considerations of the committee in developing the Code are discussed within the Commentary, with emphasis given to the explanation of new or revised provisions. 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.

Technical changes from ACI 318-11 to ACI 318-14 are outlined in the May 2014 issue of Concrete International. Transition keys showing how the code was reorganized are provided on the ACI website on the 318 Resource Page under

Topics in Concrete.

KEYWORDS admixtures; aggregates; anchorage (structural); beam-column frame; beams (supports); building codes; cements; cold

weather construction; columns (supports); combined stress; composite construction (concrete and steel); composite construc- tion (concrete to concrete); compressive strength; concrete construction; concrete slabs; concretes; construction joints; conti- nuity (structural); construction documents; contraction joints; cover; curing; deep beams; deflections; earthquake-resistant structures; embedded service ducts; flexural strength; floors; folded plates; footings; formwork (construction); frames; hot weather construction; inspection; isolation joints; joints (junctions); joists; lightweight concretes; load tests (structural); loads (forces); materials; mixing; mixture proportioning; modulus of elasticity; moments; pipe columns; pipes (tubing); placing; plain concrete; precast concrete; prestressed concrete; prestressing steels; quality control; reinforced concrete; reinforcing steels; roofs; serviceability; shear strength; shear walls; shells (structural forms); spans; splicing; strength; strength analysis; stresses; structural analysis; structural concrete; structural design; structural integrity; T-beams; torsion; walls; water; welded wire reinforcement.

NOTES FROM THE PUBLISHER ACI Committee Reports, Guides, and Commentaries are intended for guidance in planning, designing, executing, and

inspecting construction. This commentary (318RM-14) is intended for the use of individuals who are competent to evaluate the significance and limitations of its content and recommendations and who will accept responsibility for the application of the information it contains. ACI disclaims any and all responsibility for the stated principles. The Institute shall not be liable for any loss or damage arising there from. Reference to this commentary shall not be made in construction documents. If items found in this commentary are desired by the Architect/ Engineer to be a part of the construction documents, they shall be restated in mandatory language for incorporation by the Architect/Engineer.

The materials, processes, quality control measures, and inspections described in this document should be tested, monitored, or performed as applicable only by individuals holding the appropriate ACI Certification or equivalent.

ACI 318M-14, Building Code Requirements for Structural Concrete, and ACI 318RM-14, Commentary, are presented in a side-by-side column format. These are two separate but coordinated documents, with Code text placed in the left column and the corresponding Commentary text aligned in the right column. Commentary section numbers are preceded by an “R” to further distinguish them from Code section numbers.

The two documents are bound together solely for the user’s convenience. Each document carries a separate enforceable and distinct copyright.

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BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14) 3

INTRODUCTION

This Commentary discusses some of the considerations of Committee 318 in developing the provisions contained in “Building Code Requirements for Structural Concrete (ACI 318-14),” hereinafter called the Code or the 2014 Code. Emphasis is given to the explanation of new or revised provisions that may be unfamiliar to Code users. In addition, comments are included for some items contained in previous editions of the Code to make the present commentary inde- pendent of the previous editions. Comments on specific provisions are made under the corresponding chapter and section numbers of the Code.

The Commentary is not intended to provide a complete historical background concerning the development of the Code, nor is it intended to provide a detailed résumé of the studies and research data reviewed by the committee in formulating the provisions of the Code. However, references to some of the research data are provided for those who wish to study the background material in depth.

As the name implies, “Building Code Requirements for Structural Concrete” is meant to be used as part of a legally adopted building code and as such must differ in form and substance from documents that provide detailed specifica- tions, recommended practice, complete design procedures, or design aids.

The Code is intended to cover all buildings of the usual types, both large and small. Requirements more stringent than the Code provisions may be desirable for unusual construction. The Code and Commentary cannot replace sound engineering knowledge, experience, and judgment.

A building code states only the minimum requirements necessary to provide for public health and safety. The Code is based on this principle. For any structure, the owner or the licensed design professional may require the quality of materials and construction to be higher than the minimum requirements necessary to protect the public as stated in the Code. However, lower standards are not permitted.

The Commentary directs attention to other documents that provide suggestions for carrying out the requirements and intent of the Code. However, those documents and the Commentary are not a part of the Code.

The Code has no legal status unless it is adopted by the government bodies having the police power to regulate building design and construction. Where the Code has not been adopted, it may serve as a reference to good practice even though it has no legal status.

The Code provides a means of establishing minimum standards for acceptance of designs and construction by legally appointed building officials or their designated repre- sentatives. The Code and Commentary are not intended for

use in settling disputes between the owner, engineer, archi- tect, contractor, or their agents, subcontractors, material suppliers, or testing agencies. Therefore, the Code cannot define the contract responsibility of each of the parties in usual construction. General references requiring compli- ance with the Code in the project specifications should be avoided since the contractor is rarely in a position to accept responsibility for design details or construction require- ments that depend on a detailed knowledge of the design. Design-build construction contractors, however, typically combine the design and construction responsibility. Gener- ally, the contract documents should contain all of the neces- sary requirements to ensure compliance with the Code. In part, this can be accomplished by reference to specific Code sections in the project specifications. Other ACI publica- tions, such as “Specifications for Structural Concrete (ACI 301)” are written specifically for use as contract documents for construction.

It is recommended to have testing and certification programs for the individual parties involved with the execu- tion of work performed in accordance with this Code. Avail- able for this purpose are the plant certification programs of the Precast/Prestressed Concrete Institute, the Post-Tensioning Institute, and the National Ready Mixed Concrete Associa- tion; the personnel certification programs of the American Concrete Institute and the Post-Tensioning Institute; and the Concrete Reinforcing Steel Institute’s Voluntary Certifica- tion Program for Fusion-Bonded Epoxy Coating Applicator Plants. In addition, “Standard Specification for Agencies Engaged in Construction Inspecting and/or Testing” (ASTM E329-09) specifies performance requirements for inspection and testing agencies.

Design reference materials illustrating applications of the Code requirements may be found in the following docu- ments. The design aids listed may be obtained from the sponsoring organization.

Design aids: “ACI Design Handbook,” Publication SP-17(11), Amer-

ican Concrete Institute, Farmington Hills, MI, 2011, 539 pp. (This provides tables and charts for design of eccentrically loaded columns by the Strength Design Method of the 2009 Code. Provides design aids for use in the engineering design and analysis of reinforced concrete slab systems carrying loads by two-way action. Design aids are also provided for the selection of slab thickness and for reinforcement required to control deformation and assure adequate shear and flexural strengths.)

For a history of the ACI Building Code, see Kerekes, F., and Reid, H. B., Jr., “Fifty Years of Development in Building Code Requirements for Reinforced Concrete,” ACI Journal, V. 50, No. 6, Feb. 1954, p. 441. For a discussion of code philosophy, see Siess, C. P., “Research, Building Codes, and Engineering Practice,” ACI Journal, V. 56, No. 5, May 1960, p. 1105.

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4 BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14)

“ACI Detailing Manual—2004,” ACI Committee 315, Publication SP-66(04), American Concrete Institute, Farm- ington Hills, MI, 2004, 212 pp. (Includes the standard, ACI 315-99, and report, ACI 315R-04. Provides recommended methods and standards for preparing engineering drawings, typical details, and drawings placing reinforcing steel in rein- forced concrete structures. Separate sections define respon- sibilities of both engineer and reinforcing bar detailer.)

“Guide to Durable Concrete (ACI 201.2R-08),” ACI Committee 201, American Concrete Institute, Farmington Hills, MI, 2008, 49 pp. (This describes specific types of concrete deterioration. It contains a discussion of the mech- anisms involved in deterioration and the recommended requirements for individual components of the concrete, quality considerations for concrete mixtures, construction procedures, and influences of the exposure environment.)

“Guide for the Design and Construction of Durable Parking Structures (362.1R-12),” ACI Committee 362, American Concrete Institute, Farmington Hills, MI, 2012, 24 pp. (This summarizes practical information regarding design of parking structures for durability. It also includes information about design issues related to parking structure construction and maintenance.)

“CRSI Handbook,” Concrete Reinforcing Steel Institute, Schaumburg, IL, tenth edition, 2008, 777 pp. (This provides tabulated designs for structural elements and slab systems. Design examples are provided to show the basis and use of the load tables. Tabulated designs are given for beams; square, round, and rectangular columns; one-way slabs; and one-way joist construction. The design tables for two-way slab systems include flat plates, flat slabs, and waffle slabs. The chapters on foundations provide design tables for square footings, pile caps, drilled piers (caissons), and cantilevered retaining walls. Other design aids are presented for crack control and development of reinforcement and lap splices.)

“Reinforcement Anchorages and Splices,” Concrete Reinforcing Steel Institute, Schaumburg, IL, fifth edition, 2008, 100 pp. (This provides accepted practices in splicing reinforcement. The use of lap splices, mechanical splices,

and welded splices are described. Design data are presented for development and lap splicing of reinforcement.)

“Structural Welded Wire Reinforcement Manual of Standard Practice,” Wire Reinforcement Institute, Hart- ford, CT, eighth edition, Apr. 2010, 35 pp. (This describes welded wire reinforcement material, gives nomenclature and wire size and weight tables. Lists specifications and prop- erties and manufacturing limitations. Book has latest code requirements as code affects welded wire. Also gives devel- opment length and splice length tables. Manual contains customary units and soft metric units.)

“Structural Welded Wire Reinforcement Detailing Manual,” Wire Reinforcement Institute, Hartford, CT, 1994, 252 pp. (The manual, in addition to including ACI 318 provisions and design aids, also includes: detailing guid- ance on welded wire reinforcement in one-way and two-way slabs; precast/prestressed concrete components; columns and beams; cast-in-place walls; and slabs-on-ground. In addition, there are tables to compare areas and spacings of high-strength welded wire with conventional reinforcing.)

“PCI Design Handbook—Precast and Prestressed Concrete,” Precast/Prestressed Concrete Institute, Chicago, IL, seventh edition, 2010, 804 pp. (This provides load tables for common industry products, and procedures for design and analysis of precast and prestressed elements and struc- tures composed of these elements. Provides design aids and examples.)

“Design and Typical Details of Connections for Precast and Prestressed Concrete,” Precast/Prestressed Concrete Institute, Chicago, IL, second edition, 1988, 270 pp. (This updates available information on design of connections for both structural and architectural products, and presents a full spectrum of typical details. This provides design aids and examples.)

