CHAPTER 2 CODE COMMENTARY 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 Column- Member with a ratio of height-to-least lat Column- The term compression member is used in the eral dimension exceeding 3 used primarily to support code to define any member in which the primary stress is lon- axial compressive load gitudinal compression. Such a member need not be vertical but may have any orientation in space. Bearing walls, col- this definition The differentiation between columns and walls in the code is based on the principal use rather than on arbitrary rela- tionships of height and cross-sectional dimensions. The code, however, permits walls to be designed using the prin- ciples stated for column design(see 14. 4), as well as by the empirical method(see 14.5) While a wall always encloses or separates spaces, it may also be used to resist horizontal or vertical forces or bend- ing. For example, a retaining wall or a basement wall also supports various combinations of loads A column is normally used as a main vertical member carry- ing axial loads combined with bending and shear. It may however, form a small part of an enclosure or separation 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 oads 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 ompression-controlled strain limit- The net ten- sile 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, specified compressive strength of, (fc) Compressive strength of concrete used in design and evaluated in accordance with provisions of Chapter 5, expressed in megapascals(MPa). Whenever the quantity tc is under a radical sign, square root numerical value only is intended, and result has units of megapas licene with Acl ACI 318 Building Not censee-Black veatch oduction of networking permitted without loene from H ot for Resale. 11/28/2005 a
CHAPTER 2 29 CODE COMMENTARY ACI 318 Building Code and Commentary 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. Column — Member with a ratio of height-to-least lateral dimension exceeding 3 used primarily to support axial compressive load. Column — The term compression member is used in the code to define any member in which the primary stress is longitudinal compression. Such a member need not be vertical but may have any orientation in space. Bearing walls, columns, and pedestals qualify as compression members under this definition. The differentiation between columns and walls in the code is based on the principal use rather than on arbitrary relationships of height and cross-sectional dimensions. The code, however, permits walls to be designed using the principles stated for column design (see 14.4), as well as by the empirical method (see 14.5). While a wall always encloses or separates spaces, it may also be used to resist horizontal or vertical forces or bending. For example, a retaining wall or a basement wall also supports various combinations of loads. A column is normally used as a main vertical member carrying axial loads combined with bending and shear. It may, however, form a small part of an enclosure or separation. 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, specified compressive strength of, (fc′) — Compressive strength of concrete used in design and evaluated in accordance with provisions of Chapter 5, expressed in megapascals (MPa). Whenever the quantity fc′ is under a radical sign, square root of numerical value only is intended, and result has units of megapascals (MPa). Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Black & Veatch/5910842100 No reproduction or networking permitted without license from IHS Not for Resale, 11/28/2005 18:20:15 MST --`,,`,````````,,`,,`,,``,`,,,`-`-`,,`,,`,`,,`---
CHAPTER 2 CODE COMMENTARY Concrete, structural lightwelght--Concrete contain- Concrete, structural lightweight--In 2000, ASTM C 567 ing lightweight aggregate that conforms to 3.3 and has adopted"equilibrium density"as the measure for determin- an equilibrium density as determined by "Test Method ing compliance with specified in-service density require- for Determining Density of Structural Lightweight Con- ments. According to ASTM C 567, equilibrium density may crete"(ASTM C 567), not exceeding 1840 kg/m In this be determined by measurement or approximated by calcula- code, a lightweight concrete without natural sand is tion using either the measured oven-dry density or the oven termed"all-lightweight concrete"and lightweight con- dry density calculated from the mixture proportions. Unless crete in which all of the fine aggregate consists of nor- specified otherwise, ASTM C 567 requires that equilibriu mal weight sand is termed"sand-lightweight concrete density be approximated by calculation. By code definition, sand-lightweight concrete is structural lightweight concrete with all of the fine aggregate replaced by sand. This definition may not be in agreement with usage by some material suppliers or contractors where the major ity, but not all, of the lightweight fines are replaced by sand For proper application of the code provisions, the replace ment limits should be stated, with interpolation when partial sand replacement is used 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 Curvature friction- Friction resulting from bends or curves in the specified prestressing tendon profile. Deformed reinforcement- Deformed reinforcing bars, Deformed reinforcement- Deformed reinforcement is bar mats, deformed wire, and welded wire reinforcement defined as that meeting the deformed reinforcement specifi conforming to 3.5.3 cations of 3.5.3. 