Keywords: admixtures; aggregates; anchorage structural; beam-column frame; beams supports; building codes; cements; cold weather construction; columns supports; combined stress; composit
Trang 1Building Code Requirements for Structural Concrete (ACI 318-08)
and Commentary
An ACI Standard
Reported by ACI Committee 318
Deemed to satisfy ISO 19338:2007(E)
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 2
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -American Concrete Institute®
Advancing concrete knowledge
Building Code Requirements for Structural Concrete
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 occa- sionally 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.
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 regula- tions, including but not limited to, United States Occupational Safety and Health Administration (OSHA) health and safety standards.
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).
American Concrete Institute
38800 Country Club Drive
Trang 3``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -James K Wight
Chair
Basile G Rabbat
Secretary
Sergio M Alcocer Catherine E French James O Jirsa Myles A Murray
Florian G Barth Luis E Garcia Dominic J Kelly Julio A Ramirez
Roger J Becker S K Ghosh Gary J Klein Thomas C Schaeffer
Kenneth B Bondy Lawrence G Griffis Ronald Klemencic Stephen J Seguirant
John E Breen David P Gustafson Cary Kopczynski Roberto Stark
James R Cagley D Kirk Harman H S Lew Eric M Tolles
Ned M Cleland James R Harris Colin L Lobo Thomas D Verti
Michael P Collins Neil M Hawkins Robert F Mast Sharon L Wood
W Gene Corley Terence C Holland W Calvin McCall Loring A Wyllie, Jr
Charles W Dolan Kenneth C Hover Jack P Moehle Fernando V Yánez
Anthony E Fiorato
Subcommittee Members
Neal S Anderson David Darwin Andres Lepage Suzanne D Nakaki David H Sanders
Mark A Aschheim Robert J Frosch LeRoy A Lutz Theodore L Neff Guillermo Santana
F Michael Bartlett Harry A Gleich James G MacGregor Andrzej S Nowak Andrew Scanlon
John F Bonacci R Doug Hooton Joe Maffei Gustavo J Parra-Montesinos John F Stanton
JoAnn P Browning L S Paul Johal Karl F Meyer Jose A Pincheira Fernando Reboucas StucchiNicholas J Carino Michael E Kreger Denis Mitchell Randall W Poston Raj Valluvan
Ronald A Cook Jason J Krohn Vilas S Mujumdar Bruce W Russell John W Wallace
Juan P Covarrubias Daniel A Kuchma
Liaison Members
Mathias Brewer Alberto Giovambattista Hector Monzon-Despang Patricio A Placencia
Josef Farbiarz Hector Hernandez Enrique Pasquel Oscar M Ramirez
Rafael Adan Ferrera-Boza Angel E Herrera Victor F Pizano-Batlle Mario E Rodriguez
Consulting Members
C Raymond Hays Richard C Meininger Charles G Salmon
BUILDING CODE REQUIREMENTS FOR STRUCTURAL CONCRETE (ACI 318-08) AND
COMMENTARY
REPORTED BY ACI COMMITTEE 318
ACI Committee 318 Structural Building Code
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 5
The “Building Code Requirements for Structural Concrete” (“Code”) covers the materials, design, and construction
of structural concrete used in buildings and where applicable in nonbuilding structures The Code also covers the strength evaluation of existing concrete structures.
Among the subjects covered are: drawings and specifications; inspection; materials; durability requirements; concrete quality, mixing, and placing; formwork; embedded pipes; construction joints; reinforcement details; analysis and design; strength and serviceability; flexural and axial loads; shear and torsion; development and splices of reinforcement; slab systems; walls; footings; precast concrete; composite flexural members; prestressed concrete; shells and folded plate members; strength evaluation of existing structures; provisions for seismic design; structural plain concrete; strut-and-tie modeling in Appendix A ; alternative design provisions in Appendix B ; alternative load and strength reduction factors in Appendix C ; and anchoring to concrete in Appendix D
The quality and testing of materials used in construction are covered by reference to the appropriate ASTM standard specifications Welding of reinforcement is covered by reference to the appropriate AWS standard.
Uses of the Code include adoption by reference in general building codes, 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 portion cannot be included The Commentary is provided for this purpose Some of the considerations of the committee in developing the Code portion 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.
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 construction (concrete to concrete); compressive strength;
concrete construction; concrete slabs; concretes; construction joints; continuity (structural); contraction joints; cover; curing; deep beams; deflections; drawings;
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; specifications; splicing; strength; strength
analysis; stresses; structural analysis; structural concrete; structural design; structural integrity; T-beams; torsion; walls; water; welded wire reinforcement.
ACI 318-08 was adopted as a standard of the American Concrete Institute
November 2007 to supersede ACI 318-05 in accordance with the Institute’s
standardization procedure and was published January 2008.
A complete metric companion to ACI 318 has been developed, 318M;
therefore, no metric equivalents are included in this document.
ACI Committee Reports, Manuals, Guides, Standard Practices, and
Commentaries are intended for guidance in planning, designing, executing,
and inspecting construction This Commentary 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 material it contains The American Concrete Institute
disclaims any and all responsibility for the stated principles The Institute
shall not be liable for any loss or damage arising therefrom Reference to this Commentary shall not be made in contract documents If items found
in this Commentary are desired by the licensed design professional to be
a part of the contract documents, they shall be restated and incorporated
in mandatory language.
Copyright © 2008, 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 any electronic or mechanical device, printed or written or oral, or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.
BUILDING CODE REQUIREMENTS FOR
STRUCTURAL CONCRETE (ACI 318-08)
AND COMMENTARY
REPORTED BY ACI COMMITTEE 318
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 6
INTRODUCTION 7
CHAPTER 1—GENERAL REQUIREMENTS 9
1.1—Scope 9
1.2—Drawings and specifications 13
1.3—Inspection 14
1.4—Approval of special systems of design or construction 17
CHAPTER 2—NOTATION AND DEFINITIONS 19
2.1—Code notation 19
2.2—Definitions 28
CHAPTER 3—MATERIALS 41
3.1—Tests of materials 41
3.2—Cementitious materials 41
3.3—Aggregates 42
3.4—Water 42
3.5—Steel reinforcement 43
3.6—Admixtures 49
3.7—Storage of materials 49
3.8—Referenced standards 49
CHAPTER 4—DURABILITY REQUIREMENTS 55
4.1—General 55
4.2—Exposure categories and classes 55
4.3—Requirements for concrete mixtures 57
4.4—Additional requirements for freezing-and-thawing exposure 60
4.5—Alternative cementitious materials for sulfate exposure 61
CHAPTER 5—CONCRETE QUALITY, MIXING, AND PLACING 63
5.1—General 63
5.2—Selection of concrete proportions 64
5.3—Proportioning on the basis of field experience or trial mixtures, or both 64
5.4—Proportioning without field experience or trial mixtures 69
5.5—Average compressive strength reduction 69
5.6—Evaluation and acceptance of concrete 70
5.7—Preparation of equipment and place of deposit 75
5.8—Mixing 76
5.9—Conveying 76
5.10—Depositing 77
5.11—Curing 77
5.12—Cold weather requirements 78
5.13—Hot weather requirements 79
CHAPTER 6—FORMWORK, EMBEDMENTS, AND CONSTRUCTION JOINTS 81
6.1—Design of formwork 81
6.2—Removal of forms, shores, and reshoring 81
6.3—Embedments in concrete 83
6.4—Construction joints 84
CHAPTER 7—DETAILS OF REINFORCEMENT 87
7.1—Standard hooks 87
7.2—Minimum bend diameters 87
7.3—Bending 88
7.4—Surface conditions of reinforcement 88
7.5—Placing reinforcement 89
Trang 7
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -7.6—Spacing limits for reinforcement 90
7.7—Concrete protection for reinforcement 91
7.8—Reinforcement details for columns 94
7.9—Connections 95
7.10—Lateral reinforcement for compression members 96
7.11—Lateral reinforcement for flexural members 98
7.12—Shrinkage and temperature reinforcement 98
7.13—Requirements for structural integrity 100
CHAPTER 8—ANALYSIS AND DESIGN—GENERAL CONSIDERATIONS 103
8.1—Design methods 103
8.2—Loading 103
8.3—Methods of analysis 104
8.4—Redistribution of moments in continuous flexural members 105
8.5—Modulus of elasticity 107
8.6—Lightweight concrete 107
8.7—Stiffness 108
8.8—Effective stiffness to determine lateral deflections 108
8.9—Span length 109
8.10—Columns 110
8.11—Arrangement of live load 110
8.12—T-beam construction 111
8.13—Joist construction 112
8.14—Separate floor finish 113
CHAPTER 9—STRENGTH AND SERVICEABILITY REQUIREMENTS 115
9.1—General 115
9.2—Required strength 115
9.3—Design strength 117
9.4—Design strength for reinforcement 121
9.5—Control of deflections 121
CHAPTER 10—FLEXURE AND AXIAL LOADS 129
10.1—Scope 129
10.2—Design assumptions 129
10.3—General principles and requirements 131
10.4—Distance between lateral supports of flexural members 134
10.5—Minimum reinforcement of flexural members 134
10.6—Distribution of flexural reinforcement in beams and one-way slabs 135
10.7—Deep beams 137
10.8—Design dimensions for compression members 138
10.9—Limits for reinforcement of compression members 138
10.10—Slenderness effects in compression members 140
10.11—Axially loaded members supporting slab system 148
10.12—Transmission of column loads through floor system 148
10.13—Composite compression members 149
10.14—Bearing strength 152
CHAPTER 11—SHEAR AND TORSION 155
11.1—Shear strength 155
11.2—Shear strength provided by concrete for nonprestressed members 158
11.3—Shear strength provided by concrete for prestressed members 160
11.4—Shear strength provided by shear reinforcement 163
11.5—Design for torsion 168
11.6—Shear-friction 180
11.7—Deep beams 183
11.8—Provisions for brackets and corbels 184
11.9—Provisions for walls 188
11.10—Transfer of moments to columns 190
11.11—Provisions for slabs and footings 190
Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 8``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CHAPTER 12—DEVELOPMENT AND SPLICES OF REINFORCEMENT 203
12.1—Development of reinforcement—General 203
12.2—Development of deformed bars and deformed wire in tension 204
12.3—Development of deformed bars and deformed wire in compression 206
12.4—Development of bundled bars 207
12.5—Development of standard hooks in tension 207
12.6—Development of headed and mechanically anchored deformed bars in tension 210
12.7—Development of welded deformed wire reinforcement in tension 212
12.8—Development of welded plain wire reinforcement in tension 213
12.9—Development of prestressing strand 214
12.10—Development of flexural reinforcement—General 216
12.11—Development of positive moment reinforcement 218
12.12—Development of negative moment reinforcement 220
12.13—Development of web reinforcement 220
12.14—Splices of reinforcement—General 224
12.15—Splices of deformed bars and deformed wire in tension 225
12.16—Splices of deformed bars in compression 227
12.17—Splice requirements for columns 228
12.18—Splices of welded deformed wire reinforcement in tension 230
12.19—Splices of welded plain wire reinforcement in tension 231
CHAPTER 13—TWO-WAY SLAB SYSTEMS 233
13.1—Scope 233
13.2—General 234
13.3—Slab reinforcement 235
13.4—Openings in slab systems 238
13.5—Design procedures 238
13.6—Direct design method 241
13.7—Equivalent frame method 248
CHAPTER 14—WALLS 253
14.1—Scope 253
14.2—General 253
14.3—Minimum reinforcement 254
14.4—Walls designed as compression members 255
14.5—Empirical design method 255
14.6—Nonbearing walls 256
14.7—Walls as grade beams 256
14.8—Alternative design of slender walls 257
CHAPTER 15—FOOTINGS 261
15.1—Scope 261
15.2—Loads and reactions 261
15.3—Footings supporting circular or regular polygon-shaped columns or pedestals 262
15.4—Moment in footings 262
15.5—Shear in footings 263
15.6—Development of reinforcement in footings 264
15.7—Minimum footing depth 264
15.8—Transfer of force at base of column, wall, or reinforced pedestal 264
15.9—Sloped or stepped footings 266
15.10—Combined footings and mats 267
CHAPTER 16—PRECAST CONCRETE 269
16.1—Scope 269
16.2—General 269
16.3—Distribution of forces among members 270
16.4—Member design 270
16.5—Structural integrity 271
16.6—Connection and bearing design 273
Trang 9
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -16.7—Items embedded after concrete placement 275
16.8—Marking and identification 275
16.9—Handling 275
16.10—Strength evaluation of precast construction 275
CHAPTER 17—COMPOSITE CONCRETE FLEXURAL MEMBERS 277
17.1—Scope 277
17.2—General 277
17.3—Shoring 278
17.4—Vertical shear strength 278
17.5—Horizontal shear strength 278
17.6—Ties for horizontal shear 279
CHAPTER 18—PRESTRESSED CONCRETE 281
18.1—Scope 281
18.2—General 282
18.3—Design assumptions 283
18.4—Serviceability requirements—Flexural members 284
18.5—Permissible stresses in prestressing steel 287
18.6—Loss of prestress 287
18.7—Flexural strength 289
18.8—Limits for reinforcement of flexural members 290
18.9—Minimum bonded reinforcement 291
18.10—Statically indeterminate structures 293
18.11—Compression members—Combined flexure and axial loads 294
18.12—Slab systems 294
18.13—Post-tensioned tendon anchorage zones 297
18.14—Design of anchorage zones for monostrand or single 5/8 in diameter bar tendons 302
18.15—Design of anchorage zones for multistrand tendons 303
18.16—Corrosion protection for unbonded tendons 304
18.17—Post-tensioning ducts 304
18.18—Grout for bonded tendons 304
18.19—Protection for prestressing steel 306
18.20—Application and measurement of prestressing force 306
18.21—Post-tensioning anchorages and couplers 307
18.22—External post-tensioning 308
CHAPTER 19—SHELLS AND FOLDED PLATE MEMBERS 309
19.1—Scope and definitions 309
19.2—Analysis and design 311
19.3—Design strength of materials 313
19.4—Shell reinforcement 313
19.5—Construction 315
CHAPTER 20—STRENGTH EVALUATION OF EXISTING STRUCTURES 317
20.1—Strength evaluation—General 317
20.2—Determination of required dimensions and material properties 318
20.3—Load test procedure 319
20.4—Loading criteria 320
20.5—Acceptance criteria 320
20.6—Provision for lower load rating 322
20.7—Safety 322