“Post-Tensioning Manual,” Post-Tensioning Insti- tute, Farmington Hills, MI, sixth edition, 2006, 354 pp. (This provides comprehensive coverage of post-tensioning systems, specifications, design aids, and construction concepts.)

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BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14) 5

TABLE OF CONTENTS

PART 1: GENERAL

CHAPTER 1 GENERAL

1.1—Scope of ACI 318, p. 9 1.2—General, p. 9 1.3—Purpose, p. 10 1.4—Applicability, p. 10 1.5—Interpretation, p. 11 1.6—Building official, p. 12 1.7—Licensed design professional, p. 13 1.8—Construction documents and design records, p. 13 1.9—Testing and inspection, p. 13 1.10—Approval of special systems of design, construction,

or alternative construction materials, p. 13

CHAPTER 2 NOTATION AND TERMINOLOGY

2.1—Scope, p. 15 2.2—Notation, p. 15 2.3—Terminology, p. 30

CHAPTER 3 REFERENCED STANDARDS

3.1—Scope, p. 45 3.2—Referenced standards, p. 45

CHAPTER 4 STRUCTURAL SYSTEM REQUIREMENTS

4.1—Scope ,p. 49 4.2—Materials, p. 49 4.3—Design loads, p. 49 4.4—Structural system and load paths, p. 49 4.5—Structural analysis, p. 52 4.6—Strength, p. 52 4.7—Serviceability, p. 53 4.8—Durability, p. 53 4.9—Sustainability, p. 53 4.10—Structural integrity, p. 54 4.11—Fire resistance, p. 54 4.12—Requirements for specific types of construction,

p. 54 4.13—Construction and inspection, p. 56 4.14—Strength evaluation of existing structures, p. 56

PART 2: LOADS & ANALYSIS

CHAPTER 5 LOADS

5.1—Scope, p. 57 5.2—General, p. 57 5.3—Load factors and combinations, p. 58

CHAPTER 6 STRUCTURAL ANALYSIS

6.1—Scope, p. 63 6.2—General, p. 63 6.3—Modeling assumptions, p. 68 6.4—Arrangement of live load, p. 69 6.5—Simplified method of analysis for nonprestressed

continuous beams and one-way slabs, p. 70 6.6—First-order analysis, p. 71 6.7—Elastic second-order analysis, p. 79 6.8—Inelastic second-order analysis, p. 81 6.9—Acceptability of finite element analysis, p. 81

PART 3: MEMBERS

CHAPTER 7 ONE-WAY SLABS

7.1—Scope, p. 83 7.2—General, p. 83 7.3—Design limits, p. 83 7.4—Required strength, p. 85 7.5—Design strength, p. 85 7.6—Reinforcement limits, p. 86 7.7—Reinforcement detailing, p. 88

CHAPTER 8 TWO-WAY SLABS

8.1—Scope, p. 93 8.2—General, p. 93 8.3—Design limits, p. 94 8.4—Required strength, p. 97 8.5—Design strength, p. 102 8.6—Reinforcement limits, p. 103 8.7—Reinforcement detailing, p. 106 8.8—Nonprestressed two-way joist systems, p. 117 8.9—Lift-slab construction, p. 118 8.10—Direct design method, p. 118 8.11—Equivalent frame method, p. 124

CHAPTER 9 BEAMS

9.1—Scope, p. 129 9.2—General, p. 129 9.3—Design limits, p. 130 9.4—Required strength, p. 132 9.5—Design strength, p. 134 9.6—Reinforcement limits, p. 136 9.7—Reinforcement detailing, p. 140 9.8—Nonprestressed one-way joist systems, p. 149 9.9—Deep beams, p. 151

CHAPTER 10 COLUMNS

10.1—Scope, p. 153 10.2—General, p. 153 10.3—Design limits, p. 153

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6 BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14)

10.4—Required strength, p. 154 10.5—Design strength, p. 155 10.6—Reinforcement limits, p. 156 10.7—Reinforcement detailing, p. 157

CHAPTER 11 WALLS

11.1—Scope, p. 163 11.2—General, p. 163 11.3—Design limits, p. 164 11.4—Required strength, p. 164 11.5—Design strength, p. 165 11.6—Reinforcement limits, p. 168 11.7—Reinforcement detailing, p. 169 11.8—Alternative method for out-of-plane slender wall

analysis, p. 171

CHAPTER 12 DIAPHRAGMS

12.1—Scope, p. 173 12.2—General, p. 173 12.3—Design limits, p. 175 12.4—Required strength, p. 175 12.5—Design strength, p. 178 12.6—Reinforcement limits, p. 185 12.7—Reinforcement detailing, p. 185

CHAPTER 13 FOUNDATIONS

13.1—Scope, p. 187 13.2—General, p. 189 13.3—Shallow foundations, p. 192 13.4—Deep foundations, p. 193

CHAPTER 14 PLAIN CONCRETE

14.1—Scope, p. 195 14.2—General, p. 196 14.3—Design limits, p. 196 14.4—Required strength , p. 198 14.5—Design strength, p. 199 14.6—Reinforcement detailing, p. 202

PART 4: JOINTS/CONNECTIONS/ANCHORS

CHAPTER 15 BEAM-COLUMN AND SLAB-COLUMN JOINTS

15.1—Scope, p. 203 15.2—General, p. 203 15.3—Transfer of column axial force through the floor

system, p. 203 15.4—Detailing of joints, p. 204

CHAPTER 16 CONNECTIONS BETWEEN MEMBERS

16.1—Scope, p. 205 16.2—Connections of precast members, p. 205 16.3—Connections to foundations, p. 209

16.4—Horizontal shear transfer in composite concrete flexural members, p. 212

16.5—Brackets and corbels, p. 214

CHAPTER 17 ANCHORING TO CONCRETE

17.1—Scope, p. 221 17.2—General, p. 222 17.3—General requirements for strength of anchors, p. 228 17.4—Design requirements for tensile loading, p. 234 17.5—Design requirements for shear loading, p. 247 17.6—Interaction of tensile and shear forces, p. 258 17.7—Required edge distances, spacings, and thicknesses

to preclude splitting failure, p. 258 17.8—Installation and inspection of anchors, p. 260

PART 5: EARTHQUAKE RESISTANCE

CHAPTER 18 EARTHQUAKE-RESISTANT STRUCTURES

18.1—Scope, p. 263 18.2—General, p. 263 18.3—Ordinary moment frames, p. 269 18.4—Intermediate moment frames, p. 269 18.5—Intermediate precast structural walls, p. 274 18.6—Beams of special moment frames, p. 275 18.7—Columns of special moment frames, p. 280 18.8—Joints of special moment frames, p. 285 18.9—Special moment frames constructed using precast

concrete, p. 289 18.10—Special structural walls, p. 292 18.11—Special structural walls constructed using precast

concrete, p. 304 18.12—Diaphragms and trusses, p. 304 18.13—Foundations, p. 310 18.14—Members not designated as part of the seismic-

force-resisting system, p. 312

PART 6: MATERIALS & DURABILITY

CHAPTER 19 CONCRETE: DESIGN AND DURABILITY REQUIREMENTS

19.1—Scope, p. 315 19.2—Concrete design properties, p. 315 19.3—Concrete durability requirements, p. 316 19.4—Grout durability requirements, p. 324

CHAPTER 20 STEEL REINFORCEMENT PROPERTIES, DURABILITY, AND EMBEDMENTS

20.1—Scope, p. 325 20.2—Nonprestressed bars and wires, p. 325 20.3—Prestressing strands, wires, and bars, p. 330 20.4—Structural steel, pipe, and tubing for composite

columns, p. 333 20.5—Headed shear stud reinforcement, p. 334

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BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14) 7

20.6—Provisions for durability of steel reinforcement, p. 334

20.7—Embedments, p. 339

PART 7: STRENGTH & SERVICEABILITY

CHAPTER 21 STRENGTH REDUCTION FACTORS

21.1—Scope, p. 341 21.2—Strength reduction factors for structural concrete

members and connections p. 341

CHAPTER 22 SECTIONAL STRENGTH

22.1—Scope, p. 347 22.2—Design assumptions for moment and axial strength,

p. 347 22.3—Flexural strength, p. 349 22.4—Axial strength or combined flexural and axial

strength, p. 350 22.5—One-way shear strength, p. 351 22.6—Two-way shear strength, p. 360 22.7—Torsional strength, p. 371 22.8—Bearing, p. 378 22.9—Shear friction, p. 380

CHAPTER 23 STRUT-AND-TIE MODELS

23.1—Scope, p. 385 23.2—General, p. 386 23.3—Design strength, p. 392 23.4—Strength of struts, p. 392 23.5—Reinforcement crossing bottle-shaped struts, p. 394 23.6—Strut reinforcement detailing, p. 395 23.7—Strength of ties, p. 395 23.8—Tie reinforcement detailing, p. 396 23.9—Strength of nodal zones, p. 397

CHAPTER 24 SERVICEABILITY REQUIREMENTS

24.1—Scope, p. 399 24.2—Deflections due to service-level gravity loads, p. 399 24.3—Distribution of flexural reinforcement in one-way

slabs and beams, p. 403 24.4—Shrinkage and temperature reinforcement, p. 405 24.5—Permissible stresses in prestressed concrete flexural

members, p. 407

PART 8: REINFORCEMENT

CHAPTER 25 REINFORCEMENT DETAILS

25.1—Scope, p. 411 25.2—Minimum spacing of reinforcement, p. 411 25.3—Standard hooks, seismic hooks, crossties, and

minimum inside bend diameters, p. 412

25.4—Development of reinforcement, p. 414 25.5—Splices, p. 428 25.6—Bundled reinforcement, p. 433 25.7—Transverse reinforcement, p. 434 25.8—Post-tensioning anchorages and couplers, p. 443 25.9—Anchorage zones for post-tensioned tendons, p. 443

PART 9: CONSTRUCTION

CHAPTER 26 CONSTRUCTION DOCUMENTS AND INSPECTION

26.1—Scope, p. 453 26.2—Design criteria, p. 455 26.3—Member information, p. 455 26.4—Concrete materials and mixture requirements, p. 455 26.5—Concrete production and construction, p. 462 26.6—Reinforcement materials and construction

requirements, p. 468 26.7—Anchoring to concrete , p. 472 26.8—Embedments, p. 473 26.9—Additional requirements for precast concrete , p. 473 26.10—Additional requirements for prestressed concrete,

p. 474 26.11—Formwork, p. 476 26.12—Concrete evaluation and acceptance, p. 478 26.13—Inspection, p. 483

PART 10: EVALUATION

CHAPTER 27 STRENGTH EVALUATION OF EXISTING STRUCTURES

27.1—Scope, p. 487 27.2—General, p. 487 27.3—Analytical strength evaluation, p. 488 27.4—Strength evaluation by load test, p. 489 27.5—Reduced load rating, p. 492

REFERENCES & APPENDICES

COMMENTARY REFERENCES

APPENDIX A STEEL REINFORCEMENT INFORMATION

APPENDIX B EQUIVALENCE BETWEEN SI-METRIC, MKS-METRIC, AND U.S. CUSTOMARY UNITS OF NONHOMOGENOUS EQUATIONS IN THE CODE

INDEX

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8 BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14)

CHAPTER 1—GENERAL

1.1—Scope of ACI 318 1.1.1 This chapter addresses (a) through (h):

(a) General requirements of this Code (b) Purpose of this Code (c) Applicability of this Code (d) Interpretation of this Code (e) Definition and role of the building official and the licensed design professional (f) Construction documents (g) Testing and inspection (h) Approval of special systems of design, construction, or alternative construction materials

1.2—General 1.2.1 ACI 318, “Building Code Requirements for Struc-

tural Concrete,” is hereafter referred to as “this Code.”