1, or the specifications of 3.5.3.3, 3.5.3.4, 3.5.3.5, or 3.5.3.6. No other reinforcement qualifies. This definition permits ad anchor Bars or wire not meeting the deformation requirements or welded wire reinforcement not meeting the spacing require ments are"plain reinforcement, for code purposes, and may be used only for spirals Development length-Length of embedded rein forcement, including pretensioned strand, required to develop the design strength of reinforcement at a criti cal section. See 9.3.3 Drop panel-A projection below the slab at least one quarter of the slab thickness beyond the drop Duct-A conduit (plain or corrugated) to accommo date prestressing steel for post-tensioned installation Requirements for post-tensioning ducts are given in ACI 318 Building Co Not fos gesaer 12e2oo5 1820415 st
30 CHAPTER 2 CODE COMMENTARY ACI 318 Building Code and Commentary Concrete, structural lightweight — Concrete containing lightweight aggregate that conforms to 3.3 and has an equilibrium density as determined by “Test Method for Determining Density of Structural Lightweight Concrete” (ASTM C 567), not exceeding 1840 kg/m3. In this code, a lightweight concrete without natural sand is termed “all-lightweight concrete” and lightweight concrete in which all of the fine aggregate consists of normal weight sand is termed “sand-lightweight concrete.” Concrete, structural lightweight — In 2000, ASTM C 567 adopted “equilibrium density” as the measure for determining compliance with specified in-service density requirements. According to ASTM C 567, equilibrium density may be determined by measurement or approximated by calculation using either the measured oven-dry density or the ovendry density calculated from the mixture proportions. Unless specified otherwise, ASTM C 567 requires that equilibrium density be approximated by calculation. By code definition, sand-lightweight concrete is structural lightweight concrete with all of the fine aggregate replaced by sand. This definition may not be in agreement with usage by some material suppliers or contractors where the majority, but not all, of the lightweight fines are replaced by sand. For proper application of the code provisions, the replacement limits should be stated, with interpolation when partial sand replacement is used. Deformed reinforcement — Deformed reinforcement is defined as that meeting the deformed reinforcement specifications of 3.5.3.1, or the specifications of 3.5.3.3, 3.5.3.4, 3.5.3.5, or 3.5.3.6. No other reinforcement qualifies. This definition permits accurate statement of anchorage lengths. Bars or wire not meeting the deformation requirements or welded wire reinforcement not meeting the spacing requirements are “plain reinforcement,” for code purposes, and may be used only for spirals. 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. Curvature friction — Friction resulting from bends or curves in the specified prestressing tendon profile. Deformed reinforcement — Deformed reinforcing bars, bar mats, deformed wire, and welded wire reinforcement conforming to 3.5.3. Development length — Length of embedded reinforcement, 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 at least one quarter of the slab thickness beyond the drop. Duct — A conduit (plain or corrugated) to accommodate prestressing steel for post-tensioned installation. Requirements for post-tensioning ducts are given in 18.17. Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Black & Veatch/5910842100 No reproduction or networking permitted without license from IHS Not for Resale, 11/28/2005 18:20:15 MST --`,,`,````````,,`,,`,,``,`,,,`-`-`,,`,,`,`,,`---
CHAPTER 2 CODE COMMENTARY 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- nent provided beyond a critical section. Extreme tension steel- The reinforcement(pre- stressed or nonprestressed) that is the farthest from the extreme compression fiber. 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 Load, dead- Dead weight supported by a member, Loads- A number of definitions for loads are given as the as defined by general building code of which this code code contains requirements that are to be met at various load forms a part (without load factors) levels. The terms dead load and live load refer to the unfac Load, factored--Load, multiplied by appropriate load tored loads(service loads)specified or defined by the gen eral building code. Service loads(loads without load factors) factors, used to proportion members by the strength are to be used where specified in the code to proportion or design method of this code. See 8.1.1 and 9.2. investigate members for adequate serviceability, as in 9.5 Load, live-Live load specified by general building Control of Deflections. Loads used to proportion a member code of which this code forms a part (without load factors loads are service loads multiplied by the appropriate load factors specified in 9.2 for required strength. The term design Load, service- Load specified by general building loads, as used in the 1971 code edition to refer to loads multi code of which this code forms a part ( without load plied by the appropriate load factors, was discontinued in the factors) 1977 code to avoid confusion with the design load terminol- ogy used in general denote service loads posted loads in buildings. The factored load terminology, first adopted in the 1977 code, clarifies when the load factors are applied to a particular load, moment, or shear value as used in the code provisions. Modulus of elasticity-Ratio of normal stress to corresponding strain for tensile or compressive tresses 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 shall be catergorized as follows Intermediate moment frame-Acast-in-place frame complying with the requirements of licene with Acl censee-Black veatch oduction of networking permitted without loene from H ACI 318 Building Nor ot for Resale. 11/28/2005 a