CHAPTER 21—EARTHQUAKE-RESISTANT STRUCTURES 323
21.1—General requirements 323
21.2—Ordinary moment frames 328
21.3—Intermediate moment frames 329
21.4—Intermediate precast structural walls 333
21.5—Flexural members of special moment frames 333
Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 10``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -21.6—Special moment frame members subjected to bending and axial load 339
21.7—Joints of special moment frames 343
21.8—Special moment frames constructed using precast concrete 347
21.9—Special structural walls and coupling beams 349
21.10—Special structural walls constructed using precast concrete 356
21.11—Structural diaphragms and trusses 357
21.12—Foundations 362
21.13—Members not designated as part of the seismic-force-resisting system 365
CHAPTER 22—STRUCTURAL PLAIN CONCRETE 369
22.1—Scope 369
22.2—Limitations 370
22.3—Joints 370
22.4—Design method 371
22.5—Strength design 371
22.6—Walls 373
22.7—Footings 374
22.8—Pedestals 376
22.9—Precast members 376
22.10—Plain concrete in earthquake-resisting structures 376
APPENDIX A—STRUT-AND-TIE MODELS 379
A.1—Definitions 379
A.2—Strut-and-tie model design procedure 386
A.3—Strength of struts 388
A.4—Strength of ties 391
A.5—Strength of nodal zones 392
APPENDIX B—ALTERNATIVE PROVISIONS FOR REINFORCED AND PRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS 395
B.1—Scope 395
APPENDIX C—ALTERNATIVE LOAD AND STRENGTH REDUCTION FACTORS 403
C.9.1—Scope 403
C.9.2—Required strength 403
C.9.3—Design strength 405
APPENDIX D—ANCHORING TO CONCRETE 409
D.1—Definitions 409
D.2—Scope 411
D.3—General requirements 412
D.4—General requirements for strength of anchors 414
D.5—Design requirements for tensile loading 419
D.6—Design requirements for shear loading 428
D.7—Interaction of tensile and shear forces 436
D.8—Required edge distances, spacings, and thicknesses to preclude splitting failure 438
D.9—Installation of anchors 438
APPENDIX E—STEEL REINFORCEMENT INFORMATION 439
COMMENTARY REFERENCES 441
INDEX 459
Trang 11
This Commentary discusses some of the considerations of
Committee 318 in developing the provisions contained in
“Building Code Requirements for Structural Concrete (ACI
318-08),” hereinafter called the Code or the 2008 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
independent 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 specifications,
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 theCode However, lower standards are not permitted
The Commentary directs attention to other documents thatprovide suggestions for carrying out the requirements andintent of the Code However, those documents and theCommentary are not a part of the Code
The Code has no legal status unless it is adopted by thegovernment bodies having the police power to regulatebuilding design and construction Where the Code has notbeen adopted, it may serve as a reference to good practiceeven though it has no legal status
The Code provides a means of establishing minimum standardsfor acceptance of designs and construction by legallyappointed building officials or their designated representatives.The Code and Commentary are not intended for use in settlingdisputes between the owner, engineer, architect, contractor, ortheir agents, subcontractors, material suppliers, or testingagencies Therefore, the Code cannot define the contractresponsibility of each of the parties in usual construction.General references requiring compliance with the Code in theproject specifications should be avoided since the contractor israrely in a position to accept responsibility for design details orconstruction requirements that depend on a detailed knowledge
of the design Design-build construction contractors, however,typically combine the design and construction responsibility.Generally, the drawings, specifications, and contract documentsshould contain all of the necessary requirements to ensurecompliance with the Code In part, this can be accomplished
by reference to specific Code sections in the project cations Other ACI publications, such as “Specifications forStructural Concrete (ACI 301)” are written specifically foruse as contract documents for construction
specifi-It is recommended to have testing and certification programsfor the individual parties involved with the execution ofwork performed in accordance with this Code Available forthis purpose are the plant certification programs of thePrecast/Prestressed Concrete Institute, the Post-TensioningInstitute, and the National Ready Mixed Concrete Associa-tion; the personnel certification programs of the AmericanConcrete Institute and the Post-Tensioning Institute; and theConcrete Reinforcing Steel Institute’s Voluntary Certification
The ACI Building Code Requirements for Structural Concrete (“Code”) and Commentary are presented in a side-by-sidecolumn format, with Code text placed in the left column and the corresponding Commentary text aligned in the right column
To further distinguish the Code from the Commentary, the Code has been printed in Helvetica, the same type face in whichthis paragraph is set
This paragraph is set in Times Roman, and all portions of the text exclusive to the Commentary are printed in this type face Commentarysection numbers are preceded by an “R” to further distinguish them from Code section numbers
Except for Chapters 4 and 21, substantive changes from 318-05 are indicated with vertical lines in the margin (editorialchanges not indicated) Changes to the provisions of Chapters 4 and 21 are not indicated by a vertical line because theprovisions were renumbered for this edition
* 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, Proceedings 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, Proceedings V 56, No 5, May 1960, p 1105.
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 12``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -Program for Fusion-Bonded Epoxy Coating Applicator
Plants In addition, “Standard Specification for Agencies
Engaged in Construction Inspecting and/or Testing” (ASTM
E329-06a) specifies performance requirements for inspection
and testing agencies
Design reference materials illustrating applications of the
Code requirements may be found in the following documents
The design aids listed may be obtained from the sponsoring
organization
Design aids:
“ACI Design Handbook,” Publication SP-17(97),
Amer-ican Concrete Institute, Farmington Hills, MI, 1997, 482 pp
(This provides tables and charts for design of eccentrically
loaded columns by the Strength Design Method of the 1995
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.)
“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
reinforced concrete structures Separate sections define
responsibilities of both engineer and reinforcing bar detailer.)
“Guide to Durable Concrete (ACI 201.2R-01),” ACI
Committee 201, American Concrete Institute, Farmington
Hills, MI, 2001, 41 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 of Durable Parking Structures
(362.1R-97 (Reapproved 2002)),” ACI Committee 362,
American Concrete Institute, Farmington Hills, MI, 1997, 33 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, 9th Edition, 2002, 648 pp (This provides
tabulated designs for structural elements and slab systems
Design examples are provided to show the basis of 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 squarefootings, pile caps, drilled piers (caissons), and cantileveredretaining walls Other design aids are presented for crackcontrol; and development of reinforcement and lap splices.)
“Reinforcement Anchorages and Splices,” Concrete
Reinforcing Steel Institute, Schaumburg, IL, 4th Edition,
1997, 100 pp (This provides accepted practices in splicingreinforcement The use of lap splices, mechanical splices,and welded splices are described Design data are presentedfor development and lap splicing of reinforcement.)
“Structural Welded Wire Reinforcement Manual of dard Practice,” Wire Reinforcement Institute, Hartford, CT,
Stan-6th Edition, Apr 2001, 38 pp (This describes welded wirereinforcement material, gives nomenclature and wire sizeand weight tables Lists specifications and properties andmanufacturing limitations Book has latest code require-ments as code affects welded wire Also gives developmentlength and splice length tables Manual contains customaryunits 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 318provisions and design aids, also includes: detailing guidance
on welded wire reinforcement in one-way and two-wayslabs; precast/prestressed concrete components; columnsand beams; cast-in-place walls; and slabs-on-ground Inaddition, there are tables to compare areas and spacings ofhigh-strength welded wire with conventional reinforcing.)
“Strength Design of Reinforced Concrete Columns,”
Portland Cement Association, Skokie, IL, 1978, 48 pp (Thisprovides design tables of column strength in terms of load inkips versus moment in ft-kips for concrete strength of 5000 psiand Grade 60 reinforcement Design examples are included.Note that the PCA design tables do not include the strengthreduction factor φ in the tabulated values; M u/φ and P u/φmust be used when designing with this aid.)
“PCI Design Handbook—Precast and Prestressed Concrete,” Precast/Prestressed Concrete Institute, Chicago, IL,
6th Edition, 2004, 736 pp (This provides load tables forcommon industry products, and procedures for design andanalysis of precast and prestressed elements and structurescomposed 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, 2nd Edition, 1988, 270 pp (This updates availableinformation on design of connections for both structural andarchitectural products, and presents a full spectrum of typicaldetails This provides design aids and examples.)
“Post-Tensioning Manual,” Post-Tensioning Institute,
Phoenix, AZ, 6th Edition, 2006, 354 pp (This providescomprehensive coverage of post-tensioning systems, speci-fications, design aids, and construction concepts.)
Trang 13
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
1.1 — Scope
1.1.1 — This Code provides minimum requirements
for design and construction of structural concrete
members of any structure erected under requirements
of the legally adopted general building code of which
this Code forms a part In areas without a legally
adopted building code, this Code defines minimum
acceptable standards for materials, design, and
construction practice This Code also covers the
strength evaluation of existing concrete structures
For structural concrete, f c′ shall not be less than
2500 psi No maximum value of f c′ shall apply unless
restricted by a specific Code provision
R1.1 — Scope
The American Concrete Institute “Building Code
Require-ments for Structural Concrete (ACI 318-08),” referred to
as the Code or 2008 Code, provides minimum requirementsfor structural concrete design or construction
The 2008 Code revised the previous standard “Building
Code Requirements for Structural Concrete (ACI 318-05).” This standard includes in one document the rules
for all concrete used for structural purposes including bothplain and reinforced concrete The term “structuralconcrete” is used to refer to all plain or reinforced concreteused for structural purposes This covers the spectrum ofstructural applications of concrete from nonreinforcedconcrete to concrete containing nonprestressed reinforce-ment, prestressing steel, or composite steel shapes, pipe, ortubing Requirements for structural plain concrete are in
Chapter 22.Prestressed concrete is included under the definition ofreinforced concrete Provisions of the Code apply toprestressed concrete except for those that are stated to applyspecifically to nonprestressed concrete
Chapter 21 of the Code contains provisions for design anddetailing of earthquake-resistant structures See 1.1.8.Appendix A of Codes prior to 2002 contained provisions for
an alternate method of design for nonprestressed reinforcedconcrete members using service loads (without load factors)and permissible service load stresses The Alternate DesignMethod was intended to give results that were slightly moreconservative than designs by the Strength Design Method ofthe Code The Alternate Design Method of the 1999 Codemay be used in place of applicable sections of this Code
Appendix A of the Code contains provisions for the design
of regions near geometrical discontinuities, or abruptchanges in loadings
Appendix B of this Code contains provisions for
reinforce-ment limits based on 0.75ρb, determination of the strengthreduction factor φ, and moment redistribution that have been
in the Code for many years, including the 1999 Code Theprovisions are applicable to reinforced and prestressedconcrete members Designs made using the provisions of
Appendix B are equally acceptable as those based on thebody of the Code, provided the provisions of Appendix B
are used in their entirety
CHAPTER 1 — GENERAL REQUIREMENTS
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 14``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Appendix C of the Code allows the use of the factored loadcombinations given in Chapter 9 of the 1999 Code
Appendix D contains provisions for anchoring to concrete
R1.1.2 — The American Concrete Institute recommends
that the Code be adopted in its entirety; however, it is nized that when the Code is made a part of a legally adoptedgeneral building code, the general building code maymodify provisions of this Code
recog-1.1.2 — This Code supplements the general building
code and shall govern in all matters pertaining to
design and construction of structural concrete, except
wherever this Code is in conflict with requirements in
the legally adopted general building code
1.1.3 — This Code shall govern in all matters pertaining
to design, construction, and material properties wherever
this Code is in conflict with requirements contained in
other standards referenced in this Code
1.1.4 — For cast-in-place footings, foundation walls,
and slabs-on-ground for one- and two-family dwellings
and multiple single-family dwellings (townhouses) and
their accessory structures, design and construction in
accordance with ACI 332 shall be permitted
R1.1.4 — “Requirements for Residential Concrete Construction (ACI 332) and Commentary” reported by
ACI Committee 332.1.1 (This addresses only the design andconstruction of cast-in-place footings, foundation wallssupported on continuous footings, and slabs-on-ground forone- and two-family dwellings and multiple single-familydwellings [townhouses], and their accessory structures.)
