CHAPTER 1 CHAPTER 1-GENERAL REQUIREMENTS CODE COMMENTARY 11-Sc。pe Rl.1一 Scope 1.1.1-This code provides minimum requirements for The American Concrete Institute"Building Code require design and construction of structural concrete ele- I ments for Structural Concrete(ACI 318M-05), referred ments of any structure erected under requirements of to as the code, provides minimum requirements for struc the legally adopted general building code of which this tural concrete design or construction code forms a part. In areas without a legally adopte building code, this code defines minimum acceptable The 2005 code revised the previous standard"Building standards of design and construction practice 318M-02). This standard includes in one document the For structural concrete, fc shall not be less than 17 MPa. rules for all concrete used for structural purposes including No maximum value of fc shall apply unless restricted both plain and reinforced concrete. The by a specific code provision concrete"is used to refer to all plain or reinforced concrete used for structural purposes. This covers the spectrum of structural applications of concrete from nonreinforced concrete to concrete containing nonprestressed reinforcement, prestressing steel, or composite steel shapes, pipe, or tubing. quirements for structural plain concrete are in Ch Prestressed concrete is included under the definition of rein- forced concrete. Provisions of the code apply to prestressed concrete except for those that are stated to apply specifically to nonprestressed cor Chapter 21 of the code contains special provisions for design and detailing of earthquake resistant structures. See 1.1.8 In the 1999 code and earlier editions, Appendix A contained provisions for an alternate method of design for nonpre stressed reinforced concrete members using service loads (without load factors)and permissible service load stresses The Alternate Design Method was intended to give results that were slightly more conservative than designs by the Strength Design Method of the code. The Alternate Design Method of the 1999 code may be used in place of applicable sections of this code Appendix A of the code contains provisions for the design of regions near geometrical discontinuities, or abrupt Appendix B of this code contains provisions for reinforce ment limits based on 0.75p, determination of the strength reduction factor and moment redistribution that have in the code for many years, including the 1999 code. provisions are applicable to reinforced and prestressed con crete members. Designs made using the provisions of Appendix B are equally acceptable as those based on the body of the code, provided the provisions of Appendix B are used in their entirety. Appendix C of the code allows the use of the factored load combinations given in Chapter 9 of the 1999 code licene with Acl oduction of networking permitted without loene from H ACI 318 Building Nor ot for Resale, 11/28/2005 18-2015vsral
CHAPTER 1 9 CODE COMMENTARY ACI 318 Building Code and Commentary 1.1 — Scope 1.1.1 — This code provides minimum requirements for design and construction of structural concrete elements of any structure erected under requirements of the legally adopted general building code of which this code forms a part. In areas without a legally adopted building code, this code defines minimum acceptable standards of design and construction practice. For structural concrete, fc ′ shall not be less than 17 MPa. No maximum value of fc′ shall apply unless restricted by a specific code provision. R1.1 — Scope The American Concrete Institute “Building Code Requirements for Structural Concrete (ACI 318M-05),” referred to as the code, provides minimum requirements for structural concrete design or construction. The 2005 code revised the previous standard “Building Code Requirements for Structural Concrete (ACI 318M-02).” This standard includes in one document the rules for all concrete used for structural purposes including both plain and reinforced concrete. The term “structural concrete” is used to refer to all plain or reinforced concrete used for structural purposes. This covers the spectrum of structural applications of concrete from nonreinforced concrete to concrete containing nonprestressed reinforcement, prestressing steel, or composite steel shapes, pipe, or tubing. Requirements for structural plain concrete are in Chapter 22. Prestressed concrete is included under the definition of reinforced concrete. Provisions of the code apply to prestressed concrete except for those that are stated to apply specifically to nonprestressed concrete. Chapter 21 of the code contains special provisions for design and detailing of earthquake resistant structures. See 1.1.8. In the 1999 code and earlier editions, Appendix A contained provisions for an alternate method of design for nonprestressed reinforced concrete members using service loads (without load factors) and permissible service load stresses. The Alternate Design Method was intended to give results that were slightly more conservative than designs by the Strength Design Method of the code. The Alternate Design Method of the 1999 code may be used in place of applicable sections of this code. Appendix A of the code contains provisions for the design of regions near geometrical discontinuities, or abrupt changes in loadings. Appendix B of this code contains provisions for reinforcement limits based on 0.75ρb, determination of the strength reduction factor φ, and moment redistribution that have been in the code for many years, including the 1999 code. The provisions are applicable to reinforced and prestressed concrete members. Designs made using the provisions of Appendix B are equally acceptable as those based on the body of the code, provided the provisions of Appendix B are used in their entirety. Appendix C of the code allows the use of the factored load combinations given in Chapter 9 of the 1999 code. CHAPTER 1 — GENERAL REQUIREMENTS 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 CODE COMMENTARY Appendix D contains provisions for anchoring to concrete 1.1.2- This code supplements the general building R1.1. 