PROPOSED CHANGES TO ACI 318-08 OPEN FOR PUBLIC DISCUSSION

ACI Committee 318, Structural Concrete Building Code, has almost completed its work on the latest edition of

the Code, “Building Code Requirements for Structural Concrete and Commentary (ACI 318-11).” As part of its

activities at the ACI Fall Convention in Pittsburgh, PA, Committee 318 provided responses to comments from

the ACI Technical Activities Committee (TAC) on the ACI 318-11 draft. TAC has since approved the responses,

and in accordance with ACI’s standardization procedures, the draft is now available for public review for a 45-day

period. The draft can be downloaded at www.concrete.org/PUBS/STANDACTION.ASP. Interested parties are

invited to read and provide comments using the posted comments form no later than January 17, 2011. Where

renumbering of sections, tables, or equations is the only change to ACI 318-08 text, it is not listed below

Some of the changes include:

Design requirements for adhesive anchors are now included. Failure modes and corresponding nominal

strengths are defined, as are requirements for testing and evaluation of adhesive anchors for use in

cracked concrete or subject to sustained loads. The new provisions also include criteria for overhead

adhesive anchors; seismic requirements for anchoring to concrete; installation and inspection of

adhesive anchors; and certification of adhesive anchor installers. (A related draft standard, “Acceptance

Criteria for Qualification of Post-Installed Adhesive Anchors in Concrete and Commentary [ACI 355.Y],”

is a prerequisite for the design of adhesive anchors in concrete and is currently open for public

discussion until December 17, 2010.);

Reinforcement detailing requirements for seismic applications have been enhanced. These

enhancements include rules for identifying and detailing distinct segments of a special structural wall,

detailing of horizontal bars at special boundary elements, and confinement of beam flexural hinge

regions;

New test methods for sulfate resistance are included. ASTM D516 and D4130 are identified tests for

sulfate ions in water, brackish water, or seawater, and ASTM C1580 is identified as a test for water-

soluble sulfate in soil;

New deformed bars are included. Grade 80 deformed bars per ASTM A615 and A706 are allowed for

nonseismic applications. Zinc and epoxy dual-coated reinforcing bars per ASTM A1055 are also now

allowed;

Test records for determining standard deviation for mixture design may now be up to 24 months old.

Also, testing agencies performing acceptance testing concrete are now required to comply with

ASTM C1077;

New requirements for detailing of circular column ties, design and detailing of temperature and

shrinkage reinforcement for post-tensioned slabs, and minimum reinforcement for deep beams have

been added. Also, development length for headed bars has been revised; and

Factored load combinations have been revised to conform with ASCE 7-10.

318‐11 Public Discussion

Draft

BUILDING CODE REQUIREMENTS FOR STRUCTURAL 1

CONCRETE (ACI 318-08) AND COMMENTARY 2 3

REPORTED BY ACI COMMITTEE 318 4 5

ACI Committee 318 6 Structural Building Code 7

8

Voting Main Committee Members 9

Randall W. Poston Basile G. Rabbat 10 Chair Secretary 11

Sergio M. Alcocer Neal S. Anderson Florian G. Barth Roger J. Becker Kenneth B. Bondy Dean A. Browning James R. Cagley Ned M. Cleland W. Gene Corley Charles W. Dolan Anthony E. Fiorato Catherine E. French Robert J. Frosch

Luis E. Garcia Satyendra Ghosh Harry A. Gleich David P. Gustafson James R. Harris Terence C. Holland Shyh-Jiann Hwang James O. Jirsa Dominic J. Kelly Gary J. Klein Ronald Klemencic Cary S. Kopczynski Colin L. Lobo Paul F. Mlakar

Jack P. Moehle Gustavo J. Parra-Montesinos Julio A. Ramirez David M. Rogowsky David H. Sanders Guillermo Santana Thomas C. Schaeffer Stephen J. Seguirant Andrew W. Taylor Eric M. Tolles James K. Wight Sharon L. Wood Loring A. Wyllie, Jr.

Voting Subcommittee Members

F. Michael Bartlett Raul D. Bertero Allan P. Bommer JoAnn P. Browning Nicholas J. Carino Ronald A. Cook David Darwin Lisa R. Feldman Kevin J. Folliard H.R. Trey Hamilton, III R. Doug Hooton Kenneth C. Hover Steven H. Kosmatka

Michael E. Kreger Jason J. Krohn Daniel A. Kuchma Andres Lepage Raymond Lui LeRoy A. Lutz Joseph Maffei Donald F. Meinheit Fred Meyer Denis Mitchell Theodore A. Mize Suzanne Dow Nakaki Theodore L. Neff

Lawrence C. Novak Viral B. Patel Conrad Paulson Jose A. Pincheira Mario E. Rodríguez Bruce W. Russell M. Saiid Saiidi Andrea J. Schokker John F. Stanton Roberto Stark John W. Wallace

3705

International Liaison Members

Mathias Brewer F. Michael Bartlett Yosef Farbiarz Luis B. Fargier-Gabaldon

Alberto Giovambattista Hector D. Hernandez Angel E. Herrera Hector Monzon-Despang Enrique Pasquel

Patricio A. Placencia Oscar M. Ramirez Mario E. Rodriguez Fernando Reboucas Stucchi Fernando Yanez

Consulting Members John E. Breen Neil M. Hawkins

H. S. Lew James G. MacGregor

Robert F. Mast Charles G. Salmon

_________________________________

3706

1

CHAPTER 1 — GENERAL REQUIREMENTS 2 3

CODE 4

1.2 — Drawings and specificationsContract documents[13] 5

1.2.1 — Copies of design drawings, typical details, and specifications the contract documents for all 6 structural concrete construction shall bear the seal of a licensed design professional. These drawings, 7 details, and specifications contract documents shall show: [13] 8

(a) Name and date of issue of code and supplement to which design conforms; 9

(b) Live load and other loads used in design; 10

(c) Specified compressive strength of concrete at stated ages or stages of construction for which each 11 part of structure is designed; 12

(d) Specified strength or grade of reinforcement; 13

(e) Size and location of all structural elements, and reinforcement, and anchors;[13] 14

(f) Type, size, and location of anchors; requirements for anchor installation; and qualifications for 15 post-installed anchor installers as required by D.9;[2] 16

Renumber remainder of list. 17

18

COMMENTARY 19

R1.1 — Scope 20

R1.1.8 — Concrete on steel deck 21

In steel framed structures, it is common practice to cast concrete floor slabs on stay-in-place steel deck. In all cases, 22 the deck serves as the form and may, in some cases, serve an additional structural function. 23

R1.1.8.1 — In its most basic application, the noncomposite steel deck serves as a form, and the concrete slab is 24 designed to carry all superimposed loads, while in other applications the concrete slab may be designed to carry only 25 the superimposed loads. The design of the steel deck for this application is described in “Standard for Non-26 Composite Steel Floor Deck” (ANSI/SDI NC1.0-2006).1.11 This Standard refers to ACI 318 for the design and 27 construction of the structural concrete slab. [3] 28

R1.1.8.2 — Another type of steel deck commonly used develops composite action between the concrete and steel 29 deck. In this type of construction, the steel deck serves as the positive moment reinforcement. The design and 30 construction of composite slabs on steel deck is described in “Standard for the Structural Design of Composite 31 Slabs” (ANSI/ASCE 3).1.11 “Standard for Composite Steel Floor Deck” (ANSI/SDI C1.0-2006)1.12. The standard 32 refers to the appropriate portions of ACI 318 for the design and construction of the concrete portion of the composite 33 assembly. Guidelines for the construction of composite steel deck slabs are given in “Standard Practice for the 34

3707

Construction and Inspection of Composite Slabs” (ANSI/ASCE 9).1.12 Reference 1.13 also provides guidance for 1 design of composite slabs on steel deck. The design of negative moment reinforcement to make a slabcreate 2 continuous continuity at supports is a common example where a portion of the slab is designed in conformance with 3 this Code. [3] 4

R1.1.9 — Provisions for earthquake resistance 5

R1.1.9.1 — Add following at end of R1.1.9.1: The model building codes also specify overstrength factors, Ωo, 6 that are related to the seismic-force-resisting system used for the structure and used for the design of certain 7 elements.[4] 8

R1.1.10 — Add following at end of R1.1.10: Guidance for the design and construction of cooling towers and 9 circular prestressed concrete tanks may be found in the reports of ACI Committees 334,1.22 372,1.23 and 3731.24.[5] 10

3708

CHAPTER 2 — NOTATION AND DEFINITIONS 1 2

2.1 — Code notation 3

NaA

= projected influence area of a single adhesive anchor or group of adhesive anchors, for 4

calculation of bond strength in tension, in.2, see D.5.5.1, Appendix D[2] 5

NaoA = projected influence area of a single adhesive anchor, for calculation of bond strength in tension if 6

not limited by edge distance or spacing, in.2, see D.5.5.1, Appendix D[2] 7 bw = web width, wall thickness, or diameter of circular section, in., Chapters 10-12, 21, 22, Appendix 8

B[4] 9 cac = critical edge distance required to develop the basic concrete breakout strength as controlled by 10

concrete breakout or bond of a post-installed anchor in tension in uncracked concrete without 11 supplementary reinforcement to control splitting, in., see D.8.6, Appendix D[2] 12

ca1 = distance from the center of an anchor shaft to the edge of concrete in one direction, in. If shear 13 is applied to anchor, ca1 is taken in the direction of the applied shear. If tension is applied to the 14 anchor, ca1 is the minimum edge distance, Appendix D. Where anchors subject to shear are 15 located in narrow sections of limited thickness, see D.6.2.4 [2] 16

cNa = projected distance from center of an anchor shaft on one side of the anchor required to develop 17 the full bond strength of a single adhesive anchor, in., see D.5.5.1, Appendix D [2] 18

hef = effective embedment depth of anchor, in., see D.1, D.8.5, Appendix D. Where anchors subject to 19 shear are located in narrow sections of limited thickness, see D.5.2.3[2] 20

hw = height of entire wall from base to top, or clear height of the wall segment of or wall pier 21 considered, in., Chapters 11, 21[4] 22

H = loads due to weight andlateral pressure of soil, water in soil, or other materials, or related 23 internal moments and forces, lb, Chapter 9, Appendix C[6] 24

lw = length of entire wall or length of wall segment of wall or wall pier considered in direction of shear 25 force, in., Chapters 11, 14, 21[4] 26

Na = nominal bond strength in tension of a single adhesive anchor, lb, see D.5.5.1, Appendix D[2] 27 Nag = nominal bond strength in tension of a group of adhesive anchors, lb, see D.5.5.1, Appendix D[2] 28 Nba = basic bond strength in tension of a single adhesive anchor, lb, see D.5.5.2, Appendix D[2] 29 Nc = the resultant tension tensile force acting on the portion of the in concrete cross section that is 30

subjected to tensile stresses due to the combined effects of unfactored service dead loads plus 31 live load, and effective prestress, lb, Chapter 18[8] 32

Nn,e = nominal strength in tension of a single anchor or the most highly stressed individual anchor in a 33 group of anchors subject to earthquake forces, lb, see D.3.3.4.3, Appendix D[9] 34

Nsa = nominal strength of a single anchor or individual anchor in a group of anchors in tension as 35 governed by the steel strength, lb, see D.5.1.1 and D.5.1.2, Appendix D[10] 36

Nua = factored tensile force applied to anchor or individual anchor in a group of anchors, lb, Appendix 37 D[10] 38

Nua,g = total factored tensile force applied to anchor group, lb, Appendix D[10] 39

Nua,i = factored tensile force applied to most highly stressed anchor in a group of anchors, lb, Appendix 40 D[10] 41

Nua,s = factored sustained tension load, lb, see D.3.5, Appendix D[2] 42 Vsa = nominal shear strength in shear of a single anchor or individual anchor in a group of anchors as 43

governed by the steel strength, lb, see D.6.1.1 and D.6.1.2, Appendix D[10] 44

3709

Vua,i = factored shear force applied to most highly stressed anchor in a group of anchors, lb, Appendix 1 D[10] 2

Vua,g = total factored shear force applied to anchor group, lb, Appendix D[10] 3 λa = modification factor reflecting the reduced mechanical properties of lightweight concrete in certain 4 concrete anchorage applications, see D.3.6, Appendix D[2] 5 τcr = characteristic bond stress of adhesive anchor in cracked concrete, psi, see D.5.5.2, Appendix 6

D[2] 7 τuncr = characteristic bond stress of adhesive anchor in uncracked concrete, psi, see D.5.5.2, Appendix 8 D[2] 9 ψcp,N = factor used to modify tensile strength of post-installed anchors intended for use in uncracked 10

concrete without supplementary reinforcement to account for the splitting tensile stresses due to 11 installation, see D.5.2.7, Appendix D[2] 12

ψcp,Na = factor used to modify tensile strength of adhesive anchors intended for use in uncracked 13 concrete without supplementary reinforcement to account for the splitting tensile stresses due to 14 installation, see D.5.5.5, Appendix D[2] 15

ψec,Na = factor used to modify tensile strength of adhesive anchors based on eccentricity of applied 16 loads, see D.5.5.3, Appendix D[2] 17

ψed,Na = factor used to modify tensile strength of adhesive anchors based on proximity to edges of 18 concrete member, see D.5.5.4, Appendix D[2] 19

Ωo = amplification factor to account for overstrength of the seismic-force-resisting system determined 20 in accordance with the legally adopted general building code, Chapter 21 [4,11] 21

22

2.2 — Definitions 23

Headed deformed bars — Deformed reinforcing bars with heads that satisfy 3.5.9 attached at one or 24 both ends. Heads are attached to the bar end by means such as welding or forging onto the bar, internal 25 threads on the head mating to threads on the bar end, or a separate threaded nut to secure the head of 26 the bar. The net bearing area of headed deformed bar equals the gross area of the head minus the larger 27 of the area of the bar and the area of any obstruction. [14] 28

Vertical wall segment — A segment of a structural wall, bounded horizontally by two openings or by an 29 opening and an edge. Wall piers are vertical wall segments. [4] 30

Wall pier — A vertical wall segment within a structural wall, bounded horizontally by two openings or by 31 an opening and an edge, with ratio of horizontal length to wall thickness (lw/bw) less than or equal to 6.0, 32 and ratio of clear height to horizontal length (hw/lw) greater than or equal to 2.0. [4] 33

Welded wire reinforcement — Reinforcing elements consisting of carbon-steel plain or deformed wires, 34 conforming to ASTM A82 or A496, respectively, fabricated into sheets or rolls in accordance with ASTM 35 A1064; A185 or A497, respectively; or reinforcing elements consisting of stainless-steel plain or deformed 36 wires fabricated into sheets or rolls conforming to ASTM A1022. [13] 37

COMMENTARY 38

R2.1 — Commentary notation 39

= applied shear parallel to the edge, lb, Appendix D[12] 40

⊥V = applied shear perpendicular to the edge, lb, Appendix D[12] 41

3710

Wa = service-level wind load, see R14.8.4 [6] 1

R2.2 — Definitions 2

Column — The term “compression member” is used in the Code to define any member in which the primary stress 3 is longitudinal compression. Such a member need not be vertical but may have any orientation in space. Bearing 4 walls, columns, and pedestals, and wall piers qualify as compression members under this definition. [4] 5

Wall — Openings in walls create vertical and horizontal wall segments. A horizontal wall segment is shown in Fig. 6 R21.9.4.5. [4] 7

Wall pier — Wall piers are vertical wall segments with dimensions and reinforcement intended to result in shear 8 demand being limited by flexural yielding of the vertical reinforcement in the pier. [4] 9

3711

CHAPTER 3 — MATERIALS 1

2

CODE 3

3.5 — Steel reinforcement 4

3.5.3 — Deformed reinforcement 5

3.5.3.2 — Deformed reinforcing bars shall conform to one of the ASTM specifications listed in 3.5.3.1, 6 except that for bars with fy less than 60,000 psi, the yield strength shall be taken as the stress corresponding 7 to a strain of 0.5 percent and for bars with fy exceeding at least 60,000 psi, the yield strength shall be taken 8 as the stress corresponding to a strain of 0.35 percent. See 9.4. [15] 9

3.5.3.5 — Deformed wire for concrete reinforcement shall conform to ASTM A1064A496, except that 10 wire shall not be smaller than size D-4 or larger than size D-31 unless as permitted in 3.5.3.7. For wire 11 with fy exceeding 60,000 psi, the yield strength shall be taken as the stress corresponding to a strain of 12 0.35 percent. [13] 13

3.5.3.6 — Welded plain wire reinforcement shall conform to ASTM A1064A185, except that for wire 14 with fy exceeding 60,000 psi, the yield strength shall be taken as the stress corresponding to a strain of 15 0.35 percent. Spacing of welded intersections shall not exceed 12 in. in direction of calculated stress, 16 except for welded wire reinforcement used as stirrups in accordance with 12.13.2. [13] 17

3.5.3.7 — Welded deformed wire reinforcement shall conform to ASTM A1064A497, except that for 18 wire with fy exceeding 60,000 psi, the yield strength shall be taken as the stress corresponding to a strain 19 of 0.35 percent. Spacing of welded intersections shall not exceed 16 in. in direction of calculated stress, 20 except for welded deformed wire reinforcement used as stirrups in accordance with 12.13.2. Deformed 21 wire larger than D-31 is permitted when used in welded wire reinforcement conforming to ASTM 22 A1064A497, but shall be treated as plain wire for development and splice design. [13] 23

3.5.3.8 — Zinc-coated (Ggalvanized) reinforcing bars shall conform to ASTM A767. Epoxy-coated 24 reinforcing bars shall conform tocomply with ASTM A775 or with to ASTM A934. Zinc and epoxy dual-25 coated reinforcing bars shall conform to ASTM A1055. Bars to be zinc-coated (galvanized), or epoxy-26 coated, or zinc and epoxy dual-coated shall conform to one of the specifications listed in 3.5.3.1. [16] 27

3.5.4 — Plain reinforcement 28

3.5.4.2 — Plain wire for spiral reinforcement shall conform to ASTM A1064A82, except that for wire with 29 fy exceeding 60,000 psi, the yield strength shall be taken as the stress corresponding to a strain of 0.35 30 percent. [13] 31

3.5.9 — Headed deformed bars shall conform to ASTM A970 including Annex A1 Requirements for Class 32 HA Head Dimensions. and obstructions or interruptions of the bar deformations, if any, shall not extend 33 more than 2db from the bearing face of the head. [14] 34

3.8 — Referenced standards 35

3.8.1 — Standards of ASTM International referred to in this Code are listed below with their serial 36 designations, including year of adoption or revision, and are declared to be part of this Code as if fully set 37

3712

A970/A970M-0609 Standard Specification for Headed Steel Bars for Concrete Reinforcement 1 including Annex A1 Requirements for Class HA Head Dimensions[1] 2

