350M_06

ACI 350 Environmental Structures Code and Commentary

Jon B. ArdahlVice Chair

John W. BakerSecretary

Walter N. Bennett Carl A. Gentry Nicholas A. Legatos Jerry ParnesLucian I. Bogdan Gautam Ghosh Ramon E. Lucero Andrew R. PhilipSteven R. Close Charles S. Hanskat Andrew R. Minogue Risto ProticPatrick J. Creegan Keith W. Jacobson Lawrence G. Mrazek William C. ShermanRobert E. Doyle M. Reza Kianoush Javeed A. Munshi Lawrence M. TabatAnthony L. Felder

Voting Subcommittee Members

Iyad (Ed) M. Alsamsam Daniel J. McCarthyPaul Hedli Carl H. MoonLawrence E. Kaiser Rolf P. PawskiSalvatore Marques Paul J. St. John

CODE REQUIREMENTS FORENVIRONMENTAL ENGINEERING

CONCRETE STRUCTURES (ACI 350M-06)AND COMMENTARYREPORTED BY ACI COMMITTEE 350

ACI Committee 350Environmental Engineering Concrete Structures

Satish K. SachdevChair

Consulting Members

William Irwin Dennis C. KohlDov Kaminetzky Terry PatziasDavid G. Kittridge Narayan M. Prachand

INTRODUCTION 1


The code portion of this document covers the structural design, materials selection, and construction ofenvironmental engineering concrete structures. Such structures are used for conveying, storing, or treatingliquid or other materials such as solid waste. They include ancillary structures for dams, spill-ways, andchannels.

They are subject to uniquely different loadings, more severe exposure conditions, and more restrictiveserviceability requirements than non-environmental building structures.

Loadings include normal dead and live loads and vibrating equipment or hydrodynamic forces. Exposuresinclude concentrated chemicals, alternate wetting and drying, and freezing and thawing of saturatedconcrete. Serviceability requirements include liquid-tightness or gas-tightness.

Typical structures include conveyance, storage, and treatment structures.

Proper design, materials, and construction of environmental engineering concrete structures arerequired to produce serviceable concrete that is dense, durable, nearly impermeable, and resistant tochemicals, with limited deflections and cracking. Leakage must be controlled to minimize contamination ofground water or the environment, to minimize loss of product or infiltration, and to promote durability.

This code presents new material as well as modified portions of the ACI 318M-02 Building Code that areapplicable to environmental engineering concrete structures.

Because ACI 350M-06 is written as a legal document, it may be adopted by reference in a general buildingcode or in regulations governing the design and construction of environmental engineering concretestructures. Thus, it cannot present background details or suggestions for carrying out its requirements orintent. It is the function of the commentary to fill this need.

CODE REQUIREMENTS FOR ENVIRONMENTAL ENGINEERING CONCRETE STRUCTURES(ACI 350M-06) AND COMMENTARYREPORTED BY ACI COMMITTEE 350

ACI 350M-06 was adopted as a standard of the American Concrete Instituteon July 3, 2006 to supersede ACI 350M/350RM-01 in accordance with theInstitutes standardization procedure. ACI 350M-06 is a complete metriccompanion to ACI 350-06.

ACI Committee Reports, Guides, and Commentaries are intended forguidance in planning, designing, executing, and inspecting construction.This Commentary is intended for the use of individuals who are competentto evaluate the significance and limitations of its content and recommenda-tions and who will accept responsibility for the application of the materialit contains. The American Concrete Institute disclaims any and all responsi-bility for the stated principles. The Institute shall not be liable for any loss or

damage arising therefrom. Reference to this commentary shall not be madein contract documents. If items found in this Commentary are desired by theArchitect/Engineer to be a part of the contract documents, they shall berestated in mandatory language for incorporation by the Architect/Engineer.

Copyright 2006, 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, orby any electronic or mechanical device, printed or written or oral, orrecording for sound or visual reproduction or for use in any knowledge orretrieval system or device, unless permission in writing is obtained fromthe copyright proprietors.

1

2 INTRODUCTION


INTRODUCTION

The code and commentary includes excerpts from ACI 318M-02that are pertinent to ACI 350M. The commentary discusses someof the considerations of Committee ACI 350 in developing CodeRequirements for Environmental Engineering Concrete Struc-tures (ACI 350M-06), hereinafter called the code. Emphasis isgiven to the explanation of provisions that may be unfamiliar tousers of the standard. Comments on specific provisions are madeunder the corresponding chapter and section numbers of the codeand commentary.

This commentary is not intended to provide a complete histor-ical background concerning the development of the code, noris it intended to provide a detailed summary of the studies andresearch data reviewed by the committee in formulating theprovisions of the code. However, references to some of theresearch data are provided for those who wish to study thebackground material in depth.

As the name implies, Code Requirements for Environ-mental Engineering Concrete Structures may be used aspart of a legally adopted code and, as such, must differ inform and substance from documents that provide detailedspecifications, recommended practice, complete designprocedures, or design aids.

The code is intended to cover environmental engineeringconcrete structures, but is not intended to supersede ASTMstandards for precast structures.

Requirements more stringent than the code provisions may bedesirable for unusual structures. This code and this commen-tary cannot replace sound engineering knowledge, experience,and judgment.A code for design and construction states the minimumrequirements necessary to provide for public health andsafety. ACI 350M is based on this principle. For any struc-ture, the owner or the structural designer may require thequality of materials and construction to be higher than theminimum requirements necessary to provide serviceabilityand to protect the public as stated in the code. Lower stan-dards, however, are not permitted.

ACI 350M has no legal status unless it is adopted by govern-ment bodies having the power to regulate building design andconstruction. Where the code has not been adopted, it mayserve as a reference to good practice.

The code provides a means of establishing minimum standardsfor acceptance of design and construction by a legallyappointed building official or his 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 ACI 350M inthe job specifications should be avoided, since the contractor israrely in a position to accept responsibility for design

The commentary discusses some of the considerations of the committee in developing the ACI 350MCode, and its relationship with ACI 318M. Emphasis is given to the explanation of provisions that may beunfamiliar to some users of the code. References to much of the research data referred to in preparing thecode are given for those who wish to study certain requirements in greater detail.

The chapter and section numbering of the code are followed throughout the commentary.Among the subjects covered are: permits, drawings and specifications, inspections, materials, concrete

quality, mixing and placing, forming, embedded pipes, construction joints, reinforcement details, analysisand design, strength and serviceability, flexural and axial loads, shear and torsion, development of reinforce-ment, slab systems, walls, footings, precast concrete, prestressed concrete, shell structures, folded platemembers, provisions for seismic design, and an alternate design method in Appendix I.

The quality and testing of materials used in the construction are covered by reference to the appropriatestandard specifications. Welding of reinforcement is covered by reference to the appropriate AWS standard.Criteria for liquid-tightness testing may be found in 350.1.

Keywords: chemical attack; coatings; concrete durability; concrete finishing (fresh concrete); concrete slabs, crack width, and spacing; cracking(fracturing); environmental engineering; inspection; joints (junctions); joint sealers; liquid; patching; permeability; pipe columns; pipes (tubes);prestressed concrete; prestressing steels; protective coatings; reservoirs; roofs; serviceability; sewerage; solid waste facilities; tanks(containers); temperature; torque; torsion; vibration; volume change; walls; wastewater treatment; water; water-cementitious material ratio; watersupply; water treatment.

The 2006 Code Requirements for Environmental Engineering Concrete Structures and Commentary arepresented in a side-by-side column format, with code text placed in the left column and the correspondingcommentary text aligned in the right column. To further distinguish the Code from the Commentary, the Code hasbeen printed in Helvetica, the same type face in which this 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.Commentary section numbers are preceded by an R to further distinguish them from Code section numbers.

INTRODUCTION 3


details or construction requirements that depend on a detailedknowledge of the design. Generally, the drawings, speci-fications, and contract documents should contain all of thenecessary requirements to ensure compliance with the code.In part, this can be accomplished by reference to specificcode sections in the job specifications. Other ACI publi-cations, such as ACI 301M, Specifications for StructuralConcrete, are written specifically for use as contractdocuments for construction.

Committee 350 recognizes the desirability of standards ofperformance for individual parties involved in the contractdocuments. Available for this purpose are the certificationprograms of the American Concrete Institute, the plant certifi-cation programs of the Precast/Prestressed Concrete Institute,the National Ready Mixed Concrete Association, and the qual-ification standards of the American Society of ConcreteConstructors. Also available are Standard Specification forAgencies Engaged in Construction Inspection and/or Testing(ASTM E 329) and Standard Practice for LaboratoriesTesting Concrete and Concrete Aggregates for Use inConstruction and Criteria for Laboratory Evaluation (ASTMC 1077).