2- The American Concrete Institute recommends ode and shall govern in all matters pertaining to that the code be adopted in its entirety; however, it is recog- design and construction of structural concrete, except nized that when the code is made a part of a legally adopted wherever this code is in conflict with requirements in general building code, the general building code may mod- he legally adopted general building code y provisions of this code .1.- This code shall govern in all matters pertain ing to design, construction, and material properties wherever this code is in conflict with requirements con tained in other standards referenced in this code 1.1.- For special structures, such as arches, tanks, Rl. 1.4--Some special structures involve unique design and reservoirs, bins and silos, blast-resistant structures, construction problems that are not covered by the code. How- and chimneys, provisions of this code shall govern ever, many code provisions, such as the concrete quality and where applicable. See also 22.1.2 design principles, are applicable for these structures. Detailed recommendations for design and construction of some spe- cial structures are given in the following ACI publications ""Design and Construction of Reinforced Concrete Chimneys"reported by ACI Committee 307. 1.(Gives material, construction, and design requirements for circu- lar cast-in-place reinforced chimneys. It sets forth mini mum loadings for the design of reinforced concrete chimneys and contains methods for determining the stresses in the concrete and reinforcement required as a result of these loadings) " Standard Practice for Design and Construction of Con- crete Silos and Stacking Tubes for Storing Granular Materials"reported by ACI Committee 313. 1.2(Gives mate- rial, design, and construction requirements for reinforced concrete bins, silos, and bunkers and stave silos for storing granular materials. It includes recommended design and con- struction criteria based on experimental and analytical studies plus worldwide experience in silo design and construction. " Environmental Engineering Concrete Structures reported by ACI Committee 350. (Gives material, design and construction recommendations for concrete tanks, reser- voirs, and other structures commonly used in water and waste treatment works where dense, impermeable concrete with high resistance to chemical attack is required. Special empha- sis is placed on a structural design that minimizes the possibil- ity of cracking and accommodates vibrating equipment and other special loads. Proportioning of concrete, placement, curing and protection against chemicals are also described. "Code Requirements for Nuclear Safety Related Con- crete Structures"reported by ACI Committee 349. +(Pro- concrete structures that form part of a nuclear power plant and have nuclear safety related functions. The code does not cover concrete reactor vessels and concrete containment structures which are covered by ACI 359.) licene with Acl oduction of networking permitted without loene from H ACI 318 Building Co Not fos gesaer 12e2oo5 1820415 st
10 CHAPTER 1 CODE COMMENTARY ACI 318 Building Code and Commentary Appendix D contains provisions for anchoring to concrete. R1.1.2 — The American Concrete Institute recommends that the code be adopted in its entirety; however, it is recognized that when the code is made a part of a legally adopted general building code, the general building code may modify provisions of this code. 1.1.2 — This code supplements the general building code and shall govern in all matters pertaining to design and construction of structural concrete, except wherever this code is in conflict with requirements in the legally adopted general building code. 1.1.3 — This code shall govern in all matters pertaining to design, construction, and material properties wherever this code is in conflict with requirements contained in other standards referenced in this code. 1.1.4 — For special structures, such as arches, tanks, reservoirs, bins and silos, blast-resistant structures, and chimneys, provisions of this code shall govern where applicable. See also 22.1.2. R1.1.4 — Some special structures involve unique design and construction problems that are not covered by the code. However, many code provisions, such as the concrete quality and design principles, are applicable for these structures. Detailed recommendations for design and construction of some special structures are given in the following ACI publications: “Design and Construction of Reinforced Concrete Chimneys” reported by ACI Committee 307.1.1 (Gives material, construction, and design requirements for circular cast-in-place reinforced chimneys. It sets forth minimum loadings for the design of reinforced