A1055/A1055M-08aε1 Standard Specification for Zinc and Epoxy Dual-Coated Steel Reinforcing Bars[13,16] 3

A1064/A1064M-09 Standard Specification for Steel Wire and Welded Wire Reinforcement, Plain and 4 Deformed, for Concrete[13] 5

C1077-10 Standard Practice for Laboratories Testing Concrete and Concrete Aggregates 6 for Use in Construction and Criteria for Laboratory Evaluation[17] 7

C1580-09 Standard Test Method for Water-Soluble Sulfate in Soil[18] 8

D516-07 Standard Test Method for Sulfate Ion in Water[18] 9

D4130-08 Standard Test Method for Sulfate Ion in Brackish Water, Seawater, and Brine [18] 10

3.8.7 — “Qualification of Post-Installed Adhesive Anchors in Concrete (ACI 355.X-YY)” is declared to be a 11 part of this code as if fully set forth herein, for the purposes cited in Appendix D. [2] 12

3.8.73.8.8 — “Structural Welding Code—Steel (AWS D1.1/D1.1M:2010) (AWS D1.1/D1.1M:2006)” of the 13 American Welding Society is declared to be part of this Code as if fully set forth herein. [19] 14

COMMENTARY 15

16 R3.5 — Steel reinforcement 17

R3.5.2 — Replace final sentence of last paragraph: These potential concerns are not an issue for machine and 18 resistance welding as used in the manufacture of welded plain and deformed wire reinforcement covered by ASTM 19 A1064. Machine and resistance welding as used in the manufacture of welded plain and deformed wire reinforcement 20 is covered by ASTM A185 and ASTM A497, respectively, and is not part of this concern.[13] 21

R3.5.3 — Deformed reinforcement 22

R3.5.3.1 — ASTM A615 covers deformed carbon-steel reinforcing bars that are currently the most widely used 23 type of steel bar in reinforced concrete construction in the United States. The specification requires that the bars be 24 marked with the letter S for type of steel. [15] 25

ASTM A706 covers lowLow-alloy steel deformed bars conforming to ASTM A706 are intended for applications 26 where controlled tensile properties, restrictions on chemical composition to enhance weldability, or both, are required. 27 The specification requires that the bars be marked with the letter W for type of steel. [15] 28

Deformed bars produced to meet both ASTM A615 and A706 are required to be marked with the letters S and W for 29 type of steel. [15] 30

Stainless steel deformed bars are used in applications where high corrosion resistance or controlled magnetic 31 permeability are required. The physical and mechanical property requirements for stainless steel bars under ASTM 32 A955 are the same as those for carbon-steel bars under ASTM A615. [15] 33

Rail-steel deformed reinforcing bars used with this Code are required to conform to ASTM A996 including the 34 provisions for Type R bars, and marked with the letter R for type of steel. Type R bars are required to meet more 35 restrictive provisions for bend tests. [15] 36

3713

R3.5.3.2 — ASTM A615 includes provisions for Grade 75 bars in sizes No. 6 through 18.The ASTM 1 specifications require that yield strength be determined by the offset method (0.2% offset) and also include, for bars 2 with fy at least 60,000 psi, the additional requirement that the stress corresponding to a tensile strain of 0.35 percent 3 be at least fy. The 0.35 percent strain limit is necessary to ensure that the assumption of an elasto-plastic stress-strain 4 curve in 10.2.4 will not lead to unconservative values of the member strength. Therefore, the Code defines yield 5 strength in terms of the stress corresponding to a strain of 0.5 percent for fy less than 60,000 psi and the stress 6 corresponding to a strain of 0.35 percent for fy at least 60,000 psi. [15] 7

The 0.35 percent strain limit is necessary to ensure that the assumption of an elasto-plastic stress-strain curve in 8 10.2.4 will not lead to unconservative values of the member strength. [15] 9

The 0.35 strain requirement is not applied to reinforcing bars having specified yield strengths of 60,000 psi or less. 10 For steels having specified yield strengths of 40,000 psi, as were once used extensively, the assumption of an elasto-11 plastic stress-strain curve is well justified by extensive test data. For steels with specified yield strengths, up to 60,000 12 psi, the stress-strain curve may or may not be elasto-plastic as assumed in 10.2.4, depending on the properties of the 13 steel and the manufacturing process. However, when the stress-strain curve is not elasto-plastic, there is limited 14 experimental evidence to suggest that the actual steel stress at ultimate strength may not be enough less than the 15 specified yield strength to warrant the additional effort of testing to the more restrictive criterion applicable to steels 16 having specified yield strengths greater than 60,000 psi. In such cases, the φ-factor can be expected to account for 17 the strength deficiency. [15] 18

R3.5.3.6 — Welded plain wire reinforcement is made of wire conforming to ASTM A1064A82, which specifies a 19 minimum yield strength of 70,000 psi. The Code has assigned a yield strength value of 60,000 psi, but makes 20 provision for the use of higher yield strengths provided the stress corresponds to a strain of 0.35 percent. [1] 21

R3.5.3.7 — Welded deformed wire reinforcement should be made of wire conforming to ASTM A1064A497, which 22 specifies a minimum yield strength of 70,000 psi. The Code has assigned a yield strength value of 60,000 psi, but 23 makes provision for the use of higher yield strengths provided the stress corresponds to a strain of 0.35 percent. [1] 24

R3.5.3.8 — Zinc-coated (Ggalvanized) reinforcing bars (ASTM A767), and epoxy-coated reinforcing bars 25 (ASTM A775 and A934), and zinc and epoxy dual-coated reinforcing bars (ASTM A1055) are used in applications 26 were added to the 1983 Code, and epoxy-coated prefabricated reinforcing bars (ASTM A934) were added to the 27 1995 Code recognizing their usage, especially for conditions where corrosion resistance of reinforcement is of 28 particular concern. They have typically been used in parking structuresdecks, bridge structures, and other highly 29 corrosive environments. Zinc-coated (galvanized) reinforcing bars conforming to ASTM A767 are coated per the 30 hot-dipped process. [13,16] 31

R3.5.3.10 — Stainless steel wire and welded wire are used in applications where high corrosion resistance or 32 controlled magnetic permeability are required. The physical and mechanical property requirements for deformed 33 stainless steel wire and deformed and plain welded wire under ASTM A1022 are the same as those for deformed 34 wire, deformed welded wire, and plain welded wire under ASTM A1064A496, A497, and A185, respectively. [1] 35

R3.5.9 — The 2db limitation is limitation to Class HA head dimensions from Annex A1 of ASTM A970 is due to a 36 lack of test data for headed deformed bars that do not meet this requirement Class HA dimensional requirements. 37 Heads not conforming to Class HA limits on bar deformation obstructions and bearing face features could cause 38 unintended splitting forces in the concrete that may not be characteristic of the heads used in the tests that were the 39 basis for 12.6.1 and 12.6.2. Figure R3.5.9 shows a headed bar that has an obstruction of the deformations that 40 extends less than a distance 2db from the bearing face of the head and, thus, meets the limitation expressed in 3.5.9. 41 The figure also illustrates that, because the diameter of the obstruction is larger than the diameter of the bar, For 42 heads conforming to Class HA dimensional requirements, the net bearing area of the head may be less than can be 43 assumed to be equal to the gross area of the head minus the area of the bar. This assumption may not be valid for 44 heads not conforming to Class HA dimensional requirements. [14] 45

R3.8 — Referenced standards 46

3714

R3.8 — Referenced standards 1

R3.8.6 — Parallel to development of the 2005 Code provisions for anchoring to concrete, ACI 355 developed a test 2 method to define the level of performance required for post-installed anchors. This test method, ACI 355.2 contains 3 requirements for the testing and evaluation of post-installed expansion and undercut anchors for use in both cracked 4 and uncracked concrete applications. [2] 5

R3.8.7 — ACI 355.Y contains requirements for the testing and evaluation of adhesive anchors for use in both 6 cracked and uncracked concrete. [2] 7

8

9

10

11

12

13

14

Fig. R3.5.9—Headed deformed reinforcing bar with an obstruction that extends less than 2db from the bearing face 15 of the head. [14] 16

17

3715

CHAPTER 4 — DURABILITY REQUIREMENTS 1

CODE 2 3

TABLE 4.2.1 — EXPOSURE CATEGORIES AND CLASSES 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

* Percent sulfate by mass in soil shall be determined by ASTM C1580. [18] 49 † Concentration of dissolved sulfates in water in ppm shall be determined by 50 ASTM D516 or ASTM D4130. [18] 51

52

Category Severity Class Condition

F Freezing and

thawing

Not applicable

F0 Concrete not exposed to freezing-and-thawing cycles

Moderate F1 Concrete exposed to freezing-and-thawing cycles and occasional exposure to moisture

Severe F2 Concrete exposed to freezing-and-thawing cycles and in continuous contact with moisture

Very severe

F3

Concrete exposed to freezing-and-thawing and in continuous contact with moisture and exposed to deicing chemicals

S Sulfate

Water-soluble sulfate (SO4) in soil, percent by weightmass*[18]

Dissolved sulfate (SO4) in water,

ppm†

Not applicable

S0 SO4 < 0.10 SO4 < 150

Moderate S1 0.10 ≤ SO4 < 0.20150 ≤ SO4 <1500

Seawater

Severe S2 0.20 ≤ SO4 ≤ 2.001500 ≤ SO4 ≤

10,000

Very severe

S3 SO4 > 2.00 SO4 > 10,000

P Requiring low permeability

Not applicable

P0 In contact with water where low permeability is not required

Required P1 In contact with water where low permeability is required.

C Corrosion

protection of reinforcement

Not applicable

C0 Concrete dry or protected from moisture

Moderate C1 Concrete exposed to moisture but not to external sources of chlorides

Severe C2

Concrete exposed to moisture and an external source of chlorides from deicing chemicals, salt, brackish water, seawater, or spray from these sources

3716

COMMENTARY 1

R4.5 — Alternative cementitious materials for sulfate exposure 2

R4.5.1 — Moved from R4.3 to end of paragraph: ACI 222R4.7 has adopted slightly different categories and chloride 3 limits, test methods, and construction types and conditions that are slightly different from those in ACI 318, as 4 shown in Table R4.3.1. ACI 201.2R4.6 has adopted these same limits by referring to ACI 222R.13 5

3717

CHAPTER 5 — CONCRETE QUALITY, MIXING, AND PLACING 1

2

CODE 3

5.3 — Proportioning on the basis of field experience or trial mixtures, or both 4

5.3.1 — Sample standard deviation 5

5.3.1.1 — Where a concrete production facility has strength test records not more than 12 24 months 6 old, a sample standard deviation, ss, shall be established. [20] 7

5.3.1.2 — Where a concrete production facility does not have strength test records meeting 8 requirements of 5.3.1.1(c), but does have test records not more than 12 24 months old based on 15 to 29 9 consecutive tests, a sample standard deviation ss shall be established as the product of the calculated 10 sample standard deviation and modification factor of Table 5.3.1.2. To be acceptable, test records shall 11 meet requirements (a) and (b) of 5.3.1.1, and represent only a single record of consecutive tests that 12 span a period of not less than 45 calendar days. [20] 13

5.3.3 — Documentation of average compressive strength 14

Documentation that proposed concrete proportions will produce an average compressive strength equal 15 to or greater than required average compressive strength fcr′ (see 5.3.2) shall consist of a field strength 16 test record, several strength test records, one or more field strength test record(s) or trial mixtures. The 17 field strength test records or trial mixtures shall not be more than 24 months old and shall conform to 18 5.3.3.1 and 5.3.3.2, respectively. [20] 19

5.3.3.2 — When an acceptable record of field test results to document the required average strength is 20 not available, concrete proportions established from trial mixtures meeting the following requirements shall 21 be permitted: [20] 22

5.6 — Evaluation and acceptance of concrete 23

5.6.1 — Concrete shall be tested in accordance with the requirements of 5.6.2 through 5.6.5. The testing 24 agency performing acceptance testing shall comply with ASTM C1077. Qualified field testing technicians 25 shall perform tests on fresh concrete at the job site, prepare specimens required for curing under field 26 conditions, prepare specimens required for testing in the laboratory, and record the temperature of the 27 fresh concrete when preparing specimens for strength tests. Qualified laboratory technicians shall 28 perform all required laboratory tests. All reports of acceptance tests shall be provided to the licensed 29 design professional, contractor, concrete producer, and, when requested, to the owner and the building 30 official. [17] 31

32

COMMENTARY 33 34

R5.3 — Proportioning on the basis of field experience or trial mixtures, or both 35

R5.3.1 — Sample standard deviation 36

The standard deviation established from test records is a measure of the concrete supplier’s ability to manage 37 variability of materials, production, and testing of concrete. A test record obtained less than 24 months before a 38

3718

submittal is acceptable. [20] 1

R5.3.3 — Documentation of average compressive strength 2

Once the required average compressive strength fcr′ is known, the next step is to select mixture proportions that will 3 produce an average strength at least as great as the required average strength, and also meet requirements for 4 applicable exposure categories of Chapter 4. The documentation may consist of a strength test record, several 5 strength test records, one or more field strength test record(s) in accordance with 5.3.3.1, or suitable laboratory or 6 field trial mixtures in accordance with 5.3.3.2. Generally, if a test record is used, it will be the same one that was 7 used for computation of the standard deviation. However, if this test record shows either lower or higher average 8 compressive strength than the required average compressive strength, different proportions may be necessary or 9 desirable. In such instances, the average from a record of as few as 10 tests may be used, or the proportions may be 10 established by interpolation between the strengths and proportions of two such records of consecutive tests. All field 11 test records for establishing proportions necessary to produce the average compressive strength are to meet the 12 requirements of 5.3.3.1 for “similar materials and conditions.” [20] 13

R5.6 — Evaluation and acceptance of concrete 14

R5.6.1 — ASTM C1077 identifies and defines the duties and minimum technical requirements and qualifications of 15 testing laboratory personnel and requirements for testing concrete and concrete aggregates used in construction. 16 Inspection and accreditation of testing laboratories is a process that ensures that they conform to ASTM C1077. 17 Laboratory and field technicians can establish qualifications by becoming certified through certification programs. 18 Field technicians in charge of sampling concrete; testing for slump, unit weight, yield, air content, and temperature; 19 and making and curing test specimens should be certified in accordance with the requirements of ACI Concrete 20 Field Testing Technician—Grade 1 Certification Program, or the requirements of ASTM C1077,5.3 or an equivalent 21 program. Concrete testing laboratory personnel should be certified in accordance with the requirements of ACI Concrete 22 Laboratory Testing Technician, or Concrete Strength Testing Technician, or the requirements of ASTM C1077. [17] 23

Testing reports should be promptly distributed to the owner, licensed design professional responsible for the design, 24 contractor, appropriate subcontractors, appropriate suppliers, and building official The Code requires testing reports to 25 be distributed to the parties responsible for the design, construction and approval of the work. Such distribution of 26 test reports should be indicated in contracts for inspection and testing services. Prompt distribution of testing reports 27 to allows for timely identification of either compliance or the need for corrective action. A complete record of 28 testing allows the concrete producer to reliably establish the required average strength f’cr, for future work. [17] 29

R5.6.5 — Investigation of low-strength test results 30

Instructions are provided concerning the procedure to be followed when strength tests have failed to meet the 31 specified acceptance criteria. These instructions are applicable only for evaluation of in-place strength at time of 32 construction. Strength evaluation of existing structures is covered by Chapter 20. For obvious reasons, these 33 instructions cannot be dogmatic. The building official should apply judgment as to the significance of low test 34 results and whether they indicate need for concern. If further investigation is deemed necessary, such investigation 35 may include nondestructive tests or, in extreme cases, strength tests of cores taken from the structure. [21] 36

3719

CHAPTER 6 — FORMWORK, EMBEDMENTS, AND CONSTRUCTION JOINTS

1

2

3 4

No changes.

3720

CHAPTER 7 — DETAILS OF REINFORCEMENT 1

2

CODE 3 4

7.7.6 — Corrosive environments 5

In corrosive environments or other severe exposure conditions, the amount of concrete 6 protectionconcrete cover shall be suitably increased as deemed necessary and specified by the licensed 7 design professional. and tThe pertinent applicable requirements for concrete based on applicable 8 exposure categories in Chapter 4 shall be met, or other protection shall be provided.[13] 9

7.10 — Lateral Transverse reinforcement for compression members[13] 10

7.10.4 — Spirals 11

7.10.4.5 — Spiral reinforcement shall be spliced, if needed, by any one of the following methods: 12

(a) Lap splices not less than the larger of 12 in. and the length indicated in one of (1) through (5) 13 below: [16] 14

(1) deformed uncoated bar or wire, or deformed zinc-coated (galvanized) bar …………………….48db 15 (2) plain uncoated bar or wire, or plain zinc-coated (galvanized) bar.………………………………..72db 16 (3) epoxy-coated deformed bar or wire, or zinc and epoxy dual-coated deformed bar..…………..72db 17 (4) plain uncoated bar or wire, or plain zinc-coated (galvanized) bar, with which have a standard 18

stirrup or tie hook in accordance with 7.1.3 at ends of lapped spiral reinforcement. The hooks 19 shall be embedded within the core confined by the spiral reinforcement………………………...48db 20

(5) epoxy-coated deformed bar or wire, or zinc and epoxy dual-coated deformed bar, which have with 21 a standard stirrup or tie hook in accordance with 7.1.3 at ends of lapped spiral reinforcement. The 22 hooks shall be embedded within the core confined by the spiral reinforcement………………..48db 23

24

7.10.5 — Ties 25

7.10.5.3 — Rectilinear Tties shall be arranged such that every corner and alternate longitudinal bar 26 shall have lateral support provided by the corner of a tie with an included angle of not more than 135 27 degrees and no bar shall be farther than 6 in. clear on each side along the tie from such a laterally 28 supported bar. Where longitudinal bars are located around the perimeter of a circle, a complete circular 29 tie shall be permitted. [22] 30

7.10.5.4 — Where longitudinal bars are located around the perimeter of a circle, a complete circular tie 31 shall be permitted. The ends of the circular tie shall overlap by not less than 6 in. and terminate with 32 standard hooks that engage a longitudinal column bar. Overlaps at ends of adjacent circular ties shall be 33 staggered around the perimeter enclosing the longitudinal bars. [22] 34

7.12 — Shrinkage and temperature reinforcement 35

7.12.3.2 — Spacing of tendons shall not exceed 6 ft. [23] 36

7.12.3.2 — InFor monolithic cast-in-place post-tensioned beam-and-slab construction, gross concrete 37 area of a beam and tributary slab shall include the beam web and the slab within half the clear distance 38 to adjacent beam webs. It shall be permitted to include the effective force in beam tendons in the 39 calculation of total prestress force acting on gross concrete area. [23] 40

3721

7.12.3.3 — Where slabs are supported on walls or not cast monolithically with beams, gross concrete 1 area is the slab section tributary to the tendon or tendon group. [23] 2