1.2.2 In this Code, the general building code refers to the building code adopted in a jurisdiction. When adopted, this Code forms part of the general building code.

1.2.3 The official version of this Code is the English language version, using inch-pound units, published by the American Concrete Institute.

1.2.4 In case of conflict between the official version of this Code and other versions of this Code, the official version governs.

1.2.5 This Code provides minimum requirements for the materials, design, construction, and strength evaluation of structural concrete members and systems in any structure designed and constructed under the requirements of the general building code.

1.2.6 Modifications to this Code that are adopted by a particular jurisdiction are part of the laws of that jurisdic- tion, but are not a part of this Code.

1.2.7 If no general building code is adopted, this Code provides minimum requirements for the materials, design, construction, and strength evaluation of members and systems in any structure within the scope of this Code.

R1—GENERAL

R1.1—Scope of ACI 318 R1.1.1 This Code includes provisions for the design

of concrete used for structural purposes, including plain concrete; concrete containing nonprestressed reinforcement, prestressed reinforcement, or both; composite columns with structural steel shapes, pipes, or tubing; and anchoring to concrete.

This Code is substantially reorganized from the previous version, ACI 318M-11. This chapter includes a number of provisions that explain where this Code applies and how it is to be interpreted.

R1.2—General

R1.2.2 The American Concrete Institute recommends that this Code be adopted in its entirety.

R1.2.3 Committee 318 develops the Code in English, using inch-pound units. Based on that version, Committee 318 approved three other versions:

(a) In English using SI units (ACI 318M) (b) In Spanish using SI units (ACI 318S) (c) In Spanish using inch-pound units (ACI 318SUS).

Jurisdictions may adopt ACI 318, ACI 318M, ACI 318S, or ACI 318SUS.

R1.2.5 This Code provides minimum requirements and exceeding these minimum requirements is not a violation of the Code.

The licensed design professional may specify project requirements that exceed the minimum requirements of this Code.

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1.3—Purpose 1.3.1 The purpose of this Code is to provide for public

health and safety by establishing minimum requirements for strength, stability, serviceability, durability, and integrity of concrete structures.

1.3.2 This Code does not address all design considerations.

1.3.3 Construction means and methods are not addressed in this Code.

1.4—Applicability 1.4.1 This Code shall apply to concrete structures designed

and constructed under the requirements of the general building code.

1.4.2 Applicable provisions of this Code shall be permitted to be used for structures not governed by the general building code.

1.4.3 The design of thin shells and folded plate concrete structures shall be in accordance with ACI 318.2, “Building Code Requirements for Concrete Thin Shells.”

1.4.4 This Code shall apply to the design of slabs cast on stay-in-place, noncomposite steel decks.

1.4.5 For one- and two-family dwellings, multiple single- family dwellings, townhouses, and accessory structures to

R1.3—Purpose R1.3.1 This Code provides a means of establishing

minimum requirements for the design and construction of structural concrete, as well as for acceptance of design and construction of concrete structures by the building officials or their designated representatives.

This Code does not provide a comprehensive statement of all duties of all parties to a contract or all requirements of a contract for a project constructed under this Code.

R1.3.2 The minimum requirements in this Code do not replace sound professional judgment or the licensed design professional’s knowledge of the specific factors surrounding a project, its design, the project site, and other specific or unusual circumstances to the project.

R1.4—Applicability

R1.4.2 Structures such as arches, bins and silos, blast- resistant structures, chimneys, underground utility struc- tures, gravity walls, and shielding walls involve design and construction requirements that are not specifically addressed by this Code. Many Code provisions, however, such as concrete quality and design principles, are applicable for these structures. Recommendations for design and construc- tion of some of these structures are given in the following: • “Code Requirements for Reinforced Concrete Chim-

neys and Commentary” (ACI 307-08) • “Standard Practice for Design and Construction of

Concrete Silos and Stacking Tubes for Storing Granular Materials” (ACI 313-97)

• “Code Requirements for Nuclear Safety-Related Concrete Structures and Commentary” (ACI 349)

• “Code for Concrete Containments” (ACI 359)

R1.4.4 In its most basic application, the noncomposite steel deck serves as a form, and the concrete slab is designed to resist all loads, while in other applications the concrete slab may be designed to resist only the superimposed loads. The design of a steel deck in a load-resisting application is given in “Standard for Non-Composite Steel Floor Deck” (SDI NC). The SDI standard refers to this Code for the design and construction of the structural concrete slab.

R1.4.5 ACI 332 addresses only the design and construc- tion of cast-in-place footings, foundation walls supported on

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these types of dwellings, the design and construction of cast- in-place footings, foundation walls, and slabs-on-ground in accordance with ACI 332 shall be permitted.

1.4.6 This Code does not apply to the design and installa- tion of concrete piles, drilled piers, and caissons embedded in ground, except as provided in (a) or (b):

(a) For portions in air or water, or in soil incapable of providing adequate lateral restraint to prevent buckling throughout their length (b) For structures assigned to Seismic Design Categories D, E, and F

1.4.7 This Code does not apply to design and construction of slabs-on-ground, unless the slab transmits vertical loads or lateral forces from other portions of the structure to the soil.

1.4.8 This Code does not apply to the design and construc- tion of tanks and reservoirs.

1.4.9 This Code does not apply to composite design slabs cast on stay-in-place composite steel deck. Concrete used in the construction of such slabs shall be governed by this Code, where applicable. Portions of such slabs designed as reinforced concrete are governed by this Code.

1.5—Interpretation 1.5.1 The principles of interpretation in this section shall

apply to this Code as a whole unless otherwise stated.

continuous footings, and slabs-on-ground for limited resi- dential construction applications. Multiple single-family dwellings include structures such as townhomes.

R1.4.6 The design and installation of concrete piles fully embedded in the ground is regulated by the general building code. Recommendations for concrete piles are given in ACI 543R. Recommendations for drilled piers are given in ACI 336.3R. Recommendations for precast prestressed concrete piles are given in “Recommended Practice for Design, Manufacture, and Installation of Prestressed Concrete Piling” (PCI 1993).

Refer to 18.13.4 for supplemental requirements for concrete piles, drilled piers, and caissons in structures assigned to Seismic Design Categories D, E, and F.

R1.4.7 Detailed recommendations for design and construction of slabs-on-ground and floors that do not transmit vertical loads or lateral forces from other portions of the structure to the soil, and residential post-tensioned slabs-on-ground, are given in the following publications: • ACI 360R presents information on the design of slabs-

on-ground, primarily industrial floors and the slabs adjacent to them. The report addresses the planning, design, and detailing of the slabs. Background informa- tion on the design theories is followed by discussion of the soil support system, loadings, and types of slabs. Design methods are given for structural plain concrete, reinforced concrete, shrinkage-compensating concrete, and post-tensioned concrete slabs.

• The Post-Tensioning Institute (DC 10.5-12) provides standard requirements for post-tensioned slab-on- ground foundations, soil investigation, design, and anal- ysis of post-tensioned residential and light commercial slabs on expansive soils.

R1.4.8 Requirements and recommendations for the design and construction of tanks and reservoirs are given in ACI 350, ACI 334.1R, and ACI 372R.

R1.4.9 In this type of construction, the steel deck serves as the positive moment reinforcement. The design and construction of concrete-steel deck slabs is described in “Standard for Composite Steel Floor Deck-Slabs” (SDI C). The standard refers to the appropriate portions of this Code for the design and construction of the concrete portion of the composite assembly. SDI C also provides guidance for design of composite-concrete-steel deck slabs. The design of negative moment reinforcement to create continuity at supports is a common example where a portion of the slab is designed in conformance with this Code.

R1.5—Interpretation

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1.5.2 This Code consists of chapters and appendixes, including text, headings, tables, figures, footnotes to tables and figures, and referenced standards.

1.5.3 The Commentary consists of a preface, introduction, commentary text, tables, figures, and cited publications. The Commentary is intended to provide contextual informa- tion, but is not part of this Code, does not provide binding requirements, and shall not be used to create a conflict with or ambiguity in this Code.

1.5.4 This Code shall be interpreted in a manner that avoids conflict between or among its provisions. Specific provisions shall govern over general provisions.

1.5.5 This Code shall be interpreted and applied in accor- dance with the plain meaning of the words and terms used. Specific definitions of words and terms in this Code shall be used where provided and applicable, regardless of whether other materials, standards, or resources outside of this Code provide a different definition.

1.5.6 The following words and terms in this Code shall be interpreted in accordance with (a) through (e):

(a) The word “shall” is always mandatory. (b) Provisions of this Code are mandatory even if the word “shall” is not used. (c) Words used in the present tense shall include the future. (d) The word “and” indicates that all of the connected items, conditions, requirements, or events shall apply. (e) The word “or” indicates that the connected items, conditions, requirements, or events are alternatives, at least one of which shall be satisfied.

1.5.7 In any case in which one or more provisions of this Code are declared by a court or tribunal to be invalid, that ruling shall not affect the validity of the remaining provi- sions of this Code, which are severable. The ruling of a court or tribunal shall be effective only in that court’s jurisdiction, and shall not affect the content or interpretation of this Code in other jurisdictions.