Design aids (general concrete design aids are listed inACI 318M-02):

Rectangular Concrete Tanks, Portland Cement Associa-tion, Skokie, IL, 1994, 176 pp. (Presents data for design of rect-angular tanks.)

Circular Concrete Tanks Without Prestressing, PortlandCement Association, Skokie, IL, 1993, 54 pp. (Presents designdata for circular concrete tanks built in or on ground. Wallsmay be free or restrained at the top. Wall bases may be fixed,hinged, or have intermediate degrees of restraint. Variouslayouts for circular roofs are presented.)

Concrete Manual, U.S. Department of Interior, Bureau ofReclamation, 8th edition, 1981, 627 pp. (Presents technicalinformation for the control of concrete construction, includinglinings for tunnels, impoundments, and canals.)

GENERAL COMMENTARY

Because of stringent service requirements, environmentalengineering concrete structures should be designed anddetailed with care. The quality of concrete is important, andclose quality control must be performed during construction toobtain impervious concrete.

Environmental engineering concrete structures for the contain-ment, treatment, or transmission of liquid such as water andwastewater as well as solid waste disposal facilities, should bedesigned and constructed to be essentially liquid-tight, withminimal leakage under normal service conditions.

The liquid-tightness of a structure will be reasonably assured if:

a) The concrete mixture is well proportioned, well consol-idated without segregation, and properly cured.

b) Crack widths and depths are minimized.c) Joints are properly spaced, sized, designed, water-

stopped, and constructed.d) Adequate reinforcing steel is provided, properly

detailed, fabricated, and placed.e) Impervious protective coatings or barriers are used

where required.

Usually it is more economical and dependable to resist liquidpermeation through the use of quality concrete, properdesign of joint details, and adequate reinforcement, ratherthan by means of an impervious protective barrier or coating.Liquid-tightness can also be obtained by appropriate use ofshrinkage-compensating concrete. However, to achievesuccess, the engineer must recognize and account for the limita-tions, characteristics, and properties of shrinkage-compensatingconcrete as described in ACI 223 and ACI 224.2R.

Minimum permeability of the concrete will be obtained byusing water-cementitious materials ratios as low as possible,consistent with satisfactory workability and consolidation.Impermeability increases with the age of the concrete and isimproved by extended periods of moist curing. Surface treat-ment is important and use of smooth forms or trowelingimproves impermeability. Air entrainment reduces segregationand bleeding, increases workability, and provides resistance tothe effect of freeze-thaw cycles. Because of this, use of an air-entraining admixture results in better consolidated concrete.Other admixtures, such as water-reducing agents andpozzolans, are useful when they lead to increased workabilityand consolidation, and lower water-cementitious ratios.Pozzolans also reduce permeability.

Joint design should also account for movement resulting fromthermal dimensional changes and differential settlements.Joints permitting movement along predetermined controlplanes, and which form a barrier to the passage of fluids, shallinclude waterstops in complete, closed circuits. Proper rate ofconcrete placement operations, adequate consolidation, andproper curing are also essential to control of cracking in envi-ronmental engineering concrete structures. Additional infor-mation on cracking is contained in ACI 224R and ACI 224.2R.

The design of the whole environmental engineering concretestructure as well as all individual members should be inaccordance with ACI 350M-06, which has been adaptedfrom ACI 318M-02. When all relevant loading conditionsare considered, the design should provide adequate safetyand serviceability, with a life expectancy of 50 to 60 yearsfor the structural concrete. Some components of the structure,such as jointing materials, have a shorter life expectancy andwill require maintenance or replacement.

The size of elements and amount of reinforcement should beselected on the basis of the serviceability crack-width limitsand stress limits to promote long service life.

4 TABLE OF CONTENTS


CONTENTS

PART 1GENERAL

CHAPTER 1GENERAL REQUIREMENTS .......................................................... 91.1Scope 1.3Inspection1.2Drawings and specifications 1.4Approval of special systems of design or construction

CHAPTER 2DEFINITIONS ................................................................................. 21

PART 2STANDARDS FOR TESTS AND MATERIALS

CHAPTER 3MATERIALS................................................................................... 313.0Notation 3.5Steel reinforcement3.1Tests of materials 3.6Admixtures3.2Cements 3.7Storage of materials3.3Aggregates 3.8Reference standards3.4Water

PART 3CONSTRUCTION REQUIREMENTS

CHAPTER 4DURABILITY REQUIREMENTS .................................................... 474.0Notation 4.4Corrosion protection of metals4.1Water-cementitious materials ratio and 4.5Chemical effects cementitious material content 4.6Protection against erosion4.2Freezing and thawing exposures 4.7Coatings and liners4.3Sulfate exposures 4.8Joints

CHAPTER 5CONCRETE QUALITY, MIXING, AND PLACING ......................... 635.0Notation 5.6Preparation of equipment and place of deposit5.1General 5.7Mixing5.2Selection of concrete proportions 5.8Conveying5.3Proportioning on the basis of field experience, 5.9Depositing

trial mixtures, or both 5.10Curing5.4Average strength reduction 5.11Cold weather requirements5.5Evaluation and acceptance of concrete 5.12Hot weather requirements

CHAPTER 6FORMWORK, EMBEDDED PIPES, AND CONSTRUCTIONAND MOVEMENT JOINTS............................................................. 79

6.1Design of formwork 6.4Construction joints6.2Removal of forms, shores, and reshoring 6.5Movement joints6.3Conduits and pipes embedded in concrete

CHAPTER 7DETAILS OF REINFORCEMENT .................................................. 857.0Notation 7.7Concrete protection for reinforcement7.1Standard hooks 7.8Special reinforcement details for columns7.2Minimum bend diameters 7.9Connections7.3Bending 7.10Lateral reinforcement for compression members7.4Surface conditions of reinforcement 7.11Lateral reinforcement for flexural members7.5Placing reinforcement 7.12Shrinkage and temperature reinforcement7.6Spacing limits for reinforcement 7.13Requirements for structural integrity

TABLE OF CONTENTS 5


PART 4GENERAL REQUIREMENTS

CHAPTER 8ANALYSIS AND DESIGNGENERALCONSIDERATIONS ......................................................................... 101

8.0Notation 8.6Stiffness8.1Design methods 8.7Span length8.2Loading 8.8Columns8.3Methods of analysis 8.9Arrangement of live load8.4Redistribution of negative moments in continuous 8.10T-beam construction

flexural members 8.11Joist construction8.5Modulus of elasticity 8.12Separate floor finish

CHAPTER 9STRENGTH AND SERVICEABILITYREQUIREMENTS............................................................................. 111

9.0Notation 9.3Design strength9.1General 9.4Design strength for reinforcement9.2Required strength 9.5Control of deflections

CHAPTER 10FLEXURE AND AXIAL LOADS..................................................... 12710.0Notation 10.9Limits for reinforcement of compression members10.1Scope 10.10Slenderness effects in compression members10.2Design assumptions 10.11Magnified momentsGeneral10.3General principles and requirements 10.12Magnified momentsNonsway frames10.4Distance between lateral supports of 10.13Magnified momentsSway frames

flexural members 10.14Axially loaded members supporting slab system10.5Minimum reinforcement of flexural members 10.15Transmission of column loads through floor system10.6Distribution of flexural reinforcement 10.16Composite compression members10.7Deep beams 10.17Bearing strength10.8Design dimensions for compression members

CHAPTER 11SHEAR AND TORSION................................................................. 15911.0Notation 11.6Design for torsion11.1Shear strength 11.7Shear-friction11.2Lightweight concrete 11.8Deep beams11.3Shear strength provided by concrete for 11.9Special provisions for brackets and corbels

nonprestressed members 11.10Special provisions for walls11.4Shear strength provided by concrete for 11.11Transfer of moments to columns

prestressed members 11.12Special provisions for slabs and footings11.5Shear strength provided by shear reinforcement

CHAPTER 12DEVELOPMENT AND SPLICES OFREINFORCEMENT........................................................................ 205

12.0Notation 12.9Development of prestressing strand12.1Development of reinforcementGeneral 12.10Development of flexural reinforcementGeneral12.2Development of deformed bars and deformed 12.11Development of positive moment reinforcement

wire in tension 12.12Development of negative moment reinforcement12.3Development of deformed bars and deformed wire 12.13Development of web reinforcement in compression 12.14Splices of reinforcementGeneral12.4Development of bundled bars 12.15Splices of deformed bars and deformed wire in12.5Development of standard hooks in tension tension12.6Mechanical anchorage 12.16Splices of deformed bars in compression12.7Development of welded deformed wire fabric in 12.17Special splice requirements for columns

tension 12.18Splices of welded deformed wire fabric in tension12.8Development of welded plain wire fabric in tension 12.19Splices of welded plain wire fabric in tension