7.12.3.4 — In all cases, a minimum of one slab tendon is required between faces of beams or walls. 3 Spacing of slab tendons, and the distance between face of beam or wall to the nearest slab tendon, 4 shall not exceed 6 ft. [23] 5

7.12.3.37.12.3.5 — When Where spacing of slab tendons exceeds 54 in.4.5 ft, additional bonded 6 nonprestressed shrinkage and temperature reinforcement conforming to 7.12.2 shall be provided between 7 the tendons at slab edges extending from the slab edge for a distance equal to the tendon spacing 8 between faces of beams or walls, parallel to the slab shrinkage and temperature tendons. This 9 additional shrinkage and temperature reinforcement shall extend from the slab edges for a distance 10 greater than or equal to the tendon spacing, except 7.12.2.3 shall not apply. [23] 11

12

COMMENTARY 13

R7.2 — Minimum bend diameters 14

R7.2.3 — Welded wire reinforcement can be used for stirrups and ties. The wire at welded intersections does not 15 have the same uniform ductility and bendability as in areas that were not heated. These effects of the welding 16 temperature are usually dissipated in a distance of approximately four wire diameters. Minimum bend diameters 17 permitted are in most cases the same as those required in the ASTM bend tests for wire material (ASTM A1064A82 18 and A496). [1] 19

R7.10 — Lateral Transverse reinforcement for compression members[13] 20

R7.10.5 — Ties 21

R7.10.5.4 — Vertical splitting and loss of tie restraint are possible where the overlapped ends of adjacent circular 22 ties are anchored at a single longitudinal bar. Adjacent circular ties should not engage the same longitudinal bar with 23 end hook anchorages. While the transverse reinforcement in members with longitudinal bars located around the 24 periphery of a circle can be either spirals or circular ties, spirals are usually more effective. [22] 25

R7.12 — Shrinkage and temperature reinforcement 26

R7.12.3 — Prestressed reinforcement requirements have been selected to provide an effective force on the slab 27 approximately equal to the yield strength force for nonprestressed shrinkage and temperature reinforcement. This 28 amount of prestressing, 100 psi on the gross concrete area, has been successfully used on a large number of projects. 29 In monolithic beam-and-slab construction, a minimum of one shrinkage and temperature tendon is required between 30 beams, even if the beam tendons alone provide at least 100 psi average compression stress on the gross concrete area 31 as defined in 7.12.3.2. Any size tendon is permissible as long as all other requirements of 7.12.3 are satisfied. 32 Application of the provisions of 7.12.3.2 to monolithic cast-in-place post-tensioned beam-and-slab construction is 33 illustrated in Fig. R7.12.3(a). [23] 34

When Where the spacing of slab tendons used for shrinkage and temperature reinforcement exceeds 54 in.4.5 ft, 35 additional bonded nonprestressed reinforcement is required at to extend from the slab edges where the prestressing 36 forces are applied in order to adequately reinforce the area between the slab edge and the point where compressive 37 stresses behind individual anchorages have spread sufficiently such that the slab is uniformly in compression (see 38 Fig. R7.12.3(b)). Application of the provisions of 7.12.3 to monolithic cast-in-place post-tensioned beam and slab 39 construction is illustrated in Fig. R7.12.3. [23] 40

3722

Tendons used for shrinkage and temperature reinforcement should be positioned vertically in the slab as closely as 1 practicable to the centermid-depth of the slab. In cases where the shrinkage and temperature tendons are used for 2 supporting the principal tendons, variations from the slab centroid are permissible; however, the resultant of the 3 shrinkage and temperature tendons should not fall outside the kern area of the slab. [23] 4

R7.13.3 — The Code requires tension ties for precast concrete buildings of all heights. Details should provide 5 connections to resist applied loads. Connection details that rely solely on friction caused by gravity forces are not 6 permitted by 16.5.1.4.[13] 7

8

9

10

11

12

13

14

15

Fig. R7.12.3—Prestressing used for shrinkage and temperature. [23] 16

17

18

19

3723

1 [23] 2

3

4

Fig. R17.12.3(b) — Plan at slab edge showing added shrinkage and temperature reinforcement (see 5 7.12.3.5).[13] 6

7

L1 L2

3724

CHAPTER 8 — ANALYSIS AND DESIGN — GENERAL CONSIDERATIONS

1

2

3

4

No changes.

3725

CHAPTER 9 — STRENGTH AND SERVICEABILITY 1

REQUIREMENTS 2

3

CODE 4

9.2 — Required strength 5

9.2.1 — Required strength U shall be at least equal to the effects of factored loads in Eq. (9-1) through (9-6 7). The effect of one or more loads not acting simultaneously shall be investigated. 7

U = 1.4D(D + F) [6] (9-1) 8

U = 1.2D(D + F + T) + 1.6L(L + H) + 0.5(Lr or S or R) [6] (9-2) 9

U = 1.2D + 1.6(Lr or S or R) + (1.0L or 0.80.5W) [6] (9-3) 10

U = 1.2D + 1.61.0W + 1.0L + 0.5(Lr or S or R) [6] (9-4) 11

U = 1.2D + 1.0E + 1.0L + 0.2S[6] (9-5) 12

U = 0.9D + 1.61.0W + 1.6H[6] (9-6) 13

U = 0.9D + 1.0E + 1.6H [6] (9-7) 14

except as follows: 15

(a) The load factor on the live load L in Eq. (9-3) to (9-5) shall be permitted to be reduced to 0.5 except 16 for garages, areas occupied as places of public assembly, and all areas where L is greater than 100 lb/ft2. 17

(b) Where wind load W has not been reduced by a directionality factor, it shall be permitted to use 1.3W 18 in place of 1.6W in Eq. (9-4) and (9-6). Where W is based on service-level wind loads, 1.6W shall be 19 used in place of 1.0W in Eq. (9-4) and (9-6), and 0.8W shall be used in place of 0.5W in Eq. (9-3). [6] 20

(c) Where E, the load effects of earthquake, is based on service-level seismic forces, 1.4E shall be 21 used in place of 1.0E in Eq. (9-5) and (9-7). [6] 22

(d) The load factor on H, loads due to weight and pressure of soil, water in soil, or other materials, shall 23 be set equal to zero in Eq. (9-6) and (9-7) if the structural action due to H counteracts that due to W or 24 E. Where lateral earth pressure provides resistance to structural actions from other forces, it shall not 25 be included in H but shall be included in the design resistance. [6] 26

9.2.2 — Impact effects[6] 27

If resistance to impact effects is taken into account in design, such effects shall be included with L. 28

9.2.3 — Self-straining effects 29

Estimations of differential settlement, creep, shrinkage, expansion of shrinkage-compensating concrete, 30 or temperature change shall be based on a realistic assessment of such effects occurring in service. 31 Where applicable, the structural effects of T shall be considered in combination with other loads. The 32 load factor on T shall be established considering the uncertainty associated with the likely magnitude of T, 33 the probability that the maximum effect of T will occur simultaneously with other applied loads, and the 34

3726

potential adverse consequences if the effect of T is greater than assumed. The load factor on T shall not 1 have a value less than 1.0. [6] 2

9.2.4 — Fluid loads[6] 3

Where F is present, it shall be included with the same load factor as D in Eq. (9-1) through (9-5) and (9-7). [6] 4

9.2.5 — Lateral soil pressure[6] 5

Where H is present, it shall be included in the load combinations of 9.2.1 with load factors in accordance 6 with (a), (b), or (c): [6] 7

a) where H acts alone or adds to the effects of other loads, it shall be included with a load factor 8 of 1.6; [6] 9

b) where the effect of H is permanent and counteracts the effects of other loads, it shall be 10 included with a load factor of 0.9; [6] 11

c) where the effect of H is not permanent but, when present, counteracts the effects of other 12 loads, H shall not be included. [6] 13

9.2.4 9.2.6 — Flood and ice loads[6] 14

If a structure is in a flood zone, or is subjected to forces from atmospheric ice loads, the flood or ice loads 15 and the appropriate load combinations of ASCE/SEI 7 shall be used. 16

9.2.5 9.2.7 — Prestressing steel jacking force[6] 17

For post-tensioned anchorage zone design, a load factor of 1.2 shall be applied to the maximum 18 prestressing steel jacking force. 19

20

COMMENTARY 21

R9.1 — General 22

In the 2002 Code, the load factorfactored load combinations and strength reduction factors of the 1999 Code were 23 revised and moved to Appendix C. The 1999 combinations were replaced with those of SEI/ASCE 7-02.9.1 The 24 strength reduction factors were replaced with those of the 1999 Appendix C, except that the factor for flexure was 25 increased. In the 2011 Code, the factored load combinations were revised for consistency with ASCE/SEI 7-109.2. [6] 26

R9.2 — Required strength 27

In 2011, the Code removed the weight of soil and other fill materials as part of the definition of H. Consistent with 28 ASCE/SEI 7-10, the weight of these materials is part of dead load, D. The load factors for D are appropriate 29 provided the unit weight and thickness of earth or other fill materials are well controlled. If the weight of earth 30 stabilizes the structure, a load factor of zero may be appropriate. [6] 31

R9.2.1(b) — The wind load equation in SEI/ASCE 7-029.1and IBC 20039.2includes a factor for wind directionality that 32 is equal to 0.85 for buildings. The corresponding load factor for wind in the load combination equations was 33 increased accordingly (1.3/0.85 = 1.53 rounded up to 1.6). The Code allows use of the previous wind load factor of 34 1.3 when the design wind load is obtained from other sources that do not include the wind directionality factor. 35 ASCE/SEI 7-10 has converted wind loads to strength level, and reduced the wind load factor to 1.0. ACI 318 36 requires use of the previous load factor for wind loads, 1.6, when service-level wind loads are used. For 37 serviceability checks, the commentary to Appendix C of ASCE/SEI 7-10 provides service-level wind loads, Wa.

[6] 38

3727

R9.2.1(c) — In 1993, ASCE 79.3Model building codes and design load references have converted earthquake forces to 1 strength level, and reduced the earthquake load factor to 1.0. Model building codes9.4,9.5,9.6 followed. (ASCE 7-939.3; 2 BOCA/NBC 939.4; SBC 949.5; UBC 979.6; and IBC 2000). The CodeACI 318 requires use of the previous load 3 factor for earthquake loadseffects, approximately 1.4, when service-level earthquake forces effects from earlier 4 editions of these references are used. [6] 5

R9.2.3 — The effects of differential settlement, creep, shrinkage, temperature, and shrinkage-compensating concrete 6 should be considered. The term “realistic assessment” is used to indicate that the most probable values rather than 7 the upper bound values of the variables should be used. Several strategies can be used to accommodate movements 8 due to differential settlement and volume change. Forces due to T effects are not commonly calculated and 9 combined with other load effects. Rather, designs rely on successful past practices, using compliant structural 10 members and ductile connections to accommodate differential settlement and volume change movement while 11 providing the needed resistance to gravity and lateral loads. Expansion joints and construction closure strips are used 12 to limit volume change movements based on performance of similar structures. Shrinkage and temperature 13 reinforcement is commonly proportioned based on gross concrete area rather than calculated force. [6] 14

However, where structural movements can lead to damage of non-ductile elements, calculation of the predicted 15 force should consider the inherent variability of the expected movement and structure response. A long-term study 16 of the volume change behavior of precast concrete buildings9.7, completed in 2009, recommends procedures to 17 account for connection stiffness, thermal exposure, member softening due to creep, and other factors that influence 18 T forces. [6] 19

R9.2.5 — The required load factors for lateral pressures from soil, water in soil and other materials reflect their 20 variability and the possibility that the materials may be removed. [6] 21

R9.4 — Design strength for reinforcement 22

In 11.4.2, 11.5.3.4, 11.6.6, and 18.9.3.2, the maximum value of fy or fyt that may be used in design is 60,000 psi, 23 except that fy or fyt up to 80,000 psi may be used for shear reinforcement meeting the requirements of ASTM 24 A1064A497. [13] 25

26

3728

CHAPTER 10 — FLEXURE AND AXIAL LOADS 1

2

CODE 3

10.7 — Deep beams 4

10.7.1 — Deep beams are members loaded on one face and supported on the opposite face so that 5 compression struts can develop between the loads and the supports, and have either: 6

(a) clear spans, ln, equal to or less than four times the overall member depth, h; or[25] 7

(b) regions with concentrated loads within a distance 2htwice the member depth from the face of the 8 support. [25] 9

Deep beams shall be designed either taking into account nonlinear distribution of strain, or by Appendix A. 10 (See also 11.7.1 and 12.10.6.) Lateral buckling shall be considered. [25] 11

10.7.2 — Vn of deep beams shall be in accordance with Deep beams shall satisfy the requirements of 12 11.7. [25] 13

10.7.3 — Minimum area of flexural tension reinforcement, As,min, shall conform to 10.5. 14

10.7.4 — Minimum horizontal and vertical reinforcement in the side faces of deep beams shall satisfy 15 either A.3.3 or 11.7.4 and 11.7.5. [25] 16

17

COMMENTARY 18

R10.10 — Slenderness effects in compression members 19

R10.10.2 — Add to the end of the paragraph: Several methods have been developed to evaluate slenderness effects 20 in compression members that are subject to bi-axial bending. A review of some of these methods is presented in 21 Reference 10.34. [26] 22

R10.13 — Composite compression members 23

R10.13.8 — Tie reinforcement around structural steel core 24

The design yield strength of the steel core should be limited to that which exists at strains below those that can be 25 sustained withoutwould not generate spalling of the concrete. [13] 26

3729

CHAPTER 11 — SHEAR AND TORSION 1

2

CODE 3

11.7 — Deep beams 4

11.7.1 — The provisions of 11.7 shall apply to members with ln not exceeding four times the overall 5 member depth 4h or regions of beams with concentrated loads within a distance 2h twice the member 6 depth from the support that are loaded on one face and supported on the opposite face so that 7 compression struts can develop between the loads and supports. See also 12.10.6. [25] 8

11.7.2 — Deep beams shall be designed using either by taking into account nonlinear distribution analysis 9 of strain as permitted in 10.7.1, or by Appendix A. In all cases, minimum distribution reinforcement shall be 10 provided in accordance with 11.7.4. [25] 11

11.7.3 — Vn for deep beams shall not exceed Deep beams shall be proportioned such that Vu is less than 12

or equal to φ10cf ′ bwd. [25] 13

11.7.4 — Total distributed reinforcement along the two side faces of deep beams shall not be less than 14 that required in 11.7.4.1 and 11.7.4.2. [25] 15

11.7.4.1 — The area of shear reinforcement perpendicular to the longitudinal axis of the beam flexural 16 tension reinforcement, Av, shall not be less than 0.0025bws, and s shall not exceed the smaller of d/5 and 17 12 in. [25] 18

11.7.54.2 — The area of shear reinforcement parallel to the longitudinal axis of the beam flexural tension 19 reinforcement, Avh, shall not be less than 0.00150.0025bws2, and s2 shall not exceed the smaller of d/5 20 and 12 in. [25] 21

11.7.6 — It shall be permitted to provide reinforcement satisfying A.3.3 instead of the minimum horizontal 22 and vertical reinforcement specified in 11.7.4 and 11.7.5. [25] 23

COMMENTARY 24

R11.7 — Deep beams 25

R11.7.1 — The behavior of a deep beam beams is discussed in References 11.5 and 11.4611.52 through 11.54. For a 26 deep beam supporting gravity loads, this section 11.7.1 applies if the loads are applied on the top of the beam and 27 the beam is supported on its bottom face. If the loads are applied through the sides or bottom of such a member, the 28 design for shear should be the same as for ordinary beams.strut-and-tie models, as defined in Appendix A, should be 29 used to design reinforcement to suspend the loads within the beam and transfer them to adjacent supports. [25] 30

The longitudinal reinforcement in deep beams should be extended to the supports and adequately anchored by 31 embedment, hooks, headed deformed bars, or welding to special devices. Bent-up bars are not recommended. [25] 32

R11.7.2 — Deep beams can be designed using strut-and-tie models, regardless of how they are loaded and 33 supported. Section 10.7.1 allows the use of analyses that take into account nonlinear strain and stress 34 distributionsfields when proportioning deep beams. Such analyses, including nonlinear finite eliminate analyses, 35 should consider the effects of cracking on the stress distribution. [25] 36

R11.7.3 — In the 1999 and earlier Codes, a sliding maximum shear strength was specified. A re-examination of the 37

3730

test data suggests that this strength limit was derived from tests in which the beams failed due to crushing of support 1 regions. This possibility is specifically addressed in the design process specified in this Code. [25] 2

R.11.7.3 — This limit is imposed to control cracking under service loads and guard against diagonal compression 3 failures in deep beams. [25] 4

R11.7.4 and R11.7.5 — The amount of shear reinforcement required for strength shall be proportioned to be 5 consistent with the analysis method used. The minimum reinforcement requirements in 11.7.4.1 and 11.7.4.2 are to 6 be used irrespective of the analysis method and are intended to control the width and propagation of inclined cracks. 7 The relative amounts of horizontal and vertical shear reinforcement have been interchanged from those required in 8 the 1999 and earlier Codes because testsTests11.52-11.54 have shown that vertical shear reinforcement (perpendicular to 9 the longitudinal axis of the member) is more effective for member strength than horizontal shear reinforcement 10 (parallel to the longitudinal axis of the member) in a deep beam, but the specified minimum reinforcement in for 11 both directions areis required to control the growth and width of diagonal cracks. The maximum spacing of bars has 12 been reduced from 18 to 12 in. because this steel is provided to restrain the width of the cracks. [25] 13

3731

CHAPTER 12 — DEVELOPMENT AND SPLICES OF 1

REINFORCEMENT 2

3

CODE 4 5

12.2 — Development of deformed bars and deformed wire in tension 6

12.2.4 — The factors used in the expressions for development of deformed bars and deformed wires in 7 tension in 12.2 are as follows: 8

(b) For epoxy-coated bars, zinc and epoxy dual-coated bars, or epoxy-coated wires with cover less than 9 3db, or clear spacing less than 6db, ψe = 1.5. For all other epoxy-coated bars, zinc and epoxy dual-10 coated bars, or epoxy-coated wires, ψe = 1.2. For uncoated and zinc-coated (galvanized) reinforcement, 11 ψe = 1.0. [16] 12

13

12.6 — Development of headed and mechanically anchored deformed bars in 14 tension 15

12.6.2 — For headed deformed bars satisfying 3.5.9, development length in tension ldt shall be (0.016ψefy/16

′cf )db, where the value of fc′ used to calculate ldt shall not exceed 6000 psi, and factor ψe shall be taken 17

as 1.2 for epoxy-coated reinforcement and 1.0 for other cases. Where reinforcement provided is in excess 18 of that required by analysis, except where development of fy is specifically required, a factor of (As 19 required)/(As provided) may be applied to the expression for ldt. Length ldt shall not be less than the 20 larger of 8db and 6 in. [27] 21