1.5.8 If conflicts occur between provisions of this Code and those of standards and documents referenced in Chapter 3, this Code shall apply.

1.6—Building official 1.6.1 All references in this Code to the building official

shall be understood to mean persons who administer and enforce this Code.

1.6.2 Actions and decisions by the building official affect only the specific jurisdiction and do not change this Code.

R1.5.4 General provisions are broad statements, such as a building needs to be serviceable. Specific provisions, such as explicit reinforcement distribution requirements for crack control, govern over the general provisions.

R1.5.5 ACI Concrete Terminology (2013) is the primary resource to help determine the meaning of words or terms that are not defined in the Code. Dictionaries and other refer- ence materials commonly used by licensed design profes- sionals may be used as secondary resources.

R.1.5.7 This Code addresses numerous requirements that can be implemented fully without modification if other requirements in this Code are determined to be invalid. This severability requirement is intended to preserve this Code and allow it to be implemented to the extent possible following legal decisions affecting one or more of its provisions.

R1.6—Building official R1.6.1 Building official is defined in 2.3.

R1.6.2 Only the American Concrete Institute has the authority to alter or amend this Code.

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1.6.3 The building official shall have the right to order testing of any materials used in concrete construction to determine if materials are of the quality specified.

1.7—Licensed design professional 1.7.1 All references in this Code to the licensed design

professional shall be understood to mean the person who is licensed and responsible for, and in charge of, the structural design or inspection.

1.8—Construction documents and design records 1.8.1 The licensed design professional shall provide in the

construction documents the information required in Chapter 26 and that required by the jurisdiction.

1.8.2 Calculations pertinent to design shall be filed with the construction documents if required by the building offi- cial. Analyses and designs using computer programs shall be permitted provided design assumptions, user input, and computer-generated output are submitted. Model analysis shall be permitted to supplement calculations.

1.9—Testing and inspection 1.9.1 Concrete materials shall be tested in accordance with

the requirements of Chapter 26.

1.9.2 Concrete construction shall be inspected in accor- dance with the general building code and in accordance with Chapters 17 and 26.

1.9.3 Inspection records shall include information required in Chapters 17 and 26.

1.10—Approval of special systems of design, construction, or alternative construction materials

1.10.1 Sponsors of any system of design, construction, or alternative construction materials within the scope of this Code, the adequacy of which has been shown by successful use or by analysis or test, but which does not conform to or is not covered by this Code, shall have the right to present the data on which their design is based to the building official

R1.7—Licensed design professional R1.7.1 Licensed design professional is defined in 2.3.

R1.8—Construction documents and design records R1.8.1 The provisions of Chapter 26 for preparing project

drawings and specifications are, in general, consistent with those of most general building codes. Additional informa- tion may be required by the building official.

R1.8.2 Documented computer output is acceptable instead of manual calculations. The extent of input and output information required will vary according to the specific requirements of individual building officials. However, if a computer program has been used, only skeleton data should normally be required. This should consist of sufficient input and output data and other information to allow the building official to perform a detailed review and make compari- sons using another program or manual calculations. Input data should be identified as to member designation, applied loads, and span lengths. The related output data should include member designation and the shears, moments, and reactions at key points in the span. For column design, it is desirable to include moment magnification factors in the output where applicable.

The Code permits model analysis to be used to supple- ment structural analysis and design calculations. Documen- tation of the model analysis should be provided with the related calculations. Model analysis should be performed by an individual having experience in this technique.

R1.10—Approval of special systems of design, construction, or alternative construction materials

R1.10.1 New methods of design, new materials, and new uses of materials should undergo a period of development before being covered in a code. Hence, good systems or components might be excluded from use by implication if means were not available to obtain acceptance.

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or to a board of examiners appointed by the building offi- cial. This board shall be composed of competent engineers and shall have authority to investigate the data so submitted, require tests, and formulate rules governing design and construction of such systems to meet the intent of this Code. These rules, when approved by the building official and promulgated, shall be of the same force and effect as the provisions of this Code.

For special systems considered under this section, specific tests, load factors, deflection limits, and other pertinent requirements should be set by the board of examiners, and should be consistent with the intent of the Code.

The provisions of this section do not apply to model tests used to supplement calculations under 1.8.2 or to strength evaluation of existing structures under Chapter 27.

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CHAPTER 2—NOTATION AND TERMINOLOGY

2.1—Scope 2.1.1 This chapter defines notation and terminology used

in this Code.

2.2—Notation a = depth of equivalent rectangular stress block, mm av = shear span, equal to distance from center of concen-

trated load to either: (a) face of support for contin- uous or cantilevered members, or (b) center of support for simply supported members, mm

Ab = area of an individual bar or wire, mm2 Abrg = net bearing area of the head of stud, anchor bolt, or

headed deformed bar, mm2 Ac = area of concrete section resisting shear transfer, mm2 Acf = greater gross cross-sectional area of the slab-beam

strips of the two orthogonal equivalent frames intersecting at a column of a two-way slab, mm2

Ach = cross-sectional area of a member measured to the outside edges of transverse reinforcement, mm2

Acp = area enclosed by outside perimeter of concrete cross section, mm2

Acs = cross-sectional area at one end of a strut in a strut- and-tie model, taken perpendicular to the axis of the strut, mm2

Act = area of that part of cross section between the flex- ural tension face and centroid of gross section, mm2

Acv = gross area of concrete section bounded by web thickness and length of section in the direction of shear force considered in the case of walls, and gross area of concrete section in the case of diaphragms, not to exceed the thickness times the width of the diaphragm, mm2

Acw = area of concrete section of an individual pier, hori- zontal wall segment, or coupling beam resisting shear, mm2

Af = area of reinforcement in bracket or corbel resisting design moment, mm2

Ag = gross area of concrete section, mm2 For a hollow section, Ag is the area of the concrete only and does not include the area of the void(s)

Ah = total area of shear reinforcement parallel to primary tension reinforcement in a corbel or bracket, mm2

Aj = effective cross-sectional area within a joint in a plane parallel to plane of beam reinforcement generating shear in the joint, mm2

Aℓ = total area of longitudinal reinforcement to resist torsion, mm2

Aℓ,min = minimum area of longitudinal reinforcement to resist torsion, mm2

An = area of reinforcement in bracket or corbel resisting factored tensile force Nuc, mm2

Anz = area of a face of a nodal zone or a section through a nodal zone, mm2

R2—NOTATION AND TERMINOLOGY

R2.2—Notation

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ANa = projected influence area of a single adhesive anchor or group of adhesive anchors, for calculation of bond strength in tension, mm2

ANao = projected influence area of a single adhesive anchor, for calculation of bond strength in tension if not limited by edge distance or spacing, mm2

ANc = projected concrete failure area of a single anchor or group of anchors, for calculation of strength in tension, mm2

ANco = projected concrete failure area of a single anchor, for calculation of strength in tension if not limited by edge distance or spacing, mm2

Ao = gross area enclosed by torsional shear flow path, mm2

Aoh = area enclosed by centerline of the outermost closed transverse torsional reinforcement, mm2

Apd = total area occupied by duct, sheathing, and prestressing reinforcement, mm2

Aps = area of prestressed longitudinal tension reinforce- ment, mm2

Apt = total area of prestressing reinforcement, mm2 As = area of nonprestressed longitudinal tension rein-

forcement, mm2 As′ = area of compression reinforcement, mm2 Asc = area of primary tension reinforcement in a corbel or

bracket, mm2 Ase,N = effective cross-sectional area of anchor in tension,

mm2 Ase,V = effective cross-sectional area of anchor in shear,

mm2 Ash = total cross-sectional area of transverse reinforce-

ment, including crossties, within spacing s and perpendicular to dimension bc, mm2

Asi = total area of surface reinforcement at spacing si in the i-th layer crossing a strut, with reinforcement at an angle αi to the axis of the strut, mm2

As,min = minimum area of flexural reinforcement, mm2 Ast = total area of nonprestressed longitudinal reinforce-

ment including bars or steel shapes, and excluding prestressing reinforcement, mm2

Asx = area of steel shape, pipe, or tubing in a composite section, mm2

At = area of one leg of a closed stirrup, hoop, or tie resisting torsion within spacing s, mm2

Atp = area of prestressing reinforcement in a tie, mm2 Atr = total cross-sectional area of all transverse reinforce-

ment within spacing s that crosses the potential plane of splitting through the reinforcement being developed, mm2

Ats = area of nonprestressed reinforcement in a tie, mm2 Av = area of shear reinforcement within spacing s, mm2 Avd = total area of reinforcement in each group of diag-

onal bars in a diagonally reinforced coupling beam, mm2

Avf = area of shear-friction reinforcement, mm2

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Avh = area of shear reinforcement parallel to flexural tension reinforcement within spacing s2, mm2

Av,min = minimum area of shear reinforcement within spacing s, mm2

AVc = projected concrete failure area of a single anchor or group of anchors, for calculation of strength in shear, mm2

AVco = projected concrete failure area of a single anchor, for calculation of strength in shear, if not limited by corner influences, spacing, or member thickness, mm2

A1 = loaded area for consideration of bearing strength, mm2

A2 = area of the lower base of the largest frustum of a pyramid, cone, or tapered wedge contained wholly within the support and having its upper base equal to the loaded area. The sides of the pyramid, cone, or tapered wedge shall be sloped one vertical to two horizontal, mm2

b = width of compression face of member, mm bc = cross-sectional dimension of member core

measured to the outside edges of the transverse reinforcement composing area Ash, mm

bf = effective flange width of T section, mm bo = perimeter of critical section for two-way shear in

slabs and footings, mm bs = width of strut, mm bslab = effective slab width resisting γfMsc, mm bt = width of that part of cross section containing the

closed stirrups resisting torsion, mm bv = width of cross section at contact surface being

investigated for horizontal shear, mm bw = web width or diameter of circular section, mm b1 = dimension of the critical section bo measured in the

direction of the span for which moments are deter- mined, mm

b2 = dimension of the critical section bo measured in the direction perpendicular to b1, mm

Bn = nominal bearing strength, N Bu = factored bearing load, N c = distance from extreme compression fiber to neutral

axis, mm cac = critical edge distance required to develop the basic

strength as controlled by concrete breakout or bond of a post-installed anchor in tension in uncracked concrete without supplementary reinforcement to control splitting, mm

ca,max = maximum distance from center of an anchor shaft to the edge of concrete, mm

ca,min = minimum distance from center of an anchor shaft to the edge of concrete, mm

ca1 = distance from the center of an anchor shaft to the edge of concrete in one direction, mm If shear is applied to anchor, ca1 is taken in the direction of the applied shear. If tension is applied to the anchor, ca1 is the minimum edge distance. Where anchors