6 TABLE OF CONTENTS


PART 5STRUCTURAL SYSTEMS OR ELEMENTS

CHAPTER 13TWO-WAY SLAB SYSTEMS..................................................... 23113.0Notation 13.4Openings in slab systems13.1Scope 13.5Design procedures13.2Definitions 13.6Direct design method13.3Slab reinforcement 13.7Equivalent frame method

CHAPTER 14WALLS ....................................................................................... 25114.0Notation 14.5Empirical design method14.1Scope 14.6Minimum wall thickness14.2General 14.7Walls as grade beams14.3Minimum reinforcement 14.8Alternative design of slender walls14.4Walls designed as compression members

CHAPTER 15FOOTINGS ................................................................................. 25715.0Notation 15.6Development of reinforcement in footings15.1Scope 15.7Minimum footing depth15.2Loads and reactions 15.8Transfer of force at base of column, wall,15.3Footings supporting circular or regular polygon or reinforced pedestal

shaped columns or pedestals 15.9Sloped or stepped footings15.4Moment in footings 15.10Combined footings and mats15.5Shear in footings

CHAPTER 16PRECAST CONCRETE.............................................................. 26516.0Notation 16.6Connection and bearing design16.1Scope 16.7Items embedded after concrete placement16.2General 16.8Marking and identification16.3Distribution of forces among members 16.9Handling16.4Member design 16.10Strength evaluation of precast construction16.5Structural integrity

CHAPTER 17COMPOSITE CONCRETE FLEXURALMEMBERS ................................................................................. 273

17.0Notation 17.4Vertical shear strength17.1Scope 17.5Horizontal shear strength17.2General 17.6Ties for horizontal shear17.3Shoring

CHAPTER 18PRESTRESSED CONCRETE.................................................... 27718.0Notation 18.12Slab systems18.1Scope 18.13Post-tensioned tendon anchorage zones18.2General 18.14Design of anchorage zones for monostrand or18.3Design assumptions single 16 mm diameter bar tendons18.4Serviceability requirementsFlexural members 18.15Design of anchorage zone for multistrand tendons18.5Permissible stresses in prestressing steel 18.16Corrosion protection for unbonded single-strand18.6Loss of prestress prestressing tendons18.7Flexural strength 18.17Post-tensioning ducts18.8Limits for reinforcement of flexural members 18.18Grout for bonded tendons18.9Minimum bonded reinforcement 18.19Protection for prestressing steel18.10Statically indeterminate structures 18.20Application and measurement of prestressing force18.11Compression membersCombined flexure and 18.21Post-tensioning anchorages and couplers axial loads 18.22External post-tensioning

TABLE OF CONTENTS 7


CHAPTER 19SHELLS AND FOLDED PLATE MEMBERS................................. 30919.0Notation 19.3Design strength of materials19.1Scope and definitions 19.4Shell reinforcement19.2Analysis and design 19.5Construction

PART 6SPECIAL CONSIDERATIONS

CHAPTER 20STRENGTH EVALUATION OF EXISTINGSTRUCTURES ............................................................................... 317

20.0Notation 20.4Loading criteria20.1Strength evaluationGeneral 20.5Acceptance criteria20.2Determination of required dimensions and material 20.6Provision for lower load rating

properties 20.7Safety20.3Load test procedure

CHAPTER 21SPECIAL PROVISIONS FOR SEISMIC DESIGN.......................... 32321.0Notation 21.8Special structural walls constructed using precast21.1Definitions concrete21.2General requirements 21.9Structural diaphragms and trusses21.3Flexural members of special moment frames 21.10Foundations21.4Special moment frame members subjected 21.11Frame members not proportioned to resist forces

to bending and axial load induced by earthquake motions21.5Joints of special moment frames 21.12Requirements for intermediate moment frames21.6Special moment frames constructed using 21.13Intermediate precast structural walls precast concrete21.7Special reinforced concrete structural walls and coupling beams

PART 7STRUCTURAL PLAIN CONCRETE

CHAPTER 22NOT USED ..................................................................................... 365

COMMENTARY REFERENCES ..................................................................... 367

APPENDIXES

APPENDIX ANOT USED...................................................................................... 385

APPENDIX BALTERNATE PROVISIONS FOR REINFORCED ANDPRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS........387

B.0Notation B.1Scope

APPENDIX CALTERNATE LOAD FACTORS, STRENGTH REDUCTIONFACTORS, AND DISTRIBUTION OF FLEXURAL REINFORCEMENT ................. 391

C.1General

APPENDIX DANCHORING TO CONCRETE....................................................... 399D.0Notation D.6Design requirements for shear loadingD.1Definitions D.7Interaction of tensile and shear forcesD.2Scope D.8Required edge distances, spacings,D.3General requirements and thicknesses to preclude splitting failureD.4General requirements for strength of anchors D.9Installation of anchorsD.5Design requirements for tensile loading

8 TABLE OF CONTENTS


APPENDIX ENOTATION......................................................................................425

APPENDIX FMETAL REINFORCEMENT INFORMATION..................................439

APPENDIX GCIRCULAR WIRE AND STRAND WRAPPEDPRESTRESSED CONCRETE ENVIRONMENTALSTRUCTURES................................................................................441

G.0Notation G.3MaterialsG.1Scope G.4Construction proceduresG.2Design

APPENDIX HSLABS ON SOIL ............................................................................457H.1Scope H.5JointsH.2Subgrade H.6Hydrostatic upliftH.3Slab thickness H.7CuringH.4Reinforcement

APPENDIX IALTERNATE DESIGN METHOD.....................................................461I.0Notation I.4Development and splices of reinforcementI.1Scope I.5FlexureI.2General I.6Compression members with or without flexureI.3Permissible service load stresses I.7Shear and torsion

INDEX.......................................................................................................................473

SUMMARY OF CHANGES FOR 350M-06 CODE ...................................................479

CHAPTER 1 9

CODE COMMENTARY


1.1 Scope R1.1 ScopeThe American Concrete Institute Code Requirements forEnvironmental Engineering Concrete Structures (ACI350M-06), hereinafter referred to as the code, provideminimum requirements for environmental engineeringconcrete structural design and construction practices.

The 2006 edition of the code revised the previous code,Code Requirements of Environmental EngineeringConcrete Structures (ACI 350M-01). This code includesin one document the rules for all reinforced concrete usedfor environmental engineering structural purposes. Thiscovers the spectrum of structural applications of concretecontaining nonprestressed reinforcement, prestressing steel,or composite steel shapes, pipe, or tubing.

Prestressed concrete is included under the definition of rein-forced concrete. Provisions of ACI 350M-06 apply toprestressed concrete except in cases in which the provisionsof the code are stated to apply specifically to nonprestressedconcrete.

Chapter 21 of the code contains special provisions for designand detailing of earthquake-resistant structures. See 1.1.8.

Appendix I of the 2006 code, formerly Appendix A of the2001 code, contains provisions for an alternate method ofdesign for nonprestressed reinforced concrete membersusing service loads (without load factors) and permissibleservice load stresses. The strength design method of thiscode is intended to give design results similar to the Alter-nate Design Method.

Appendix A of the ACI 318M-02 code has not yet beenadopted for environmental engineering concrete structures.Applicability of strut-and-tie models to environmental struc-tures may be addressed in future revisions to ACI 350M.

Appendix B of the 2006 code contains provisions for rein-forcement limits based on 0.75b, determination of thestrength reduction factor , and moment redistribution thathave been in the 318M codes for many years, including the1999 318M code. The provisions are applicable to reinforcedand prestressed concrete members. Designs made using theprovisions of Appendix B are used in their entirety.

Appendix C of the 2006 code allows the use of load, envi-ronmental durability, strength reduction factors, and flexuralreinforcement distribution provisions similar to those InChapters 9 and 10 of ACI 350M-01. Designs made using theprovisions of Appendix C are equally acceptable as those

CHAPTER 1 GENERAL REQUIREMENTS

PART 1 GENERAL

10 CHAPTER 1

CODE COMMENTARY


1.1.1 Except for primary containment of hazardousmaterials, this code provides minimum requirementsfor the design and construction of reinforced concretestructural elements of any environmental engineeringconcrete structure erected under the requirements ofthe legally adopted building code where this code hasbeen adopted to be a part of such code. In areaswithout a legally adopted building code, this codedefines minimum acceptable standards of design andconstruction practice.