12.6.4 — Any mechanical attachment or device capable of developing fy of reinforcement deformed bars 22 is allowed, provided that test results showing the adequacy of such attachment or device are approved by 23 the building official. Development of reinforcement deformed bars shall be permitted to consist of a 24 combination of mechanical anchorage plus additional embedment length of reinforcement deformed 25 bars between the critical section and the mechanical attachment or device. [27] 26

COMMENTARY 27

R12.2 — Development of deformed bars and deformed wire in tension 28

R12.2.4 — Because the bond of epoxy-coated bars or zinc and epoxy dual-coated bars is already reduced due to the 29 loss of adhesion between the bar and the concrete, an upper limit of 1.7 is established for the product of the factors 30 for top reinforcement and epoxy-coated reinforcement or zinc and epoxy dual-coated reinforcementfactors.[16] 31

R12.6 — Development of headed and mechanically anchored deformed bars in tension 32

The development of headed deformed bars and the development and anchorage of reinforcement deformed bars 33 through the use of mechanical devices within concrete are addressed in 12.6. As used in 12.6, development describes 34 cases in which the force in the bar is transferred to the concrete through a combination of a bearing force at the head 35 and bond forces along the bar,. Suchsuch cases are covered in 12.6.1 and 12.6.2. In contrast, anchorage describes 36 cases in which the force in the bar is transferred through bearing to the concrete at the head alone. General 37

3732

provisions Design requirements for anchorsanchorage are given in Appendix D. The limitation on obstructions and 1 interruptions of the deformations is included in 3.5.9 because there is a wide variety of methods to attach heads to 2 bars, some of which involve obstructions or interruptions of the deformations that extend more than 2db from the 3 bearing face of the head. These systems were not evaluated in the tests used to formulate the provisions in 12.6.2, 4 which were limited to systems that meet the criteria in 3.5.9. Headed bars are limited to those types that meet the 5 requirements of HA heads in ASTM A970 because a wide variety of methods are used to attach heads to bars, some 6 of which involve significant obstructions or interruptions of the bar deformations. Headed bars with significant 7 obstructions or interruptions of the bar deformations were not evaluated in the tests used to formulate the provisions 8 in 12.6.2. The headed bars evaluated in the tests were limited to those types that meet the criteria in 3.5.9 for HA 9 heads. [14] 10 11 Insert before final paragraph: In 2011, the excess reinforcement factor for headed bars was removed from the Code. 12 The excess reinforcement factor (As required/As provided), applicable to deformed bars without heads, is not applicable for 13 headed bars where force is transferred through a combination of bearing at the head and bond along the bar. 14 Concrete breakout due to bearing at the head was considered in developing the provisions of 12.6. Because the 15 concrete breakout capacity of a headed bar is a function of the embedment depth to the 1.5 power (see Appendix D 16 Eq. D-6), a reduction in development length with the application of the excess reinforcement factor could result in a 17 potential concrete breakout failure. [27] 18

R12.6.3 — No data are available that demonstrate that the use of heads adds significantly to anchorage strength in 19 compression. 20

R12.6.4 — Headed deformed reinforcement bars that dodoes not meet the requirements in 3.5.9, including the 21 limitation on obstructions and interruptions of the deformations, or is are not anchored in accordance with 12.6.1 22 and 12.6.2 may be used if tests demonstrate the ability of the head and bar system to develop or anchor the desired 23 force in the bar, as described in 12.6.4. [14] 24

R12.7 — Development of welded deformed wire reinforcement in tension 25

Figure R12.7 shows the development requirements for welded deformed wire reinforcement with one cross wire within 26 the development length. ASTM A1064A497 for welded deformed wire reinforcement requires the same strength of the 27 weld as required for welded plain wire reinforcement (ASTM A185). [13] 28

3733

CHAPTER 13 — TWO-WAY SLAB SYSTEMS 1

2

CODE 3

13.3 — Slab reinforcement 4

13.3.8 — Details of reinforcement in slabs without beams 5

13.3.8.6 — In slabs with shearheads and in lift-slab construction where it is not practical to pass the 6 bottom bars required by 13.3.8.5 through the column, at least two bonded bottom bars or wires in each 7 direction shall pass through the shearhead or lifting collar as close to the column as practicable and be 8 continuous or spliced with a Class A B tension lap splice or with mechanical or welded splices satisfying 9 12.14.3. At exterior columns, the reinforcement shall be anchored at the shearhead or lifting collar. [24] 10

3734

CHAPTER 14 — WALLS 1

2

3

COMMENTARY 4

5

R14.8 — Alternative design of slender walls 6

R14.8.4 — Service-level load combinations are not defined in Chapter 9 of ACI 318, but they are discussed in 7 Appendix C of ASCE/SEI 7-0510.14.7 Unlike ACI 318, however, appendixes to ASCE/SEI 7 are not considered to be 8 mandatory parts of the standard. For calculating service-level lateral deflections of structures, Appendix C of 9 ASCE/SEI 7-05 10 recommends using the following load combination 10

D + 0.5L + 0.7W[6] 11

12

D + 0.5L + Wa[6] 13

in which Wa is wind load based on serviceability wind speeds provided in the commentary to Appendix C of 14 ASCE/SEI 7-10. which corresponds to a 5 percent annual probability of exceedance. If the slender wall is designed to 15 resist earthquake effects, E, and E is based on strength-level earthquake effectsseismic forces, the following load 16 combination is considered to be appropriate for evaluating the service-level lateral deflections[6] 17

D + 0.5L + 0.7E 18

3735

CHAPTER 15 — FOOTINGS 1

2

3

4

5

No changes.

3736

CHAPTER 16 — PRECAST CONCRETE 1 2

COMMENTARY 3

R16.5 — Structural integrity 4

R16.5.1.2 — Diaphragms are typically provided as part of the lateral load-resisting system. The ties prescribed in 5 16.5.1.2 are the minimum required to attach members to the floor or roof diaphragms. The tie force is equivalent to 6 the service load value of 200 lb/ft given in the Uniform Building Code.[38] 7

3737

1

2

3

4

CHAPTER 17 — COMPOSITE CONCRETE FLEXURAL MEMBERS

No changes.

3738

CHAPTER 18 — PRESTRESSED CONCRETE 1

2

CODE 3

18.5 — Permissible stresses in prestressing steel 4

18.5.1 — Tensile stress in prestressing steel shall not exceed the following: 5

(a) Due to prestressing steel jacking force………………………………………………………………….0.94fpy 6

but not greater than the lesser of 0.80fpu and the maximum value recommended by the manufacturer 7 of prestressing steel or anchorage devices. 8

(b) Immediately after prestress transfer…………………………………………………………………..0.82fpy 9

but not greater than 0.74fpu. [28] 10

(c) (b) Post-tensioning tendons, at anchorage devices and couplers, immediately after force transfer ..0.70fpu 11

18.6 — Loss of prestress 12

18.6.2 — Friction loss in post-tensioning tendons 13

18.6.2.1 — Ppx, force in post-tensioning tendons a distance lpx from the jacking end shall be computed by[7] 14

Ppx = Ppj

μ α (18-1) [7] 15

Where (Klpx + μpαpx) is not greater than 0.3, Ppx shall be permitted to be computed by[7] 16

Ppx = Ppj(1 + Klpx + μpαpx)–1 (18-2) [7] 17

18.6.2.1 — The required effective prestress force shall be indicated in the contract documents. [7] 18

18.6.2.2 — Friction Computed friction loss shall be based on experimentally determined wobble K and 19 curvature μp friction coefficients., and shall be verified during tendon stressing operations. [7] 20

18.6.2.3 — Values of K and μp used in design shall be shown on design drawings. The prestress force 21 and friction losses shall be verified during tendon stressing operations as specified in 18.20. [7] 22

COMMENTARY 23

R18.5 — Permissible stresses in prestressing steel 24

R18.5.1 — With the 1983 Code, permissible stresses in prestressing steel were revised to recognize Because of the 25 higher yield strength of low-relaxation wire and strand meeting the requirements of ASTM A421 and A416,. For such 26 prestressing steel, it is more appropriate to specify permissible stresses in terms of specified minimum ASTM yield 27 strength rather than along with the specified minimum ASTM tensile strength. For the low-relaxation wire and 28 strands, with fpy equal to 0.90fpu, the 0.94fpy and 0.82fpy limits are equivalent to 0.85fpu and 0.74fpu, respectively. In 29 the 1986 supplement and in the 1989 Code, the maximum jacking stress for low-relaxation prestressing steel was 30 reduced to 0.80fpu to ensure closer compatibility with the maximum prestressing steel stress value of 0.74fpu 31 immediately after prestress transfer. The higher yield strength of the low-relaxation prestressing steel does not 32

3739

change the effectiveness of tendon anchorage devices; thus, the permissible stress at post-tensioning anchorage 1 devices and couplers is not increased above the previously permitted value of 0.70fpu. For ordinary prestressing steel 2 (wire, strands, and bars) with fpy equal to 0.85fpu, the 0.94fpy and 0.82fpy limits are equivalent to 0.80fpu and 0.70fpu, 3 respectively, the same as permitted in the 1977 Code. For bar prestressing steel with fpy equal to 0.80fpu, the same 4 limits are equivalent to 0.75fpu and 0.66fpu, respectively. [28] 5

R18.6 — Loss of prestress 6

R18.6.2 — Friction loss in post-tensioning tendons 7

Estimation of friction losses in post-tensioned tendons is addressed in Reference 18.10. The coefficients tabulated in 8 Table R18.6.2 give a range that generally can be expected. Due to the many types of prestressing steel ducts and 9 sheathing available, these values can only serve as a guide. Where rigid conduit is used, the wobble coefficient K 10 can be considered as zero. For large-diameter prestressing steel in semirigid type conduit, the wobble factor can also 11 be considered zero. Values of the wobble and curvature friction coefficients to be used for the particular types of 12 prestressing steel and particular types of ducts should be obtained from the manufacturers of the tendons. An 13 unrealistically low evaluation estimate of the friction loss can lead to improper camber, or potential deflection, of the 14 member and inadequate prestress. [7] 15

R18.7 — Flexural strength 16

R18.7.2 — Insert after first paragraph: The γp term in Eq. (18-1) reflects the influence of different types of 17 prestressing reinforcement on the value of fps. For high-strength prestressing bars conforming to ASTM A722 (Type 18 I), fpy/fpu is equal to or greater than 0.85; for high-strength prestressing bars conforming to ASTM A722 (Type II), 19 fpy/fpu is equal to or greater than 0.80; for stress-relieved strand and wire conforming to ASTM A416 and A421, 20 fpy/fpu is equal to or greater than 0.85; and for low-relaxation strand and wire conforming to ASTM A416 and A421, 21 fpy/fpu is equal to or greater than 0.90. [2922

23 TABLE R18.6.2 — FRICTION COEFFICIENTS FOR POST-TENSIONED 24

TENDONS FOR USE IN EQ. (18-1) OR (18-2) 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 [7] 48

Wobble coefficient, K per

foot

Curvature coefficient, μp per

radian

Gro

uted

tend

ons

in

met

al s

heat

hing

Wire tendons 0.0010-0.0015 0.15-0.25

High-strength bars 0.0001-0.0006 0.08-0.30

7-wire strand 0.0005-0.0020 0.15-0.25

Unb

onde

d te

ndon

s

Mas

tic

coat

ed Wire tendons 0.0010-0.0020 0.05-0.15

7-wire strand 0.0010-0.0020 0.05-0.15

Pre-

grea

sed

Wire tendons 0.0003-0.0020 0.05-0.15

7-wire strand 0.0003-0.0020 0.05-0.15

3740

R18.9.3.2 — In positive moment areas, where the maximum computed concrete tensile stresses are between exceeds 1 2 ′cf and but is less than 6 ′cf , in accordance with 18.3.3, a minimum bonded reinforcement area proportioned to resist 2

Nc according to Eq. (18-75) is required. The tensile force Nc is computed at service load on the basis of an uncracked, 3 homogeneous section. [8] 4

5

3741

CHAPTER 19 — SHELLS AND FOLDED PLATE MEMBERS 1

2 3

COMMENTARY 4

R19.1 — Scope and definitions 5

R19.1.1 — Discussion of the application of thin shells in structures such as cooling towers and circular prestressed 6 concrete tanks may be found in the reports of ACI Committee 33419.4 and ACI Committee 373.19.5[5] 7

3742

CHAPTER 20 — STRENGTH EVALUATION OF EXISTING STRUCTURES

1

2

3 4

5

No changes.

3743

CHAPTER 21 — EARTHQUAKE-RESISTANT STRUCTURES 1

2

CODE 3

21.1 — General requirements 4

21.1.4 — Concrete in special moment frames and special structural walls 5

21.1.4.1 — Requirements of 21.1.4 apply to special moment frames, and special structural walls, and 6 all components of special structural walls including coupling beams and wall piers. [4] 7

21.4.4 — In structures assigned to SDC D, E, or F, wall piers shall be designed in accordance with 21.9 8 or 21.13. [4] 9

21.1.5 — Reinforcement in special moment frames and special structural walls 10

21.1.5.1 — Requirements of 21.1.5 apply to special moment frames, and special structural walls, and 11 all components of special structural walls including coupling beams and wall piers. [4] 12

21.1.5.2 — Deformed reinforcement resisting earthquake-induced flexural and axial forces in frame 13 members, structural walls, and coupling beams, shall comply with ASTM A706, Grade 60. ASTM A615 14 Grades 40 and 60 reinforcement shall be permitted in these members if: [13,30] 15

21.3 — Intermediate moment frames 16

21.3.3 — Shear strength[11] 17

21.3.3.1 — φVn of beams and columns resisting earthquake effect, E, shall not be less than the smaller of 18 (a) and (b): [11] 19

(a) The sum of the shear associated with development of nominal moment strengths of the member 20 beam at each restrained end of the clear span due to reverse curvature bending and the shear 21 calculated for factored gravity loads; [11] 22

(b) The maximum shear obtained from design load combinations that include E, with E assumed to be 23 twice that prescribed by the legally adopted general building code for earthquake-resistant design. 24

21.3.3.2 — φVn of columns resisting earthquake effect, E, shall not be less than the smaller of (a) and (b): [11] 25

(a) The shear associated with development of nominal moment strengths of the column at each 26 restrained end of the unsupported length due to reverse curvature bending. Column flexural strength 27 shall be calculated for the factored axial force, consistent with the direction of the lateral forces 28 considered, resulting in the highest flexural strength. [11] 29

(b) The maximum shear obtained from design load combinations that include E, with E increased by Ωo. [11] 30

21.5 — Flexural members of special moment frames 31

21.5.3 — Transverse reinforcement 32

21.5.3.2 — The first hoop shall be located not more than 2 in. from the face of a supporting member. 33 Spacing of the hoops shall not exceed the smallest of (a), (b), and (c) and (d): 34

(a) d/4; 35

3744

(b) Eight Six times the diameter of the smallest longitudinal bars primary flexural reinforcing bars 1 excluding longitudinal skin reinforcement required by 10.6.7; and[31] 2

(c) 24 times the diameter of the hoop bars; and[31] 3

(d) 12 in. [31] 4

(c) 6 in. [31] 5

21.5.3.3 — Where hoops are required, longitudinal bars on the perimeter primary flexural reinforcing 6 bars closest to the tension and compression faces shall have lateral support conforming to 7.10.5.3 or 7 7.10.5.4. shall have lateral support conforming to 7.10.5.3. The spacing of laterally supported flexural 8 reinforcing bars shall not exceed 14 in. Skin reinforcement required by 10.6.7 need not be laterally 9 supported. [13,22,31] 10

21.6 — Special moment frame members subjected to bending and axial load 11

21.6.3 — Longitudinal reinforcement 12

21.6.3.2 — In columns with circular hoops, the minimum number of longitudinal bars shall be 6. [22] 13

21.6.4 — Transverse reinforcement 14

21.6.4.6 — Columns supporting reactions from discontinued stiff members, such as walls, shall satisfy 15 (a) and (b): 16

(b) The transverse reinforcement shall extend into the discontinued member at least a distance equal to 17 ld of the largest longitudinal column bar, where ld is determined in accordance with 21.7.5 for the largest 18 longitudinal column bar. Where the lower end of the column terminates on a wall, the required 19 transverse reinforcement shall extend into the wall at least ld of the largest longitudinal column bar at 20 the point of termination. Where the column terminates on a footing or mat, the required transverse 21 reinforcement shall extend at least 12 in. into the footing or mat.[13] 22

21.7 — Joints of special moment frames 23

21.7.4 — Shear strength 24

21.7.4.1 — For normalweight concrete, Vn of the joint shall not be taken as greater than the values 25 specified below for normalweight concrete. [32] 26

For joints confined by beams on all four faces…………………………………………………….20 ′cf Aj

[32] 27

For joints confined by beams on three faces or on two opposite faces………………………….15 ′cf28

Aj[32]

29

For others cases……………………………………………………………………………………..12 ′cf Aj

[32] 30

A member beam that frames into a face is considered to provide confinement to the joint if it covers at least 31 three-quarters of the face of the joint is covered by the framing member. Extensions of beams at least one 32 overall beam depth h beyond the joint face are permitted to be considered adequate for confining that 33 joint face. as confining members. Extensions of beams shall satisfy 21.5.1.3, 21.5.2.1, 21.5.3.2, 21.5.3.3, 34 and 21.5.3.6. A joint is considered to be confined if such confining members frame into all faces of the 35 joint. [32] 36

3745

21.9 — Special structural walls and coupling beams 1

21.9.1 — Scope 2

Requirements of 21.9 apply to special structural walls and all components of special structural walls 3 including, cast-in-place or precast, and coupling beams and wall piers forming part of the seismic-force-4 resisting system. Special structural walls constructed using precast concrete shall also comply with 21.10. [4] 5

21.9.4 — Shear strength 6

21.9.4.4 — For all vertical wall segments wall piers sharing resisting a common lateral force, combined 7 Vn shall not be taken larger than 8Acv

′cf , where Acv is the gross combined area of concrete bounded by 8

web thickness and length of sectionof all vertical wall segments. For any one of the individual vertical wall 9 segmentswall piers, Vn shall not be taken larger than 10Acw

′cf , where Acw is the area of concrete section 10

of the individual vertical wall segment pier considered. [13,4] 11

21.9.6 — Boundary elements of special structural walls 12

21.9.6.4 — Where special boundary elements are required by 21.9.6.2 or 21.9.6.3, (a) through (e) shall 13 be satisfied: 14