concrete chimneys and contains methods for determining the stresses in the concrete and reinforcement required as a result of these loadings.) “Standard Practice for Design and Construction of Concrete Silos and Stacking Tubes for Storing Granular Materials” reported by ACI Committee 313.1.2 (Gives material, design, and construction requirements for reinforced concrete bins, silos, and bunkers and stave silos for storing granular materials. It includes recommended design and construction criteria based on experimental and analytical studies plus worldwide experience in silo design and construction.) “Environmental Engineering Concrete Structures” reported by ACI Committee 350.1.3 (Gives material, design and construction recommendations for concrete tanks, reservoirs, and other structures commonly used in water and waste treatment works where dense, impermeable concrete with high resistance to chemical attack is required. Special emphasis is placed on a structural design that minimizes the possibility of cracking and accommodates vibrating equipment and other special loads. Proportioning of concrete, placement, curing and protection against chemicals are also described. Design and spacing of joints receive special attention.) “Code Requirements for Nuclear Safety Related Concrete Structures” reported by ACI Committee 349.1.4 (Provides minimum requirements for design and construction of concrete structures that form part of a nuclear power plant and have nuclear safety related functions. The code does not cover concrete reactor vessels and concrete containment structures which are covered by ACI 359.) 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 1 CODE COMMENTARY "Code for Concrete Reactor Vessels and Containments" reported by ACI-ASME Committee 359.(Provides requirements for the design, construction, and use of con- crete reactor vessels and concrete containment structures for nuclear power plants. 1.1.5- This code does not govern design and instal- R1.1.5- The design and installation of piling fully embed lation of portions of concrete piles, drilled piers, and cais- ded in the ground is regulated by the general building code sons embedded in ground except for structures in For portions of piling in air or water, or in soil not capable regions of high seismic risk or assigned to high seis- of providing adequate lateral restraint throughout the piling nic performance or design categories. See 21.10. 4 length to prevent buckling, the design provisions of this for requirements for concrete piles, drilled piers, and code govern where applicable caissons in structures in regions of high seismic risk or assigned to high seismic performance or design Recommendations for concrete piles are given in detail in categories "Recommendations for Design, Manufacture, and Instal- ition of Concrete Piles"reported by ACI Committee 543.(Provides recommendations for the design and use of most types of concrete piles for many kinds of construction. Recommendations for drilled piers are given in detail in ""Design and Construction of Drilled Piers"reported by ACI Committee 336.1.7(Provides recommendations for design and construction of foundation piers 0. 75 m in diameter or larger made by excavating a hole in the soil and then filling it with concrete.) Detailed recommendations for precast prestressed concrete piles are given in"Recommended Practice for Design, Manufac- ture, and Installation of Prestressed Concrete Piling pre pared by the PCI Committee on Prestressed Concrete Pilin 1.1.6- This code does not govern design ar portions RI. 1.6- Detailed recommendations for design and con- struction of soil-supported slabs, unless the slab struction of soil-supported slabs and floors that do not trans- mits vertical loads or lateral forces from other mit vertical loads or lateral forces from other portions of the of the structure to the soil structure to the soil, and residential post-tensioned slabs-on- ground, are given in the following publications: grade, primarily industrial floors and the slabs adjacent to them. The report addresses the planning, design, and detailing of the slabs. Background information on the design theories is followed by discussion of the soil support system, loadings, and types of slabs. Design methods are given for plain concrete, reinforced concrete, shrinkage compensating concrete, and post-tensioned concrete slabs.) Design of Post-Tensioned Slabs-on-Ground, "PTI.10(Pro- vides recommendations for post-tensioned slab-on-ground foundations. Presents guidelines for soil investigation, and design and construction of post-tensioned residential and light commercial slabs on expansive or compressible soils. 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 1 11 CODE COMMENTARY ACI 318 Building Code and Commentary 1.1.5 — This code does not govern design and installation of portions of concrete piles, drilled piers, and caissons embedded in ground except for structures in regions of high seismic risk or assigned to high seismic performance or design categories. See 21.10.4 for requirements for concrete piles, drilled piers, and caissons in structures in regions of high seismic risk or assigned to high seismic performance or design categories. 1.1.6 — This code does not govern design and construction of soil-supported slabs, unless the slab transmits vertical loads or lateral forces from other portions of the structure to the soil. “Code for Concrete Reactor Vessels and Containments” reported by ACI-ASME Committee 359. 