CHAPTER 2 31 CODE COMMENTARY ACI 318 Building Code and Commentary Effective depth of section (d) — Distance measured from extreme compression fiber to centroid of longitudinal tension reinforcement. Effective prestress — Stress remaining in prestressing steel after all losses have occurred. Embedment length — Length of embedded reinforcement provided beyond a critical section. Extreme tension steel — The reinforcement (prestressed or nonprestressed) that is the farthest from the extreme compression fiber. 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 relative 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. Loads — A number of definitions for loads are given as the code contains requirements that are to be met at various load levels. The terms dead load and live load refer to the unfactored loads (service loads) specified or defined by the general building code. Service loads (loads without load factors) are to be used where specified in the code to proportion or investigate members for adequate serviceability, as in 9.5, Control of Deflections. Loads used to proportion a member for adequate strength are defined as factored loads. Factored loads are service loads multiplied by the appropriate load factors specified in 9.2 for required strength. The term design loads, as used in the 1971 code edition to refer to loads multiplied by the appropriate load factors, was discontinued in the 1977 code to avoid confusion with the design load terminology used in general building codes to denote service loads, or posted loads in buildings. The factored load terminology, first adopted in the 1977 code, clarifies when the load factors are applied to a particular load, moment, or shear value as used in the code provisions. 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 shall be catergorized as follows: Intermediate moment frame — A cast-in-place frame complying with the requirements of Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Black & Veatch/5910842100 No reproduction or networking permitted without license from IHS Not for Resale, 11/28/2005 18:20:15 MST --`,,`,````````,,`,,`,,``,`,,,`-`-`,,`,,`,`,,`---
CHAPTER 2 CODE COMMENTARY 21.2.2. 3 and 21.12 in addition to the require- ments for ordinary moment frames Ordinary moment frame A cast-in-place or precast concrete frame complying with the requirements of Chapters 1 through 18. Special moment frame-A cast-in-place frame complying with the requirements of 21.2 through 21.5, or a precast frame complying with the requirements of 21.2 through 21.6. In addition, the requirements for ordinary moment frames hall be satisfied Net tensile strain The tensile strain at nomina strength exclusive of strains due to effective prestress, creep, shrinkage, and temperature Pedestal- Upright compression member with a ratio of unsupported height to average least lateral dimen ion not exceeding Plain concrete- Structural concrete with no rein- forcement or with less reinforcement than the mini Plain reinforcement- Reinforcement that does not onform to definition of deformed reinforcement. see 3.5.4 Post-tensioning- Method of prestressing in which restressing 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 pre tressed member where flexural tension calculated sing gross section properties, would occur under unfactored dead and live loads if the prestress force were not present Prestressed concrete- Structural concrete in which Prestressed concrete- Reinforced concrete is defined to internal stresses have been introduced to reduce include prestressed concrete. Although the behavior of a pre- potential tensile stresses in concrete resulting from stressed member with unbonded tendons may vary from that of members with continuously bonded tendons, bonded and unbonded prestressed concrete are combined with conven- forced concrete "Provisions common to both prestressed and conventionally reinforced concrete tegrated to avoid overlapping and conflicting provisions. Prestressing steel igth steel element such as wire bar or strand or a bundle of such ele- ments, used to impart prestress forces to concrete Pretensioning- Method of prestressing in which prestressing steel is tensioned before concrete is licene with Acl o reproducion of networking permitted without loene from H ACI 318 Building CoNot fos gesaer 12e2oo5 1820415 st