R1.1.5 — Some structures involve unique design and
construction problems that are not covered by the Code.However, many Code provisions, such as the concretequality and design principles, are applicable for these struc-tures Detailed recommendations for design and construc-tion of some special structures are given in the followingACI publications:
“Design and Construction of Reinforced Concrete Chimneys” reported by ACI Committee 307.1.2 (This givesmaterial, construction, and design requirements for circularcast-in-place reinforced chimneys It sets forth minimumloadings for the design of reinforced concrete chimneys andcontains methods for determining the stresses in the concreteand reinforcement required as a result of these loadings.)
“Standard Practice for Design and Construction of Concrete Silos and Stacking Tubes for Storing Granular Materials” reported by ACI Committee 313.1.3 (This givesmaterial, design, and construction requirements for reinforcedconcrete bins, silos, and bunkers and stave silos for storing gran-ular materials It includes recommended design and construc-tion criteria based on experimental and analytical studiesplus worldwide experience in silo design and construction.)
“Code Requirements for Nuclear Safety-Related Concrete Structures and Commentary” reported by ACI Committee
349.1.4 (This provides minimum requirements for design andconstruction of concrete structures that form part of a nuclearpower plant and have nuclear safety-related functions Thecode does not cover concrete reactor vessels and concretecontainment structures, which are covered by ACI 359.)
1.1.5 — For unusual structures, such as arches, bins
and silos, blast-resistant structures, and chimneys,
provisions of this Code shall govern where applicable
See also 22.1.3
Trang 15``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
1.1.6 — This Code does not govern design and
instal-lation of portions of concrete piles, drilled piers, and
caissons embedded in ground except for structures
assigned to Seismic Design Categories D, E, and F
See 21.12.4 for requirements for concrete piles, drilled
piers, and caissons in structures assigned to Seismic
Design Categories D, E, and F
“Code for Concrete Containments” reported by Joint
ACI-ASME Committee 359.1.5 (This provides requirementsfor the design, construction, and use of concrete reactorvessels and concrete containment structures for nuclearpower plants.)
R1.1.6 — The design and installation of piling fully
embedded in the ground is regulated by the general buildingcode For portions of piling in air or water, or in soil notcapable of providing adequate lateral restraint throughoutthe piling length to prevent buckling, the design provisions
of this code govern where applicable
Recommendations for concrete piles are given in detail in
“Recommendations for Design, Manufacture, and Installation of Concrete Piles” reported by ACI
Committee 543.1.6 (This provides recommendations for thedesign and use of most types of concrete piles for manykinds of construction.)
Recommendations for drilled piers are given in detail in
“Design and Construction of Drilled Piers” reported by
ACI Committee 336.1.7 (This provides recommendationsfor design and construction of foundation piers 2-1/2 ft indiameter or larger made by excavating a hole in the soil andthen filling it with concrete.)
Detailed recommendations for precast prestressed concrete
piles are given in “Recommended Practice for Design,
Manufacture, and Installation of Prestressed Concrete Piling” prepared by the PCI Committee on Prestressed
Concrete Piling.1.8
R1.1.7 — Detailed recommendations for design and
construction of slabs-on-ground and floors that do nottransmit vertical loads or lateral forces from other portions
of the structure to the soil, and residential post-tensionedslabs-on-ground, are given in the following publications:
“Design of Slabs-on-Ground” reported by ACI Committee
360.1.9 (This presents information on the design of ground, primarily industrial floors and the slabs adjacent tothem The report addresses the planning, design, anddetailing of the slabs Background information on thedesign theories is followed by discussion of the soil supportsystem, loadings, and types of slabs Design methods aregiven for structural plain concrete, reinforced concrete,shrinkage-compensating concrete, and post-tensionedconcrete slabs.)
slabs-on-“Design of Post-Tensioned Slabs-on-Ground,” PTI1.10
(This provides recommendations for post-tensioned ground foundations Presents guidelines for soil investigation,and design and construction of post-tensioned residential andlight commercial slabs on expansive or compressible soils.)
slab-on-1.1.7 — This Code does not govern 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
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 16``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
R1.1.8 — Concrete on steel deck
In steel framed structures, it is common practice to castconcrete floor slabs on stay-in-place steel deck In all cases,the deck serves as the form and may, in some cases, serve anadditional structural function
R1.1.8.1 — In its most basic application, the noncomposite
steel deck serves as a form, and the concrete slab is designed
to carry all superimposed loads
R1.1.8.2 — Another type of steel deck commonly used
develops composite action between the concrete and steeldeck In this type of construction, the steel deck serves asthe positive moment reinforcement The design of
composite slabs on steel deck is described in “Standard for
the Structural Design of Composite Slabs” (ANSI/
ASCE 3).1.11 The standard refers to the appropriate portions ofACI 318 for the design and construction of the concreteportion of the composite assembly Guidelines for theconstruction of composite steel deck slabs are given in
“Standard Practice for the Construction and Inspection
of Composite Slabs” (ANSI/ASCE 9).1.12 Reference 1.13
also provides guidance for design of composite slabs on steeldeck The design of negative moment reinforcement to make
a slab continuous is a common example where a portion ofthe slab is designed in conformance with this Code
R1.1.9 — Provisions for earthquake resistance R1.1.9.1 — Design requirements for an earthquake-resis-
tant structure in this Code are determined by the Seismic
Design Category (SDC) to which the structure is assigned.
In general, the SDC relates to seismic hazard level, soiltype, occupancy, and use of the building Assignment of abuilding to a SDC is under the jurisdiction of a generalbuilding code rather than ACI 318
Seismic Design Categories in this Code are adopted directlyfrom the 2005 ASCE/SEI 7 standard.1.14 Similar designations
are used by the 2006 edition of the “International Building
Code” (IBC),1.15 and the 2006 NFPA 5000 “Building
Construction and Safety Code.”1.16 The “BOCA National
Building Code” (NBC)1.17 and “Standard Building Code”
(SBC)1.18 use Seismic Performance Categories The 1997
“Uniform Building Code” (UBC)1.19 relates seismic designrequirements to seismic zones, whereas previous editions ofACI 318 related seismic design requirements to seismic risklevels Table R1.1.9.1 correlates Seismic Design Categories
to the low, moderate/intermediate, and high seismic riskterminology used in ACI 318 for several editions before the
2008 edition, and to the various methods of assigningdesign requirements in use in the U.S under the variousmodel building codes, the ASCE/SEI 7 standard, and theNEHRP Recommended Provisions.1.20
1.1.8 — Concrete on steel deck
1.1.8.1 — Design and construction of structural
concrete slabs cast on stay-in-place, noncomposite
steel deck are governed by this Code
1.1.8.2 — This Code does not govern the composite
design of structural concrete slabs cast on
stay-in-place, composite steel deck Concrete used in the
construction of such slabs shall be governed by
Chapters 1 through 6 of this Code, where applicable
Portions of such slabs designed as reinforced concrete
are governed by this Code
1.1.9 —Provisions for earthquake resistance
1.1.9.1 — The seismic design category of a structure
shall be determined in accordance with the legally
adopted general building code of which this Code forms
a part, or determined by other authority having
jurisdic-tion in areas without a legally adopted building code
Trang 17``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
In the absence of a general building code that prescribesearthquake loads and seismic zoning, it is the intent ofCommittee 318 that application of provisions for seismicdesign be consistent with national standards or modelbuilding codes such as References 1.14, 1.15, and 1.16
R1.1.9.2 — Structures assigned to Seismic design category
(SDC) A have the lowest seismic hazard and performancerequirements Provisions of Chapters 1 through 19 and
Chapter 22 are considered sufficient for these structures Forstructures assigned to other SDCs, the design requirements
of Chapter 21 apply, as delineated in 21.1
R1.1.10 — Code Requirements for Environmental neering Concrete Structures” reported by ACI Committee
Engi-350.1.21 (This gives material, design and constructionrecommendations for concrete tanks, reservoirs, and otherstructures commonly used in water and waste treatmentworks where dense, impermeable concrete with high resis-tance to chemical attack is required Special emphasis isplaced on a structural design that minimizes the possibility
of cracking and accommodates vibrating equipment andother special loads Proportioning of concrete, placement,curing, and protection against chemicals are also described.Design and spacing of joints receive special attention.)
R1.2 — Drawings and specifications
R1.2.1 — The provisions for preparation of design drawings
and specifications are, in general, consistent with those ofmost general building codes and are intended as supplements.The Code lists some of the more important items of infor-mation that should be included in the design drawings,details, or specifications The Code does not imply an all-inclusive list, and additional items may be required by thebuilding official
TABLE R1.1.9.1 — CORRELATION BETWEEN SEISMIC-RELATED TERMINOLOGY IN MODEL CODES
Code, standard, or resource document and edition
Level of seismic risk or assigned seismic performance or design categories as defined in the Code ACI 318-08; IBC 2000, 2003,
2006; NFPA 5000, 2003, 2006; ASCE 7-98, 7-02, 7-05;
Seismic Zone 2
Seismic Zone
3, 4
* SDC = Seismic design category as defined in code, standard, or resource document.
† SPC = Seismic performance category as defined in code, standard, or resource document.