For structural concrete, the specified concrete strengthshall not be less than 28 MPa. No maximum specifiedcompressive strength shall apply unless restricted by aspecific code provision.

1.1.1.1 Environmental engineering concretestructures are defined as concrete structures intendedfor conveying, storing, or treating water, wastewater, orother liquids and non-hazardous materials such assolid waste, and for secondary containment ofhazardous liquids or solid waste. Ancillary structuresfor which liquid-tightness, gas-tightness, or enhanceddurability are essential design considerations shallalso conform to requirements of environmental engi-neering concrete structures. Precast concrete environ-mental structures designed and constructed inaccordance with ASTM or AWWA standards, with theexception of circular tanks, are not covered in this code.

1.1.2 This code supplements the general buildingcode and shall govern in all matters pertaining todesign and construction of reinforced concrete struc-tural elements of any environmental engineeringconcrete structure, except wherever this code is inconflict with requirements in legally-adopted applicablecodes addressing environmental engineering concretestructures.

1.1.3 This code shall apply in all matters pertainingto design, construction, and material properties wher-ever this code is in conflict with requirementscontained in other standards referenced in this code.

1.1.4 The provisions of this code shall govern fortanks, reservoirs, and other reinforced concreteelements of any environmental engineering concretestructure. Special structures such as arches, bins andsilos, blast-resistant structures, and chimneys are notcovered in this code.

based on the body of the code, provided the provisions ofAppendix C are used in their entirety.

Appendix D contains provisions for anchoring to concrete.

R1.1.1 A hazardous material is defined as having one ormore of the following characteristics: ignitable (NFPA 49),corrosive, reactive, or toxic. The Environmental ProtectionAgency (EPA)-listed wastes are organized into three catego-ries under RCRA: source specific wastes, generic wastes, andcommercial chemical products. Source specific wastesinclude sludges and wastewaters from treatment and produc-tion processes in specific industries such as petroleumrefining and wood preserving. The list of generic wastesincludes wastes from common manufacturing and industrialprocesses such as solvents used in degreasing operations. Thethird list contains specific chemical products such as benzine,creosote, mercury, and various pesticides.

Below-grade structures, such as pump stations and pipegalleries, which are part of treatment facilities and which maybe exposed to external groundwater pressures, generally aredesigned as environmental concrete structures. Above-gradebuilding structures that are not directly exposed to liquids,solid wastes, corrosive chemicals, corrosive gases, or highhumidity associated with treatment facilities generally maybe designed in accordance with the general building code orapplicable industry standards. Nevertheless, consideration ofcorrosive effects on such structures may still be advisable.

R1.1.2 The American Concrete Institute recommendsthat the code be adopted in its entirety; however, it is recog-nized that when the code is made a part of a legally adoptedgeneral building code, that general building code maymodify some provisions of this code.

R1.1.4 Environmental engineering projects can containseveral types of structures. For example, a treatment plantcan contain environmental engineering concrete structuressuch as tanks and reservoirs, as well and building structures.The ACI 350M code would apply to the environmental struc-tures, while the ACI 318M code or the following ACI publi-cations could apply to the other structures.

Design and Construction of Reinforced ConcreteChimneys reported by ACI Committee 307.1.1 (Gives

CHAPTER 1 11

CODE COMMENTARY


1.1.5 This code does not govern design and instal-lation of portions of concrete piles and drilled piersembedded in ground except for structures in regions ofhigh seismic risk or assigned to high seismic perfor-mance or design categories. See 21.10.4 for require-ments for concrete piles, drilled piers, and caissons instructures in regions of high seismic risk or assignedto high seismic performance or design categories.

material, 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 theconcrete and reinforcement required as a result of theseloadings.)Standard Practice for Design and Construction ofConcrete Silos and Stacking Tubes for Storing GranularMaterials reported by ACI Committee 313.1.2 (Givesmaterial, design, and construction requirements for rein-forced concrete bins, silos, and bunkers and stave silos forstoring granular materials. It includes recommended designand construction criteria based on experimental and analyticalstudies plus worldwide experience in silo design andconstruction.)(Bins, silos, and bunkers are special structures, posingspecial problems not encountered in normal building design.While this standard practice refers to Building CodeRequirements for Structural Concrete (ACI 318M) formany applicable requirements, it provides supplementaldetail requirements and ways of considering the uniqueproblems of static and dynamic loading of silo structures.Much of the method is empirical, but this standard practicedoes not preclude the use of more sophisticated methods thatgive equivalent or better safety and reliability.)(This standard practice sets forth recommended loadingsand methods for determining the stresses in the concrete andreinforcement resulting from these loadings. Methods arerecommended for determining the thermal effects resultingfrom stored material and for determining crack width inconcrete walls due to pressure exerted by the stored material.Appendices provide recommended minimum values ofoverpressure and impact factors.)Code Requirements for Nuclear Safety Related ConcreteStructures reported by ACI Committee 349.1.3 (Providesminimum requirements for design and construction ofconcrete structures that form part of a nuclear power plantand which have nuclear safety related functions. The codedoes not cover concrete reactor vessels and concretecontainment structures that are covered by ACI 359.)Code for Concrete Reactor Vessels and Containmentsreported by Joint ACI-ASME Committee 359.1.4 (Providesrequirements for the design, construction, and use ofconcrete reactor vessels and concrete containment structuresfor nuclear power plants.)R1.1.5 The design and installation of piling fullyembedded 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 provisionsof this code govern where applicable.

12 CHAPTER 1

CODE COMMENTARY


1.1.6 This code governs the design and constructionof soil-supported slabs as required by Appendix H.Slabs that transmit vertical loads from other portions ofthe structure to the soil shall meet the requirements ofother chapters of this code as applicable.

1.1.7 Concrete on steel form deck

1.1.7.1 Design and construction of structuralconcrete slabs cast on stay-in-place, noncompositesteel form deck are governed by this code.

Recommendations for concrete piles are given in detail inDesign, Manufacture, and Installation of ConcretePiles reported by ACI Committee 543.1.5 (Provides recom-mendations for the design and use of most types of concretepiles for many kinds of construction.)Recommendations for drilled piers are given in detail inDesign and Construction of Drilled Piers reported byACI Committee 336.1.6 (Provides recommendations fordesign and construction of foundation piers 750 mm indiameter or larger made by excavating a hole in the soil andthen filling it with concrete.)Detailed recommendations for precast, prestressed concretepiles are given in Recommended Practice for Design,Manufacture, and Installation of Prestressed ConcretePiling prepared by the PCI Committee on PrestressedConcrete Piling.1.7

R1.1.6 Since tank floor slabs frequently directly transferthe loads from liquid contents to the soil below, Appendix H hasbeen added to this code to provide appropriate requirements.

R1.1.7 Concrete on steel form deck

In steel-framed structures, it is common practice to castconcrete floor slabs on stay-in-place steel form deck. In allcases, the deck serves as the form and may, in some cases,serve an additional structural function.

R1.1.7.1 In its most basic application, the steel formdeck serves as a form, and the concrete serves a structuralfunction and, therefore, must be designed to carry all super-imposed loads.

R1.1.7.2 Another type of steel form deck commonlyused develops composite action between the concrete andsteel deck. In this type of construction, the steel deck servesas the positive moment reinforcement. The design of compositeslabs on steel deck is regulated by Standard for theStructural Design of Composite Slabs (ANSI/ASCE 3).1.8However, ANSI/ASCE 3 references the appropriate portionsof ACI 318M for the design and construction of the concreteportion of the composite assembly. Guidelines for theconstruction of composite steel deck slabs are given inStandard Practice for the Construction and Inspectionof Composite Slabs (ANSI/ASCE 9).1.9

R1.1.8 Special provisions for earthquake resistance

Special provisions for seismic design were first introducedin Appendix A of the ACI 318-71 Building Code and werecontinued without revision in ACI 318-77. These provisionswere originally intended to apply only to reinforcedconcrete structures located in regions of highest seismicity.

The special provisions were extensively revised in the ACI318M-83 code edition to include new requirements for

1.1.7.2 This code does not govern the design ofstructural concrete slabs cast on stay-in-place,composite steel form deck. Concrete used in theconstruction of such slabs shall be governed by Parts1, 2, and 3 of this code, where applicable.

1.1.8 Special provisions for earthquake resistance

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1.1.8.1 In all regions of seismic risk, and allseismic performance or design categories, provisionsof Chapter 21 shall be satisfied as described in 21.2.1.

certain earthquake-resisting systems located in regions ofmoderate seismicity. In the 318M-89 code, the specialprovisions were moved to Chapter 21.