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c′a1 = limiting value of ca1 where anchors are located less than 1.5ca1 from three or more edges, mm; see Fig. R17.5.2.4

C = compressive force acting on a nodal zone, N

dburst = distance from the anchorage device to the centroid of the bursting force, Tburst, N

eanc = eccentricity of the anchorage device or group of devices with respect to the centroid of the cross section, mm

subject to shear are located in narrow sections of limited thickness, see 17.5.2.4

ca2 = distance from center of an anchor shaft to the edge of concrete in the direction perpendicular to ca1, mm

cb = lesser of: (a) the distance from center of a bar or wire to nearest concrete surface, and (b) one-half the center-to-center spacing of bars or wires being developed, mm

cc = clear cover of reinforcement, mm cNa = projected distance from center of an anchor shaft

on one side of the anchor required to develop the full bond strength of a single adhesive anchor, mm

ct = distance from the interior face of the column to the slab edge measured parallel to c1, but not exceeding c1, mm

c1 = dimension of rectangular or equivalent rectangular column, capital, or bracket measured in the direc- tion of the span for which moments are being deter- mined, mm

c2 = dimension of rectangular or equivalent rectangular column, capital, or bracket measured in the direc- tion perpendicular to c1, mm

C = cross-sectional constant to define torsional proper- ties of slab and beam

Cm = factor relating actual moment diagram to an equiv- alent uniform moment diagram

d = distance from extreme compression fiber to centroid of longitudinal tension reinforcement, mm

d′ = distance from extreme compression fiber to centroid of longitudinal compression reinforcement, mm

da = outside diameter of anchor or shaft diameter of headed stud, headed bolt, or hooked bolt, mm

da′ = value substituted for da if an oversized anchor is used, mm

dagg = nominal maximum size of coarse aggregate, mm db = nominal diameter of bar, wire, or prestressing

strand, mm

dp = distance from extreme compression fiber to centroid of prestressing reinforcement, mm

dpile = diameter of pile at footing base, mm D = effect of service dead load

eh = distance from the inner surface of the shaft of a J- or L-bolt to the outer tip of the J- or L-bolt, mm

e′N = distance between resultant tension load on a group of anchors loaded in tension and the centroid of the group of anchors loaded in tension, mm; eN′ is always positive

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e′V = distance between resultant shear load on a group of anchors loaded in shear in the same direction, and the centroid of the group of anchors loaded in shear in the same direction, mm; eV′ is always positive

E = effect of horizontal and vertical earthquake-induced forces

Ec = modulus of elasticity of concrete, MPa Ecb = modulus of elasticity of beam concrete, MPa Ecs = modulus of elasticity of slab concrete, MPa EI = flexural stiffness of member, N-mm2 (EI)eff = effective flexural stiffness of member, N-mm2 Ep = modulus of elasticity of prestressing reinforcement,

MPa Es = modulus of elasticity of reinforcement and struc-

tural steel, excluding prestressing reinforcement, MPa

fc′ = specified compressive strength of concrete, MPa ′fc = square root of specified compressive strength of

concrete, MPa fci′ = specified compressive strength of concrete at time

of initial prestress, MPa ′fci = square root of specified compressive strength of

concrete at time of initial prestress, MPa fce = effective compressive strength of the concrete in a

strut or a nodal zone, MPa fcm = measured average compressive strength of concrete,

MPa fct = measured average splitting tensile strength of light-

weight concrete, MPa fd = stress due to unfactored dead load, at extreme fiber

of section where tensile stress is caused by exter- nally applied loads, MPa

fdc = decompression stress; stress in the prestressing reinforcement if stress is zero in the concrete at the same level as the centroid of the prestressing rein- forcement, MPa

fpc = compressive stress in concrete, after allowance for all prestress losses, at centroid of cross section resisting externally applied loads or at junction of web and flange where the centroid lies within the flange, MPa. In a composite member, fpc is the resul- tant compressive stress at centroid of composite section, or at junction of web and flange where the centroid lies within the flange, due to both prestress and moments resisted by precast member acting alone

fpe = compressive stress in concrete due only to effective prestress forces, after allowance for all prestress losses, at extreme fiber of section if tensile stress is caused by externally applied loads, MPa

fps = stress in prestressing reinforcement at nominal flexural strength, MPa

fpu = specified tensile strength of prestressing reinforce- ment, MPa

fpy = specified yield strength of prestressing reinforce- ment, MPa

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fr = modulus of rupture of concrete, MPa fs = tensile stress in reinforcement at service loads,

excluding prestressing reinforcement, MPa fs′ = compressive stress in reinforcement under factored

loads, excluding prestressing reinforcement, MPa fse = effective stress in prestressing reinforcement, after

allowance for all prestress losses, MPa

ft = extreme fiber stress in the precompressed tension zone calculated at service loads using gross section properties after allowance of all prestress losses, MPa

futa = specified tensile strength of anchor steel, MPa fy = specified yield strength for nonprestressed rein-

forcement, MPa fya = specified yield strength of anchor steel, MPa fyt = specified yield strength of transverse reinforce-

ment, MPa F = effect of service lateral load due to fluids with well-

defined pressures and maximum heights Fnn = nominal strength at face of a nodal zone, N Fns = nominal strength of a strut, N Fnt = nominal strength of a tie, N Fun = factored force on the face of a node, N Fus = factored compressive force in a strut, N Fut = factored tensile force in a tie, N h = overall thickness, height, or depth of member, mm ha = thickness of member in which an anchor is located,

measured parallel to anchor axis, mm

hef = effective embedment depth of anchor, mm

hsx = story height for story x, mm hu = laterally unsupported height at extreme compres-

sion fiber of wall or wall pier, mm, equivalent to ℓu for compression members

hv = depth of shearhead cross section, mm hw = height of entire wall from base to top, or clear

height of wall segment or wall pier considered, mm hx = maximum center-to-center spacing of longitudinal

bars laterally supported by corners of crossties or hoop legs around the perimeter of the column, mm

H = effect of service load due to lateral earth pressure, ground water pressure, or pressure of bulk mate- rials, N

I = moment of inertia of section about centroidal axis, mm4

Ib = moment of inertia of gross section of beam about centroidal axis, mm4

Icr = moment of inertia of cracked section transformed to concrete, mm4

Ie = effective moment of inertia for calculation of deflection, mm4

fsi = stress in the i-th layer of surface reinforcement, MPa

hanc = dimension of anchorage device or single group of closely spaced devices in the direction of bursting being considered, mm

h′ef = limiting value of hef where anchors are located less than 1.5hef from three or more edges, mm; refer to Fig. R17.4.2.3

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Ig = moment of inertia of gross concrete section about centroidal axis, neglecting reinforcement, mm4

Is = moment of inertia of gross section of slab about centroidal axis, mm4

Ise = moment of inertia of reinforcement about centroidal axis of member cross section, mm4

Isx = moment of inertia of structural steel shape, pipe, or tubing about centroidal axis of composite member cross section, mm4

k = effective length factor for compression members kc = coefficient for basic concrete breakout strength in

tension kcp = coefficient for pryout strength kf = concrete strength factor kn = confinement effectiveness factor

Ktr = transverse reinforcement index, mm

ℓ = span length of beam or one-way slab; clear projec- tion of cantilever, mm

ℓa = additional embedment length beyond centerline of support or point of inflection, mm

ℓc = length of compression member, measured center- to-center of the joints, mm

ℓd = development length in tension of deformed bar, deformed wire, plain and deformed welded wire reinforcement, or pretensioned strand, mm

ℓdc = development length in compression of deformed bars and deformed wire, mm

ℓdb = debonded length of prestressed reinforcement at end of member, mm

ℓdh = development length in tension of deformed bar or deformed wire with a standard hook, measured from outside end of hook, point of tangency, toward critical section, mm

ℓdt = development length in tension of headed deformed bar, measured from the bearing face of the head toward the critical section, mm

ℓe = load bearing length of anchor for shear, mm ℓext = straight extension at the end of a standard hook, mm ℓn = length of clear span measured face-to-face of

supports, mm ℓo = length, measured from joint face along axis of

member, over which special transverse reinforce- ment must be provided, mm

ℓsc = compression lap splice length, mm ℓst = tension lap splice length, mm ℓt = span of member under load test, taken as the shorter

span for two-way slab systems, mm. Span is the lesser of: (a) distance between centers of supports, and (b) clear distance between supports plus thick- ness h of member. Span for a cantilever shall be

Kt = torsional stiffness of member; moment per unit rotation

K05 = coefficient associated with the 5 percent fractile

ℓanc = length along which anchorage of a tie must occur, mm

ℓb = width of bearing, mm

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CODE COMMENTARY 2

taken as twice the distance from face of support to cantilever end

ℓtr = transfer length of prestressed reinforcement, mm ℓu = unsupported length of column or wall, mm ℓv = length of shearhead arm from centroid of concen-

trated load or reaction, mm ℓw = length of entire wall, or length of wall segment or

wall pier considered in direction of shear force, mm ℓ1 = length of span in direction that moments are being

determined, measured center-to-center of supports, mm

ℓ2 = length of span in direction perpendicular to ℓ1, measured center-to-center of supports, mm

L = effect of service live load Lr = effect of service roof live load

Ma = maximum moment in member due to service loads at stage deflection is calculated, N-mm

Mc = factored moment amplified for the effects of member curvature used for design of compression member, N-mm

Mcr = cracking moment, N-mm Mcre = moment causing flexural cracking at section due to

externally applied loads, N-mm Mmax = maximum factored moment at section due to exter-

nally applied loads, N-mm Mn = nominal flexural strength at section, N-mm Mnb = nominal flexural strength of beam including slab

where in tension, framing into joint, N-mm Mnc = nominal flexural strength of column framing into

joint, calculated for factored axial force, consis- tent with the direction of lateral forces considered, resulting in lowest flexural strength, N-mm

Mo = total factored static moment, N-mm Mp = required plastic moment strength of shearhead

cross section, N-mm Mpr = probable flexural strength of members, with or

without axial load, determined using the proper- ties of the member at joint faces assuming a tensile stress in the longitudinal bars of at least 1.25fy and a strength reduction factor ϕ of 1.0, N-mm