1.1.9.2 — All structures shall satisfy the applicable
provisions of Chapter 21 except those assigned to
Seismic Design Category A and those otherwise
exempted by the legally adopted general building
code See 21.1.1
1.1.10 — This Code does not govern design and
construction of tanks and reservoirs
1.2 — Drawings and specifications
1.2.1 — Copies of design drawings, typical details, and
specifications for all structural concrete construction
shall bear the seal of a licensed design professional
These drawings, details, and specifications shall show:
(a) Name and date of issue of code and supplement
to which design conforms;
(b) Live load and other loads used in design;
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 18``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
R1.2.2 — Documented computer output is acceptable
instead of manual calculations The extent of input andoutput information required will vary according to thespecific requirements of individual building officials
However, when a computer program has been used, onlyskeleton data should normally be required This shouldconsist of sufficient input and output data and other infor-mation to allow the building official to perform a detailedreview and make comparisons using another program ormanual calculations Input data should be identified as tomember designation, applied loads, and span lengths Therelated output data should include member designation andthe shears, moments, and reactions at key points in the span
For column design, it is desirable to include moment fication factors in the output where applicable
magni-The Code permits model analysis to be used to supplementstructural analysis and design calculations Documentation
of the model analysis should be provided with the relatedcalculations Model analysis should be performed by anindividual having experience in this technique
R1.3 — Inspection
The quality of concrete structures depends largely on manship in construction The best of materials and designpractices will not be effective unless the construction is
work-(c) Specified compressive strength of concrete at
stated ages or stages of construction for which each
part of structure is designed;
(d) Specified strength or grade of reinforcement;
(e) Size and location of all structural elements,
reinforcement, and anchors;
(f) Provision for dimensional changes resulting from
creep, shrinkage, and temperature;
(g) Magnitude and location of prestressing forces;
(h) Anchorage length of reinforcement and location
and length of lap splices;
(i) Type and location of mechanical and welded
splices of reinforcement;
(j) Details and location of all contraction or isolation
joints specified for structural plain concrete in
Chapter 22;
(k) Minimum concrete compressive strength at time
of post-tensioning;
(l) Stressing sequence for post-tensioning tendons;
(m) Statement if slab-on-ground is designed as a
structural diaphragm, see 21.12.3.4
1.2.2 — Calculations pertinent to design shall be filed
with the drawings when required by the building official
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
1.3 — Inspection
Trang 19``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
1.3.1 — Concrete construction shall be inspected as
required by the legally adopted general building code In
the absence of such inspection requirements, concrete
construction shall be inspected throughout the various
Work stages by or under the supervision of a licensed
design professional or by a qualified inspector
performed well Inspection is necessary to confirm that theconstruction is in accordance with the design drawings andproject specifications Proper performance of the structuredepends on construction that accurately represents thedesign and meets code requirements within the tolerancesallowed Qualification of the inspectors can be obtainedfrom a certification program, such as the ACI CertificationProgram for Concrete Construction Special Inspector
R1.3.1 — Inspection of construction by or under the
supervision of the licensed design professional responsiblefor the design should be considered because the person incharge of the design is usually the best qualified to determine ifconstruction is in conformance with construction documents.When such an arrangement is not feasible, inspection ofconstruction through other licensed design professionals orthrough separate inspection organizations with demonstratedcapability for performing the inspection may be used.Qualified inspectors should establish their qualification bybecoming certified to inspect and record the results ofconcrete construction, including preplacement, placement,and postplacement operations through the ACI InspectorCertification Program: Concrete Construction SpecialInspector
When inspection is done independently of the licenseddesign professional responsible for the design, it is recom-mended that the licensed design professional responsible forthe design be employed at least to oversee inspection andobserve the Work to see that the design requirements areproperly executed
In some jurisdictions, legislation has established registration
or licensing procedures for persons performing certaininspection functions A check should be made in the generalbuilding code or with the building official to ascertain if anysuch requirements exist within a specific jurisdiction.Inspection reports should be promptly distributed to theowner, licensed design professional responsible for thedesign, contractor, appropriate subcontractors, appropriatesuppliers, and the building official to allow timely identifi-cation of compliance or the need for corrective action.Inspection responsibility and the degree of inspectionrequired should be set forth in the contracts between theowner, architect, engineer, contractor, and inspector.Adequate fees should be provided consistent with the workand equipment necessary to properly perform the inspection
R1.3.2 — By inspection, the Code does not mean that the
inspector should supervise the construction Rather, it meansthat the one employed for inspection should visit the projectwith the frequency necessary to observe the various stages
1.3.2 — The inspector shall require compliance with
design drawings and specifications Unless specified
otherwise in the legally adopted general building code,
inspection records shall include:
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 20``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
(a) Delivery, placement, and testing reports
docu-menting the quantity, location of placement, fresh
concrete tests, strength, and other test of all classes
of concrete mixtures;
(b) Construction and removal of forms and reshoring;
(c) Placing of reinforcement and anchors;
(d) Mixing, placing, and curing of concrete;
(e) Sequence of erection and connection of precast
members;
(f) Tensioning of tendons;
(g) Any significant construction loadings on
completed floors, members, or walls;
(h) General progress of Work
of Work and ascertain that it is being done in compliancewith contract documents and Code requirements Thefrequency should be at least enough to provide generalknowledge of each operation, whether this is several times aday or once in several days
Inspection in no way relieves the contractor from the obligation
to follow the plans and specifications and to provide thedesignated quality and quantity of materials and workman-ship for all job stages Some of the information regardingdesignated concrete mixtures on a project is often provided
in a preconstruction submittal to the licensed design sional For instance, concrete mixture ingredients andcomposition are often described in detail in the submittaland are subsequently identified by a mixture designation(reflected on a delivery ticket) that can also identify theplacement location in the structure The inspector should bepresent as frequently as necessary to judge whether thequality, as measured by quality assurance tests, quantity, andplacement of the concrete comply with the contract docu-ments; to counsel on possible ways of obtaining the desiredresults; to see that the general system proposed for form-work appears proper (though it remains the contractor’sresponsibility to design and build adequate forms and toleave them in place until it is safe to remove them); to seethat reinforcement is properly installed; to see that concrete
profes-is delivered as required and profes-is of the correct quality, properlyplaced, and cured; and to see that tests for quality assuranceare being made as specified
The Code prescribes minimum requirements for inspection
of all structures within its scope It is not a constructionspecification and any user of the Code may require higherstandards of inspection than cited in the legal code ifadditional requirements are necessary
Recommended procedures for organization and conduct of
concrete inspection are given in detail in “Guide for
Concrete Inspection,” reported by ACI Committee 311.1.22
(This sets forth procedures relating to concrete construction
to serve as a guide to owners, architects, and engineers inplanning an inspection program.)
Detailed methods of inspecting concrete construction are
given in “ACI Manual of Concrete Inspection” (SP-2)
reported by ACI Committee 311.1.23 (This describesmethods of inspecting concrete construction that are gener-ally accepted as good practice Intended as a supplement tospecifications and as a guide in matters not covered byspecifications.)
R1.3.3 — The term “ambient temperature” means the
temperature of the environment to which the concrete isdirectly exposed Concrete temperature as used in thissection may be taken as the surface temperature of the
1.3.3 — When the ambient temperature falls below
40 °F or rises above 95 °F, a record shall be kept of
concrete temperatures and of protection given to
concrete during placement and curing
Trang 21
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
concrete Surface temperatures may be determined byplacing temperature sensors in contact with concretesurfaces or between concrete surfaces and covers used forcuring, such as insulation blankets or plastic sheeting
R1.3.4 — A record of inspection in the form of a job diary is
required in case questions subsequently arise concerning theperformance or safety of the structure or members Photo-graphs documenting job progress may also be desirable.Records of inspection should be preserved for at least 2 yearsafter the completion of the project The completion of theproject is the date at which the owner accepts the project, orwhen a certificate of occupancy is issued, whichever date islater The general building code or other legal requirementsmay require a longer preservation of such records
R1.3.5 — The purpose of this section is to ensure that the
detailing required in special moment frames is properlyexecuted through inspection by personnel who are qualified
to do this Work Qualifications of inspectors should be able to the jurisdiction enforcing the general building code
accept-1.3.4 — Records of inspection required in 1.3.2 and
1.3.3 shall be preserved by the inspecting engineer or
architect for 2 years after completion of the project
1.3.5 — For special moment frames designed in
accordance with Chapter 21, continuous inspection of
the placement of the reinforcement and concrete shall
be made by a qualified inspector The inspector shall
be under the supervision of the licensed design
professional responsible for the structural design or
under the supervision of a licensed design
profes-sional with demonstrated capability for supervising
inspection of construction of special moment frames
1.4 — Approval of special systems of
design or construction
Sponsors of any system of design or construction
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 or
to a board of examiners appointed by the building official
This board shall be composed of competent engineers
and shall have authority to investigate the data so
submitted, to require tests, and to 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
or components might be excluded from use by implication ifmeans were not available to obtain acceptance
For special systems considered under this section, specifictests, load factors, deflection limits, and other pertinentrequirements should be set by the board of examiners, andshould be consistent with the intent of the Code
The provisions of this section do not apply to model testsused to supplement calculations under 1.2.2 or to strengthevaluation of existing structures under Chapter 20
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 22
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE Notes COMMENTARY
Trang 23``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -2.1 — Code notation
The terms in this list are used in the Code and as
needed in the Commentary
a = depth of equivalent rectangular stress block
as defined in 10.2.7.1, in., Chapter 10
a v = shear span, equal to distance from center of
concentrated load to either: (a) face ofsupport for continuous or cantileveredmembers, or (b) center of support for simplysupported members, in., Chapter 11,Appendix A
A b = area of an individual bar or wire, in.2,
Chapters 10, 12
A brg = net bearing area of the head of stud, anchor
bolt, or headed deformed bar, in.2, Chapter 12,Appendix D
A c = area of concrete section resisting shear
transfer, in.2, Chapters 11, 21
A cf = larger gross cross-sectional area of the
slab-beam strips of the two orthogonal equivalentframes intersecting at a column of a two-wayslab, in.2, Chapter 18
A ch = cross-sectional area of a structural member
measured to the outside edges of transversereinforcement, in.2, Chapters 10, 21
A cp = area enclosed by outside perimeter of
concrete cross section, in.2, see 11.5.1,Chapter 11
A cs = cross-sectional area at one end of a strut in
a strut-and-tie model, taken perpendicular tothe axis of the strut, in.2, Appendix A
A ct = area of that part of cross section between
the flexural tension face and center of gravity
of gross section, in.2, Chapter 18
A cv = gross area of concrete section bounded by
web thickness and length of section in thedirection of shear force considered, in.2,Chapter 21
A cw = area of concrete section of an individual pier,
horizontal wall segment, or coupling beamresisting shear, in.2, Chapter 21
A f = area of reinforcement in bracket or corbel
resisting factored moment, in.2, see 11.8,Chapter 11
A g = gross area of concrete section, in.2 For a
hollow section, A g is the area of the concreteonly and does not include the area of thevoid(s), see 11.5.1, Chapters 9-11, 14-16,
21, 22, Appendixes B, C