R1.1.8.1 Some structures and elements of structureswill have their design governed by hydrodynamic forces,even when located in areas of low seismic risk, due to theirconfiguration and position. Portions of Chapter 21 (21.2,21.7, 21.8, and 21.9) apply to liquid-containing structuresfor all levels of seismic risk.

Aside from provisions given in 21.2, 21.7, 21.8, and 21.9,for structures located in regions of low seismic risk, or forstructures assigned to low seismic performance or designcategories, no special design or detailing is required; thegeneral requirements of the main body of the code apply forproportioning and detailing environmental engineeringconcrete structures. It is the intent of this code that concretestructures proportioned by Chapters 1 to 18 of this code andthe provisions given in 21.2, 21.7, 21.8, and 21.9 will providea level of toughness adequate for low earthquake intensity.

For structures in regions of moderate seismic risk, or forstructures assigned to intermediate seismic performance ordesign categories, reinforced concrete moment framesproportioned to resist earthquake effects require somespecial reinforcement details, as specified in 21.12. Thespecial details apply only to beams, columns, and slabs towhich the earthquake-induced forces have been assigned indesign. The special reinforcement details will serve toprovide a suitable level of inelastic behavior if the frame issubjected to an earthquake of such intensity as to require itto perform inelastically. There are no Chapter 21 require-ments for cast-in-place structural walls provided to resistseismic effects, or for other structural components that arenot part of the lateral-force-resisting system of structures inregions of moderate seismic risk, or assigned to interme-diate seismic performance or design categories. For precastwall panels designed to resist forces induced by earthquakemotions, special requirements are specified in 21.13 forconnections between panels or between panels and thefoundation. Cast-in-place structural walls proportioned tomeet provisions of Chapters 1 through 18 and Chapter 21are considered to have sufficient toughness at anticipateddrift levels for these structures.

For structures located in regions of high seismic risk, allstructure components, structural and nonstructural, shouldsatisfy requirements of 21.2 through 21.10. In addition,frame members that are not assumed in the design to be partof the lateral-force-resisting system should comply with21.11. The special proportioning and detailing provisions ofChapter 21 are intended to provide a monolithic reinforcedconcrete structure with adequate toughness to respondinelastically under severe earthquake motions. See alsoR21.2.1.

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1.1.8.2 Seismic risk level of a region, or seismicperformance or design category of a structure, shallbe regulated by the legally adopted general buildingcode of which this code forms a part, or determined bylocal authority.

R1.1.8.2 Seismic risk levels (seismic zone maps) areunder the jurisdiction of a general building code rather thanACI 350M. This edition of ACI 350M adopts the changes interminology made to the 1999 and 2002 editions of the 318code to make it compatible with the latest editions of modelbuilding codes in use in the United States. For example, thephrase seismic performance or design categories was intro-duced. Over the past decade, the manner in which seismic risklevels have been expressed in United States building codeshas changed. Previously, they have been represented in termsof seismic zones. Recent editions of the BOCA NationalBuilding Code (NBC)1.10 and Standard Building Code(SBC),1.11 which are based on the 1991 NEHRP,1.12 haveexpressed risk not only as a function of expected intensity ofground shaking on solid rock, but also on the nature of theoccupancy and use of the structure. These two items areconsidered in assigning the structure to a seismic performancecategory (SPC), which in turn is used to trigger differentlevels of detailing requirements for the structure. The 2000International Building Code (IBC)1.13 also uses the twocriteria of the NBC and SBC and also considers the effects ofsoil amplification on the ground motion when assigning aseismic risk. Under the IBC, each structure is assigned aseismic design category (SDC). Among its several uses, ittriggers different levels of detailing requirements. TableR1.1.8.2 correlates low, moderate/intermediate, and highseismic risk, which has been the terminology used in the318 code for several editions, to the various methods ofassigning risk in use in the U.S. under the various modelbuilding codes, the ASCE 7 standard, and the NEHRPRecommended Provisions.

In the absence of a general building code that addressesearthquake loads and seismic zoning, it is the intent ofCommittee 350 that the local authorities (engineers, geolo-gists, and building code officials) should decide on properneed and proper application of the special provisions forseismic design. Seismic ground-motion maps or zoning

TABLE R1.1.8.2CORRELATION BETWEENSEISMIC-RELATED TERMINOLOGY INMODEL CODES

Code, standard, or resourcedocument and edition

Level of seismic risk or assigned seismic performance or design categories as

defined in the code section

Low (21.2.1.2)

Moderate/intermediate

(21.2.1.3)High

(21.2.1.4)International Building Code

2000; NEHRP 1997 SDC1 A, B SDC C SDC D, E, F

BOCA National Building Code 1993, 1996, 1999; Standard Building Code 1994, 1997,

1999; ASCE 7-93, 7-95, 7-98; NEHRP 1991, 1994

SPC2 A, B SPC C SPC D, E

Uniform Building Code1991, 1994, 1997

Seismic Zone 0, 1

Seismic Zone 2

Seismic Zone 3, 4

1SDC = Seismic design category as defined in code, standard, or resource document.2SPC = Seismic performance category as defined in code, standard, or resourcedocument.

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maps, such as recommended in References 1.9, 1.14, and1.15, are suitable for correlating seismic risk.

R1.1.9 Appendix G is incorporated to address thoseaspects of circular wrapped prestressed concrete environmentalstructures that are not directly covered within the main bodyof the code. Thus, Appendix G deals with items that areunique to circular wrapped prestressed structures, such assteel diaphragm, wrapped prestressing, and shotcrete.

R1.2 Drawings and specifications

R1.2.1 The provisions for preparation of design drawingsand 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 informationthat must be included in the design drawings, details, or specifi-cations. The code does not imply an all inclusive list, andadditional items may be required by the building official.

1.1.9 For prestressed concrete environmentalstructures, Chapters 1 through 21 cover prestressingin general. Chapters 1 through 21 plus Appendix Gcover the use of circular wire and strand wrappedprestressed concrete environmental structures.

1.2 Drawings and specifications1.2.1 Copies of design drawings, typical details, andspecifications for all structural concrete constructionshall bear the seal of a licensed engineer or architect.These drawings, details, and specifications shall show:

(a) Name and date of issue of the applicable buildingcode and supplement to which design conforms;

(b) Live load and other loads used in design;(c) Specified compressive strength of concrete atstated ages or stages of construction for which eachpart of structure is designed;

(d) Specified strength or grade of reinforcement;(e) Size and location of all structural elements andreinforcement and anchors;

(f) Provision for dimensional changes resulting fromcreep, shrinkage, and change in temperature;

(g) Magnitude and location of prestressing forces;(h) Anchorage length of reinforcement and locationand length of lap splices;

(i) Type and location of welded splices and mechanicalconnections of reinforcement;

(j) The design liquid level for any structure designedto contain liquid;

(k) Stressing sequence for post-tensioning tendons;(l) Statement if slab on grade is designed as a struc-tural diaphragm, see 21.10.3.4;

(m) Design gas pressure for structural elementssubjected to pressurized gas or liquid;(n) Concrete properties and ingredients includingtype of cement, water-cementitious materials ratio,and, if allowed, admixtures, additives, andpozzolans;

(o) Additional requirements, such as limitations ondrying shrinkage;

(p) Requirements for liquid-tightness testing,including liquid-tightness testing before backfilling.

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1.2.2 Calculations pertinent to design shall be filedwith the drawings when required by the building official.Analyses and designs using computer programs shallbe permitted provided design assumptions, user input,and computer-generated output are submitted. Modelanalysis shall be permitted to supplement calculations.

1.2.3 Building official means the officer or otherdesignated authority charged with the administrationand enforcement of this code, or his duly authorizedrepresentative.

R1.2.2 Documented computer output is acceptable inlieu of manual calculations. The extent of input and outputinformation required will vary, according to the specificrequirements of individual building officials. When acomputer program has been used by the designer, however,only skeleton 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 magni-fication factors in the output where applicable.

The code permits model analysis to be used to supplementstructural analysis and design calculations. Documentationof the model analysis should be provided with the relatedcalculations. Model analysis should be performed by anengineer or architect having experience in this technique.

R1.2.3 Building official is the term used by manygeneral building codes to identify the person charged withadministration and enforcement of the provisions of thebuilding code. Such terms as building commissioner orbuilding inspector, however, are variations of the title, andthe term building official as used in this code is intendedto include those variations as well as others that are used inthe same sense.

R1.3 InspectionThe quality of concrete structures depends largely on work-manship in construction. The best of materials and designpractice will not be effective unless the construction isperformed well. Inspection is provided to assure satisfactorywork in accordance with the design drawings and specifica-tions. Proper performance of the structure depends onconstruction that accurately represents the design and meetscode requirements within the tolerances allowed. In thepublic interest, local building ordinances should require theowner to provide inspections.