1.5 (Provides requirements for the design, construction, and use of concrete reactor vessels and concrete containment structures for nuclear power plants.) R1.1.5 — The design and installation of piling fully embedded in the ground is regulated by the general building code. For portions of piling in air or water, or in soil not capable of providing adequate lateral restraint throughout the piling length to prevent buckling, the design provisions of this code govern where applicable. Recommendations for concrete piles are given in detail in “Recommendations for Design, Manufacture, and Installation of Concrete Piles” reported by ACI Committee 543.1.6 (Provides recommendations for the design and use of most types of concrete piles for many kinds of construction.) Recommendations for drilled piers are given in detail in “Design and Construction of Drilled Piers” reported by ACI Committee 336.1.7 (Provides recommendations for design and construction of foundation piers 0.75 m in diameter or larger made by excavating a hole in the soil and then filling it with concrete.) Detailed recommendations for precast prestressed concrete piles are given in “Recommended Practice for Design, Manufacture, and Installation of Prestressed Concrete Piling” prepared by the PCI Committee on Prestressed Concrete Piling.1.8 R1.1.6 — Detailed recommendations for design and construction of soil-supported slabs and floors that do not transmit vertical loads or lateral forces from other portions of the structure to the soil, and residential post-tensioned slabs-onground, are given in the following publications: “Design of Slabs on Grade” reported by ACI Committee 360.1.9 (Presents information on the design of slabs on grade, primarily industrial floors and the slabs adjacent to them. The report addresses the planning, design, and detailing of the slabs. Background information on the design theories is followed by discussion of the soil support system, loadings, and types of slabs. Design methods are given for plain concrete, reinforced concrete, shrinkagecompensating concrete, and post-tensioned concrete slabs.) “Design of Post-Tensioned Slabs-on-Ground,” PTI1.10 (Provides recommendations for post-tensioned slab-on-ground foundations. Presents guidelines for soil investigation, and design and construction of post-tensioned residential and light commercial slabs on expansive or compressible soils.) 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 CODE COMMENTARY 1.1.7-Concrete on steel form deck RI.1.7-Concrete on steel form deck In steel framed structures, it is common practice to cast con- crete floor slabs on stay-in-place steel form deck. In all cases, the deck serves as the form and may, in some cases, serve an additional structural function 1.1.7.1- Design and construction of structural RI.1.7.1-In its most basic application, the steel form concrete slabs cast on stay-in-place, noncomposite deck serves as a form, and the concrete serves a structural steel form deck are governed by this code function and, therefore, are to be designed to carry all super imposed load 1.1.7.2- This code does not govern the design of RI.1.7. 2- Another type of steel form deck commonly structural concrete slabs cast on stay-in-place, com- used develops composite action between the concrete an posite steel form deck. Concrete used in the construc- steel deck. In this type of construction, the steel deck serves tion of such slabs shall be governed by Chapters 1 as the positive moment reinforcement. The design of com- through 7 of this code, where applicable posite slabs on steel deck is regulated by"Standard for the Structural Design of Composite Slabs"(ANSI/ASCE 3). However, ANSI/ASCE 3 references the appropriate portions of ACI 318 for the design and construction of the concrete portion of the composite assembly. Guidelines for the construction of composite steel deck slabs are given in Standard Practice for the Construction and Inspectio of Composite Slabs"(ANSI/ASCE 9). 1. 1.1.8- Special provisions for earthquake resistance R1 1.8- Special provisions for earthquake resistance Special provisions for seismic design were first introduced in Appendix A of the 1971 code and were continued with- out revision in the 1977 code. These provisions were origi nally intended to apply only to reinforced concrete structures located in regions of highest seismicity special provisions were extensively revised in the 1983 code to include new requirements for certain earthquake-resist- ing systems located in regions of moderate seismicity. In the 1989 code, the special provisions were moved to Chapter 21 1.1. 8. -In regions of low seismic risk, or for struc RI 1.8.1- For structures located in regions of low seis- tures assigned to low seismic performance or desig mic risk, or for structures assigned to low seismic perfor- categories, provisions of Chapter 21 shall not apply. mance or design categories, no special design or detailing is required; the general requirements of the main body of the code apply for proportioning and detailing of reinforced concrete structures. It is the intent of Committee 31 8 that concrete structures proportioned by the main body of the code will provide a level of toughness adequate for low 1.1.8.- In regions of moderate or high seismic R1.1.8.2--For structures in regions of moderate seismic risk, or for structures assigned to intermediate or high risk, or for structures assigned to intermediate seismic per seismic performance or design categories, provisions formance or design categories, reinforced concrete moment of Chapter 21 shall be satisfied. See 21.2.1 frames proportioned to resist seismic effects require special reinforcement details, as specified in 21.12. The special details apply only to beams, columns, and slabs to which the earthquake-induced forces have been assigned in design The special reinforcement details will serve to provide a suitable level of inelastic behavior if the frame is subjected to an earthquake of such intensity as to require it to perform elastically. There are no Chapter 21 requirements for cast- licene with Acl oduction of networking permitted without loene from H ACI 318 Building Co No ns esae 1i 2e2to5 1820415Ms