A h = total area of shear reinforcement parallel to
primary tension reinforcement in a corbel orbracket, in.2, see 11.9, Chapter 11
A j = effective cross-sectional area within a joint in
a plane parallel to plane of reinforcementgenerating shear in the joint, in.2, see21.7.4.1, Chapter 21
A l = total area of longitudinal reinforcement to
resist torsion, in.2, Chapter 11
A l ,min = minimum area of longitudinal reinforcement to
resist torsion, in.2, see 11.5.5.3, Chapter 11
A n = area of reinforcement in bracket or corbel
resisting tensile force N uc, in.2, see 11.8,Chapter 11
A nz = area of a face of a nodal zone or a section
through a nodal zone, in.2, Appendix A
A Nc = projected concrete failure area of a single
anchor or group of anchors, for calculation ofstrength in tension, in.2, see D.5.2.1,Appendix D
A Nco = projected concrete failure area of a single
anchor, for calculation of strength in tension
if not limited by edge distance or spacing,
in.2, see D.5.2.1, Appendix D
A o = gross area enclosed by shear flow path, in.2,
Chapter 11
A oh = area enclosed by centerline of the outermost
closed transverse torsional reinforcement,
in.2, Chapter 11
A ps = area of prestressing steel in flexural tension
zone, in.2, Chapter 18, Appendix B
A s = area of nonprestressed longitudinal tension
reinforcement, in.2, Chapters 10-12, 14, 15,
18, Appendix B
A s′ = area of compression reinforcement, in.2,
Appendix A
A sc = area of primary tension reinforcement in a
corbel or bracket, in.2, see 11.8.3.5,Chapter 11
A se,N = effective cross-sectional area of anchor in
tension, in.2, Appendix D
A se,V = effective cross-sectional area of anchor in
shear, in.2, Appendix D
A sh = total cross-sectional area of transverse
reinforcement (including crossties) within
spacing s and perpendicular to dimension
b c, in.2, Chapter 21
A si = total area of surface reinforcement at
spacing s i in the i-th layer crossing a strut,
with reinforcement at an angle αi to the axis
of the strut, in.2, Appendix A
CHAPTER 2 — NOTATION AND DEFINITIONS
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 24``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -A s,min= minimum area of flexural reinforcement, in.2,
see 10.5, Chapter 10
A st = total area of nonprestressed longitudinal
reinforcement (bars or steel shapes), in.2,Chapters 10, 21
A sx = area of structural steel shape, pipe, or tubing
in a composite section, in.2, Chapter 10
A t = area of one leg of a closed stirrup resisting
torsion within spacing s, in.2, Chapter 11
A tp = area of prestressing steel in a tie, in.2,
Appendix A
A tr = total cross-sectional area of all transverse
reinforcement within spacing s that crosses
the potential plane of splitting through thereinforcement being developed, in.2,Chapter 12
A ts = area of nonprestressed reinforcement in a
tie, in.2, Appendix A
A v = area of shear reinforcement spacing s, in.2,
Chapters 11, 17
A Vc = projected concrete failure area of a single
anchor or group of anchors, for calculation ofstrength in shear, in.2, see D.6.2.1, Appendix D
A Vco = projected concrete failure area of a single
anchor, for calculation of strength in shear, ifnot limited by corner influences, spacing, ormember thickness, in.2, see D.6.2.1,Appendix D
A vd = total area of reinforcement in each group of
diagonal bars in a diagonally reinforcedcoupling beam, in.2, Chapter 21
A vf = area of shear-friction reinforcement, in.2,
Chapters 11, 21
A vh = area of shear reinforcement parallel to
flex-ural tension reinforcement within spacing s2,
in.2, Chapter 11
A v,min= minimum area of shear reinforcement within
spacing s, in.2, see 11.4.6.3 and 11.4.6.4,Chapter 11
A1 = loaded area, in.2, Chapters 10, 22
A2 = area of the lower base of the largest frustum
of a pyramid, cone, or tapered wedgecontained wholly within the support andhaving for its upper base the loaded area,and having side slopes of 1 vertical to 2horizontal, in.2, Chapters 10, 22
b = width of compression face of member, in.,
Chapter 10, Appendix B
b c = cross-sectional dimension of member core
measured to the outside edges of the
trans-verse reinforcement composing area A sh, in.,Chapter 21
b o = perimeter of critical section for shear in slabs
and footings, in., see 11.11.1.2, Chapters 11,22
b s = width of strut, in., Appendix A
b t = width of that part of cross section containing
the closed stirrups resisting torsion, in.,Chapter 11
b v = width of cross section at contact surface
being investigated for horizontal shear, in.,Chapter 17
b w = web width, or diameter of circular section, in.,
Chapters 10-12, 21, 22, Appendix B
b1 = dimension of the critical section b o measured
in the direction of the span for whichmoments are determined, in., Chapter 13
b2 = dimension of the critical section b o measured
in the direction perpendicular to b1, in.,Chapter 13
B n = nominal bearing strength, lb, Chapter 22
B u = factored bearing load, lb, Chapter 22
c = distance from extreme compression fiber to
neutral axis, in., Chapters 9, 10, 14, 21
c ac = critical edge distance required to develop the
basic concrete breakout strength of a installed anchor in uncracked concretewithout supplementary reinforcement tocontrol splitting, in., see D.8.6, Appendix D
post-c a,max= maximum distance from center of an anchor
shaft to the edge of concrete, in., Appendix D
c a,min = minimum distance from center of an anchor
shaft to the edge of concrete, in., Appendix D
c a1 = distance from the center of an anchor shaft
to the edge of concrete in one direction, in If
shear is applied to anchor, c a1 is taken in thedirection of the applied shear If tension
is applied to the anchor, c a1 is the minimumedge distance, Appendix D
c a2 = distance from center of an anchor shaft to
the edge of concrete in the direction
perpen-dicular to c a1, in., Appendix D
c b = smaller of: (a) the distance from center of a
bar or wire to nearest concrete surface, and(b) one-half the center-to-center spacing ofbars or wires being developed, in., Chapter 12
c c = clear cover of reinforcement, in., see 10.6.4,
Chapter 10
c t = distance from the interior face of the column
to the slab edge measured parallel to c1, but
not exceeding c1, in., Chapter 21
rectangular column, capital, or bracketmeasured in the direction of the span forwhich moments are being determined, in.,Chapters 11, 13, 21
rectangular column, capital, or bracketmeasured in the direction perpendicular to
c1, in., Chapter 13
C = cross-sectional constant to define torsional
properties of slab and beam, see 13.6.4.2,Chapter 13
C m = factor relating actual moment diagram to an ``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -
Trang 25equivalent uniform moment diagram,Chapter 10
d = distance from extreme compression fiber to
centroid of longitudinal tension ment, in., Chapters 7, 9-12, 14, 17, 18, 21,Appendixes B, C
reinforce-d′ = distance from extreme compression fiber to
centroid of longitudinal compression forcement, in., Chapters 9, 18, Appendix C
rein-d a = outside diameter of anchor or shaft diameter
of headed stud, headed bolt, or hooked bolt,in., see D.8.4, Appendix D
d a′ = value substituted for d a when an oversized
anchor is used, in., see D.8.4, Appendix D
prestressing strand, in., Chapters 7, 12, 21
d p = distance from extreme compression fiber to
centroid of prestressing steel, in., Chapters11,18, Appendix B
d pile = diameter of pile at footing base, in., Chapter 15
d t = distance from extreme compression fiber to
centroid of extreme layer of longitudinaltension steel, in., Chapters 9, 10, Appendix C
D = dead loads, or related internal moments and
forces, Chapters 8, , 20, 21, Appendix C
e = base of Napierian logarithms, Chapter 18
e h = distance from the inner surface of the shaft of a
J- or L-bolt to the outer tip of the J- or L-bolt, in.,Appendix D
e N′ = distance between resultant tension load on a
group of anchors loaded in tension and thecentroid of the group of anchors loaded in
tension, in.; e N′ is always positive, Appendix D
e V′ = distance between resultant shear load on a
group of anchors loaded in shear in the samedirection, and the centroid of the group ofanchors loaded in shear in the same direction,
in.; e V′ is always positive, Appendix D
E = load effects of earthquake, or related internal
moments and forces, Chapters 9, 21,Appendix C
E c = modulus of elasticity of concrete, psi, see
EI = flexural stiffness of compression member,
in.2-lb, see 10.10.6, Chapter 10
E p = modulus of elasticity of prestressing steel,
psi, see 8.5.3, Chapter 8
E s = modulus of elasticity of reinforcement and
structural steel, psi, see 8.5.2, Chapters 8,
10, 14
f c′ = specified compressive strength of concrete,
psi, Chapters 4, 5, 8-12, 14, 18, 19, 21, 22,Appendixes A-D
= square root of specified compressivestrength of concrete, psi, Chapters 8, 9, 11,
12, 18, 19, 21, 22, Appendix D
concrete in a strut or a nodal zone, psi,Chapter 15, Appendix A
f ci′ = specified compressive strength of concrete
at time of initial prestress, psi, Chapters 7, 18
= square root of specified compressivestrength of concrete at time of initialprestress, psi, Chapter 18
f cr′ = required average compressive strength of
concrete used as the basis for selection ofconcrete proportions, psi, Chapter 5
f ct = average splitting tensile strength of
light-weight concrete, psi, Chapters 5, , 11, 12, 22
extreme fiber of section where tensile stress
is caused by externally applied loads, psi,Chapter 11
prestressing steel when stress is zero in theconcrete at the same level as the centroid ofthe prestressing steel, psi, Chapter 18
f pc = compressive stress in concrete (after
allow-ance for all prestress losses) at centroid ofcross section resisting externally appliedloads or at junction of web and flange whenthe centroid lies within the flange, psi (In a
composite member, f pc is the resultantcompressive stress at centroid of compositesection, or at junction of web and flangewhen the centroid lies within the flange, due
to both prestress and moments resisted byprecast member acting alone), Chapter 11
f pe = compressive stress in concrete due to
effec-tive prestress forces only (after allowance forall prestress losses) at extreme fiber ofsection where tensile stress is caused byexternally applied loads, psi, Chapter 11
f ps = stress in prestressing steel at nominal flexural
strength, psi, Chapters 12, 18
f pu = specified tensile strength of prestressing
steel, psi, Chapters 11, 18
f py = specified yield strength of prestressing steel,
psi, Chapter 18
f r = modulus of rupture of concrete, psi, see
9.5.2.3, Chapters 9, 14, 18, Appendix B
f s = calculated tensile stress in reinforcement at
service loads, psi, Chapters 10, 18
f s′ = stress in compression reinforcement under
factored loads, psi, Appendix A
f se = effective stress in prestressing steel (after
allowance for all prestress losses), psi,Chapters 12, 18, Appendix A
f t = extreme fiber stress in tension in the
precom-pressed tensile zone calculated at service
f c′
f ci′
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 26``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -loads using gross section properties, psi, see18.3.3, Chapter 18
f uta = specified tensile strength of anchor steel, psi,
Appendix D
f y = specified yield strength of reinforcement, psi,
Chapters 3, 7, 9-12, 14, 17-19, 21, dixes A-C
Appen-f ya = specified yield strength of anchor steel, psi,
Appendix D
f yt = specified yield strength f y of transverse
reinforcement, psi, Chapters 10-12, 21
F = loads due to weight and pressures of fluids
with well-defined densities and controllablemaximum heights, or related internalmoments and forces, Chapter 9, Appendix C
F n = nominal strength of a strut, tie, or nodal
zone, lb, Appendix A
F nn = nominal strength at face of a nodal zone, lb,
Appendix A
F ns = nominal strength of a strut, lb, Appendix A
F nt = nominal strength of a tie, lb, Appendix A
F u = factored force acting in a strut, tie, bearing
area, or nodal zone in a strut-and-tie model,
lb, Appendix A
h = overall thickness or height of member, in.,
Chapters 9-12, 14, 17, 18, 20-22, dixes A, C
Appen-h a = thickness of member in which an anchor is
located, measured parallel to anchor axis,in., Appendix D
h ef = effective embedment depth of anchor, in.,
see D.8.5, Appendix D
Chapter 11
h w = height of entire wall from base to top or
height of the segment of wall considered, in.,Chapters 11, 21
spacing of crossties or hoop legs on all faces
of the column, in., Chapter 21
H = loads due to weight and pressure of soil,
water in soil, or other materials, or relatedinternal moments and forces, Chapter 9,Appendix C
I = moment of inertia of section about centroidal
axis, in.4, Chapters 10, 11
I b = moment of inertia of gross section of beam
about centroidal axis, in.4, see 13.6.1.6,Chapter 13
I cr = moment of inertia of cracked section
trans-formed to concrete, in.4, Chapter 9
I e = effective moment of inertia for computation of
deflection, in.4, see 9.5.2.3, Chapter 9
I g = moment of inertia of gross concrete section
about centroidal axis, neglecting ment, in.4,Chapters 9, 10, 14
reinforce-I s = moment of inertia of gross section of slab
about centroidal axis defined for calculating
αf and βt, in.4, Chapter 13
I se = moment of inertia of reinforcement about
centroidal axis of member cross section, in.4,Chapter 10
I sx = moment of inertia of structural steel shape,
pipe, or tubing about centroidal axis ofcomposite member cross section, in.4,Chapter 10
members, Chapters 10, 14
k c = coefficient for basic concrete breakout
strength in tension, Appendix D
k cp = coefficient for pryout strength, Appendix D
K = wobble friction coefficient per foot of tendon,
Chapter 18
K tr = transverse reinforcement index, see 12.2.3,
Chapter 12
l = span length of beam or one-way slab; clear
projection of cantilever, in., see 8.7, Chapter 9
l a = additional embedment length beyond
center-line of support or point of inflection, in.,Chapter 12
l c = length of compression member in a frame,
measured center-to-center of the joints in theframe, in., Chapters 10, 14, 22
l d = development length in tension of deformed
bar, deformed wire, plain and deformedwelded wire reinforcement, or pretensionedstrand, in., Chapters 7, 12, 19, 21
deformed bars and deformed wire, in.,Chapter 12
l dh = development length in tension of deformed
bar or deformed wire with a standard hook,measured from critical section to outside end
of hook (straight embedment length betweencritical section and start of hook [point oftangency] plus inside radius of bend and onebar diameter), in., see 12.5 and 21.7.5,Chapters 12, 21
l dt = development length in tension of headed
deformed bar, measured from the criticalsection to the bearing face of the head, in.,see 12.6, Chapter 12