Msa = maximum moment in wall due to service loads, excluding P∆ effects, N-mm

Msc = factored slab moment that is resisted by the column at a joint, N-mm

Mu = factored moment at section, N-mm Mua = moment at midheight of wall due to factored lateral

and eccentric vertical loads, not including P∆ effects, N-mm

Mv = moment resistance contributed by shearhead rein- forcement, N-mm

M1 = lesser factored end moment on a compression member, N-mm

M1ns = factored end moment on a compression member at the end at which M1 acts, due to loads that cause no

M = moment acting on anchor or anchor group, N-mm

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appreciable sidesway, calculated using a first-order elastic frame analysis, N-mm

M1s = factored end moment on compression member at the end at which M1 acts, due to loads that cause appreciable sidesway, calculated using a first-order elastic frame analysis, N-mm

M2 = greater factored end moment on a compression member. If transverse loading occurs between supports, M2 is taken as the largest moment occur- ring in member. Value of M2 is always positive, N-mm

M2,min = minimum value of M2, N-mm M2ns = factored end moment on compression member at

the end at which M2 acts, due to loads that cause no appreciable sidesway, calculated using a first-order elastic frame analysis, N-mm

M2s = factored end moment on compression member at the end at which M2 acts, due to loads that cause appreciable sidesway, calculated using a first-order elastic frame analysis, N-mm

n = number of items, such as, bars, wires, monostrand anchorage devices, anchors, or shearhead arms

nℓ = number of longitudinal bars around the perimeter of a column core with rectilinear hoops that are later- ally supported by the corner of hoops or by seismic hooks. A bundle of bars is counted as a single bar

Na = nominal bond strength in tension of a single adhe- sive anchor, N

Nag = nominal bond strength in tension of a group of adhesive anchors, N

Nb = basic concrete breakout strength in tension of a single anchor in cracked concrete, N

Nba = basic bond strength in tension of a single adhesive anchor, N

Nc = resultant tensile force acting on the portion of the concrete cross section that is subjected to tensile stresses due to the combined effects of service loads and effective prestress, N

Ncb = nominal concrete breakout strength in tension of a single anchor, N

Ncbg = nominal concrete breakout strength in tension of a group of anchors, N

Ncp = basic concrete pryout strength of a single anchor, N Ncpg = basic concrete pryout strength of a group of

anchors, N Nn = nominal strength in tension, N Np = pullout strength in tension of a single anchor in

cracked concrete, N Npn = nominal pullout strength in tension of a single

anchor, N Nsa = nominal strength of a single anchor or individual

anchor in a group of anchors in tension as governed by the steel strength, N

Nsb = side-face blowout strength of a single anchor, N

nt = number of threads per inch N = tension force acting on anchor or anchor group, N

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CODE COMMENTARY 2

Nsbg = side-face blowout strength of a group of anchors, N Nu = factored axial force normal to cross section occur-

ring simultaneously with Vu or Tu; to be taken as positive for compression and negative for tension, N

Nua = factored tensile force applied to anchor or indi- vidual anchor in a group of anchors, N

Nua,g = total factored tensile force applied to anchor group, N

Nua,i = factored tensile force applied to most highly stressed anchor in a group of anchors, N

Nua,s = factored sustained tension load, N Nuc = factored horizontal tensile force applied at top of

bracket or corbel acting simultaneously with Vu, to be taken as positive for tension, N

pcp = outside perimeter of concrete cross section, mm ph = perimeter of centerline of outermost closed trans-

verse torsional reinforcement, mm

Pc = critical buckling load, N Pn = nominal axial compressive strength of member, N Pn,max = maximum nominal axial compressive strength of a

member, N Pnt = nominal axial tensile strength of member, N Pnt,max = maximum nominal axial tensile strength of member,

N Po = nominal axial strength at zero eccentricity, N Ppu = factored prestressing force at anchorage device, N Ps = unfactored axial load at the design, midheight

section including effects of self-weight, N Pu = factored axial force; to be taken as positive for

compression and negative for tension, N PΔ = secondary moment due to lateral deflection, N-mm qDu = factored dead load per unit area, N/m2 qLu = factored live load per unit area, N/m2 qu = factored load per unit area, N/m2 Q = stability index for a story r = radius of gyration of cross section, mm R = cumulative load effect of service rain load s = center-to-center spacing of items, such as longi-

tudinal reinforcement, transverse reinforcement, tendons, or anchors, mm

si = center-to-center spacing of reinforcement in the i-th direction adjacent to the surface of the member, mm

so = center-to-center spacing of transverse reinforce- ment within the length ℓo, mm

ss = sample standard deviation, MPa sw = clear distance between adjacent webs, mm s2 = center-to-center spacing of longitudinal shear or

torsional reinforcement, mm S = effect of service snow load Se = moment, shear, or axial force at connection corre-

sponding to development of probable strength at intended yield locations, based on the governing

Pδ = secondary moment due to individual member slen- derness, N-mm

R = reaction, N

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mechanism of inelastic lateral deformation, consid- ering both gravity and earthquake effects

Sm = elastic section modulus, mm3 Sn = nominal moment, shear, axial, torsional, or bearing

strength Sy = yield strength of connection, based on fy of the

connected part, for moment, shear, or axial force, MPa t = wall thickness of hollow section, mm tf = thickness of flange, mm T = cumulative effects of service temperature, creep,

shrinkage, differential settlement, and shrinkage- compensating concrete

Tcr = cracking torsional moment, N-mm Tt = total test load, N Tth = threshold torsional moment, N-mm Tn = nominal torsional moment strength, N-mm Tu = factored torsional moment at section, N-mm U = strength of a member or cross section required to

resist factored loads or related internal moments and forces in such combinations as stipulated in this Code

vc = stress corresponding to nominal two-way shear strength provided by concrete, MPa

vn = equivalent concrete stress corresponding to nominal two-way shear strength of slab or footing, MPa

vs = equivalent concrete stress corresponding to nominal two-way shear strength provided by reinforcement, MPa

vu = maximum factored two-way shear stress calculated around the perimeter of a given critical section, MPa

vug = factored shear stress on the slab critical section for two-way action due to gravity loads without moment transfer, MPa

Vb = basic concrete breakout strength in shear of a single anchor in cracked concrete, N

Vc = nominal shear strength provided by concrete, N Vcb = nominal concrete breakout strength in shear of a

single anchor, N Vcbg = nominal concrete breakout strength in shear of a

group of anchors, N Vci = nominal shear strength provided by concrete where

diagonal cracking results from combined shear and moment, N

Vcp = nominal concrete pryout strength of a single anchor, N

Vcpg = nominal concrete pryout strength of a group of anchors, N

Vcw = nominal shear strength provided by concrete where diagonal cracking results from high principal tensile stress in web, N

T = tension force acting on a nodal zone in a strut-and- tie model, N (T is also used to define the cumula- tive effects of service temperature, creep, shrinkage, differential settlement, and shrinkage-compensating concrete in the load combinations defined in 5.3.6.)

Tburst = tensile force in general zone acting ahead of the anchorage device caused by spreading of the anchorage force, N

V = shear force acting on anchor or anchor group, N

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CODE COMMENTARY 2

Vd = shear force at section due to unfactored dead load, N

Ve = design shear force for load combinations including earthquake effects, N

Vi = factored shear force at section due to externally applied loads occurring simultaneously with Mmax, N

Vn = nominal shear strength, N Vnh = nominal horizontal shear strength, N Vp = vertical component of effective prestress force at

section, N Vs = nominal shear strength provided by shear reinforce-

ment, N Vsa = nominal shear strength of a single anchor or indi-

vidual anchor in a group of anchors as governed by the steel strength, N

Vu = factored shear force at section, N Vua = factored shear force applied to a single anchor or

group of anchors, N Vua,g = total factored shear force applied to anchor group, N Vua,i = factored shear force applied to most highly stressed

anchor in a group of anchors, N Vuh = factored shear force along contact surface in

composite concrete flexural member, N Vus = factored horizontal shear in a story, N

wc = density, unit weight, of normalweight concrete or equilibrium density of lightweight concrete, kg/m3

wu = factored load per unit length of beam or one-way slab, N/mm

w/cm = water-cementitious material ratio W = effect of wind load

x = shorter overall dimension of rectangular part of cross section, mm

y = longer overall dimension of rectangular part of cross section, mm

yt = distance from centroidal axis of gross section, neglecting reinforcement, to tension face, mm

α = angle defining the orientation of reinforcement αc = coefficient defining the relative contribution of

concrete strength to nominal wall shear strength αf = ratio of flexural stiffness of beam section to flex-

ural stiffness of a width of slab bounded laterally by centerlines of adjacent panels, if any, on each side of the beam

V|| = maximum shear force that can be applied parallel to the edge, N

V┴ = maximum shear force that can be applied perpen- dicular to the edge, N

ws = width of a strut perpendicular to the axis of the strut, mm

wt = effective height of concrete concentric with a tie, used to dimension nodal zone, mm

wt,max = maximum effective height of concrete concentric with a tie, mm

Wa = service-level wind load, N

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αfm = average value of αf for all beams on edges of a panel

αf1 = αf in direction of ℓ1 αf2 = αf in direction of ℓ2 αi = angle between the axis of a strut and the bars in the

i-th layer of reinforcement crossing that strut αs = constant used to calculate Vc in slabs and footings αv = ratio of flexural stiffness of shearhead arm to that of

the surrounding composite slab section α1 = orientation of distributed reinforcement in a strut α2 = orientation of reinforcement orthogonal to α1 in a

strut β = ratio of long to short dimensions: clear spans for

two-way slabs, sides of column, concentrated load or reaction area; or sides of a footing

βb = ratio of area of reinforcement cut off to total area of tension reinforcement at section

βdns = ratio used to account for reduction of stiffness of columns due to sustained axial loads

βds = the ratio of maximum factored sustained shear within a story to the maximum factored shear in that story associated with the same load combination

βn = factor used to account for the effect of the anchorage of ties on the effective compressive strength of a nodal zone

βs = factor used to account for the effect of cracking and confining reinforcement on the effective compres- sive strength of the concrete in a strut

βt = ratio of torsional stiffness of edge beam section to flexural stiffness of a width of slab equal to span length of beam, center-to-center of supports

β1 = factor relating depth of equivalent rectangular compressive stress block to depth of neutral axis

γf = factor used to determine the fraction of Msc trans- ferred by slab flexure at slab-column connections

γp = factor used for type of prestressing reinforcement γs = factor used to determine the portion of reinforce-

ment located in center band of footing γv = factor used to determine the fraction of Msc trans-

ferred by eccentricity of shear at slab-column connections

δ = moment magnification factor used to reflect effects of member curvature between ends of a compres- sion member