32 CHAPTER 2 CODE COMMENTARY ACI 318 Building Code and Commentary 21.2.2.3 and 21.12 in addition to the requirements for ordinary moment frames. Ordinary moment frame — A cast-in-place or precast concrete frame complying with the requirements of Chapters 1 through 18. Special moment frame — A cast-in-place frame complying with the requirements of 21.2 through 21.5, or a precast frame complying with the requirements of 21.2 through 21.6. 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. Pedestal — Upright compression member with a ratio of unsupported height to average least lateral dimension not exceeding 3. Plain concrete — Structural concrete with no reinforcement or with less reinforcement than the minimum amount specified for reinforced concrete. Plain reinforcement — Reinforcement that does not conform to definition of deformed reinforcement. See 3.5.4. 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, calculated using gross section properties, would occur under unfactored dead and live loads if the prestress force were 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 a prestressed member with unbonded tendons may vary from that of members with continuously bonded tendons, bonded and unbonded prestressed concrete are combined with conventionally reinforced concrete under the generic term “reinforced concrete.” Provisions common to both prestressed and conventionally reinforced concrete are integrated to avoid overlapping 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. Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Black & Veatch/5910842100 No reproduction or networking permitted without license from IHS Not for Resale, 11/28/2005 18:20:15 MST --`,,`,````````,,`,,`,,``,`,,,`-`-`,,`,,`,`,,`---
CHAPTER 2 CODE COMMENTARY Registered design professional- An individual who is registered or licensed to practice the respective design profession as defined by the statutory require ments of the professional registration laws of the state or jurisdiction in which the project is to be constructed Reinforced concrete Structural concrete rein- forced with no less than the minimum amounts of pre stressing steel or nonprestressed reinforcement specified in Chapters 1 through 21 and Appendices A nrough Reinforcement Material that conforms to 3.5 excluding prestressing steel unless specifically ncluded 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 resor Sheathing- A material encasing prestressing steel Sheathing- Typically, sheathing is a continuous, seam- to prevent bonding of the prestressing steel with the less, high-density polyethylene material extruded directly surrounding concrete, to provide corrosion protection, on the coated prestressing steel and to contain the corrosion inhibiting coating Shores Vertical or inclined support members designed to carry the weight of the formwork, con- crete, and construction loads above Span length- See 8.7. Special anchorage device- Anchorage device that Special anchorage devices are any devices(monostrand or satisfies 18.15. 1 and the standardized acceptance multistrand) that do not meet the relevant Pti or AAShtO tests of AASHTo"Standard Specifications for Highway bearing stress and, where applicable, stiffness requirements. Bridges, " Division ll, Article 10.3.2.3 Most commercially marketed multibearing surface anchor age devices are Special Anchorage Devices. As provided in 18.15.1, such devices can be used only when they have been shown experimentally to be in compliance with the AASHTO requirements. This demonstration of compliance will ordinarily be furnished by the device manufacturer Spiral reinforcement-Continuously wound rein- forcement in the form of a cylindrical helix. Splitting tensile strength(fct)- Tensile strength of concrete determined in accordance with ASTm C 496M as described in "Standard Specification for Lightweight Aggregates for Structural Concrete (ASTM C 330 ). See 5.1.4. licene with Acl oduction of networking permitted without loene from H ACI 318 Building Nor censee-Black veatch ot for Resale. 11/28/2005 a
CHAPTER 2 33 CODE COMMENTARY ACI 318 Building Code and Commentary Registered design professional — An individual who is registered or licensed to practice the respective design profession as defined by the statutory requirements of the professional registration laws of the state or jurisdiction in which the project is to be constructed. 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 Appendices A through C. 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. 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 8.7. 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. Sheathing — Typically, sheathing is a continuous, seamless, high-density polyethylene material extruded directly on the coated prestressing steel. Special anchorage devices are any devices (monostrand or multistrand) that do not meet the relevant PTI or AASHTO bearing stress and, where applicable, stiffness requirements. Most commercially marketed multibearing surface anchorage devices are Special Anchorage Devices. As provided in 18.15.1, such devices can be used only when they have been shown experimentally to be in compliance with the AASHTO requirements. This demonstration of compliance will ordinarily be furnished by the device manufacturer. Spiral reinforcement — Continuously wound reinforcement in the form of a cylindrical helix. Splitting tensile strength (fct) — Tensile strength of concrete determined in accordance with ASTM C 496M as described in “Standard Specification for Lightweight Aggregates for Structural Concrete” (ASTM C 330). See 5.1.4. Copyright American Concrete Institute Provided by IHS under license with ACI Licensee=Black & Veatch/5910842100 No reproduction or networking permitted without license from IHS Not for Resale, 11/28/2005 18:20:15 MST --`,,`,````````,,`,,`,,``,`,,,`-`-`,,`,,`,`,,`---