l e = load bearing length of anchor for shear, in.,
see D.6.2.2, Appendix D
l n = length of clear span measured face-to-face of
supports, in., Chapters 8-11, 13, 16, 18, 21
l o = length, measured from joint face along axis
of structural member, over which specialtransverse reinforcement must beprovided, in., Chapter 21
l px = distance from jacking end of prestressing
steel element to point under consideration, ft,see 18.6.2, Chapter 18
l t = span of member under load test, taken as ``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -
Trang 27the shorter span for two-way slab systems,
in Span is the smaller of: (a) distancebetween centers of supports, and (b) clear
distance between supports plus thickness h
of member Span for a cantilever shall betaken as twice the distance from face ofsupport to cantilever end, Chapter 20
l u = unsupported length of compression member,
in., see 10.10.1.1, Chapter 10
l v = length of shearhead arm from centroid of
concentrated load or reaction, in., Chapter 11
l w = length of entire wall or length of segment of
wall considered in direction of shear force,in., Chapters 11, 14, 21
l1 = length of span in direction that moments are
being determined, measured center of supports, in., Chapter 13
center-to-l2 = length of span in direction perpendicular to
l1, measured center-to-center of supports,in., see 13.6.2.3 and 13.6.2.4, Chapter 13
L = live loads, or related internal moments and
forces, Chapters 8, , 20, 21, Appendix C
L r = roof live load, or related internal moments
and forces, Chapter 9
M a = maximum moment in member due to service
loads at stage deflection is computed, in.-lb,Chapters 9, 14
M c = factored moment amplified for the effects of
member curvature used for design ofcompression member, in.-lb, see 10.10.6,Chapter 10
M cr = cracking moment, in.-lb, see 9.5.2.3,
Chap-ters 9, 14
M cre = moment causing flexural cracking at section
due to externally applied loads, in.-lb,Chapter 11
M m = factored moment modified to account for
effect of axial compression, in.-lb, see11.2.2.2, Chapter 11
M max = maximum factored moment at section due to
externally applied loads, in.-lb, Chapter 11
M n = nominal flexural strength at section, in.-lb,
Chapters 11, 12, 14, 18, 21, 22
M nb = nominal flexural strength of beam including
slab where in tension, framing into joint,
in.-lb, see 21.6.2.2, Chapter 21
M nc = nominal flexural strength of column framing
into joint, calculated for factored axial force,consistent with the direction of lateral forcesconsidered, resulting in lowest flexuralstrength, in.-lb, see 21.6.2.2, Chapter 21
M o = total factored static moment, in.-lb, Chapter 13
M p = required plastic moment strength of
shear-head cross section, in.-lb, Chapter 11
M pr = probable flexural strength of members, with
or without axial load, determined using theproperties of the member at the joint faces
assuming a tensile stress in the longitudinal
bars of at least 1.25f y and a strength reductionfactor, φ, of 1.0, in.-lb, Chapter 21
appreciable sway, in.-lb, Chapter 10
M slab = portion of slab factored moment balanced by
support moment, in.-lb, Chapter 21
M u = factored moment at section, in.-lb, Chapters 10,
11, 13, 14, 21, 22
M ua = moment at midheight of wall due to factored
lateral and eccentric vertical loads, not
including PΔ effects, in.-lb, Chapter 14
M v = moment resistance contributed by
shear-head reinforcement, in.-lb, Chapter 11
M1 = smaller factored end moment on a
compres-sion member, to be taken as positive ifmember is bent in single curvature, andnegative if bent in double curvature, in.-lb,Chapter 10
member at the end at which M1 acts, due toloads that cause no appreciable sidesway,calculated using a first-order elastic frameanalysis, in.-lb, Chapter 10
member at the end at which M1 acts, due toloads that cause appreciable sidesway,calculated using a first-order elastic frameanalysis, in.-lb, Chapter 10
M2 = larger factored end moment on compression
member If transverse loading occurs
between supports, M2 is taken as the largest
moment occurring in member Value of M2 isalways positive, in.-lb, Chapter 10
M 2,min = minimum value of M2, in.-lb, Chapter 10
member at the end at which M2 acts, due toloads that cause no appreciable sidesway,calculated using a first-order elastic frameanalysis, in.-lb, Chapter 10
member at the end at which M2 acts, due toloads that cause appreciable sidesway,calculated using a first-order elastic frameanalysis, in.-lb, Chapter 10
bars, wires, monostrand anchorage devices,anchors, or shearhead arms, Chapters 5, 11,
12, 18, Appendix D
N b = basic concrete breakout strength in tension
of a single anchor in cracked concrete, lb,see D.5.2.2, Appendix D
N c = tension force in concrete due to unfactored
dead load plus live load, lb, Chapter 18
N cb = nominal concrete breakout strength in
tension of a single anchor, lb, see D.5.2.1,Appendix D
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 28``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -N cbg = nominal concrete breakout strength in
tension of a group of anchors, lb, seeD.5.2.1, Appendix D
N n = nominal strength in tension, lb, Appendix D
N p = pullout strength in tension of a single anchor
in cracked concrete, lb, see D.5.3.4 andD.5.3.5, Appendix D
N pn = nominal pullout strength in tension of a
single anchor, lb, see D.5.3.1, Appendix D
N sa = nominal strength of a single anchor or group
of anchors in tension as governed by thesteel strength, lb, see D.5.1.1 and D.5.1.2,Appendix D
N sb = side-face blowout strength of a single
anchor, lb, Appendix D
N sbg = side-face blowout strength of a group of
anchors, lb, Appendix D
N u = factored axial force normal to cross section
occurring simultaneously with V u or T u ; to be
taken as positive for compression andnegative for tension, lb, Chapter 11
N ua = factored tensile force applied to anchor or
group of anchors, lb, Appendix D
N uc = factored horizontal tensile force applied at
top of bracket or corbel acting
simulta-neously with V u, to be taken as positive fortension, lb, Chapter 11
p cp = outside perimeter of concrete cross section,
in., see 11.5.1, Chapter 11
p h = perimeter of centerline of outermost closed
transverse torsional reinforcement, in.,Chapter 11
P b = nominal axial strength at balanced strain
conditions, lb, see 10.3.2, Chapters 9, 10,Appendixes B, C
P c = critical buckling load, lb, see 10.10.6,
P pj = prestressing force at jacking end, lb, Chapter 18
P pu = factored prestressing force at anchorage
device, lb, Chapter 18
P px = prestressing force evaluated at distance l px
from the jacking end, lb, Chapter 18
(midheight) section including effects of weight, lb, Chapter 14
self-P u = factored axial force; to be taken as positive
for compression and negative for tension, lb,Chapters 10, 14, 21, 22
q Du = factored dead load per unit area, Chapter 13
q Lu = factored live load per unit area, Chapter 13
q u = factored load per unit area, Chapter 13
Q = stability index for a story, see 10.10.5.2,
Chapter 10
compression member, in., Chapter 10
R = rain load, or related internal moments and
forces, Chapter 9
s = center-to-center spacing of items, such as
longitudinal reinforcement, transversereinforcement, prestressing tendons, wires,
or anchors, in., Chapters 10-12, 17-21,Appendix D
s i = center-to-center spacing of reinforcement in
the i-th layer adjacent to the surface of the
member, in., Appendix A
s o = center-to-center spacing of transverse
rein-forcement within the length l o, in., Chapter 21
s s = sample standard deviation, psi, Chapter 5,
Appendix D
s2 = center-to-center spacing of longitudinal shear
or torsion reinforcement, in., Chapter 11
S = snow load, or related internal moments and
forces, Chapters 9, 21
S e = moment, shear, or axial force at connection
corresponding to development of probablestrength at intended yield locations, based
on the governing mechanism of inelasticlateral deformation, considering both gravityand earthquake load effects, Chapter 21
S m = elastic section modulus, in.3, Chapter 22
S n = nominal flexural, shear, or axial strength of
connection, Chapter 21
S y = yield strength of connection, based on f y, for
moment, shear, or axial force, Chapter 21
t = wall thickness of hollow section, in., Chapter 11
shrinkage, differential settlement, andshrinkage-compensating concrete, Chapter 9,Appendix C
T n = nominal torsional moment strength, in.-lb,
Chapter 11
T u = factored torsional moment at section, in.-lb,
Chapter 11
U = required strength to resist factored loads or
related internal moments and forces,Chapter 9, Appendix C
v n = nominal shear stress, psi, see 11.11.6.2,
Chapters 11, 21
V b = basic concrete breakout strength in shear of
a single anchor in cracked concrete, lb, seeD.6.2.2 and D.6.2.3, Appendix D
concrete, lb, Chapters 8, 11, 13, 21
V cb = nominal concrete breakout strength in shear
of a single anchor, lb, see D.6.2.1, Appendix D
V cbg = nominal concrete breakout strength in shear
of a group of anchors, lb, see D.6.2.1,Appendix D
Trang 29``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -V ci = nominal shear strength provided by concrete
when diagonal cracking results fromcombined shear and moment, lb, Chapter 11
V cp = nominal concrete pryout strength of a single
anchor, lb, see D.6.3.1, Appendix D
V cpg = nominal concrete pryout strength of a group
of anchors, lb, see D.6.3.1, Appendix D
V cw = nominal shear strength provided by concrete
when diagonal cracking results from highprincipal tensile stress in web, lb, Chapter 11
V d = shear force at section due to unfactored
dead load, lb, Chapter 11
V e = design shear force corresponding to the
development of the probable momentstrength of the member, lb, see 21.5.4.1 and21.6.5.1, Chapter 21
V i = factored shear force at section due to externally
applied loads occurring simultaneously with
V p = vertical component of effective prestress
force at section, lb, Chapter 11
V s = nominal shear strength provided by shear
reinforcement, lb, Chapter 11
V sa = nominal strength in shear of a single anchor
or group of anchors as governed by the steelstrength, lb, see D.6.1.1 and D.6.1.2,Appendix D
V u = factored shear force at section, lb, Chapters
11-13, 17, 21, 22
V ua = factored shear force applied to a single
anchor or group of anchors, lb, Appendix D
V ug = factored shear force on the slab critical
section for two-way action due to gravityloads, lb, see 21.13.6
V us = factored horizontal shear in a story, lb,
Chapter 10
w c = unit weight of normalweight concrete or
equilibrium density of lightweight concrete,lb/ft3, Chapters 8, 9
w u = factored load per unit length of beam or
one-way slab, Chapter 8
W = wind load, or related internal moments and
forces, Chapter 9, Appendix C
x = shorter overall dimension of rectangular part
of cross section, in., Chapter 13
y = longer overall dimension of rectangular part
of cross section, in., Chapter 13
section, neglecting reinforcement, to tensionface, in., Chapters 9, 11
α = angle defining the orientation of
reinforce-ment, Chapters 11, 21, Appendix A
αc = coefficient defining the relative contribution of
concrete strength to nominal wall shearstrength, see 21.9.4.1, Chapter 21
αf = ratio of flexural stiffness of beam section to
flexural stiffness of a width of slab boundedlaterally by centerlines of adjacent panels (ifany) on each side of the beam, see 13.6.1.6,Chapters 9, 13
αfm = average value of αf for all beams on edges of
a panel, Chapter 9
αf1 = αf in direction of l1, Chapter 13
αf2 = αf in direction of l2, Chapter 13
αi = angle between the axis of a strut and the
bars in the i-th layer of reinforcement
crossing that strut, Appendix A
αpx = total angular change of tendon profile from
tendon jacking end to point under ation, radians, Chapter 18
consider-αs = constant used to compute V c in slabs and
footings, Chapter 11
αv = ratio of flexural stiffness of shearhead arm to
that of the surrounding composite slabsection, see 11.11.4.5, Chapter 11
β = ratio of long to short dimensions: clear spans
for two-way slabs, see 9.5.3.3 and 22.5.4;sides of column, concentrated load or reactionarea, see 11.11.2.1; or sides of a footing,see 15.4.4.2, Chapters 9, 11, 15, 22
βb = ratio of area of reinforcement cut off to total
area of tension reinforcement at section,Chapter 12
βdns = ratio used to account for reduction of
stiff-ness of columns due to sustained axialloads, see 10.10.6.2, Chapter 10
βds = ratio used to account for reduction of stiffness
of columns due to sustained lateral loads,see 10.10.4.2, Chapter 10
βn = factor to account for the effect of the
anchorage of ties on the effective compressivestrength of a nodal zone, Appendix A
βp = factor used to compute V c in prestressed
slabs, Chapter 11
βs = factor to account for the effect of cracking
and confining reinforcement on the effectivecompressive strength of the concrete in astrut, Appendix A
βt = ratio of torsional stiffness of edge beam
section to flexural stiffness of a width of slabequal to span length of beam, center-to-center of supports, see 13.6.4.2, Chapter 13
β1 = factor relating depth of equivalent
rectan-gular compressive stress block to neutralaxis depth, see 10.2.7.3, Chapters 10, 18,Appendix B
γf = factor used to determine the unbalanced
moment transferred by flexure at slab-columnconnections, see 13.5.3.2, Chapters 11,
13, 21
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 30
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -γp = factor for type of prestressing steel, see
18.7.2, Chapter 18
γs = factor used to determine the portion of
reinforcement located in center band offooting, see 15.4.4.2, Chapter 15
γv = factor used to determine the unbalanced
moment transferred by eccentricity of shear
at slab-column connections, see 11.11.7.1,Chapter 11
δ = moment magnification factor to reflect effects
of member curvature between ends ofcompression member, Chapter 10
δs = moment magnification factor for frames not
braced against sidesway, to reflect lateraldrift resulting from lateral and gravity loads,Chapter 10
δu = design displacement, in., Chapter 21
midheight of wall corresponding to cracking
moment, M cr, in., Chapter 14
Δf p = increase in stress in prestressing steel due
to factored loads, psi, Appendix A
Δf ps = stress in prestressing steel at service loads
less decompression stress, psi, Chapter 18
midheight of wall corresponding to nominal
flexural strength, M n, in., Chapter 14
Δo = relative lateral deflection between the top
and bottom of a story due to lateral forcescomputed using a first-order elastic frameanalysis and stiffness values satisfying10.10.5.2, in., Chapter 10