(e) Horizontal reinforcement in the wall web shall extend to within 6 in. of the end of the wall. be 15 anchored to develop fy within the confined core of the boundary element Reinforcement shall be 16 anchored to develop fy within the confined core of the boundary element using standard hooks or 17 heads. Where the confined boundary element has sufficient length to develop the horizontal web 18 reinforcement, and Avfy/s of the web reinforcement is not greater than Ashfyt/s of the boundary element 19 transverse reinforcement parallel to the web reinforcement, it shall be permitted to terminate the web 20 reinforcement without a standard hook or head.[13,33] 21

21.9.8 — Wall piers[4] 22

21.9.8.1 — Wall piers shall satisfy the special moment frame requirements for columns of 21.6.3, 21.6.4, 23 and 21.6.5, with joint faces taken as the top and bottom of the clear height of the wall pier. Alternatively, 24 wall piers with ( w/bw) > 2.5 shall satisfy (a) through (f): [4] 25

(a) Design shear force shall be determined in accordance with 21.6.5.1 with joint faces taken as the 26 top and bottom of the clear height of the wall pier. Where the legally adopted general building 27 code includes provisions to account for overstrength of the seismic-force-resisting system, the 28 design shear force need not exceed Ω0 times the factored shear determined by analysis of the 29 structure for earthquake load effects. [4] 30

(b) Vn and distributed shear reinforcement shall satisfy 21.9.4. [4] 31

(c) Transverse reinforcement shall be in the form of hoops except it shall be permitted to use single-32 leg horizontal reinforcement parallel to w where only one curtain of distributed shear 33

reinforcement is provided. Single-leg horizontal reinforcement shall have 180-degree bends at 34 each end that engage wall pier boundary longitudinal reinforcement. [4] 35

(d) Vertical spacing of transverse reinforcement shall not exceed 6 in. [4] 36

(e) Transverse reinforcement shall extend at least 12 in. above and below the clear height of the wall 37 pier. [4] 38

3746

(f) Special boundary elements shall be provided if required by 21.9.6.3. [4] 1

21.9.8.2 — For wall piers at the edge of a wall, horizontal reinforcement shall be provided in adjacent wall 2 segments above and below the wall pier and be proportioned to transfer the design shear force from the 3 wall pier into the adjacent wall segments. [4] 4

21.13 — Members not designated as part of the seismic-force-resisting system 5

21.13.1 — Scope 6

Requirements of 21.13 apply to frame members not designated as part of the seismic-force-resisting 7 system in structures assigned to SDC D, E, and F. [4] 8

21.13.2 — Frame mMembers assumed not to contribute to lateral resistance, except two-way slabs without 9 beams and wall piers, shall be detailed according to 21.13.3 or 21.13.4 depending on the magnitude of 10 moments induced in those members when subjected to the design displacement δu. If effects of δu are not 11 explicitly checked, it shall be permitted to apply the requirements of 21.13.4. Slab-column connections of For 12 two-way slabs without beams, slab-column connections shall meet shall satisfy the requirements of 21.13.6. 13 Wall piers shall satisfy the requirements of 21.13.7. [4] 14

21.13.7 — Wall piers not designated as part of the seismic-force-resisting system shall satisfy the 15 requirements of 21.9.8. Where the legally adopted general building code includes provisions to account 16 for overstrength of the seismic-force-resisting system, it shall be permitted to determine the design shear 17 force as Ωo times the shear induced under design displacements, δu.

[4] 18 19

COMMENTARY 20

21

R21.1.5 — Reinforcement in special moment frames and special structural walls 22

Use of longitudinal reinforcement with strength substantially higher than that assumed in design will lead to higher 23 shear and bond stresses at the time of development of yield moments. These conditions may lead to brittle failures in 24 shear or bond and should be avoided even if such failures may occur at higher loads than those anticipated in design. 25 Therefore, a ceiling is placed on the actual yield strength of the steel [see 21.1.5.2(a)]. ASTM A706/A706M for low-26 alloy steel reinforcing bars now includes both Grade 60 (442) and Grade 80 (550); however, only Grade 60 is 27 generally permitted because of insufficient data to confirm applicability of existing code provisions for structures 28 using the higher grade. Section 21.1.1.8 permits alternative material such as ASTM A706 Grade 80 if results of tests 29 and analytical studies are presented in support of its use. [30] 30

R21.1.6 — Mechanical splices in special moment frames and special structural walls 31

In a structure undergoing inelastic deformations during an earthquake, the tensile stresses in reinforcement may 32 approach the tensile strength of the reinforcement. The requirements for Type 2 mechanical splices are intended to 33 avoid a splice failure when the reinforcement is subjected to expected stress levels in yielding regions. Type 1 34 splices are not required to satisfy the more stringent requirements for Type 2 splices, and may not be capable of 35 resisting the stress levels expected in yielding regions. The locations of Type 1 splices are restricted because 36 tensile stresses in reinforcement in yielding regions can exceed the strength requirements of 12.14.3.2. The 37 restriction on Type 1 splices applies to all reinforcement resisting earthquake effects, including transverse 38 reinforcement. [22] 39

R21.1.7 — Welded splices in special moment frames and special structural walls 40

3747

R21.1.7 — Welded splices in special moment frames and special structural walls 1

R21.1.7.1 — Welding of reinforcement should be according to AWS D1.4 as required in Chapter 3. The locations of 2 welded splices are restricted because reinforcement tension stresses in yielding regions can exceed the strength 3 requirements of 12.14.3.4. The restriction on welded splices applies to all reinforcement resisting earthquake effects, 4 including transverse reinforcement. [22] 5

R21.3 — Intermediate moment frames 6

The objective of the requirements in 21.3.3 is to reduce the risk of failure in shear in beams and columns during an 7 earthquake. Two options are provided to determine the factored shear force. 8

According to option (a) of 21.3.3.1(a) and 21.3.3.2(a), the factored shear force is determined from a free-body 9 diagram obtained by cutting through the member ends, with end moments assumed equal to the nominal moment 10 strengths of the member acting in reverse curvature bendingand the gravity load on it. Examples for a beam and a 11 column are illustrated in Fig. R21.3.3. In all applications of 21.3.3.1(a) and 21.3.3.2(a), shears are required to be 12 calculated for moments due to reverse curvature bending, acting both clockwise and counterclockwise. Figure 13 R21.3.3 demonstrates only one of the two options that are to be considered for every member. The factored axial 14 force, Pu, should be chosen to develop the largest moment strength of the column. [11] 15

To determine the maximum beam shear, it is assumed that its nominal moment strengths (φ = 1.0) are developed 16 simultaneously at both ends of its clear span. As indicated in Fig. R21.3.3, the shear associated with this condition 17 [(Mnl + Mnr)/ln] is added algebraically to the shear due to the factored gravity loads to obtain the design shear for the 18 beam. For this the example shown, both the dead load wD and the live load wL have been assumed to be uniformly 19 distributed. Effects of E acting vertically are to be included if required by the general building code. [11] 20

Determination of the design shear for a column is also illustrated for a particular example in Fig. R21.3.3. The 21 factored axial force, Pu, should be chosen to develop the largest moment strength of the column. [11] 22

In all applications of option (a) of 21.3.3, shears are required to be calculated for moments, acting both clockwise 23 and counterclockwise. Figure R21.3.3 demonstrates only one of the two conditions that are to be considered for 24 every member. Option 21.3.3.1(b) for beams bases Vu on the load combination including the earthquake effect, E, 25 which should be doubled. For example, the load combination defined by Eq. (9-5) would be[11] 26

U = 1.2D + 2.0E + 1.0L + 0.2S 27

where E is the value specified by the governing code. The factor of 1.0 applied to L is allowed to be reduced to 0.5 28 in accordance with 9.2.1(a). [11] 29

Option 21.3.3.2(b) for columns is similar to that for beams except it bases Vu on load combinations including the 30 earthquake effect, E, with E increased by the overstrength factor, Ωo, rather than the factor 2.0. In ASCE 7-05, Ωo = 31 3.0 for intermediate moment frames. The higher factor for columns relative to beams is because of greater concerns 32 about shear failures in columns. [11] 33

R21.5.3 —Transverse reinforcement 34

Insert after first paragraph: For many years, the upper limit on hoop spacing was the smallest of d/4, 8 longitudinal 35 bar diameters, 24 tie bar diameters, and 12 in. The upper limits were changed because of concerns about adequacy 36 of longitudinal bar buckling restraint and confinement of large beams. [11] 37

R21.7.4 — Shear strength 38

The requirements in Chapter 21 for proportioning joints are based on Reference 21.8 in that behavioral phenomena 39 within the joint are interpreted in terms of a nominal shear strength of the joint. Because tests of joints21.28 and deep 40 beams21.14 indicated that shear strength was not as sensitive to joint (shear) reinforcement as implied by the 41

3748

expression developed by Joint ACI-ASCE Committee 32621.34 for beams, Committee 318 set the strength of the joint 1 as a function of only the compressive strength of the concrete (see 21.7.4) and requires a minimum amount of 2 transverse reinforcement in the joint (see 21.7.3). The effective area of joint Aj is illustrated in Fig. R21.7.4. In no 3 case is Aj greater than the column cross-sectional area. A circular column should be considered as having a square 4 section of equivalent area. [32] 5

R21.9 — Special structural walls and coupling beams 6

R21.9.1 — Scope 7

This section contains requirements for the dimensions and details of special structural walls and all components 8 including coupling beams and wall piers. Wall piers are defined in 2.2. Design provisions for vertical wall segments 9 depend on the aspect ratio of the wall segment in the plane of the wall (hw/lw), and the aspect ratio of the horizontal 10 cross section (lw/bw), and generally follow the descriptions in Table R21.9.1. The limiting aspect ratios for wall piers 11 are based on engineering judgment. It is intended that flexural yielding of the vertical reinforcement in the pier 12 should limit shear demand on the pier. [4] 13

R21.9.4 — Shear strength 14

A vertical wall segment refers to a part of a wall bounded horizontally by openings or by an opening and an edge. 15 Traditionally, a vertical wall segment bounded by two window openings has been referred to as a pier. When 16 designing an isolated wall or a vertical wall segment, ρt refers to horizontal reinforcement and ρ

l refers to vertical 17

reinforcement. [4] 18

If the factored shear force at a given level in a structure is resisted by several walls or several piers vertical wall 19 segments of a perforated wall, the average unit shear strength assumed for the total available cross-sectional area is 20

limited to 8 cf ′ with the additional requirement that the unit shear strength assigned to any single pier vertical wall 21

segment does not exceed 10 cf ′ . The upper limit of strength to be assigned to any one member is imposed to limit 22

the degree of redistribution of shear force. [4] 23

“Horizontal wall segments” in 21.9.4.5 refers to wall sections between two vertically aligned openings (see Fig. 24 R21.9.4.5). It is, in effect, a pier vertical wall segment rotated through 90 degrees. A horizontal wall segment is also 25 referred to as a coupling beam when the openings are aligned vertically over the building height. When designing a 26 horizontal wall segment or coupling beam, ρt refers to vertical reinforcement and ρ

l refers to horizontal 27

reinforcement. [4] 28

R21.9.6.4 — The value of c/2 in 21.9.6.4(a) is to provide a minimum length of the special boundary element. 29 Where flanges are heavily stressed in compression, the web-to-flange interface is likely to be heavily stressed and 30 may sustain local crushing failure unless special boundary element reinforcement extends into the web. Equation (21-4) 31 does not apply to walls. 32

Because horizontal reinforcement is likely to act as web reinforcement in walls requiring boundary elements, it 33 should be fully anchored in boundary elements that act as flanges (21.9.6.4). Achievement of this anchorage is difficult 34 when large transverse cracks occur in the boundary elements. Therefore, standard 90-degree hooks or mechanical 35 anchorage schemes are recommended instead of straight bar development. [33] 36

The horizontal reinforcement in a structural wall with low shear to moment ratio resists shear through truss action, 37 with the horizontal bars acting like the stirrups in a beam. Thus, the horizontal bars provided for shear reinforcement 38 must be developed within the confined core of the boundary element and extended as close to the end of the wall as 39 cover requirements and proximity of other reinforcement permit. The requirement that the horizontal web 40 reinforcement be anchored within the confined core of the boundary element and extended to within 6 in. from the 41 end of the wall applies to all horizontal bars whether straight, hooked, or headed, as illustrated in Fig. R21.9.6.4. [33] 42

R21.9.8 — Wall piers[4] 43

3749

Door and window placements in structural walls sometimes lead to narrow vertical wall segments that are 1 considered to be wall piers. The dimensions defining wall piers are given in 2.2. Shear failures of wall piers have 2 been observed in previous earthquakes. The intent of 21.9.8 is to provide sufficient shear strength to wall piers so 3 that a flexural yielding mechanism will develop. The provisions apply to wall piers designated as part of the seismic-4 force-resisting system. Provisions for wall piers not designated as part of the seismic-force-resisting system are 5 given in 21.13. The effect of all vertical wall segments on the response of the structural system, whether designated 6 as part of the seismic-force-resisting system or not, should be considered as required by 21.1.2. [4] 7

Wall piers having ( w/ bw) ≤ 2.5 behave essentially as columns. Section 21.9.8.1 requires that such members satisfy 8 reinforcement and shear strength requirements of 21.6.3 through 21.6.5. Alternative provisions are provided for wall 9 piers having ( w/ bw) > 2.5. [4] 10

The design shear force determined according to 21.6.5.1 may be unrealistically large in some cases. As an 11 alternative, 21.9.8.1(a) permits the design shear force to be determined using load combinations in which the 12 earthquake load effect has been amplified to account for system overstrength. Documents such as the NEHRP 13 provisions,21.4 ASCE/SEI 7,21.1 and the International Building Code21.2 represent the amplified earthquake load effect 14 using the factor Ωo.

[4] 15

Section 21.9.8.2 addresses wall piers at the edge of a wall. Under in-plane shear, inclined cracks can propagate into 16 segments of the wall directly above and below the wall pier. Unless there is sufficient reinforcement in the adjacent 17 wall segments, shear failure within the adjacent wall segments can occur. The length of embedment of the provided 18 reinforcement into the adjacent wall segments should be determined considering both development length 19 requirements and shear strength of the wall segments. See Fig. R21.9.8. [4] 20

R21.10 — Special structural walls constructed using precast concrete 21

R21.10.3 — Add after last paragraph: ACI ITG-5.221.57 defines design requirements for one type of special 22 structural wall constructed using precast concrete and unbonded post-tensioning tendons, and validated for use in 23 accordance with 21.10.3. [34] 24

R21.13 — Members not designated as part of the seismic-force-resisting system 25

This section applies only to structures assigned to SDC D, E, or F. Model building codes, such as the 2006 IBC, 26 require all structural members not designated as a part of the seismic-force-resisting system to be designed to 27 support gravity loads while subjected to the design displacement. For concrete structures, the provisions of 21.13 28 satisfy this requirement for columns, beams, and slabs, and wall piers of the gravity system. The design 29 displacement is defined in 2.2. [4] 30

The principle behind the provisions of 21.1.3 are intended to provide sufficient confinement and shear strength 31 in elements that yield so that they will sustain flexural rather than shear or axial failure. is to allow flexural 32 yielding of columns, beams, and slabs under the design displacement, and to provide sufficient confinement and shear 33 strength in elements that yield. By the provisions of 21.13.2 through 21.13.4 and 21.13.7, columns, and beams, and 34 wall piers, respectively, are assumed to yield if the combined effects of factored gravity loads and design displacements 35 exceed the corresponding strengths specified in those provisions, or if the effects of design displacements are not 36 calculated. Requirements for transverse reinforcement and shear strength vary with the axial load on the member and 37 whether or not the member yields under the design displacement. [4] 38

R21.13.7 — Section 21.9.8 requires that the design shear force be determined according to 21.6.5.1, which in some 39 cases may result in unrealistically large forces. As an alternative, the design shear force can be determined as the 40 product of an overstrength factor and the shear induced when the wall pier is displaced by δu. The overstrength 41 factor Ωo included in documents such as the NEHRP provisions,21.4 ASCE/SEI 7,21.1 and the International Building 42 Code21.2 can be used for this purpose. [4] 43

Table R21.9.1 — Governing Design Provisions for Vertical Wall Segments*[4] 44

3750

1 2 3 4 5 6 7 8 9 10 11 12 13 14

15

* hw is the clear height, w is the horizontal length, and bw is the width of the web of the wall segment. [4] 16

17

Clear height of vertical wall segment / length

of vertical wall segment, (hw/ w)

Length of vertical wall segment / Wall thickness, ( w/bw)

( w/bw) ≤ 2.5 2.5 < ( w/ bw) ≤ 6.0 ( w/ bw) > 6.0

hw/ w < 2.0 Wall Wall Wall

hw/ w ≥ 2.0

Wall pier required to satisfy specified column design

requirements, see 21.9.8.1

Wall pier required to satisfy specified column design requirements or

alternative requirements, see 21.9.8.1

Wall

3751

1

2

3

4

Fig. R21.5.3 — Examples of overlapping hoops and illustration of limit on maximum horizontal spacing of 5 supported longitudinal bars. [31] 6

7

3752

1

Fig. R21.7.4—Effective joint area. [32] 2 3

4 [13] 5

6

3753

Fig R21.9.8—Required horizontal reinforcement in wall segments above and below wall piers at the edge of a wall. [4]

1

3754

CHAPTER 22 — STRUCTURAL PLAIN CONCRETE 1

2

3

4

No changes.

3755

APPENDIX A — STRUT-AND-TIE MODELS 1

2

3 4

No changes.

3756

APPENDIX B — ALTERNATIVE PROVISIONS FOR REINFORCED AND PRESTRESSED CONCRETE FLEXURAL AND COMPRESSION MEMBERS

1

2

3

4 5

6

No change.