R1.3.1 Inspection of construction by or under the super-vision of the licensed design professional responsible forthe design should be recommended because the person incharge of the design is the best qualified to inspect forconformance with the design. When such an arrangement isnot feasible, inspection of construction through otherlicensed design professionals or through separate accreditedinspection organizations, with demonstrated capability forperforming the inspection, may be used.

Qualified inspectors should establish their qualifications bybecoming certified to inspect and record the results ofconcrete construction, including preplacement, placement,and postplacement operations through the Reinforced

1.3 Inspection

1.3.1 Concrete construction shall be inspected asrequired by the legally adopted general building code.In the absence of such requirements, concreteconstruction shall be inspected throughout the variouswork stages by or under the supervision of a licenseddesign professional or by a qualified inspector.

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1.3.2 The inspector shall require compliance withdesign drawings and specifications. Unless specifiedotherwise in the legally adopted general building code,inspection records shall include:

(a) Quality and proportions of concrete materialsand strength of concrete;

(b) Construction and removal of forms andreshoring;

(c) Placing of reinforcement and anchors;(d) Mixing, placing, and curing of concrete;(e) Sequence of erection and connection of precastmembers;

(f) Tensioning of tendons;(g) Any significant construction loadings oncompleted floors, members, or walls;

(h) Description and results of tightness testing ofliquid and/or gas-containing structures;

(i) General progress of work.

Concrete Special Inspection program sponsored by ACI,ICBO, BOCA, and SBCCI or equivalent.

When inspection is done independently of the licenseddesign professional responsible for the design, it is recom-mended that the licensed design professional responsiblefor the design be employed to oversee inspection andobserve the work to see that his design requirements areproperly executed.

In some jurisdictions, legislation has established specialregistration or licensing procedures for persons performingcertain inspection functions. A check should be made in thegeneral building code or with the building official to ascertainif any such 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, and contractor. Adequate feesshould be provided consistent with the work and equipmentnecessary to properly perform the inspection.

R1.3.2 By inspection, the code does not mean that theinspector should supervise the construction. Rather, itmeans that the one employed for inspection should visit theproject with the frequency necessary to observe the variousstages of work and ascertain that it is being done in compli-ance with 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 his obliga-tion to follow the plans and specifications implicitly and toprovide the designated quality and quantity of materials andworkmanship for all job stages. The inspector should bepresent as frequently as he/she deems necessary to judgewhether the quality and quantity of the work complies withthe contract documents; to counsel on possible ways ofobtaining the desired results; to see that the general systemproposed for formwork appears proper (though it remainsthe contractors responsibility to design and build adequateforms and to leave them in place until it is safe to removethem); to see that reinforcement is properly installed; to seethat concrete is of the correct quality, properly placed, andcured; and to see that tests for quality control are beingmade as specified.

The code prescribes minimum requirements for inspectionof 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.

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Recommended procedures for organization and conduct ofconcrete inspection are given in detail in Guide forConcrete Inspection.1.16 (Sets forth procedures relating toconcrete construction to serve as a guide to owners, archi-tects, and engineers in planning an inspection program.)Detailed methods of inspecting concrete construction aregiven in ACI Manual of Concrete Inspection (SP-2)reported by ACI Committee 311.1.17 (Describes methods ofinspecting concrete construction that are generally acceptedas good practice. Intended as a supplement to specificationsand as a guide in matters not covered by specifications.)ACI 311.5 provides the Guide for Concrete Plant Inspec-tion and Testing of Ready-Mixed Concrete.1.18

R1.3.3 The term ambient temperature means thetemperature of the environment to which the concrete isdirectly exposed. Concrete temperature as used in thissection may be taken as the air temperature near the surfaceof the concrete; however, during mixing and placing, it ispractical to measure the temperature of the mixture.

R1.3.4 A record of inspection in the form of a job diary isrequired 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 must 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 thespecial detailing required in concrete ductile frames is prop-erly executed through inspection by personnel who are qual-ified to do this work. Qualifications of inspectors should bedetermined by the jurisdiction enforcing the generalbuilding code.

1.3.3 When the ambient temperature falls below 4 Cor rises above 35 C, a record shall be kept of concretetemperatures and of protection given to concreteduring placement and curing.

1.3.4 Records of inspection required in 1.3.2 and1.3.3 shall be preserved by the inspecting engineer orarchitect for 2 years after completion of the project.

1.3.5 For special moment frames resisting seismicloads in regions of high seismic risk, or in structuresassigned to high seismic performance or design cate-gories, continuous inspection of the placement of thereinforcement and concrete shall be made by a quali-fied inspector. The inspector shall be under the super-vision of the engineer responsible for the structuraldesign or under the supervision of an engineer withdemonstrated capability for supervising inspection ofspecial moment frames resisting seismic loads inregions of high seismic risk, or in structures assignedto high seismic performance or design categories.

1.4 Approval of special systems of design or construction

Sponsors of any system of design or constructionwithin the scope of this code, the adequacy of whichhas been shown by successful use or by analysis ortest, but which does not conform to or is not coveredby this code, shall have the right to present the data onwhich their design is based to the building official or toa board of examiners appointed by the building official.

R1.4 Approval of special systems of design or construction

New methods of design, new materials, and new uses ofmaterials must undergo a period of development beforebeing specifically covered in a code. Hence, good systemsor components might be excluded from use by implication ifmeans were not available to obtain acceptance.

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This board shall be composed of competent engineersand shall have authority to investigate the data sosubmitted, to require tests, and to formulate rulesgoverning design and construction of such systems tomeet the intent of this code. These rules whenapproved by the building official and promulgated shallbe of the same force and effect as the provisions ofthis code.

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.

20 CHAPTER 1

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Notes

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2.1 The following terms are defined for general usein this code. Specialized definitions appear in individualchapters.

R2.1 For consistent application of the code, it is neces-sary that terms be defined where they have particular mean-ings in the code. The definitions given are for use inapplication of this code only and do not always correspondto ordinary usage. A glossary of most used terms relating tocement manufacturing, concrete design and construction,and research in concrete is contained in Cement andConcrete Terminology reported by ACI Committee 116.2.1

By code definition, sand-lightweight concrete is structurallightweight concrete with all of the fine aggregate replacedby sand. This definition may not be in agreement with usageby 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 must be stated, with interpolation whenpartial sand replacement is used.

Deformed reinforcement is defined as that meeting thedeformed bar specifications of 3.5.3.1, or the specificationsof 3.5.3.3, 3.5.3.4, 3.5.3.5, or 3.5.3.6. No other bar or fabricqualifies. This definition permits accurate statement ofanchorage lengths. Bars or wire not meeting the deformationrequirements or fabric not meeting the spacing requirementsare plain reinforcement, for code purposes, and may beused only for spirals.

A number of definitions for loads are given as the codecontains requirements that must be met at various loadlevels. The terms dead load and live load refer to theunfactored loads (service loads) specified or defined by thegeneral 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 in9.5, Control of Deflections. Loads used to proportion amember for adequate strength are defined as factoredloads. Factored loads are service loads multiplied by theappropriate load factors specified in 9.2 for requiredstrength. The term design loads, as used in the ACI 318-71code to refer to loads multiplied by appropriate load factors,was discontinued in the ACI 318-77 code to avoid confusionwith the design load terminology used in general buildingcodes to denote service loads or posted loads in buildings.The factored load terminology, first adopted in the ACI 318-77code, clarifies when the load factors are applied to a particularload, moment, or shear value as used in the code provisions.

Reinforced concrete is defined to include prestressedconcrete. Although the behavior of a prestressed memberwith unbonded tendons may vary from that of memberswith continuously bonded tendons, bonded and unbondedprestressed concrete are combined with conventionallyreinforced concrete under the generic term reinforced

CHAPTER 2 DEFINITIONS

22 CHAPTER 2

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concrete. Provisions common to both prestressed andconventionally reinforced concrete are integrated to avoidoverlapping and conflicting provisions.

Strength of a member or cross section calculated using stan-dard assumptions and strength equations, and nominal(specified) values of material strengths and dimensions isreferred to as nominal strength. The subscript n is used todenote the nominal strengths; nominal axial load strengthPn, nominal moment strength Mn, and nominal shearstrength Vn. Design strength or usable strength of amember or cross section is the nominal strength reduced bythe strength reduction factor .