Δr = difference between initial and final (after load
removal) deflections for load test or repeatload test, in., Chapter 20
midheight of wall due to service loads, in.,Chapter 14
Δu = computed deflection at midheight of wall due
to factored loads, in., Chapter 14
Δ1 = measured maximum deflection during first
load test, in., see 20.5.2, Chapter 20
second load test relative to the position ofthe structure at the beginning of second loadtest, in., see 20.5.2, Chapter 20
εt = net tensile strain in extreme layer of longitudinal
tension steel at nominal strength, excludingstrains due to effective prestress, creep,shrinkage, and temperature, Chapters 8-10,Appendix C
diagonal, or compression field and thetension chord of the member, Chapter 11,Appendix A
λ = modification factor reflecting the reduced
mechanical properties of lightweight concrete,
all relative to normalweight concrete of thesame compressive strength, see 8.6.1,11.6.4.3, 12.2.4(d), 12.5.2, Chapters 9, 11,12,19, 21, 22, and Appendixes A, D
λΔ = multiplier for additional deflection due to
long-term effects, see 9.5.2.5, Chapter 9
μ = coefficient of friction, see 11.6.4.3, Chapters
ρ′ = ratio of A s′ to bd, Chapter 9, Appendix B
ρb = ratio of A s to bd producing balanced strain
conditions, see 10.3.2, Chapters 10, 13, 14,Appendix B
ρl = ratio of area of distributed longitudinal
reinforcement to gross concrete areaperpendicular to that reinforcement ,Chapters 11, 14, 21
ρp = ratio of A ps to bd p, Chapter 18
ρs = ratio of volume of spiral reinforcement to
total volume of core confined by the spiral(measured out-to-out of spirals), Chapters
10, 21
ρt = ratio of area distributed transverse
reinforce-ment to gross concrete area perpendicular tothat reinforcement, Chapters 11, 14, 21
ρv = ratio of tie reinforcement area to area of
contact surface, see 17.5.3.3, Chapter 17
ρw = ratio of A s to b w d, Chapter 11
φ = strength reduction factor, see 9.3, Chapters
8-11, 13, 14, 17-22, Appendixes A-D
ψc,N = factor used to modify tensile strength of
anchors based on presence or absence ofcracks in concrete, see D.5.2.6, Appendix D
ψc,P = factor used to modify pullout strength of
anchors based on presence or absence ofcracks in concrete, see D.5.3.6, Appendix D
ψc,V = factor used to modify shear strength of
anchors based on presence or absence ofcracks in concrete and presence or absence
of supplementary reinforcement, see D.6.2.7for anchors in shear, Appendix D
ψcp,N = factor used to modify tensile strength of
post-installed anchors intended for use inuncracked concrete without supplementaryreinforcement, see D.5.2.7, Appendix D
ψe = factor used to modify development length
based on reinforcement coating, see 12.2.4,Chapter 12
ψec,N = factor used to modify tensile strength of
anchors based on eccentricity of appliedloads, see D.5.2.4, Appendix D
ψec,V = factor used to modify shear strength of ``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -
Trang 31anchors based on eccentricity of appliedloads, see D.6.2.5, Appendix D
ψed,N = factor used to modify tensile strength of
anchors based on proximity to edges ofconcrete member, see D.5.2.5, Appendix D
ψed,V = factor used to modify shear strength of
anchors based on proximity to edges ofconcrete member, see D.6.2.6, Appendix D
ψh,V = factor used to modify shear strength of
anchors located in concrete members with
h a < 1.5c a1, see D.6.2.8, Appendix D
ψs = factor used to modify development length
based on reinforcement size, see 12.2.4,Chapter 12
ψt = factor used to modify development length
based on reinforcement location, see 12.2.4,Chapter 12
ψw = factor used to modify development length for
welded deformed wire reinforcement intension, see 12.7, Chapter 12
ωw = tension reinforcement index for flanged
sections, see B.18.8.1, Appendix B
ωw′ = compression reinforcement index for flanged
sections, see B.18.8.1, Appendix B
R2.1 — Commentary notation
The terms used in this list are used in the Commentary, but
not in the Code
Units of measurement are given in the Notation to assist the
user and are not intended to preclude the use of other correctly
applied units for the same symbol, such as feet or kips
c a1′ = limiting value of c a1 when anchors are located
less than 1.5h ef from three or more edges (see
h anc = dimension of anchorage device or single group of
closely spaced devices in the direction of burstingbeing considered, in., Chapter 18
h ef′ = limiting value of h ef when anchors are located
less than 1.5h ef from three or more edges (see
Fig RD.5.2.3), Appendix D
K t = torsional stiffness of torsional member; moment
per unit rotation, see R13.7.5, Chapter 13
K05 = coefficient associated with the 5 percent fractile,
Appendix D
l anc = length along which anchorage of a tie must occur,
in., Appendix A
l b = width of bearing, in., Appendix A
M = moment acting on anchor or anchor group,
w s = width of a strut perpendicular to the axis of the
strut, in., Appendix A
w t = effective height of concrete concentric with a tie,
used to dimension nodal zone, in., Appendix A
w t,max = maximum effective height of concrete concentric
with a tie, in., Appendix A
Δf pt = f ps at the section of maximum moment minus the
stress in the prestressing steel due to prestressingand factored bending moments at the section underconsideration, psi, see R11.5.3.10, Chapter 11
εcu = maximum usable strain at extreme concrete
compression fiber, Fig R10.3.3
φK = stiffness reduction factor, see R10.10, Chapter 10
Ωo = amplification factor to account for overstrength
of the seismic-force-resisting system, specified indocuments such as NEHRP,21.4 ASCE/SEI,21.1IBC,21.2 and UBC,21.3Chapter 21
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 32``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
R2.2 — Definitions
For consistent application of the Code, it is necessary thatterms be defined where they have particular meanings in theCode The definitions given are for use in application of thisCode only and do not always correspond to ordinary usage
A glossary of most-used terms relating to cement turing, concrete design and construction, and research in
manufac-concrete is contained in “Cement and Concrete
Termi-nology” available on the ACI website.
2.2 — Definitions
The following terms are defined for general use in this
Code Specialized definitions appear in individual
chapters
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 a hydraulic cement
concrete or mortar
Aggregate, lightweight — Aggregate meeting the
requirements of ASTM C330 and having a loose bulk
density of 70 lb/ft3 or less, determined in accordance
with ASTM C29
Anchorage device — In post-tensioning, the
hard-ware used for transferring a post-tensioning force from
the prestressing steel to the concrete
Anchorage device — Most anchorage devices for
post-tensioning are standard manufactured devices availablefrom commercial sources In some cases, “special” details
or assemblages are developed that combine various wedgesand wedge plates for anchoring prestressing steel Theseinformal designations as standard anchorage devices orspecial anchorage devices have no direct relation to theCode and AASHTO “Standard Specifications for HighwayBridges” classification of anchorage devices as BasicAnchorage Devices or Special Anchorage Devices
Anchorage zone — The terminology “ahead of” and “behind”
the anchorage device is illustrated in Fig R18.13.1(b)
Anchorage zone — In post-tensioned members, the
portion of the member through which the
concen-trated 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
Base of structure — Level at which the horizontal
earthquake ground motions are assumed to be
imparted to a building This level does not necessarily
coincide with the ground level See Chapter 21
Basic monostrand anchorage device — Anchorage
device used with any single strand or a single 5/8 in or
smaller diameter bar that satisfies 18.21.1 and the
anchorage device requirements of ACI 423.7
Basic anchorage devices — Devices that are so
propor-tioned that they can be checked analytically for compliancewith bearing stress and stiffness requirements withouthaving to undergo the acceptance-testing program required
of special anchorage devices
Trang 33``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Basic multistrand anchorage device — Anchorage
device used with multiple strands, bars, or wires, or with
single bars larger than 5/8 in diameter, that satisfies
18.21.1 and the bearing stress and minimum plate
stiffness requirements of AASHTO Bridge
Specifica-tions, Division I, Articles 9.21.7.2.2 through 9.21.7.2.4
Bonded tendon — Tendon in which prestressing steel
is bonded to concrete either directly or through
grouting
Boundary element — Portion along structural wall
and structural diaphragm edge strengthened by
longi-tudinal and transverse reinforcement Boundary
elements do not necessarily require an increase in the
thickness of the wall or diaphragm Edges of openings
within walls and diaphragms shall be provided with
boundary elements as required by 21.9.6 or 21.11.7.5
See Chapter 21
Building official — The officer or other designated
authority charged with the administration and
enforce-ment of this Code, or a duly authorized representative
Building official — The term used by many general
building codes to identify the person charged with tration and enforcement of provisions of the building code.Such terms as building commissioner or building inspectorare variations of the title and the term “building official” asused in this Code, is intended to include those variations, aswell as others that are used in the same sense
adminis-Cementitious materials — Materials as specified in
Chapter 3, which have cementing value when 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/or ground granulated blast-furnace slag
Collector element — Element that acts in axial
tension or compression to transmit
earthquake-induced forces between a structural diaphragm and a
vertical element of the seismic-force-resisting system
See Chapter 21
Column — Member with a ratio of height-to-least
lateral dimension exceeding 3 used primarily to
support axial compressive load For a tapered
member, the least lateral dimension is the average of
the top and bottom dimensions of the smaller side
Column — The term “compression member” is used in the
Code to define any member in which the primary stress islongitudinal compression Such a member need not bevertical but may have any orientation in space Bearing walls,columns, and pedestals qualify as compression membersunder this definition
The differentiation between columns and walls in theCode is based on the principal use rather than on arbitraryrelationships of height and cross-sectional dimensions TheCode, however, permits walls to be designed using theprinciples stated for column design (see 14.4), as well as bythe empirical method (see 14.5)
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 34``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Composite concrete flexural members — Concrete
flexural members of precast or cast-in-place concrete
elements, or both, constructed in separate placements
but so interconnected that all elements respond to
loads as a unit
Compression-controlled section — A cross section
in which the net tensile strain in the extreme tension
steel at nominal strength is less than or equal to the
compression-controlled strain limit
Compression-controlled strain limit — The net
tensile strain at balanced strain conditions See 10.3.3
Concrete — Mixture of portland cement or any other
hydraulic cement, 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 C330
Concrete, lightweight — Concrete containing
light-weight aggregate and an equilibrium density, as
deter-mined by ASTM C567, between 90 and 115 lb/ft3
While a wall always encloses or separates spaces, it mayalso be used to resist horizontal or vertical forces orbending For example, a retaining wall or a basement wallalso supports various combinations of loads
A column is normally used as a main vertical member carryingaxial loads combined with bending and shear It may,however, form a small part of an enclosure or separation
In the 2008 Code, the definitions for column and pedestalwere revised to provide consistency between the definitions
Concrete, lightweight — In 2000, ASTM C567 adopted
“equilibrium density” as the measure for determiningcompliance with specified in-service density requirements.According to ASTM C567, equilibrium density may bedetermined by measurement or approximated by calculationusing either the measured oven-dry density or the oven-drydensity calculated from the mixture proportions Unless spec-ified otherwise, ASTM C567 requires that equilibrium density
be approximated by calculation
By Code definition, sand-lightweight concrete is structurallightweight 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 themajority, but not all, of the lightweight fines are replaced bysand For proper application of the Code provisions, thereplacement limits should be stated, with interpolation whenpartial sand replacement is used
Trang 35``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Concrete, sand-lightweight — Lightweight concrete
containing only normalweight fine aggregate that
conforms to ASTM C33 and only lightweight aggregate
that conforms to ASTM C330
Concrete, specified compressive strength of, (f c′) —
Compressive strength of concrete used in design and
evaluated in accordance with provisions of Chapter 5,
expressed in pounds per square inch (psi) Whenever
the quantity f c′ is under a radical sign, square root of
numerical value only is intended, and result has units
of pounds per square inch (psi)
Connection — A region that joins two or more
members In Chapter 21, a connection also refers to a
region that joins members of which one or more is
precast, for which the following more specific definitions
apply:
Ductile connection — Connection that experiences
yielding as a result of the earthquake design
displacements
Strong connection — Connection that remains
elastic while adjoining members experience yielding
as a result of the earthquake design displacements
Contract documents — Documents, including the
project drawings and project specifications, covering
the required Work
Contraction joint — Formed, sawed, or tooled groove
in a concrete structure to create a weakened plane
and regulate the location of cracking resulting from the
dimensional change of different parts of the structure
Cover, specified concrete — The distance between
the outermost surface of embedded reinforcement and
the closest outer surface of the concrete indicated on
design drawings or in project specifications
Crosstie — A continuous reinforcing bar having a