12 CHAPTER 1 CODE COMMENTARY ACI 318 Building Code and Commentary 1.1.8 — Special provisions for earthquake resistance 1.1.8.1 — In regions of low seismic risk, or for structures assigned to low seismic performance or design categories, provisions of Chapter 21 shall not apply. R1.1.7 — Concrete on steel form deck In steel framed structures, it is common practice to cast concrete floor slabs on stay-in-place steel form deck. In all cases, 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 form deck serves as a form, and the concrete serves a structural function and, therefore, are to be designed to carry all superimposed loads. R1.1.7.2 — Another type of steel form deck commonly used develops composite action between the concrete and steel deck. In this type of construction, the steel deck serves as the positive moment reinforcement. The design of composite slabs on steel deck is regulated by “Standard for the Structural Design of Composite Slabs” (ANSI/ASCE 3). 1.11 However, ANSI/ASCE 3 references the appropriate portions of ACI 318 for the design and construction of the concrete portion of the composite assembly. Guidelines for the construction of composite steel deck slabs are given in “Standard Practice for the Construction and Inspection of Composite Slabs” (ANSI/ASCE 9). 1.12 R1.1.8 — Special provisions for earthquake resistance Special provisions for seismic design were first introduced in Appendix A of the 1971 code and were continued without revision in the 1977 code. These provisions were originally intended to apply only to reinforced concrete structures located in regions of highest seismicity. The special provisions were extensively revised in the 1983 code to include new requirements for certain earthquake-resisting systems located in regions of moderate seismicity. In the 1989 code, the special provisions were moved to Chapter 21. R1.1.8.1 — For structures located in regions of low seismic risk, or for structures assigned to low seismic performance or design categories, no special design or detailing is required; the general requirements of the main body of the code apply for proportioning and detailing of reinforced concrete structures. It is the intent of Committee 318 that concrete structures proportioned by the main body of the code will provide a level of toughness adequate for low earthquake intensity. R1.1.8.2 — For structures in regions of moderate seismic risk, or for structures assigned to intermediate seismic performance or design categories, reinforced concrete moment frames proportioned to resist seismic effects require special reinforcement details, as specified in 21.12. The special details apply only to beams, columns, and slabs to which the earthquake-induced forces have been assigned in design. The special reinforcement details will serve to provide a suitable level of inelastic behavior if the frame is subjected to an earthquake of such intensity as to require it to perform inelastically. There are no Chapter 21 requirements for cast- 1.1.7.2 — This code does not govern the design of structural concrete slabs cast on stay-in-place, composite steel form deck. Concrete used in the construction of such slabs shall be governed by Chapters 1 through 7 of this code, where applicable. 1.1.7 — Concrete on steel form deck 1.1.7.1 — Design and construction of structural concrete slabs cast on stay-in-place, noncomposite steel form deck are governed by this code. 1.1.8.2 — In regions of moderate or high seismic risk, or for structures assigned to intermediate or high seismic performance or design categories, provisions of Chapter 21 shall be satisfied. See 21.2.1. 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 1 CODE COMMENTARY in-place structural walls provided to resist seismic effects, or for other structural components that are not part of the lateral-force-resisting system of structures in regions of moderate seismic risk, or assigned to intermediate seismic performance or design categories. For precast wall panels designed to resist forces induced by earthquake mo special requirements are specified in 21 13 for connections between panels or between panels and the foundation. Cast in-place structural walls proportioned to meet provisions of Chapters I through 18 and Chapter 22 are considered to have sufficient toughness at anticipated drift levels for these For structures located in regions of high seismic risk, or for structures assigned to high seismic performance or lesign categories, all building components that are part of the lateral-force-resisting system, including foundations (except plain concrete foundations as allowed by 22. 