The required axial load, moment, and shear strengths usedto proportion members are referred to either as factoredaxial loads, factored moments, and factored shears, orrequired axial loads, moments, and shears. The factoredload effects are calculated from the applied factored loadsand forces in such load combinations as are stipulated in thecode (see 9.2).The subscript u is used only to denote the requiredstrengths: required axial load strength Pu, required momentstrength Mu, and required shear strength Vu, calculatedfrom the applied factored loads and forces.

The basic requirement for strength design may be expressedas follows:

Design strength Required strength

Pn PuMn MuVn Vu

For additional discussion on the concepts and nomenclaturefor strength design, see Commentary, Chapter 9.

The term compression member is used in the code to defineany member in which the primary stress is longitudinalcompression. Such a member need not be vertical, but may haveany orientation in space. Bearing walls, columns, and pedestalsqualify as compression members under this definition.

The differentiation between columns and walls in the codeis based on the principal use rather than on arbitrary relation-ships of height and cross-sectional dimensions. The code,however, permits walls to be designed using the principlesstated for column design (see 14.4), as well as by theempirical method (see 14.5).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 membercarrying axial loads combined with bending and shear. Itmay, however, form a small part of an enclosure or separation.

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Admixture Material other than water, aggregate, orhydraulic cement, used as an ingredient of concreteand added to concrete before or during its mixing tomodify its properties.

Aggregate Granular material, such as sand, gravel,crushed stone, and iron blast-furnace slag, used witha cementing medium to form a hydraulic cementconcrete or mortar.

Aggregate, lightweight Aggregate with a dry,loose density of 1120 kg/m3 or less.

Anchorage device In post-tensioning, the hard-ware used for transferring a post-tensioning force fromthe prestressing steel to the concrete.

Anchorage zone In post-tensioned members, theportion of the member through which the concentratedprestressing force is transferred to the concrete anddistributed more uniformly across the section. Itsextent is equal to the largest dimension of the crosssection. For anchorage devices located away from theend of a member, the anchorage zone includes thedisturbed regions ahead of and behind the anchoragedevices.

Basic monostrand anchorage device Anchoragedevice used with any single strand or a single 15 mmor smaller diameter bar that satisfies 18.21.1 and theanchorage device requirements of ACI 423.6, Specifi-cation for Unbonded Single-Strand Tendons.

Basic multistrand anchorage device Anchoragedevice used with multiple strands, bars, or wires, orwith single bars larger than 15 mm diameter, that satis-fies 18.21.1 and the bearing stress and minimum platestiffness 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 steelis bonded to concrete either directly or throughgrouting.

Building official See 1.2.3.

Cementitious materials Materials as specified inChapter 3, which have cementing value when used inconcrete either by themselves, such as portlandcement, blended hydraulic cements, and expansivecement, or such materials in combination with fly ash,other raw or calcined natural pozzolans, silica fume,and/or ground granulated blast-furnace slag.

Anchorage device Most anchorage devices for post-tensioning are standard manufactured devices availablefrom commercial sources. In some cases, designers orconstructors develop special details or assemblages thatcombine various wedges and wedge plates for anchoringprestressing steel with specialty end plates or diaphragms.These informal designations as standard anchorage devicesor special anchorage devices have no direct relation to theACI 350M Code classification of anchorage devices asbasic anchorage devices or special anchorage devices.

Anchorage zone The terminology ahead of and behindthe anchorage device is illustrated in Fig. R18.13.1(b).

Basic anchorage devices are those devices that are soproportioned that they can be checked analytically forcompliance with bearing stress and stiffness requirementswithout having to undergo the acceptance-testing programrequired of special anchorage devices.

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Column Member with a ratio of height-to-leastlateral dimension exceeding 3 used primarily tosupport axial compressive load.

Composite concrete flexural members Concreteflexural members of precast and/or cast-in-placeconcrete elements constructed in separate place-ments but so interconnected that all elements respondto loads as a unit.

Concrete Mixture of portland cement or any otherhydraulic cement, fine aggregate, coarse aggregate,and water, with or without admixtures.

Concrete, specified compressive strength of, ( f c ) Compressive strength of concrete used in design andevaluated in accordance with provisions of Chapter 5,expressed in megapascals (MPa). Whenever thequantity fc is under a radical sign, square root ofnumerical value only is intended, and result has unitsof megapascals (MPa).Concrete, structural lightweight Concretecontaining lightweight aggregate that conforms to 3.3and has an air-dry unit weight as determined by TestMethod for Unit Weight of Structural LightweightConcrete (ASTM C 567), not exceeding 1840 kg/m3.In this code, a lightweight concrete without naturalsand is termed all-lightweight concrete and light-weight concrete in which all of the fine aggregateconsists of normalweight sand is termed sand-light-weight concrete.

Contraction joint Formed, sawed, or tooled groovein a concrete structure to create a weakened planeand regulate the location of cracking resulting from thedimensional change of different parts of the structure.

Curvature friction Friction resulting from bends orcurves in the specified prestressing tendon profile.

Deformed reinforcement Deformed reinforcingbars, bar mats, deformed wire, welded plain wirefabric, and welded deformed wire fabric conforming to3.5.3.

Development length Length of embedded reinforce-ment required to develop the design strength ofreinforcement at a critical section. See 9.3.3.

Duct A conduit (plain or corrugated) to accommo-date prestressing steel for post-tensioned installation.Requirements for post-tensioning ducts are given inSection 18.15.

Effective depth of section (d) Distance measuredfrom extreme compression fiber to centroid of tensionreinforcement.

Effective prestress Stress remaining in prestressingsteel after all losses have occurred.

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Embedment length Length of embedded reinforce-ment provided beyond a critical section.

Extreme tension steel The reinforcement(prestressed or nonprestressed) that is the farthestfrom the extreme compression fiber.

Isolation joint A separation between adjoiningparts of a concrete structure, usually a vertical plane,at a designed location such as to interfere least withperformance of the structure, yet such as to allow rela-tive movement in three directions and avoid formationof cracks elsewhere in the concrete and through whichall or part of the bonded reinforcement is interrupted.

Jacking force In prestressed concrete, temporaryforce exerted by device that introduces tension intoprestressing steel.

Load, dead Dead weight supported by a member,as defined by general building code of which this codeforms a part (without load factors).Load, factored Load, multiplied by appropriate loadfactors, used to proportion members by the strengthdesign method of this code. See 8.1.1 and 9.2.

Load, live Live load specified by general buildingcode of which this code forms a part (without loadfactor).Load, service Load specified by general buildingcode of which this code forms a part (without loadfactors).Modulus of elasticity Ratio of normal stress tocorresponding strain for tensile or compressivestresses below proportional limit of material. See 8.5.

Moment frame Frame in which members and jointsresist forces through flexure, shear, and axial force.Moment frames shall be categorized as follows:

Intermediate moment frame A cast-in-place frame complying with the requirementsof 21.2.2.3 and 21.12 in addition to therequirements for ordinary moment frames.

Ordinary moment frame A cast-in-place orprecast concrete frame complying with therequirements of Chapters 1 through 18.

Special moment frame A cast-in-placeframe complying with the requirements of 21.2through 21.5, or a precast frame complyingwith the requirements of 21.2 through 21.6. Inaddition, the requirements for ordinarymoment frames shall be satisfied.

Net tensile strain The tensile strain at nominalstrength exclusive of strains due to effective prestress,creep, shrinkage, and temperature.

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Normal environmental exposure Exposure toliquids with a pH greater than 5, or exposure to sulfatesolutions 1000 ppm or less.

Pedestal Upright compression member with a ratioof unsupported height to average least lateral dimen-sion of less than 3.

Plain concrete Structural concrete with no reinforce-ment or with less reinforcement than the minimumamount specified for reinforced concrete.

Plain reinforcement Reinforcement that does notconform to definition of deformed reinforcement. See3.5.4.

Post-tensioning Method of prestressing in whichprestressing steel is tensioned after concrete hashardened.

Precast concrete Structural concrete element castelsewhere than its final position in the structure.

Prestressed concrete Structural concrete in whichinternal stresses have been introduced to reducepotential tensile stresses in concrete resulting fromloads.

Prestressing steel High-strength steel elementsuch as wire, bar, or strand, or a bundle of suchelements, used to impart prestress forces to concrete.

Pretensioning Method of prestressing in whichprestressing steel is tensioned before concrete isplaced.

Reinforced concrete Structural concrete rein-forced with no less than the minimum amounts ofprestressing steel or nonprestressed reinforcementspecified in Chapters 1 through 21 and Appendices Athrough C.

Reinforcement Material that conforms to 3.5,excluding prestressing steel unless specificallyincluded.