δs = moment magnification factor used for frames not braced against sidesway, to reflect lateral drift resulting from lateral and gravity loads

δu = design displacement, mm Δcr = calculated out-of-plane deflection at midheight of

wall corresponding to cracking moment Mcr, mm Δn = calculated out-of-plane deflection at midheight of

wall corresponding to nominal flexural strength Mn, mm

Δo = relative lateral deflection between the top and bottom of a story due to Vus, mm

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CODE COMMENTARY 2

Δfp = increase in stress in prestressing reinforcement due to factored loads, MPa

Δfps = stress in prestressing reinforcement at service loads less decompression stress, MPa

Δr = residual deflection measured 24 hours after removal of the test load. For the first load test, residual deflection is measured relative to the position of the structure at the beginning of the first load test. For the second load test, residual deflection is measured relative to the position of the structure at the begin- ning of the second load test, mm

Δs = out-of-plane deflection due to service loads, mm Δu = calculated out-of-plane deflection at midheight of

wall due to factored loads, mm Δx = design story drift of story x, mm Δ1 = maximum deflection, during first load test, measured

24 hours after application of the full test load, mm Δ2 = maximum deflection, during second load test,

measured 24 hours after application of the full test load. Deflection is measured relative to the position of the structure at the beginning of the second load test, mm

εt = net tensile strain in extreme layer of longitu- dinal tension reinforcement at nominal strength, excluding strains due to effective prestress, creep, shrinkage, and temperature

εty = value of net tensile strain in the extreme layer of longitudinal tension reinforcement used to define a compression-controlled section

θ = angle between axis of strut, compression diagonal, or compression field and the tension chord of the members

λ = modification factor to reflect the reduced mechan- ical properties of lightweight concrete relative to normalweight concrete of the same compressive strength

λa = modification factor to reflect the reduced mechan- ical properties of lightweight concrete in certain concrete anchorage applications

λΔ = multiplier used for additional deflection due to long-term effects

μ = coefficient of friction ξ = time-dependent factor for sustained load ρ = ratio of As to bd ρ′ = ratio of As′ to bd ρℓ = ratio of area of distributed longitudinal reinforce-

ment to gross concrete area perpendicular to that reinforcement

Δfpt = difference between the stress that can be developed in the strand at the section under consideration and the stress required to resist factored bending moment at section, Mu/ϕ, MPa

εcu = maximum usable strain at extreme concrete compression fiber

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ρp = ratio of Aps to bdp ρs = ratio of volume of spiral reinforcement to total

volume of core confined by the spiral, measured out-to-out of spirals

ρt = ratio of area of distributed transverse reinforce- ment to gross concrete area perpendicular to that reinforcement

ρv = ratio of tie reinforcement area to area of contact surface

ρw = ratio of As to bwd

ϕ = strength reduction factor

τcr = characteristic bond stress of adhesive anchor in cracked concrete, MPa

τuncr = characteristic bond stress of adhesive anchor in uncracked concrete, MPa

ψc = factor used to modify development length based on cover

ψc,N = factor used to modify tensile strength of anchors based on presence or absence of cracks in concrete

ψc,P = factor used to modify pullout strength of anchors based on presence or absence of cracks in concrete

ψc,V = factor used to modify shear strength of anchors based on presence or absence of cracks in concrete and presence or absence of supplementary reinforcement

ψcp,N = factor used to modify tensile strength of post- installed anchors intended for use in uncracked concrete without supplementary reinforcement to account for the splitting tensile stresses due to installation

ψcp,Na = factor used to modify tensile strength of adhesive anchors intended for use in uncracked concrete without supplementary reinforcement to account for the splitting tensile stresses due to installation

ψe = factor used to modify development length based on reinforcement coating

ψec,N = factor used to modify tensile strength of anchors based on eccentricity of applied loads

ψec,Na = factor used to modify tensile strength of adhesive anchors based on eccentricity of applied loads

ψec,V = factor used to modify shear strength of anchors based on eccentricity of applied loads

ψed,N = factor used to modify tensile strength of anchors based on proximity to edges of concrete member

ψed,Na = factor used to modify tensile strength of adhesive anchors based on proximity to edges of concrete member

ψed,V = factor used to modify shear strength of anchors based on proximity to edges of concrete member

ς = exponent symbol in tensile/shear force interaction equation

ϕK = stiffness reduction factor σ = wall boundary extreme fiber concrete nominal

compressive stress, MPa

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CODE COMMENTARY 2

ψh,V = factor used to modify shear strength of anchors located in concrete members with ha < 1.5ca1

ψr = factor used to modify development length based on confining reinforcement

ψs = factor used to modify development length based on reinforcement size

ψt = factor used to modify development length for casting location in tension

ψw = factor used to modify development length for welded deformed wire reinforcement in tension

Ωo = amplification factor to account for overstrength of the seismic-force-resisting system determined in accordance with the general building code

2.3—Terminology adhesive—chemical components formulated from

organic polymers, or a combination of organic polymers and inorganic materials that cure if blended together.

admixture—material other than water, aggregate, or hydraulic cement, used as an ingredient of concrete and added to concrete before or during its mixing to modify its properties.

aggregate—granular material, such as sand, gravel, crushed stone, and iron blast-furnace slag, used with a cementing medium to form concrete or mortar.

aggregate, lightweight—aggregate meeting the require- ments of ASTM C330M and having a loose bulk density of 1120 kg/m3 or less, determined in accordance with ASTM C29M.

anchor—a steel element either cast into concrete or post-installed into a hardened concrete member and used to transmit applied loads to the concrete.

anchor, adhesive—a post-installed anchor, inserted into hardened concrete with an anchor hole diameter not greater than 1.5 times the anchor diameter, that transfers loads to the concrete by bond between the anchor and the adhesive, and bond between the adhesive and the concrete.

anchor, cast-in—headed bolt, headed stud, or hooked bolt installed before placing concrete.

anchor, expansion—post-installed anchor, inserted into hardened concrete that transfers loads to or from the concrete by direct bearing or friction, or both.

R2.3—Terminology

aggregate, lightweight—In some standards, the term “lightweight aggregate” is being replaced by the term “low- density aggregate.”

anchor—Cast-in anchors include headed bolts, hooked bolts (J- or L-bolt), and headed studs. Post-installed anchors include expansion anchors, undercut anchors, and adhe- sive anchors; steel elements for adhesive anchors include threaded rods, deformed reinforcing bars, or internally threaded steel sleeves with external deformations. Anchor types are shown in Fig. R2.1.

anchor, adhesive—The design model included in Chapter 17 for adhesive anchors is based on the behavior of anchors with hole diameters not exceeding 1.5 times the anchor diameter. Anchors with hole diameters exceeding 1.5 times the anchor diameter behave differently and are therefore excluded from the scope of Chapter 17 and ACI 355.4. To limit shrinkage and reduce displacement under load, most adhesive anchor systems require the annular gap to be as narrow as practical while still maintaining sufficient clear- ance for insertion of the anchor element in the adhesive filled hole and ensuring complete coverage of the bonded area over the embedded length. The annular gap for reinforcing bars is generally greater than that for threaded rods. The required hole size is provided in the Manufacturer’s Printed Installa- tion Instructions (MPII).

anchor, expansion—Expansion anchors may be torque- controlled, where the expansion is achieved by a torque acting on the screw or bolt; or displacement controlled, where the expansion is achieved by impact forces acting on

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anchor, horizontal or upwardly inclined—Anchor installed in a hole drilled horizontally or in a hole drilled at any orientation above horizontal.

anchor, post-installed—anchor installed in hardened concrete; adhesive, expansion, and undercut anchors are examples of post-installed anchors.

anchor, undercut—post-installed anchor that develops its tensile strength from the mechanical interlock provided by undercutting of the concrete at the embedded end of the anchor. Undercutting is achieved with a special drill before installing the anchor or alternatively by the anchor itself during its installation.

a sleeve or plug and the expansion is controlled by the length of travel of the sleeve or plug.

anchor, horizontal or upwardly inclined—Figure R2.2 illustrates the potential hole orientations for horizontal or upwardly inclined anchors.

Fig. R2.1––Types of anchors.

Fig. R2.2––Possible orientations of overhead, upwardly inclined, or horizontal anchors.

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CODE COMMENTARY 2

anchor group—a number of similar anchors having approximately equal effective embedment depths with spacing s between adjacent anchors such that the projected areas overlap.

anchor pullout strength—the strength corresponding to the anchoring device or a major component of the device sliding out from the concrete without breaking out a substan- tial portion of the surrounding concrete.

anchorage device—in post-tensioned members, the hard- ware used to transfer force from prestressed reinforcement to the concrete.

anchorage device, basic monostrand—anchorage device used with any single strand or a single 15 mm or smaller diameter bar that is in accordance with 25.8.1, 25.8.2, and 25.9.3.1(a).

anchorage device, basic multistrand—anchorage device used with multiple strands, bars, or wires, or with single bars larger than 15 mm diameter that satisfies 25.8.1, 25.8.2 and 25.9.3.1(b).

anchorage device, special—anchorage device that satis- fies tests required in 25.9.3.1(c).

anchorage zone—in post-tensioned members, portion of the member through which the concentrated prestressing force is transferred to concrete and distributed more uniformly across the section; its extent is equal to the largest dimen- sion of the cross section; for anchorage devices located away from the end of a member, the anchorage zone includes the disturbed regions ahead of and behind the anchorage device.

attachment—structural assembly, external to the surface of the concrete, that transmits loads to or receives loads from the anchor.