3757

APPENDIX C — ALTERNATIVE LOAD AND STRENGTH 1

REDUCTION FACTORS 2

3

CODE 4

C.9.2 — Required strength 5

C.9.2.2 — For structures that also resist W, wind load, or E, the load effects of earthquake, U shall not be 6 less than the larger of Eq. (C.9-1), (C.9-2), and (C.9-3) 7

U = 0.75(1.4D + 1.7L) + (1.61.0W or 1.0E) [6] (C.9-2) 8

and 9

U = 0.9D + (1.61.0W or 1.0E) [6] (C.9-3) 10

Where W has not been reduced by a directionality factor, it shall be permitted to use 1.3W in place of 11 1.6W in Eq. (C.9-2) and (C.9-3). Where W is based on service-level wind loads, 1.6W shall be used in 12 place of 1.0W in Eq. (C.9-2) and (C.9-3). Where E is based on service-level earthquake effectsseismic 13 forces, 1.4E shall be used in place of 1.0E in Eq. (C.9-2) and (C.9-3). [6] 14

C.9.2.3 — For structures that resist H, loads due to weight andlateral pressure of soil, water in soil, or 15 other related materials, U shall not be less than the larger of Eq. (C.9-1) and (C.9-4): [6] 16

17

COMMENTARY 18

19

RC.9.2 — Required strength 20

The wind load equation in ASCE 7-98 and IBC 2000C.1 includes a factor for wind directionality that is equal to 0.85 21 for buildings. The corresponding load factor for wind in the load combination equations was increased accordingly 22 (1.3 /0.85 = 1.53, rounded up to 1.6). The Code allows use of the previous wind load factor of 1.3 when the design 23 wind load is obtained from other sources that do not include the wind directionality factor. ASCE/SEI 7-10 has con-24 verted wind loads to strength level, and reduced the wind load factor to 1.0. ACI 318 requires use of the previous 25 load factor for wind loads, 1.6, when service-level wind loads are used. [6] 26

27

3758

APPENDIX D — ANCHORING TO CONCRETE 1

2

CODE 3

D.1 — Definitions 4

Adhesive —Chemical components formulated from organic polymers, or a combination of organic 5 polymers and inorganic materials that cure when blended together. [2] 6

Adhesive anchor — A post-installed anchor, inserted into hardened concrete with an anchor hole 7 diameter not greater than 1.5 times the anchor diameter, that transfers loads to the concrete by bond 8 between the anchor and the adhesive, and bond between the adhesive and the concrete. [2] 9

Anchor — A steel element either cast into concrete or post-installed into a hardened concrete member 10 and used to transmit applied loads to the concrete., including Cast-in anchors include headed bolts, 11 hooked bolts (J- or L-bolt), and headed studs., Post-installed anchors include expansion anchors, or 12 undercut anchors, and adhesive anchors. Steel elements for adhesive anchors include threaded rods, 13 deformed reinforcing bars, or internally threaded steel sleeves with external deformations. [2] 14

Anchor group — A number of similar anchors of having approximately equal effective embedment depths 15 with each anchor spaced at less than 3hef from one or more adjacent anchors when subjected to tension, or 16 3ca1 from one or more adjacent anchors when subjected to shear. with spacing s between adjacent anchors 17 such that the projected areas overlap. See D.3.1.1. Only those anchors susceptible to the particular failure 18 mode under investigation shall be included in the group. [10] 19

Horizontal and upwardly inclined anchor — An anchor installed in a hole drilled horizontally or in a 20 hole drilled at any orientation above horizontal. [2] 21

Post-installed anchor — An anchor installed in hardened concrete. Expansion anchors, and undercut, 22 and adhesive anchors are examples of post-installed anchors. [2] 23

Projected area — The area on the free surface of the concrete member that is used to represent the 24 larger base of the assumed rectilinear failure surface. See D.5.2.1 and D.6.2.1. [2] 25

Projected influence area — The rectilinear area on the free surface of the concrete member that is used 26 to calculate the bond strength of adhesive anchors. See D.5.5.1. [2] 27

Stretch length — Length of anchor over which inelastic elongations are designed to occur for earthquake 28 loadings. Examples illustrating stretch length are shown in Fig. RD.1.3. [9] 29

30

D.2 — Scope 31

D.2.2 — This appendix applies to both cast-in anchors and to post-installed expansion (torque-controlled 32 and displacement-controlled), undercut, and adhesive anchors. Adhesive anchors shall be installed in 33 concrete having a minimum age of 21 days at time of anchor installation. Specialty inserts, through-bolts, 34 multiple anchors connected to a single steel plate at the embedded end of the anchors, adhesive or grouted 35 anchors, and direct anchors such as powder or pneumatic actuated nails or bolts, are not included in the 36 provisions of Appendix D. Reinforcement used as part of the embedment shall be designed in accordance 37 with other parts of this Code. [2] 38

D.2.3 — Headed studs and headed bolts having a geometry that has been demonstrated to result in a 39 pullout strength in uncracked concrete equal or exceeding 1.4Np (where Np is given by Eq. (D-15)) are 40

3759

included. Hooked bolts that have a geometry that has been demonstrated to result in a pullout strength 1 without the benefit of friction in uncracked concrete equal or exceeding 1.4Np (where Np is given by Eq. 2 (D-16)) are included. Post-installed anchors that meet the assessment requirements of ACI 355.2 are 3 included. The suitability of the post-installed anchor for use in concrete shall have been demonstrated by 4 the ACI 355.2 prequalification tests. [2] 5

D.2.3 — Design provisions are included for the following types of anchors: [2] 6

(a) Headed studs and headed bolts having a geometry that has been demonstrated to result in a 7 pullout strength in uncracked concrete equal to or exceeding 1.4 Np, where Np is given in Eq. (D-8 14); [2] 9

(b) Hooked bolts having a geometry that has been demonstrated to result in a pullout strength 10

without the benefit of friction in uncracked concrete equal to or exceeding 1.4 Np, where Np is 11

given in Eq. (D-15); [2] 12

(c) Post-installed expansion and undercut anchors that meet the assessment criteria of ACI 355.2; 13 and[2] 14

(d) Adhesive anchors that meet the assessment criteria of ACI 355.Y. [2] 15 16

D.3 — General requirements 17

D.3.1.1 — Anchor group effects shall be considered wherever two or more anchors have spacing less 18 than the critical spacing as follows: [2,10] 19

20 21 22 23 24 25 [2,10] 26 Only those anchors susceptible to the particular failure mode under investigation shall be included in the 27 group. [2,10] 28

D.3.3 — Seismic design requirements[9] 29

D.3.3.1 — When aAnchors design includes earthquake forces for in structures assigned to Seismic 30 Design Category C, D, E, or F, shall satisfy the additional requirements of D.3.3.12 through D.3.3.67 shall 31 apply. [9] 32

D.3.3.23 — Post-installed structural anchors shall be qualified for use in cracked concrete and shall 33 have passed the Simulated Seismic Tests earthquake loading in accordance with ACI 355.2 or ACI 34 355.Y. The Ppullout strength Np and steel strength of the anchor in shear Vsa of expansion and undercut 35 anchors shall be based on the results of the ACI 355.2 Simulated Seismic Tests. For adhesive anchors, 36 the steel strength in shear Vsa and the characteristic bond stresses τuncr and τcr shall be based on results of 37 the ACI 355.Y Simulated Seismic Tests. [2,9] 38

D.3.3.3 — The anchor design strength associated with concrete failure modes shall be taken as 39 0.75φNn and 0.75φVn, where φ is given in D.4.4 or D.4.5, and Nn and Vn are determined in accordance with 40 D.5.2, D.5.3, D.5.4, D.6.2, and D.6.3, assuming the concrete is cracked unless it can be demonstrated 41 that the concrete remains uncracked. [9] 42

D.3.3.4 — Anchors shall be designed to be governed by the steel strength of a ductile steel element as 43

Failure mode under investigation Critical spacing

Concrete breakout in tension 3hef

Bond strength in tension 2cNa

Concrete breakout in shear 3ca1

3760

determined in accordance with D.5.1 and D.6.1, unless either D.3.3.5 or D.3.3.6 is satisfied.[9] 1

D.3.3.5 — Instead of D.3.3.4, the attachment that the anchor is connecting to the structure shall be 2 designed so that the attachment will undergo ductile yielding at a force level corresponding to anchor 3 forces no greater than the design strength of anchors specified in D.3.3.3. [9] 4

D.3.3.6 — As an alternative to D.3.3.4 and D.3.3.5, it shall be permitted to take the design strength of 5 the anchors as 0.4 times the design strength determined in accordance with D.3.3.3. For the anchors of 6 stud bearing walls, it shall be permitted to take the design strength of the anchors as 0.5 times the design 7 strength determined in accordance with D.3.3.3. [9] 8

D.3.3.4 Requirements for tensile loading[9] 9

D.3.3.4.1 — Where the tension component of the strength-level earthquake force applied to the anchor or 10 group of anchors is equal to or less than 20 percent of the total factored anchor tensile force, it shall be 11 permitted to design the anchor or group of anchors to satisfy D.5 and Table D.4.1.1. [9] 12

D.3.3.4.2 — Where the tension component of the strength-level earthquake force applied to anchors 13 exceeds 20 percent of the total factored anchor tensile force for the same load combination, anchors and 14 their attachments shall be designed in accordance with D.3.3.4.3. The anchor design tensile strength, 15 φNn,e, shall be determined using D.3.3.4.4. [9] 16

D.3.3.4.3 — Anchors and their attachments shall be designed using one of options (a) through (d): [9] 17

(a) The anchor or group of anchors shall have a concrete-governed design strength in tension not 18 less than 1.2 times the steel-governed design strength of the anchor or group. The concrete-19 governed design strength shall be calculated from D.3.3.4.4 (b), (c) and (d). Anchors shall have a 20 ductile steel element with a stretch length of at least eight anchor diameters unless otherwise 21 determined by analysis. Where anchors are subject to load reversals, the anchor shall be protected 22 against buckling. The ratio of futa/fya shall not be less than 1.3 for threaded connections unless the 23 threaded portions are upset. The upset portions shall not be included in the stretch length. [9] 24

(b) The anchor or group of anchors shall have φNn,e not less than the maximum force that can be 25 transmitted to the anchor or group of anchors based on the development of a ductile yield 26 mechanism in the attachment in flexure, shear, or bearing, or a combination of those conditions, 27 and considering both material overstrength and strain hardening effects for the attachment. [9] 28

(c) The anchor or group of anchors shall have φNn,e not less than the maximum tension that can be 29 transmitted to the anchors by a non-yielding attachment. [9] 30

(d) The anchor or group of anchors shall have φNn,e not less than the maximum tension obtained 31 from design load combinations that include E, with E increased by Ω0 . The anchor design tensile 32 strength shall satisfy Table D.4.1.1 Where adhesive anchors are used to resist sustained tension 33 loads the anchor design tensile strength shall also satisfy Eq. (D-1). [9] 34

D.3.3.4.4 — The anchor design tensile strength for resisting earthquake forces, φNn,e, shall be the 35 lowest design strength in tension of a single anchor or group of anchors as determined from consideration 36 of (a) through (d) and assuming the concrete is cracked unless it can be demonstrated that the concrete 37 remains uncracked: [9] 38

(a) φNsa for a single anchor, or for the most highly stressed individual anchor in a group of anchors, [9] 39

(b) 0.75φNcb or 0.75φNcbg, except that Ncb or Ncbg need not be calculated where anchor reinforcement 40 satisfying D.5.2.9 is provided, [9] 41

3761

(c) 0.75φ Npn for a single anchor, or for the most highly stressed individual anchor in a group of 1 anchors, and [9] 2

(d) 0.75φNsb or 0.75φNsbg [9] 3

where φ is in accordance with D.4.3 or D.4.4. [9] 4

D.3.3.4.5 — Where anchor reinforcement is provided in accordance with D.5.2.9, no reduction in 5 design tension strength beyond that specified in D.5.2.9 shall be required. [9] 6

D.3.3.5 — Requirements for shear loading[9] 7

D.3.3.5.1 — Where the shear component of the strength-level earthquake force applied to the anchor or 8 group of anchors is equal to or less than 20 percent of the total factored anchor shear force, it shall be 9 permitted to design the anchor or group of anchors to satisfy D.6 and the shear strength requirements of 10 D.4.1.1. [9] 11

D.3.3.5.2 — Where the shear component of the strength-level earthquake force applied to anchors 12 exceeds 20 percent of the total factored anchor shear force, anchors and their attachments shall be 13 designed in accordance with D.3.3.5.3. The anchor design shear strength for resisting earthquake forces 14 shall be determined in accordance with D.6.[9] 15

D.3.3.5.3 — Anchors and their attachments shall be designed using one of options (a) through (c): [9] 16

(a) The anchor or group of anchors shall have φVn not less than the maximum force that can be 17 transmitted to the anchor or group of anchors based on the development of a ductile yield 18 mechanism in the attachment in flexure, shear, or bearing, or a combination of those conditions, 19 and considering both material overstrength and strain hardening effects in the attachment. [9] 20

(b) The anchor or group of anchors shall have φVn not less than the maximum shear that can be 21 transmitted to the anchors by a non-yielding attachment. [9] 22

(c) The anchor or group of anchors shall have φVn not less than the maximum shear obtained from 23 design load combinations that include E, with E increased by Ω0 . The anchor design shear strength 24 shall satisfy the shear strength requirements of D.4.1.1. [9] 25

D.3.3.5.4 — Where anchor reinforcement is provided in accordance with D.6.2.9, no reduction in 26 design shear strength beyond that specified in D.6.2.9 shall be required. [9] 27

D.3.3.6 — Single anchors or groups of anchors that are subjected to both tension and shear forces shall 28 be designed to satisfy the requirements of D.7, with φNn,e substituted for φNn.

[9] 29

D.3.3.7 — Anchor reinforcement used in structures assigned to Seismic Design Category C, D, E or F 30 shall be deformed reinforcement satisfying requirements of 21.1.5.2. [9] 31

D.3.4 — Adhesive anchors installed horizontally or upwardly inclined shall be qualified in accordance with 32 ACI 355.Y requirements for sensitivity to installation direction. [2] 33

D.3.5 — For adhesive anchors subjected to sustained tension loading, D.4.1.2 shall be satisfied. For 34 groups of adhesive anchors, Eq. (D-1) shall be satisfied for the anchor that resists the highest sustained 35 tension load. Installer certification and inspection requirements for horizontal and upwardly inclined 36 adhesive anchors subjected to sustained tension loading shall be in accordance with D.9.2.2 through 37 D.9.2.4, respectively. [2] 38

3762

D.3.4D.3.6 — Modification factor λa for lightweight concrete in this appendix shall be in accordance with 1 8.6.1 unless specifically noted otherwise. taken as: [2] 2

Cast-in and undercut anchor concrete failure..................................... 1.0 λ[2] 3

Expansion and adhesive anchor concrete failure ............................... 0.8 λ[2] 4

Adhesive anchor bond failure per Eq. (D-22) ..................................... 0.6 λ[2] 5

where λ is determined in accordance with 8.6.1. It shall be permitted to use an alternate value of λa where 6 tests have been performed and evaluated in accordance with ACI 355.2 or ACI 355.Y. [2] 7

D.4 — General requirements for strength of anchors 8

D.4.1 — Strength design of anchors shall be based either on computation using design models that 9 satisfy the requirements of D.4.2, or on test evaluation using the 5 percent fractile of applicable test 10 results for the following: [2] 11

(a) Steel strength of anchor in tension (D.5.1); 12

(b) Steel strength of anchor in shear (D.6.1); [2] 13

(cb) Concrete breakout strength of anchor in tension (D.5.2); 14

(d) Concrete breakout strength of anchor in shear (D.6.2); [2] 15

(ec) Pullout strength of cast-in, post-installed expansion or undercut anchor in tension (D.5.3); [2] 16

(d) Concrete side-face blowout strength of headed anchor in tension (D.5.4); [2] 17

(e) Bond strength of adhesive anchor in tension (D.5.5); [2] 18

(f) Concrete side-face blowout strength of anchor in tension (D.5.4); and[2] 19

(f) Steel strength of anchor in shear (D.6.1); [2] 20

(g) Concrete breakout strength of anchor in shear (D.6.2); [2] 21

(gh) Concrete pryout strength of anchor in shear (D.6.3). 22

In addition, anchors shall satisfy the required edge distances, spacings, and thicknesses to preclude 23 splitting failure, as required in D.8. 24

D.4.1.1 — The design of anchors, except as noted in D.3.3, shall be in accordance with Table D.4.1.1. [10] 25

D.4.1.1 — For the design of anchors, except as required in D.3.3, [10] 26

φNn ≥ Nua (D-1) [10] 27

φVn ≥ Vua (D-2) [10] 28

29

30

31

32

33

3763

Table D.4.1.1 — Required strength of anchors, except as noted in D.3.3[2,10] 1

2 3 4 5 6 7 8 9 10 11

12 13

14

15

16

17

18

19

20

21

22

D.4.1.2 — For the design of adhesive anchors to resist sustained tension loads, in addition to (D.4.1.1), [2,10] 23

φ ≥ ,0.55 ba ua sN N [2,10] (D-1) 24

where Nba is determined in accordance with D.5.5.2. [2,10] 25

D.4.1.2 — In Eq. (D-1) and (D-2), φNn and φVn are the lowest design strengths determined from all 26 appropriate failure modes. φNn is the lowest design strength in tension of an anchor or group of anchors 27 as determined from consideration of φNsa, φnNpn, either φNsb or φNsbg, and either φNcb or φNcbg. φVn is the 28 lowest design strength in shear of an anchor or a group of anchors as determined from consideration of: 29 φVsa, either φVcb or φVcbg, and either φVcp or φVcpg.