Reshores Shores placed snugly under a concreteslab or other structural member after the original formand shores have been removed from a larger area,thus requiring the new slab or structural member todeflect and support its own weight and existingconstruction loads applied prior to the installation ofthe reshores.

Severe environmental exposure Exposure condi-tions in which the limits defining normal environmentalexposure are exceeded.

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Sheathing A material encasing prestressing steelto prevent bonding of the prestressing steel with thesurrounding concrete, to provide corrosion protection,and to contain the corrosion inhibiting coating.

Shores Vertical or inclined support membersdesigned to carry the weight of the formwork,concrete, and construction loads above.

Span length See 8.7.

Special anchorage device Anchorage device thatsatisfies 18.15.1 and the standardized acceptancetests of AASHTO Standard Specifications for HighwayBridges, Division ll, Article 10.3.2.3.

SheathingTypically, sheathing is a continuous, seamless,high-density polyethylene material extruded directly on thecoated prestressing steel. In environmental concrete struc-tures, only seamless, extruded sheathing is acceptable foruse in unbonded, monostrand prestressing steel.

Special anchorage devices are any devices (monostrand ormultistrand) that do not meet the relevant PTI or AASHTObearing stress and, where applicable, stiffness requirements.Most commercially marketed multibearing surfaceanchorage devices are special anchorage devices. As providedin 18.15.1, such devices can be used only when they havebeen shown experimentally to be in compliance with theAASHTO requirements. This demonstration of compliancewill ordinarily be furnished by the device manufacturer.

Spiral reinforcement Continuously wound reinforce-ment in the form of a cylindrical helix.

Splitting tensile strength (fct) Tensile strength ofconcrete determined in accordance with ASTM C496M as described in Specification for LightweightAggregates for Structural Concrete (ASTM C 330).Stirrup Reinforcement used to resist shear andtorsion stresses in a structural member; typically bars,wires, or welded wire fabric (plain or deformed) eithersingle leg or bent into L, U, or rectangular shapes andlocated perpendicular to or at an angle to longitudinalreinforcement. The term stirrups is usually applied tolateral reinforcement in flexural members and the termties to those in compression members.) See also Tie.Strength, design Nominal strength multiplied by astrength reduction factor . See 9.3.

Strength, nominal Strength of a member or crosssection calculated in accordance with provisions andassumptions of the strength design method of thiscode before application of any strength reductionfactors. See 9.3.1.

Strength, required Strength of a member or crosssection required to resist factored loads or relatedinternal moments and forces in such combinations asare stipulated in this code. See 9.1.1.

Stress Intensity of force per unit area.

Structural concrete All concrete used for structuralpurposes including plain and reinforced concrete.

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Structural walls Walls proportioned to resistcombinations of shears, moments, and axial forcesinduced by earthquake motions. A shearwall is a struc-tural wall. Structural walls shall be categorized asfollows:

Intermediate precast structural wall A wallcomplying with all applicable requirements ofChapters 1 through 18 in addition to 21.13.

Ordinary reinforced concrete structural wall A wall complying with the requirements ofChapters 1 through 18.

Special precast structural wall A precastwall complying with the requirements of 21.8. Inaddition, the requirements of ordinary reinforcedconcrete structural walls and the requirements of21.2 shall be satisfied.

Special reinforced concrete structural wall Acast-in-place wall complying with the requirementsof 21.2 and 21.7 in addition to the requirementsfor ordinary reinforced concrete structural walls.

Tendon In pretensioned applications, the tendon isthe prestressing steel. In post-tensioned applications,the tendon is a complete assembly consisting ofanchorages, prestressing steel, and sheathing withcoating for unbonded applications or ducts with groutfor bonded applications.

Tie Loop of reinforcing bar or wire enclosing longi-tudinal reinforcement. A continuously wound bar orwire in the form of a circle, rectangle, or other polygonshape without re-entrant corners is acceptable. Seealso Stirrup.

Transfer Act of transferring stress in prestressingsteel from jacks or pretensioning bed to concretemember.

Unbonded tendon Tendon in which theprestressing steel is prevented from bonding to theconcrete and is free to move relative to the concrete.The prestressing force is permanently transferred to theconcrete at the tendon ends by the anchorages only.

Wall Member, usually vertical, used to enclose orseparate spaces.

Wobble friction In prestressed concrete, frictioncaused by unintended deviation of prestressing sheathor duct from its specified profile.

Yield strength Specified minimum yield strength oryield point of reinforcement in pounds per square inch.Yield strength or yield point shall be determined intension according to applicable ASTM standards asmodified by 3.5 of this code.

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2.2 The following additional terms are defined for general use in this code

Backer rod A compressible rod placed betweenjoint filler and sealant and used to provide support forand to control the depth of sealant.

An ideal backer rod will permit compression to one-half itsoriginal width and will re-expand to fill the joint when theadjacent members contract. Neoprene and open or closedcell plastic foams are satisfactory materials for backer rods.The backer rod should be compatible with the adjacent jointsealant.

Refer to Chapter 9 of this Code for rules on the applicationof this factor. When the environmental durability factor isused, members proportioned using the strength designapproach are similar to those proportioned using the alter-nate design method (Appendix I).

Cork, neoprene, rubber, foam, and other materialsconforming to ASTM D 1056 and D 1752 are satisfactoryjoint fillers. The preformed filler should be compatible withadjacent joint sealant.Sealants used in water treatment plants, reservoirs, andother structural facilities that will be in contact with potablewater should be certified as compliant with ANSI/NSF 61.In addition, the sealant should be resistant to chlorinatedwater and suitable for immersion service.

Waterstops are available in various sizes, shapes, andmaterials. Environmental concrete structures commonly usewaterstops of preformed rubber or polyvinyl chloride with aminimum thickness of 10 mm. They should normally be atleast 230 mm wide for expansion joints and 150 mm widefor other types of joints to provide adequate embedment inthe concrete. Metal waterstops are used for special exposureenvironments. Expansive rubber or adhesive waterstopsmay be used in joints cast against previously placedconcrete, or in new construction when approved by theengineer. Chemical resistance, joint movement capacity,and design temperature range are among the items thatshould be investigated when selecting waterstops. Jointmovement capacity and design temperature range areamong the items that should be investigated whenselecting waterstops. Joint details are further described inACI 350.4R.

R2.2

Environmental durability factor Factor used tocontrol reinforcement stresses and crack widths inmembers designed using the strength design approach.

Joint filler A compressible, preformed materialused to fill an expansion joint to prevent the infiltrationof debris and to provide support for backer rod andsealants.

Joint sealant A synthetic elastomeric material usedto finish a joint and to exclude solid foreign materials.

Waterstop A continuous preformed strip of metal,rubber, plastic, or other material inserted across a jointto prevent the passage of liquid through the joint.

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Notes

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3.0 Notation

fy = specified yield strength of nonprestressedreinforcement, MPa

R3.0 NotationUnits of measurement are given in the Notation to assist theuser and are not intended to preclude the use of othercorrectly applied units for the same symbol, such as m or kN.

R3.1 Tests of materials

CHAPTER 3 MATERIALS

PART 2 STANDARDS FOR TESTS ANDMATERIALS

3.2 Cements3.2.1 Cement shall conform to one of the followingspecifications:

(a) Specification for Portland Cement (ASTM C 150);(b) Specification for Blended Hydraulic Cements(ASTM C 595M), excluding Types S and SA, whichare not intended as principal cementing constituentsof structural concrete;

(c) Specification for Expansive Hydraulic Cement(ASTM C 845).

R3.1.3 The record of tests of materials and of concretemust be preserved for at least 2 years after completion of theproject. Completion of the project is the date at which theowner accepts the project or when the certificate of occupancyis issued, whichever date is later. Local legal requirementsmay require longer preservation of such records.

R3.2 CementsR3.2.1 Different cements or cements from differentproducers should not be used interchangeably in the sameelement or portion of the work. Additional guidance oncement may be found in ACI 225R.3.1

Concrete made with expansive cement can be used toreduce drying-shrinkage cracking in environmental engi-neering concrete structures, but the ACI 350 committee isnot yet in a position to recommend detailed requirementsfor its use. For the design to be successful, the engineermust recognize the characteristics and properties ofshrinkage compensating concrete and cement as describedin ACI 223 and ASTM C 845 (Type E1-K), respectively.Type K cement has historically shown very satisfactoryresistance to sulfate attack in both the laboratory and thefield. Additional care and control should be exercisedduring design and construction. Detailed information onshrinkage-compensating concrete is contained in ACI 223.3.2

R3.2.2 Depending on the circumstances, the provision of3.2.2 may require only the same type of cement or mayrequire cement from the ide

350M_06

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