B-region—portion of a member in which it is reasonable to assume that strains due to flexure vary linearly through section.

base of structure—level at which horizontal earthquake ground motions are assumed to be imparted to a building. This level does not necessarily coincide with the ground level.

beam—member subjected primarily to flexure and shear, with or without axial force or torsion; beams in a moment frame that forms part of the lateral-force-resisting system are predominantly horizontal members; a girder is a beam.

anchor group—For all potential failure modes (steel, concrete breakout, pullout, side-face blowout, and pryout), only those anchors susceptible to a particular failure mode should be considered when evaluating the strength associ- ated with that failure mode.

anchorage device—Most anchorage devices for post- tensioning are standard manufactured devices available from commercial sources. In some cases, non-standard details or assemblages are developed that combine various wedges and wedge plates for anchoring prestressed reinforcement. Both standard and non-standard anchorage devices may be classified as basic anchorage devices or special anchorage devices as defined in this Code and AASHTO LFRDUS.

anchorage device, basic—Devices that are so propor- tioned that they can be checked analytically for compli- ance with bearing stress and stiffness requirements without having to undergo the acceptance-testing program required of special anchorage devices.

anchorage device, special—Special anchorage devices are any devices (monostrand or multistrand) that do not meet the relevant PTI or AASHTO LFRDUS bearing stress and, where applicable, stiffness requirements. Most commer- cially marketed multi-bearing surface anchorage devices are special anchorage devices. As provided in 25.9.3, such devices can be used only if they have been shown experi- mentally to be in compliance with the AASHTO require- ments. This demonstration of compliance will ordinarily be furnished by the device manufacturer.

anchorage zone—In post-tensioned members, the portion of the member through which the concentrated prestressing force is transferred to the concrete and distributed more uniformly across the section. Its extent is equal to the largest dimension of the cross section. For anchorage devices located away from the end of a member, the anchorage zone includes the disturbed regions ahead of and behind the anchorage devices. Refer to Fig. R25.9.1.1b.

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boundary element—portion along wall and diaphragm edge, including edges of openings, strengthened by longitu- dinal and transverse reinforcement.

breakout strength, concrete—strength corresponding to a volume of concrete surrounding the anchor or group of anchors separating from the member.

building official—term used to identify the Authority having jurisdiction or individual charged with administra- tion and enforcement of provisions of the building code. Such terms as building commissioner or building inspector are variations of the title, and the term “building official” as used in this Code, is intended to include those variations, as well as others that are used in the same sense.

cementitious materials—materials that have cementing value if used in concrete either by themselves, such as portland cement, blended hydraulic cements, and expansive cement; or such materials in combination with fly ash, other raw or calcined natural pozzolans, silica fume, and slag cement.

collector—element that acts in axial tension or compres- sion to transmit forces between a diaphragm and a vertical element of the lateral-force-resisting system.

column—member, usually vertical or predominantly vertical, used primarily to support axial compressive load, but that can also resist moment, shear, or torsion. Columns used as part of a lateral-force-resisting system resist combined axial load, moment, and shear. See also moment frame.

column capital—enlargement of the top of a concrete column located directly below the slab or drop panel that is cast monolithically with the column.

compliance requirements—construction-related code requirements directed to the contractor to be incorporated into construction documents by the licensed design profes- sional, as applicable.

composite concrete flexural members—concrete flex- ural members of precast or cast-in-place concrete elements, constructed in separate placements but connected so that all elements respond to loads as a unit.

compression-controlled section—cross section in which the net tensile strain in the extreme tension reinforcement at nominal strength is less than or equal to the compression- controlled strain limit.

compression-controlled strain limit—net tensile strain at balanced strain conditions.

concrete—mixture of portland cement or any other cementitious material, fine aggregate, coarse aggregate, and water, with or without admixtures.

concrete, all-lightweight—lightweight concrete containing only lightweight coarse and fine aggregates that conform to ASTM C330M.

concrete, lightweight—concrete containing lightweight aggregate and having an equilibrium density, as determined by ASTM C567, between 1440 and 1840 kg/m3.

concrete, nonprestressed—reinforced concrete with at least the minimum amount of nonprestressed reinforcement

compliance requirements—Although primarily directed to the contractor, the compliance requirements are also commonly used by others involved with the project.

concrete, nonprestressed—Nonprestressed concrete usually contains no prestressed reinforcement. Prestressed two-way slabs require a minimum level of compressive

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CHAPTER 2—NOTATION AND TERMINOLOGY 33

CODE COMMENTARY 2

stress in the concrete due to effective prestress in accordance with 8.6.2.1. Two-way slabs with less than this minimum level of precompression are required to be designed as nonprestressed concrete.

concrete, normalweight—Normalweight concrete typi- cally has a density (unit weight) between 2155 and 2560 kg/m3, and is normally taken as 2320 to 2400 kg/m3.

concrete, plain—The presence of reinforcement, nonpre- stressed or prestressed, does not exclude the member from being classified as plain concrete, provided all requirements of Chapter 14 are satisfied.

concrete, prestressed—Classes of prestressed flex- ural members are defined in 24.5.2.1. Prestressed two-way slabs require a minimum level of compressive stress in the concrete due to effective prestress in accordance with 8.6.2.1. Although the behavior of prestressed members with unbonded tendons may vary from that of members with continuously bonded prestressed reinforcement, bonded and unbonded prestressed concrete are combined with nonprestressed concrete under the generic term “reinforced concrete.” Provisions common to both prestressed and nonprestressed concrete are integrated to avoid overlapping and conflicting provisions.

concrete, reinforced—Includes members satisfying the requirements for nonprestressed and prestressed concrete.

concrete, sand-lightweight—By Code terminology, sand-lightweight concrete is lightweight concrete with all of the fine aggregate replaced by sand. This definition may not be in agreement with usage by some material suppliers or contractors where the majority, but not all, of the light- weight fines are replaced by sand. For proper application of the Code provisions, the replacement limits should be stated, with interpolation if partial sand replacement is used.

and no prestressed reinforcement; or for two-way slabs, with less than the minimum amount of prestressed reinforcement.

concrete, normalweight—concrete containing only coarse and fine aggregates that conform to ASTM C33M.

concrete, plain—structural concrete with no reinforce- ment or with less than the minimum amount of reinforce- ment specified for reinforced concrete.

concrete, precast—structural concrete element cast else- where than its final position in the structure.

concrete, prestressed—reinforced concrete in which internal stresses have been introduced by prestressed rein- forcement to reduce potential tensile stresses in concrete resulting from loads, and for two-way slabs, with at least the minimum amount of prestressed reinforcement.

concrete, reinforced—structural concrete reinforced with at least the minimum amount of nonprestressed reinforcement, prestressed reinforcement, or both, as specified in this Code.

concrete, sand-lightweight—lightweight concrete containing only normalweight fine aggregate that conforms to ASTM C33M and lightweight coarse aggregate that conforms to ASTM C330M.

concrete, steel fiber-reinforced—concrete containing a prescribed amount of dispersed, randomly oriented, discon- tinuous deformed steel fibers.

concrete strength, specified compressive, (fc′)—compres- sive strength of concrete used in design and evaluated in accordance with provisions of this Code, MPa; wherever the quantity fc′ is under a radical sign, the square root of numer- ical value only is intended, and the result has units of MPa.

connection—region of a structure that joins two or more members; a connection also refers to a region that joins members of which one or more is precast.

connection, ductile—connection between one or more precast elements that experiences yielding as a result of the earthquake design displacements.

connection, strong—connection between one or more precast elements that remains elastic while adjoining members experience yielding as a result of earthquake design displacements.

construction documents—written and graphic documents and specifications prepared or assembled for describing the

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34 BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318M-14) AND COMMENTARY (ACI 318RM-14)

CODE COMMENTARY

location, design, materials, and physical characteristics of the elements of a project necessary for obtaining a building permit and construction of the project.

contraction joint—formed, sawed, or tooled groove in a concrete structure to create a weakened plane and regu- late the location of cracking resulting from the dimensional change of different parts of the structure.

cover, specified concrete—distance between the outer- most surface of embedded reinforcement and the closest outer surface of the concrete.

crosstie—a continuous reinforcing bar having a seismic hook at one end and a hook not less than 90 degrees with at least a 6db extension at the other end. The hooks shall engage peripheral longitudinal bars. The 90-degree hooks of two successive crossties engaging the same longitudinal bars shall be alternated end for end.

D-region—portion of a member within a distance h of a force discontinuity or a geometric discontinuity.

design displacement—total calculated lateral displace- ment expected for the design-basis earthquake.

design information—project-specific information to be incorporated into construction documents by the licensed design professional, as applicable.

design load combination—combination of factored loads and forces.

design story drift ratio—relative difference of design displacement between the top and bottom of a story, divided by the story height.

development length—length of embedded reinforce- ment, including pretensioned strand, required to develop the design strength of reinforcement at a critical section.

discontinuity—abrupt change in geometry or loading. distance sleeve—sleeve that encases the center part of an

undercut anchor, a torque-controlled expansion anchor, or a displacement-controlled expansion anchor, but does not expand.

drop panel—projection below the slab used to reduce the amount of negative reinforcement over a column or the minimum required slab thickness, and to increase the slab shear strength.

duct—conduit, plain or corrugated, to accommodate prestressing reinforcement for post-tensioning applications.

durability—ability of a structure or member to resist dete- rioration that impairs performance or limits service life of the structure in the relevant environment considered in design.

design displacement—The design displacement is an index of the maximum lateral displacement expected in design for the design-basis earthquake. In documents such as ASCE/SEI 7 and the International Building Code, the design displacement is calculated using static or dynamic linear elastic analysis under code-specified actions consid- ering effects of cracked sections, effects of torsion, effects of vertical forces acting through lateral displacements, and modification factors to account for expected inelastic response. The design displacement generally is greater than the displacement calculated from design-level forces applied to a linear-elastic model of the building.

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CHAPTER 2—NOTATION AND TERMINOLOGY 35

CODE COMMENTARY 2

edge distance—distance from the edge of the concrete surface to the center of the nearest anchor.

effective depth of section—distance measured from extreme compression fiber to centroid of longitudinal tension reinforcement.

effective embedment depth—overall depth through which the anchor transfers force to or from the surrounding concrete; effective embedment depth will normally be the depth of the concrete failure surface in tension applications; for cast-in headed anchor bolts and headed studs, the effec- tive embedment depth is measured from the bearing contact surface of the head.

effective prestress—stress remaining in prestressed rein- forcement after losses in 20.3.2.6 have occurred.

embedments—items embedded in concrete, excluding reinforcement as defined in Chapter 20 and anchors as defined in Chapter 17. Reinforcement or anchors welded, bolted or otherwise connected to the embedded item to develop the strength of the assembly, are considered to be part of the embedment.

embedments, pipe—embedded pipes, conduits, and sleeves.

embedment length—length of embedded reinforcement provided beyond a critical section.

equilibrium density—density of lightweight concrete determined in accordance with ASTM C567 after exposure to a relative humidity of 50 ± 5 percent and a temperature of 23 ± 2°C for a period of time sufficient to reach constant density.

expansion sleeve—outer part of an expansion anchor that is forced outward by the center part, either by applied torque or impact, to bear against the sides of the predrilled hole. See also anchor, expansion.