seismic hook at one end and a hook not less than
90 degrees with at least a six-diameter extension at
the other end The hooks shall engage peripheral
longitudinal bars The 90-degree hooks of two
succes-sive crossties engaging the same longitudinal bars
shall be alternated end for end See Chapters 7, 21
Curvature friction — Friction resulting from bends or
curves in the specified prestressing tendon profile
Concrete, normalweight — Normalweight concrete
typi-cally has a density (unit weight) between 135 and 160 lb/ft3,and is normally taken as 145 to 150 lb/ft3
Concrete, normalweight — Concrete containing only
aggregate that conforms to ASTM C33
Cover, specified concrete — Tolerances on specified concrete
cover are provided in 7.5.2.1
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 36``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Deformed reinforcement — Deformed reinforcing bars,
bar mats, deformed wire, and welded wire reinforcement
conforming to 3.5.3
Design displacement — Total lateral displacement
expected for the design-basis earthquake, as required
by the governing code for earthquake-resistant design
See Chapter 21
Deformed reinforcement — Deformed reinforcement is
defined as that meeting the deformed reinforcement cations of 3.5.3.1, or the specifications of 3.5.3.3, 3.5.3.4,
specifi-3.5.3.5, 3.5.3.6, or 3.5.3.7 No other reinforcement qualifies.This definition permits accurate statement of anchoragelengths Bars or wire not meeting the deformation require-ments or welded wire reinforcement not meeting thespacing requirements are “plain reinforcement,” for codepurposes, and may be used only for spirals
Design displacement — The design displacement is an
index of the maximum lateral displacement expected indesign for the design-basis earthquake In documents such
as ASCE/SEI 7-05 and the 2006 International BuildingCode, the design displacement is calculated using static ordynamic linear elastic analysis under code-specified actionsconsidering effects of cracked sections, effects of torsion,effects of vertical forces acting through lateral displacements,and modification factors to account for expected inelasticresponse The design displacement generally is larger thanthe displacement calculated from design-level forcesapplied to a linear-elastic model of the building
Design load combination — Combination of factored
loads and forces in 9.2
Design story drift ratio — Relative difference of
design displacement between the top and bottom of a
story, divided by the story height See Chapter 21
Development length — Length of embedded
reinforce-ment, including pretensioned strand, required to develop
the design strength of reinforcement at a critical
section See 9.3.3
Drop panel — A 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 See 13.2.5 and
13.3.7
Duct — A conduit (plain or corrugated) to accommodate
prestressing steel for post-tensioned installation
Requirements for post-tensioning ducts are given in
18.17
Effective depth of section (d) — Distance measured
from extreme compression fiber to centroid of
longitu-dinal tension reinforcement
Effective prestress — Stress remaining in prestressing
steel after all losses have occurred
Embedment length — Length of embedded
reinforce-ment provided beyond a critical section
Trang 37
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Equilibrium density — Density of lightweight
concrete after exposure to a relative humidity of 50
± 5 percent and a temperature of 73.5 ± 3.5 °F for a
period of time sufficient to reach constant density (see
ASTM C567)
Extreme tension steel — The reinforcement
(prestressed or nonprestressed) that is the farthest
from the extreme compression fiber
Headed deformed bars — Deformed reinforcing bars
with heads attached at one or both ends Heads are
attached to the bar end by means such as welding or
forging onto the bar, internal threads on the head
mating to threads on the bar end, or a separate
threaded nut to secure the head of the bar The net
bearing area of headed deformed bar equals the gross
area of the head minus the larger of the area of the bar
and the area of any obstruction
Headed deformed bars — The bearing area of a headed
deformed bar is, for the most part, perpendicular to the baraxis, as shown in Fig R3.5.9 In contrast, the bearing area ofthe head of headed stud reinforcement is a nonplanar spatialsurface of revolution, as shown in Fig R3.5.5 The two types
of reinforcement differ in other ways The shanks of headedstuds are smooth, not deformed as with headed deformedbars The minimum net bearing area of the head of a headeddeformed bar is permitted to be as small as four times the bararea In contrast, the minimum stud head area is not specified
in terms of the bearing area, but by the total head area whichmust be at least 10 times the area of the shank
Headed shear stud reinforcement — Reinforcement
consisting of individual headed studs, or groups of
studs, with anchorage provided by a head at each end
or by a common base rail consisting of a steel plate or
shape
Hoop — A closed tie or continuously wound tie A
closed tie can be made up of several reinforcement
elements each having seismic hooks at both ends A
continuously wound tie shall have a seismic hook at
both ends See Chapter 21
Isolation joint — A separation between adjoining
parts of a concrete structure, usually a vertical plane,
at a designed location such as to interfere least with
performance of the structure, yet such as to allow
rela-tive movement in three directions and avoid formation
of cracks elsewhere in the concrete and through which
all or part of the bonded reinforcement is interrupted
Jacking force — In prestressed concrete, temporary
force exerted by device that introduces tension into
prestressing steel
Joint — Portion of structure common to intersecting
members The effective cross-sectional area of a joint
of a special moment frame, A j, for shear strength
computations is defined in 21.7.4.1 See Chapter 21
Licensed design professional — An individual who
is licensed to practice structural design as defined by
the statutory requirements of the professional
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 38``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Loads — A number of definitions for loads are given as the
Code contains requirements that are to be met at variousload levels The terms “dead load” and “live load” refer tothe unfactored loads (service loads) specified or defined bythe general building code Service loads (loads without loadfactors) are to be used where specified in the Code to propor-tion or investigate members for adequate serviceability, as
in 9.5, Control of Deflections Loads used to proportion amember for adequate strength are defined as factored loads.Factored loads are service loads multiplied by the appro-priate load factors specified in 9.2 for required strength Theterm “design loads,” as used in the 1971 Code edition torefer to loads multiplied by the appropriate load factors, wasdiscontinued in the 1977 Code to avoid confusion with thedesign load terminology used in general building codes todenote service loads, or posted loads in buildings Thefactored load terminology, first adopted in the 1977 Code,clarifies when the load factors are applied to a particularload, moment, or shear value as used in the Code provisions
licensing laws of the state or jurisdiction in which the
project is to be constructed and who is in responsible
charge of the structural design; in other documents,
also referred to as registered design professional.
Load, dead — Dead weight supported by a member,
as defined by general building code of which this Code
forms a part (without load factors)
Load, factored — Load, multiplied by appropriate load
factors, used to proportion members by the strength
design method of this Code See 8.1.1 and 9.2
Load, live — Live load specified by general building
code of which this Code forms a part (without load
factors)
Load, service — Load specified by general building
code of which this Code forms a part (without load
factors)
Modulus of elasticity — Ratio of normal stress to
corresponding strain for tensile or compressive
stresses below proportional limit of material See 8.5
Moment frame — Frame in which members and joints
resist forces through flexure, shear, and axial force
Moment frames designated as part of the
seismic-force-resisting system shall be categorized as follows:
Ordinary moment frame — A cast-in-place or
precast concrete frame complying with the
require-ments of Chapters 1 through 18, and, in the case of
ordinary moment frames assigned to Seismic
Design Category B, also complying with 21.2
Intermediate moment frame — A cast-in-place
frame complying with the requirements of 21.3 in
addition to the requirements for ordinary moment
frames
Special moment frame — A cast-in-place frame
complying with the requirements of 21.1.3 through
21.1.7, 21.5 through 21.7, or a precast frame
complying with the requirements of 21.1.3 through
21.1.7 and 21.5 through 21.8 In addition, the
requirements for ordinary moment frames shall be
satisfied
Net tensile strain — The tensile strain at nominal
strength exclusive of strains due to effective prestress,
creep, shrinkage, and temperature
Trang 39
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Pedestal — In the 2008 Code, the definitions for column
and pedestal were revised to provide consistency betweenthe definitions
Pedestal — Member with a ratio of height-to-least
lateral dimension less than or equal to 3 used primarily
to support axial compressive load For a tapered
member, the least lateral dimension is the average of
the top and bottom dimensions of the smaller side
Plain concrete — Structural concrete with no
reinforce-ment or with less reinforcereinforce-ment than the minimum
amount specified for reinforced concrete
Plain concrete — The presence of reinforcement
(nonprestressed or prestressed) does not prohibit themember from being classified as plain concrete, provided allrequirements of Chapter 22 are satisfied
Plain reinforcement — Reinforcement that does not
conform to definition of deformed reinforcement
See 3.5.4
Plastic hinge region — Length of frame element over
which flexural yielding is intended to occur due to
earthquake design displacements, extending not less
than a distance h from the critical section where flexural
yielding initiates See Chapter 21
Post-tensioning — Method of prestressing in which
prestressing steel is tensioned after concrete has
hardened
Precast concrete — Structural concrete element cast
elsewhere than its final position in the structure
Precompressed tensile zone — Portion of a
prestressed member where flexural tension,
calcu-lated using gross section properties, would occur
under unfactored dead and live loads if the prestress
force was not present
Prestressed concrete — Structural concrete in which
internal stresses have been introduced to reduce
potential tensile stresses in concrete resulting from
loads
Prestressed concrete — Reinforced concrete is defined to
include prestressed concrete Although the behavior of aprestressed member with unbonded tendons may vary fromthat of members with continuously bonded tendons, bondedand unbonded prestressed concrete are combined withconventionally reinforced concrete under the generic term
“reinforced concrete.” Provisions common to both prestressedand conventionally reinforced concrete are integrated to avoidoverlapping and conflicting provisions
Prestressing steel — High-strength steel element
such as wire, bar, or strand, or a bundle of such
elements, used to impart prestress forces to concrete
Pretensioning — Method of prestressing in which
prestressing steel is tensioned before concrete is
placed
Reinforced concrete — Structural concrete reinforced
with no less than the minimum amounts of prestressing
steel or nonprestressed reinforcement specified in
Chapters 1 through 21 and Appendixes A through C
Copyright American Concrete Institute
Provided by IHS under license with ACI Licensee=Bechtel Corp Loc 1-19/9999056100
Trang 40
``,`,,,```,``,`,,`,,`,`,`,-`-`,,`,,`,`,,` -CODE COMMENTARY
Sheathing — Typically, sheathing is a continuous,
seam-less, high-density polyethylene material extruded directly
on the coated prestressing steel
Reinforcement — Material that conforms to 3.5,
excluding prestressing steel unless specifically
included
Reshores — Shores placed snugly under a concrete
slab or other structural member after the original forms
and shores have been removed from a larger area,
thus requiring the new slab or structural member to
deflect and support its own weight and existing
construction loads applied prior to the installation of
the reshores
Seismic design category — A classification assigned
to a structure based on its occupancy category and
the severity of the design earthquake ground motion at
the site, as defined by the legally adopted general
building code
Seismic-force-resisting system — Portion of the
structure designed to resist earthquake design forces
required by the legally adopted general building code
using the applicable provisions and load combinations
Seismic hook — A hook on a stirrup, or crosstie
having a bend not less than 135 degrees, except
that circular hoops shall have a bend not less than
90 degrees Hooks shall have a 6d b (but not less than
3 in.) extension that engages the longitudinal
reinforce-ment and projects into the interior of the stirrup or hoop
See 7.1.4 and Chapter 21
Shear cap — A project below the slab used to
increase the slab shear strength See 13.2.6
Sheathing — A material encasing prestressing steel
to prevent bonding of the prestressing steel with the
surrounding concrete, to provide corrosion protection,
and to contain the corrosion inhibiting coating
Shores — Vertical or inclined support members
designed to carry the weight of the formwork,
concrete, and construction loads above
Span length — See 8.9
Special anchorage device — Anchorage device that
satisfies 18.15.1 and the standardized acceptance
tests of AASHTO “Standard Specifications for Highway
Bridges,” Division II, Article 10.3.2.3
Special anchorage devices — Special anchorage devices
are any devices (monostrand or multistrand) that do notmeet the relevant PTI or AASHTO bearing stress and,where applicable, stiffness requirements Most commer-cially marketed multibearing surface anchorage devices arespecial anchorage devices As provided in 18.15.1, suchdevices can be used only when they have been shown exper-imentally to be in compliance with the AASHTO require-ments This demonstration of compliance will ordinarily befurnished by the device manufacturer