[10] 30

D.4.1.3 — When both Nua and Vua are present, interaction effects shall be considered in accordance with 31 D.4.3.using an interaction expression that results in computation of strength in substantial agreement with 32 results of comprehensive tests. This requirement shall be considered statisfied by D.7.[13] 33

D.4.2.2 — For anchors with diameters not exceeding 42 in., and tensile embedments not exceeding 25 34 in. in depth, the concrete breakout strength requirements shall be considered satisfied by the design 35 procedure of D.5.2 and D.6.2. [35] 36

Failure mode

Single anchor

Anchor group*

Individual anchor in a group

Anchors as a group

Steel strength in tension (D.5.1) φ ≥sa uaN N φ ≥ ,sa ua iN N

Concrete breakout strength in tension (D.5.2)

φ ≥cb uaN N φ ≥ ,cbg ua gN N

Pullout strength in tension (D.5.3) φ ≥pn uaN N φ ≥ ,pn ua iN N

Concrete side-face blowout strength in tension (D.5.4)

φ ≥sb uaN N φ ≥ ,sbg ua gN N

Bond strength of adhesive anchor in tension (D.5.5)

φ ≥a uaN N φ ≥ ,ag ua gN N

Steel strength in shear (D.6.1) φ ≥sa uaV V φ ≥ ,sa ua iV V

Concrete breakout strength in shear (D.6.2)

φ ≥cb uaV V φ ≥ ,cbg ua gV V

Concrete pryout strength in shear (D.6.3)

φ ≥cp uaV V φ ≥ ,cpg ua gV V

* Required strengths of anchors in groups shall resist applicable failure modes for individual anchors and for the

group.[10]

3764

D.4.2.3 — For adhesive anchors with embedment depths 4da ≤ hef ≤ 20da, the bond strength 1 requirements shall be considered satisfied by the design procedure of D.5.5. [2] 2

D.4.3 — Resistance to combined tensile and shear loads shall be considered in design using an interaction 3 expression that results in computation of strength in substantial agreement with results of comprehensive 4 tests. This requirement shall be considered satisfied by D.7. [36] 5

D.4.43 — Strength reduction factor φ for anchors in concrete shall be as follows when the load combinations 6 of 9.2 are used: 7

a) Anchor governed by strength of a ductile steel element 8

i) Tension loads…………………………………………………………………………………………….0.75 9 ii) Shear loads………………………………………………………………………………………………0.65 10

b) Anchor governed by strength of a brittle steel element 11

i) Tension loads…………………………………………………………………………………………….0.65 12 ii) Shear loads………………………………………………………………………………………………0.60 13

c) Anchor governed by concrete breakout, side-face blowout, pullout, or pryout strength 14

Condition A Condition B 15

i) Shear loads 0.75 0.70 16 ii) Tension loads 17 18

Cast-in headed studs, headed bolts, or hooked bolts 0.75 0.70 19

Post-installed anchors with category as determined from ACI 355.2 or ACI 355.X[2] 20

Category 1 0.75 0.65 21 (Low sensitivity to installation and high reliability) 22 23 Category 2 0.65 0.55 24 (Medium sensitivity to installation and medium reliability) 25 26 Category 3 0.55 0.45 27 (High sensitivity to installation and lower reliability) 28

29 Condition A applies where supplementary reinforcement is present except for pullout and pryout strengths. 30

Condition B applies where supplementary reinforcement is not present, and for pullout or pryout strength. 31

D.4.54 — Strength reduction factor φ for anchors in concrete shall be as follows when the load combinations 32 referenced in Appendix C are used: 33

a) Anchor governed by strength of a ductile steel element 34

i) Tension loads…………………………………………………………………………………………0.80 35 ii) Shear loads…………………………………………………………………………………………...0.75 36

b) Anchor governed by strength of a brittle steel element 37

i) Tension loads…………………………………………………………………………………………0.70 38 ii) Shear loads…………………………………………………………………………………………...0.65 39

c) Anchor governed by concrete breakout, side-face blowout, pullout, or pryout strength 40

3765

Condition A Condition B 1

i) Shear loads 0.85 0.75 2 ii) Tension loads 3 4

Cast-in headed studs, headed bolts, or hooked bolts 0.85 0.75 5

Post-installed anchors with category as determined from ACI 355.2 or ACI 355.Y[2] 6

Category 1 0.85 0.75 7 (Low sensitivity to installation and high reliability) 8 9 Category 2 0.75 0.65 10 (Medium sensitivity to installation and medium reliability) 11 12 Category 3 0.65 0.55 13 (High sensitivity to installation and lower reliability) 14

15 Condition A applies where supplementary reinforcement is present except for pullout and pryout strengths. 16

Condition B applies where supplementary reinforcement is not present, and for pullout and pryout strengths. 17

D.5 — Design requirements for tensile loading 18

D.5.1 — Steel strength of anchor in tension 19

D.5.1.2 — The nominal strength of an single anchor or group of anchors in tension, Nsa, shall not 20 exceed[10] 21

Nsa = nAse,Nfuta Nsa = Ase,Nfuta[10] (D-32) 22

where n is the number of anchors in the group, Ase,N is the effective cross-sectional area of an single 23 anchor in tension, in.2, and futa shall not be taken greater than the smaller of 1.9fya and 125,000 psi. [10] 24

D.5.2 — Concrete breakout strength of anchor in tension 25

D.5.2.1 — The nominal concrete breakout strength in tension, Ncb of a single anchor or Ncbg of a single 26 anchor or group of anchors, in tension shall not exceed[2] 27

D.5.2.2 — 28

The value of kc for post-installed anchors shall be permitted to be increased above 17 based on ACI 29 355.2 or ACI 355.Y product-specific tests, but shall in no case exceed 24. [2] 30

Alternatively, for cast-in headed studs and headed bolts with 11 in. ≤ hef ≤ 25 in., Nb shall not exceed 31

Nb = 16λa ′

cf hef

5/3 (D-87) [2] 32

D.5.2.3 — Where anchors are located less than 1.5hef from three or more edges, the value of hef used 33 for the calculation of ANc in accordance with D.5.2.1, as well as in Eq. (D-4) (D-3) through (D-1110) shall 34 be the greater larger of ca,max/1.5 and s/3, one-third of where s is the maximum spacing between anchors 35 within the group. [36] 36

D.5.2.6 — For anchors located in a region of a concrete member where analysis indicates no cracking 37

3766

at service load levels, the following modification factor shall be permitted: 1

ψc,N = 1.25 for cast-in anchors; and 2

ψc,N = 1.4 for post-installed anchors, where the value of kc used in Eq. (D-76) is 17. 3

Where the value of kc used in Eq. (D-76) is taken from the ACI 355.2 or ACI 355.Y product evaluation 4 report for post-installed anchors qualified for use in both cracked and uncracked concrete, the values of kc 5 and ψc,N shall be based on the ACI 355.2 or ACI 355.Y product evaluation report. [2] 6

Where the value of kc used in Eq. (D-76) is taken from the ACI 355.2 or ACI 355.Y product evaluation 7 report for post-installed anchors qualified for use in uncracked concrete, ψc,N shall be taken as 1.0. [2] 8

D.5.3 — Pullout strength of cast-in, and post-installed expansion and undercut anchors in 9 tension[2] 10

D.5.3.1 — The nominal pullout strength of a single cast-in, post-installed expansion, and post-installed 11 undercut anchor in tension, Npn, shall not exceed[2] 12

D.5.5 — Bond strength of adhesive anchor in tension[2] 13

D.5.5.1 — The nominal bond strength in tension, Na of a single adhesive anchor or Nag of a group of 14 adhesive anchors, shall not exceed[2] 15

(a) For a single adhesive anchor: [2]

16

ψ ψ= , ,

Naa ed Na cp Na ba

Nao

AN N

A

(D-18) [2] 17

(b) For a group of adhesive anchors: [2] 18

ψ ψ ψ= , , ,Na

ag ec Na ed Na cp Na baNao

AN N a

A (D-19) [2] 19

Factors ψec,Na, ψed,Na, and ψcp,Na are defined in D.5.5.3, D.5.5.4, and D5.5.5, respectively. ANa is the projected 20

influence area of a single adhesive anchor or group of adhesive anchors that shall be approximated as a 21 rectilinear area that projects outward cNa from the centerline of the adhesive anchor, or in the case of a 22 group of adhesive anchors, from a line through a row of adjacent adhesive anchors. ANa

shall not exceed 23 nANao, where n is the number of adhesive anchors in the group that resist tension loads. ANao is the 24 projected influence area of a single adhesive anchor with an edge distance equal to or greater than cNa:

[2] 25

= 2(2 )Nao NaA c (D-20) [2] 26

where 27

28

τ= 10

1100uncr

Na ac d

(D-21) [2] 29

30

and constant 1100 carries the unit of lb/in.2 [2] 31

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D.5.5.2 — The basic bond strength of a single adhesive anchor in tension in cracked concrete, Nba, 1 shall not exceed[2] 2

λ τ π=ba a cr a efN d h (D-22) [2] 3

The characteristic bond stress, τcr, shall be taken as the 5 percent fractile of results of tests performed 4 and evaluated according to ACI 355.Y. [2] 5

Where analysis indicates cracking at service load levels, adhesive anchors shall be qualified for use in 6 cracked concrete in accordance with ACI 355.Y. [2] 7

For adhesive anchors located in a region of a concrete member where analysis indicates no cracking at 8 service load levels, τuncr

shall be permitted to be used in place of τcr in Eq. (D-22) and shall be taken as the 9

5 percent fractile of results of tests performed and evaluated according to ACI 355.Y. [2] 10

It shall be permitted to use the minimum characteristic bond stress values in Table D.5.5.2 provided (a) 11 through (e) are satisfied: [2] 12

(a) Anchors shall meet the requirements of ACI 355.Y; [2] 13

(b) Anchors shall be installed in holes drilled with a rotary impact drill or rock drill;[2] 14

(c) Concrete at time of anchor installation shall have a minimum compressive strength of 2500 psi; [2] 15

(d) Concrete at time of anchor installation shall have a minimum age of 21 days; [2] 16

(e) Concrete temperature at time of anchor installation shall be at least 50oF. [2] 17

18

19

20

21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37

38 D.5.5.3 — The modification factor for adhesive anchor groups loaded eccentrically in tension, ψec,Na, shall 39 be computed as: [2] 40

ψ =⎛ ⎞

+⎜ ⎟⎝ ⎠

, '

1

1ec Na

N

Na

ec

(D-23) [2] 41

TABLE D.5.5.2 — MINIMUM CHARACTERISTIC BOND STRESSESa,b[2]

Installation and service

environment

Moisture content of concrete at time of anchor installation

Peak in‐service temperature of

concrete

τ cr

τ uncr

°F (psi) (psi)

Outdoor Dry to fully saturated

175 200 650

Indoor Dry 110 300 1000 aWhere anchor design includes sustained tension loading, multiply values of τcr and τuncr by 0.4. bWhere anchor design includes earthquake loads for structures assigned to Seismic Design Category C, D, E,

or F, multiply values of τcr by 0.8 and τuncr by 0.4.

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but ψec,Na shall not be taken greater than 1.0. [2] 1

If the loading on an adhesive anchor group is such that only some adhesive anchors are in tension, only 2 those adhesive anchors that are in tension shall be considered when determining the eccentricity eN′

for 3

use in Eq. (D-23) and for the calculation of Nag according to Eq. (D-19). [2] 4

In the case where eccentric loading exists about two orthogonal axes, the modification factor, ψec,Na, shall 5 be computed for each axis individually and the product of these factors used as ψec,Na in Eq. (D-19). [2] 6

D.5.5.4 — The modification factor for edge effects for single adhesive anchors or adhesive anchor 7 groups loaded in tension, ψed,Na, shall be computed as[2] 8

If ≥a,min Nac c 9

then ψed,Na = 1.0 (D-24) [2] 10

If <a ,min Nac c 11

then ψ = +0 7 0 3 a,mined ,Na

Na

c. .

c

(D-25) [2] 12

D.5.5.5 — The modification factor for adhesive anchors designed for uncracked concrete in accordance 13 with D.5.5.2 without supplementary reinforcement to control splitting, ψcp,Na, shall be computed as: [2] 14

If ≥a ,min acc c 15

then ψcp,Na = 1.0 (D-26) [2] 16

If <a ,min acc c 17

then ψ = a ,mincp ,Na

ac

c

c

(D-27) [2] 18

but ψcp,Na determined from Eq. (D-27) shall not be taken less than Na

ac

cc

where the critical edge distance, 19

cac, is defined in D.8.6. [2] 20

D.6 — Design requirements for shear loading 21

D.6.1 — Steel strength of anchor in shear 22

D.6.1.1 — The nominal strength of an anchor in shear as governed by steel, Vsa, shall be evaluated by 23 calculations based on the properties of the anchor material and the physical dimensions of the anchor. 24 Where concrete breakout is a potential failure mode, the required steel shear strength shall be consistent 25 with the assumed breakout surface. [12] 26

D.6.1.2 — The nominal strength of an single anchor or group of anchors in shear, Vsa, shall not exceed 27 (a) through (c): 28

(a) For cast-in headed stud anchor 29

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Vsa = nAse,Vfuta Vsa = Ase,Vfuta (D-1928) [10] 1

where n is the number of anchors in the group, Ase,V is the effective cross-sectional area of an single 2 anchor in shear, in.2, and futa shall not be taken greater than the smaller of 1.9fya and 125,000 psi. [10] 3

(b) For cast-in headed bolt and hooked bolt anchors and for post-installed anchors where sleeves do 4 not extend through the shear plane 5

Vsa = n0.6Ase,Vfuta Vsa = 0.6Ase,Vfuta (D-2029) [10] 6

where n is the number of anchors in the group, Ase,V is the effective cross-sectional area of an single 7 anchor in shear, in.2, and futa shall not be taken greater than the smaller of 1.9fya and 125,000 psi. [10] 8

D.6.2 — Concrete breakout strength of anchor in shear 9

D.6.2.1 — The nominal concrete breakout strength in shear, Vcb of a single anchor or Vcbg , in shear of a 10 single anchor or group of anchors, shall not exceed: [2] 11

D.6.2.2 — The basic concrete breakout strength in shear of a single anchor in cracked concrete, Vb, 12

shall not exceedbe the smaller of (a) and (b): [35] 13

(a) ( )λ⎛ ⎞⎛ ⎞

′⎜ ⎟= ⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠

0.21.5

17 eb a a c a

a

V d f cdl

(D-2433) [35] 14

where le is the load-bearing length of the anchor for shear: 15

le = hef for anchors with a constant stiffness over the full length of embedded section, such as headed 16 studs and post-installed anchors with one tubular shell over full length of the embedment depth, 17

le = 2da for torque-controlled expansion anchors with a distance sleeve separated from expansion sleeve, 18

and 19

le ≤ 8da in all cases. 20

(b) λ= 1.519 ' ( )b a c aV f c (D-34) [35] 21

D.6.2.3 — For cast-in headed studs, headed bolts, or hooked bolts that are continuously welded to 22 steel attachments having a minimum thickness equal to the greater of 3/8 in. and half of the anchor 23 diameter, the basic concrete breakout strength in shear of a single anchor in cracked concrete, Vb, shall 24 not exceedbe the smaller of Eq. (D-34) and Eq. (D-35): [35] 25

( )λ⎛ ⎞⎛ ⎞

′⎜ ⎟= ⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠

0.21.5

18 eb a a c a

a

V d f cdl (D-2535) [35] 26

where le is defined in D.6.2.2. 27

D.6.2.4 — Where anchors are influenced by three or more edges located in narrow sections of limited 28 thickness such that both edge distances ca2 and thickness ha are less than 1.5ca1, the value of ca1 used for 29 the calculation of AVc in accordance with D.6.2.1 as well as in Eq. (D-2330) through (D-2939) shall not 30 exceed the greatest largest of: ca2/1.5 in either direction, ha/1.5; and one-third of the maximum spacing 31 between anchors within the group. [36] 32

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(a) ca2/1.5, where ca2 is the largest edge distance; [36] 1

(b) ha/1.5; and[36] 2

(c) s/3, where s is the maximum spacing perpendicular to direction of shear, between anchors within a 3 group. [36] 4

D.6.2.6 — The modification factor for edge effect for a single anchor or group of anchors loaded in 5 shear, ψed,V, shall be computed as follows using the smaller value of ca2.

[36] 6

D.6.3 — Concrete pryout strength of anchor in shear 7

D.6.3.1 — The nominal pryout strength, Vcp for a single anchor or Vcpg for a group of anchors, shall not 8

exceed: [2] 9

(a) For a single anchor 10

Vcp = kcpNcb Vcp = kcpNcp (D-3040) [2] 11

For cast-in, expansion, and undercut anchors, Ncp shall be taken as Ncb determined from Eq. (D-3), and 12 for adhesive anchors, Ncp

shall be the lesser of Na determined from Eq. (D-18) and Ncb determined from 13 Eq. (D-3). [2] 14

(b) For a group of anchors 15

Vcpg = kcpNcbg Vcpg = kcpNcpg 16 (D-3141) [2] 17

For cast-in, expansion, and undercut anchors, Ncpg shall be taken as Ncbg determined from Eq. (D-4), and 18

for adhesive anchors Ncpg shall be the lesser of Nag

determined from Eq. (D-19) and Ncbg determined from 19

Eq. (D-4). [2] 20

whereIn Eq. (D-40) and (D-41), kcp = 1.0 for hef < 2.5 in.; and kcp = 2.0 for hef ≥ 2.5 in. [2] 21

22 Ncb and Ncbg shall be determined from Eq. (D-4) and (D-5), respectively. [2] 23

24

D.8 — Required edge distances, spacings, and thicknesses to preclude splitting 25 failure 26

Minimum spacings and edge distances for anchors and minimum thicknesses of members shall conform 27 to D.8.1 through D.8.6, unless supplementary reinforcement is provided to control splitting. Lesser values 28 from product-specific tests performed in accordance with ACI 355.2 or ACI 355.Y shall be permitted. [2] 29

D.8.1 — Unless determined in accordance with D.8.4, minimum center-to-center spacing of anchors shall 30 be 4da for untorqued cast-in anchors that will not be torqued, and 6da for torqued cast-in anchors and 31 post-installed anchors.[13] 32

D.8.2 — Unless determined in accordance with D.8.4, minimum edge distances for cast-in headed 33 anchors that will not be torqued shall be based on specified cover requirements for reinforcement in 7.7. 34 For cast-in headed anchors that will be torqued, the minimum edge distances shall be 6da.

[37] 35

D.8.3 — Unless determined in accordance with D.8.4, minimum edge distances for post-installed anchors 36

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shall be based on the greater of specified cover requirements for reinforcement in 7.7, or minimum edge 1 distance requirements for the products as determined by tests in accordance with ACI 355.2 or ACI 2 355.Y, and shall not be less than 2.0 timestwice the maximum aggregate size. In the absence of product-3 specific ACI 355.2 or ACI 355.Y test information, the minimum edge distance shall be taken as not be 4 less than: [2] 5

Adhesive anchors…...…………………………………...……………………………………………………6da

[2] 6

Undercut anchors……………………………………………………………………………………………….6da 7

Torque-controlled anchors……………………………………………………………………………………..8da 8

Displacement-controlled anchors…………………………………………………………………………….10da 9

D.8.4 — For anchors where installation does not produce a splitting force and that will not be remain 10 untorqued, if the edge distance or spacing is less than those specified in D.8.1 to D.8.3, calculations shall be 11 performed by substituting for da a smaller value da′ that meets the requirements of D.8.1 to D.8.3. Calculated 12 forces applied to the anchor shall be limited to the values corresponding to an anchor having a diameter of da′.