10.1), should satisfy requirements of 21.2 through 21.10. In addi- tion, frame members that are not assumed in the design to be part of the lateral-force-resisting system should comply with 21.11. The special proportioning and detailing require- ments of Chapter 21 are intended to provide a monolithic reinforced concrete or precast concrete structure with ade quate" toughness"to respond inelastically under severe earthquake motions. See also R21.2.1 1.1.8.3-The seismic risk level of a region or seismic R1 1.8.3- Seismic risk levels(Seismic Zone Maps)and performance or design category of a structure, shall seismic performance or design categories are under the be regulated by the legally adopted general building jurisdiction of a general building code rather than ACI 318 code of which this code forms a part, or determined by Changes in terminology were made to the 1999 edition of ocal authority the code to make it compatible with the latest editions of model building codes in use in the United States For exam ple, the phrase"seismic performance or design categories was introduced. Over the past decade, the manner in which seismic risk levels have been expressed in United States building codes has changed. Previously they have been rep- resented in terms of seismic zones Recent editions of the “ BOCA National building code”(NBC)13and“ " Standard Building Code"(SBC), 1. 14 which are based on the 1991 NEHRP, have expressed risk not only as a function of expected intensity of ground shaking on solid rock, but also These two items are considered in assigning the structure to a Seismic Performance Category(SPC), which in turn is used to trigger different levels of detailing requirements for the structure. The 2000 and 2003 editions of the ""Interna- tional Building Code"(IBC).16, 1. 17 and the 2003 NFPA 5000"Building Construction and Safety Code".also con- sider the effects of soil amplification on the ground motion when assigning seismic risk. Under the IBC and NFPA codes, each structure is assigned a Seismic Design Category (SDC). Amor SDC levels of detailing requirements. Table RI 1.8.3 correlates 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 1 13 CODE COMMENTARY ACI 318 Building Code and Commentary in-place structural walls provided to resist seismic effects, or for other structural components that are not part of the lateral-force-resisting system of structures in regions of moderate seismic risk, or assigned to intermediate seismic performance or design categories. For precast wall panels designed to resist forces induced by earthquake motions, special requirements are specified in 21.13 for connections between panels or between panels and the foundation. Castin-place structural walls proportioned to meet provisions of Chapters 1 through 18 and Chapter 22 are considered to have sufficient toughness at anticipated drift levels for these structures. For structures located in regions of high seismic risk, or for structures assigned to high seismic performance or design categories, all building components that are part of the lateral-force-resisting system, including foundations (except plain concrete foundations as allowed by 22.10.1), should satisfy requirements of 21.2 through 21.10. In addition, frame members that are not assumed in the design to be part of the lateral-force-resisting system should comply with 21.11. The special proportioning and detailing requirements of Chapter 21 are intended to provide a monolithic reinforced concrete or precast concrete structure with adequate “toughness” to respond inelastically under severe earthquake motions. See also R21.2.1. R1.1.8.3 — Seismic risk levels (Seismic Zone Maps) and seismic performance or design categories are under the jurisdiction of a general building code rather than ACI 318. Changes in terminology were made to the 1999 edition of the code to make it compatible with the latest editions of model building codes in use in the United States. For example, the phrase “seismic performance or design categories” was introduced. Over the past decade, the manner in which seismic risk levels have been expressed in United States building codes has changed. Previously they have been represented in terms of seismic zones. Recent editions of the “BOCA National Building Code” (NBC)1.13 and “Standard Building Code” (SBC), 1.14 which are based on the 1991 NEHRP, 1.15 have expressed risk not only as a function of expected intensity of ground shaking on solid rock, but also on the nature of the occupancy and use of the structure. These two items are considered in assigning the structure to a Seismic Performance Category (SPC), which in turn is used to trigger different levels of detailing requirements for the structure. The 2000 and 2003 editions of the “International Building Code” (IBC) 1.16, 1.17 and the 2003 NFPA 5000 “Building Construction and Safety Code”1.18 also consider the effects of soil amplification on the ground motion when assigning seismic risk. Under the IBC and NFPA codes, each structure is assigned a Seismic Design Category (SDC). Among its several uses, the SDC triggers different levels of detailing requirements. Table R1.1.8.3 correlates 1.1.8.3 — The seismic risk level of a region, or seismic performance or design category of a structure, shall be regulated by the legally adopted general building code of which this code forms a part, or determined by local authority. 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 --`,,`,````````,,`,,`,,``,`,,,`-`-`,,`,,`,`,,`---