[13] 13

D.8.5 — Unless determined from tests in accordance with ACI 355.2, Tthe value of hef for an expansion or 14 undercut post-installed anchor shall not exceed the greater of 2/3 of the member thickness, ha, and the 15 member thickness minus 4 in. [2] 16

D.8.6 — Unless determined from tension tests in accordance with ACI 355.2 or ACI 355.Y, the critical 17 edge distance, cac, shall not be taken less than: [2] 18

Adhesive anchors…………………………………………………………………………………………….2hef

[2] 19 Undercut anchors…………………………………………………………………………………………….2.5hef 20 Torque-controlled expansion anchors…………………………………………………………………….4hef

[2]

21 Displacement-controlled expansion anchors……………………………………………………………..4hef

[2]

22

D.9 — Installation and inspection of anchors[2] 23

D.9.1 — Anchors shall be installed by qualified personnel in accordance with the contract documents 24 project drawings and project specifications. The contract documents shall require installation of post-25 installed anchors in accordance with the manufacturer’s printed instructions. Installation of adhesive 26 anchors shall be performed by personnel trained to install adhesive anchors. [2] 27

D.9.2 — Installation of anchors shall be inspected in accordance with 1.3 and the general building code. 28 Adhesive anchors shall be subject to the following additional requirements: [2] 29

D.9.2.1 — For adhesive anchors, the contract documents shall specify proof loading where required in 30 accordance with ACI 355.Y. The contract documents shall also specify all parameters associated with the 31 characteristic bond stress used for the design according to D.5.5 including minimum age of concrete, 32 concrete temperature range, moisture condition of concrete at time of installation, type of lightweight 33 concrete if applicable, and requirements for hole drilling and preparation. [2] 34

D.9.2.2 — Installation of adhesive anchors horizontally or upwardly inclined to support sustained 35 tension loads shall be performed by personnel certified by an applicable certification program. 36 Certification shall include written and performance tests in accordance with the ACI/CRSI Adhesive 37 Anchor Installer Certification program, or equivalent. [2] 38

D.9.2.3 — The acceptability of certification other than the ACI/CRSI Adhesive Anchor Installer 39 Certification shall be the responsibility of the licensed design professional. [2] 40

D.9.2.4 — Adhesive anchors installed in horizontal and upwardly inclined orientations to resist 41 sustained tension loads shall be continuously inspected during installation by an inspector specially 42

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approved for that purpose by the building official. The special inspector shall furnish a report to the 1 licensed design professional and building official that the work covered by the report has been performed 2 and that the materials used and the installation procedures used conform with the approved contract 3 documents and the manufacturer’s printed installation instructions. [2] 4

5

COMMENTARY 6

RD.1 — Definitions 7

Adhesive—Organic polymers used in adhesives can include, but are not limited to, epoxies, polyurethanes, 8 polyesters, methyl methacrylates, and vinyl esters. 9

Adhesive anchor — The design model included in Appendix D for adhesive anchors is based on the behavior of 10 anchors with hole diameters not exceeding 1.5 times the anchor diameter. Anchors with hole diameters exceeding 11 1.5 times the anchor diameter behave differently and are therefore excluded from the scope of Appendix D and ACI 12 355.Y. To limit shrinkage and reduce displacement under load, most adhesive anchor systems require the annular 13 gap to be as thin as practical while still maintaining sufficient clearance for insertion of the anchor element in the 14 adhesive-filled hole and ensuring complete coverage of the anchor area. The annular gap for reinforcing bars is 15 generally larger than that for threaded rods. The required hole size is provided in the manufacturer's printed 16 installation instructions. [2] 17

Brittle steel element and ductile steel element — The 14 percent elongation should be measured over the gauge 18 length specified in the appropriate ASTM standard for the steel. [2] 19

Ductile steel element — The 14 percent elongation should be measured over the gauge length specified in the 20 appropriate ASTM standard for the steel. [2] 21

Horizontal and upwardly inclined anchor — Fig. RD.1.2 illustrates the potential hole orientations for horizontal 22 and upwardly inclined anchors. [2] 23

Stretch length — Length of anchor over which inelastic elongations are designed to occur for earthquake loadings. 24 Examples illustrating stretch length are shown in Fig. RD.1.3. [9] 25

RD.2 — Scope 26

RD.2.2 — Provisions for design of adhesive anchors were added in the 2011 Code. Adhesive anchors are 27 particularly sensitive to a number of factors including installation direction and loading type. Where adhesive 28 anchors are used to resist sustained tension, the provisions include testing requirements for horizontal and upwardly 29 inclined installations in D.3.4 and design and certification requirements for sustained tension load cases in D.3.5 and 30 D.9.2.2 through D.9.2.4, respectively. Adhesive anchors qualified in accordance with ACI 355.Y are tested in concrete31 with compressive strengths within two ranges: 2500 to 4500 psi and 6500 to 8500 psi. While bond strength is in 32 general not highly sensitive to concrete compressive strength, it is sensitive to the age of the concrete during the 33 initial curing period. For this reason, a minimum concrete age of 21 days is specified for the provisions of Appendix 34 D to be applicable. [2] 35

The wide variety of shapes and configurations of specialty inserts precludes prescription of generalized tests and 36 design equations. Specialty inserts are not covered by Appendix D provisions. makes it difficult to prescribe 37 generalized tests and design equations for many insert types. Hence, they have been excluded from the scope of 38 Appendix D. Adhesive anchors are widely used and can perform adequately. At this time, however, such anchors are 39 outside the scope of this appendix. [2] 40

RD.2.3 — Typical cast-in headed studs and headed bolts with geometries consistent with ANSI/ASME B1.1,D.1 41 B18.2.1,D.2 and B18.2.6D.3 have been tested and proven to behave predictably, so calculated pullout values strengths are 42

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acceptable.[2] 1

Post-installed anchors do not have predictable pullout strengths capacities, and therefore qualification tests to 2 establish the pullout strengths per ACI 355.2 are required to be tested. For a post-installed anchor to be used in 3 conjunction with the requirements of this appendix, the results of the ACI 355.2 tests have to indicate that pullout 4 failures exhibit an acceptable load-displacement characteristic or that pullout failures are precluded by another failure 5 mode. For adhesive anchors, the characteristic bond stress and suitability for structural applications are established 6 by testing in accordance with ACI 355.Y. [2] 7

RD.3 — General requirements 8

RD.3.3 — Unless D.3.3.4.1 or D.3.3.5.1 apply all anchors in structures assigned to Seismic Design Categories C, D, 9 E, or F are required to satisfy the additional requirements of D.3.3.1 through D.3.3.7 regardless of whether 10 earthquake loads are included in the controlling load combination for the anchor design. In addition, all Ppost-11 installed structural anchors in structures assigned to are required to be qualified for Seismic Design Categories C, D, 12 E, or F must meet the requirements by demonstrating the ability to undergo large displacements through several 13 cycles as specified in the seismic simulation tests of ACI 355.2 or ACI 355.Y for prequalification of anchors to 14 resist earthquake loads. Because ACI 355.2 excludes plastic hinge zones, Appendix D is not applicable to the design 15 of anchors in plastic hinge zones under seismic forces. In addition, the design of anchors for earthquake forces is 16 based on a more conservative approach by the introduction of 0.75 factor on the design strength φNn and φVn for the 17 concrete failure modes, and by requiring the system to have adequate ductility. Ideally, for tension loadings, anchor 18 strength should be governed by ductile yielding of a the ductile steel element of the anchor. If the anchor cannot 19 meet these specified ductility requirements of D.3.3.4.3(a), then either the attachment isshould be either designed to 20 yield or the calculated anchor strength is substantially reduced to minimize the possibility of a brittle failure if it is 21 structural or light gage steel, or designed to crush if it is wood. If ductility requirements of D.3.3.4.3(a) are satisfied 22 then any attachments to the anchor should be designed not to yield. In designing attachments using yield mechanisms 23 to provide for adequate ductility, as permitted by D.3.3.4.3(b) and D.3.3.5.3(a), the ratio of specified yield strength to 24 expected design strength for the material of the attachment should be considered in determining the design force. A 25 connection element could yield only to result in a secondary failure as one or more elements strain harden and fail if the 26 design strength is excessive when compared to the yield strength. The value used for the expected strength should consider 27 both material overstrength and strain-hardening effects. For example, the material in a connection element could yield and, 28 due to an increase in its strength with strain hardening, cause a secondary failure of a sub-element or place extra force or 29 deformation demands on the anchors. For a structural steel attachment, if only the specified yield strength of the steel is30 known, the expected strength should be taken as about 1.5 times the specified yield strength. If the actual yield strength of 31 the steel is known the expected strength should be taken as about 1.25 times the actual yield strength. [9] 32

Under seismic conditions, the direction of shear may not be predictable. The full shear force should be assumed in 33 any direction for a safe design. 34

RD.3.3.12 — Section 3.1 of ACI 355.2 specifically states that the seismic test procedures do not simulate the 35 behavior of anchors in plastic hinge zones. The design provisions in Appendix D do not apply for anchors in plastic 36 hinge zones. The possible higher levels of cracking and spalling in plastic hinge zones are beyond the damage 37 statesconditions for which Appendix D is applicable for which the nominal concrete-governed strength values in 38 Appendix D are applicable. Plastic hinge zones are considered to extend a distance equal to twice the member depth 39 from any column or beam face, and also include any other sections in walls, frames and slabs where yielding of 40 reinforcement is likely to occur as a result of lateral displacements. [9] 41

Where anchors must be located in plastic hinge regions, they should be detailed so that the anchor forces are 42 transferred directly to anchor reinforcement that is specifically designed to carry the anchor forces into the body of 43 the member beyond the anchorage region. Configurations that rely on concrete tensile strength should not be used. [9] 44

RD.3.3.23 — Anchors that are not suitable for use in cracked concrete should not be used to resist seismic 45 earthquake loads. Qualification of post-installed anchors for use in cracked concrete is an integral part of the 46 qualification for resisting earthquake loads in ACI 355.2 and ACI 355.Y. The design values obtained from the 47 Simulated Seismic Tests of ACI 355.2 and ACI 355.Y are expected to be less than those for static load applications. [9] 48

RD.3.3.3 — The anchor strength associated with concrete failure modes is to account for increased damage states 49

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in the concrete resulting from seismic actions. Because seismic design generally assumes that all or portions of the 1 structure are loaded beyond yield, it is likely that the concrete is cracked throughout for the purpose of determining the 2 anchor strength unless it can be demonstrated that the concrete remains uncracked. [9] 3

RD.3.3.4 — Ductile steel anchor elements are required to satisfy the requirements of D.1, Ductile Steel Element. 4 For anchors loaded with a combination of tension and shear, the strength in all loading directions must be controlled 5 by the steel strength of the ductile steel anchor element. [9] 6

RD.3.3.6 — As a matter of good practice, a ductile failure mode in accordance with D.3.3.4 or D.3.3.5 should be 7 provided for in the design of the anchor or the load should be transferred to anchor reinforcement in the concrete. 8 Where this is not possible due to geometric or material constraints, D.3.3.6 permits the design of anchors for non-9 ductile failure modes at a reduced permissible strength to minimize the possibility of a brittle failure. The attachment 10 of light frame stud walls typically involves multiple anchors that allow for load redistribution. This justifies the use 11 of a less conservative factor for this case. [9] 12

RD.3.3.4.1 — The requirements of D.3.3.4.3 need not apply where the applied earthquake forces are a 13 small fraction of the total factored tension force. [9] 14

RD.3.3.4.2 — If the ductile steel element is ASTM A36 or ASTM A307 steel, the futa /fya value is typically 15 about 1.5 and the anchor can stretch considerably before rupturing at the threads. For other steels, calculations may 16 need to be made to ensure that a similar behavior can occur. RD.5.1.2 provides additional information on the steel 17 properties of anchors. Provision of upset threaded ends, whereby the threaded end of the rod is enlarged to 18 compensate for the area reduction associated with threading, can ensure that yielding occurs over the stretch length 19 regardless of the ratio of the yield to ultimate strength of the anchor. [9] 20

RD.3.3.4.3 — Four options are provided for determining the required anchor or attachment strength to 21 protect against non-ductile tension failure: [9] 22

In option (a) anchor ductility requirements are imposed and the required anchor strength is that determined using 23 strength-level earthquake forces acting on the structure. ResearchD.7,D.8 has shown that if the steel of the anchor yields 24 before the concrete anchorage fails, no reduction in the anchor tensile strength is needed for earthquake loadings. 25 Ductile steel anchors should satisfy the definition for ductile steel elements in D.1. [9] 26

For some structures, anchors provide the best locations for energy-dissipation in the nonlinear range of response. 27 The stretch length of the anchor affects the lateral displacement capacity of the structure and therefore that length 28 needs to be sufficient such that the displacement associated with the design-basis earthquake can be achievedD.9 . 29 Observations from earthquakes indicate that the provision of a stretch length of eight anchor diameters results in 30 good structural performance. Where the required stretch length is calculated the relative stiffness of the connected 31 elements needs to be considered. When an anchor is subject to load reversals, and its yielding length outside the 32 concrete exceeds six anchor diameters, buckling of the anchor in compression is likely. Buckling can be restrained 33 by placing the anchor in a tube. However, care must be taken that the tube does not share in resisting the tensile load 34 assumed to act on the anchor. [9] 35

In option (b) the anchor is designed for the tension force associated with the expected strength of the metal or 36 similar material of the attachment. For option (b), as discussed in RD.3.3, care must be taken in design to consider 37 the consequences of potential differences between the specified yield strength and the expected strength of the 38 attachment. An example is 21.4.3 for the design of connections of intermediate precast walls where a connection not 39 designed to yield should develop at least 1.5Sy, where Sy is the nominal strength of the yielding element based on its 40 specified yield strength. Similarly steel design manuals require structural steel connections that are designated non-41 yielding and part of the seismic load path to have design strengths that exceed a multiple of the nominal strength. 42 That multiple depends on a factor relating the likely actual to specified yield strength of the material and an 43 additional factor exceeding unity to account for material strain hardening. For attachments of cold-formed steel or 44 wood, similar principles should be used for determining the expected strength of the attachment in order to 45 determine the required strength of the anchorage. [9] 46

Additional guidance on the use of options (a) through (d) is provided in the 2009 NEHRP ProvisionsD.9. The design 47 of anchors in accordance with option (a) should be used only where the anchor yield behavior is well defined and 48 where the interaction of the yielding anchor with other elements in the load path has been adequately addressed. For 49 the design of anchors per option (b), the force associated with yield of a steel attachment, such as an angle, 50 baseplate, or web tab, should be the expected strength, rather than the specified yield strength of the steel. Option (c) 51

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may apply to a variety of special cases, such as the design of sill bolts where the crushing of the wood limits the 1 force that can be transferred to the bolt, or where the provisions of AISC 341, Seismic Provisions for Structural Steel 2 BuildingsD.10, specify loads based on member strengths. [9] 3

RD.3.3.4.4 — The reduced anchor nominal tensile strengths associated with concrete failure modes is to 4 account for increased cracking and spalling in the concrete resulting from seismic actions. Because seismic design 5 generally assumes that all or portions of the structure are loaded beyond yield, it is likely that the concrete is cracked 6 throughout for the purpose of determining the anchor strength. In locations where it can be demonstrated that the 7 concrete does not crack, uncracked concrete may be assumed for determining the anchor strength as governed by 8 concrete failure modes. [9] 9

RD.3.3.4.5 — Where anchor reinforcement as defined in D.5.2.9 and D.6.2.9 is used, with the properties as 10 defined in 21.1.5.2, no separation of the potential breakout prism from the substrate is likely to occur provided the 11 anchor reinforcement is designed for a load greater than the concrete breakout strength. [9] 12

RD.3.3.5 — Where the shear component of the earthquake force applied to the anchor exceeds 20 percent of the 13 total anchor shear force, three options are recognized for determining the required shear strength to protect the 14 anchor or group of anchors against premature shear failure. There is no option corresponding to option (a) of 15 D.3.3.4.3 because the cross section of the steel element of the anchor cannot be configured so that steel failure in 16 shear provides any meaningful degree of ductility. [9] 17

Design of the anchor or group of anchors for the strength associated with force-limiting mechanisms under option 18 (b), such as the bearing strength at holes in a steel attachment or the combined crushing and bearing strength for 19 wood members may be particularly relevant. Tests on typical anchor bolt connections for wood framed shear 20 wallsD.11 showed that wood components attached to concrete with minimum edge distances exhibited ductile 21 behavior. Wood “yield” (crushing) was the first limiting state and resulted in nail slippage in shear. Nail slippage 22 combined with bolt bending provided the required ductility and toughness for the shear walls and limited the loads 23 acting on the bolts. Procedures for defining bearing and shear limit states for connections to cold formed steel are 24 described in AISI S100-07D.12 and examples of strength calculations are provided in the AISI Cold-Formed Steel 25 Design Manual. In such cases, consideration should be given to whether exceedance of the bearing strength may 26 lead to tearing and an unacceptable loss of connectivity. Where anchors are located far from edges it may not be 27 possible to design such that anchor reinforcement controls the anchor strength. In such cases anchors should be 28 designed for overstrength in accordance with option (c). [9] 29

RD.3.3.5.1 — The requirements of D.3.3.5.3 need not apply where the applied earthquake forces are a small 30 fraction of the total factored shear force. [9] 31

RD.3.4 — ACI 355.Y includes optional tests to confirm the suitability of adhesive anchors for horizontal and 32 upwardly inclined installations. [2] 33

RD.3.5 — For adhesive anchors subjected to sustained tension loading, an additional calculation for the sustained 34 portion of the factored load for a reduced bond resistance is required to account for possible bond strength 35 reductions under sustained load. The resistance of adhesive anchors to sustained tension load is particularly 36 dependent on correct installation, including hole cleaning, adhesive metering and mixing, and prevention of voids in 37 the adhesive bond line (annular gap). In addition, care should be taken in the selection of the correct adhesive and 38 bond strength for the expected conditions on-site such as the concrete condition during installation (dry or saturated, 39 cold or hot), the drilling method used (rotary impact drill/rock drill or core drill), and anticipated in-service 40 temperature variations in the concrete. Installer certification and inspection requirements associated with the use of 41 adhesive anchors for horizontal and upwardly inclined installations to resist sustained tension loads are addressed in 42 D.9.2.2 through D.9.2.4. [2] 43

Adhesive anchors are particularly sensitive to installation direction and loading type. Adhesive anchors installed 44 overhead that resist sustained tension loads are of concern since previous applications of this type have led to 45 failures. Other anchor types may be more appropriate for such cases. Where adhesive anchors are used in overhead 46 applications subjected to sustained tension loading, it is essential to meet test requirements of ACI 355.Y for 47 sensitivity to installation direction, use certified installers, and require special inspection. [2] 48

RD.3.6 — The number of tests available to establish the strength of anchors in lightweight concrete is limited. 49 Lightweight concrete tests of cast-in headed studs indicate that the present reduction factor λ adequately captures the 50

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influence of lightweight concrete.D.13,D.14 Anchor manufacturer data developed for evaluation reports on both post-1 installed expansion and adhesive anchors indicate that a reduced λ is needed to provide the necessary safety factor for 2 the respective design strength. ACI 335.2 and ACI 355.Y provide procedures whereby a specific value of λa can be 3 used based on testing, assuming the lightweight concrete is similar to the reference test material. [2] 4

5 RD.3.5RD.3.7 — A limited number of tests of cast-in-place and post-installed anchors in high-strength concreteD.715 6 indicate that the design procedures contained in this appendix become unconservative, particularly for cast-in 7 anchors in concrete with compressive strengths in the range of 11,000 to 12,000 psi. Until further tests are available, 8 an upper limit on fc′ of 10,000 psi has been imposed in the design of cast-in-place anchors. This limitation is 9 consistent with Chapters 11 and 12. The companion ACI 355.2 and ACI 355.Y does not require testing of post-10 installed anchors in concrete with fc′ greater than 8000 psi. because sSome post-installed expansion anchors may have 11 difficulty expanding in very high-strength concretes and the bond strength of adhesive anchors may be negatively 12 affected by very high-strength concrete. Because of this Therefore, fc′ is limited to 8000 psi in the design of post-13 installed anchors unless testing is performed. [2] 14

RD.4 — General requirements for strength of anchors 15

RD.4.1 — This section provides requirements for establishing the strength of anchors to in concrete. The various 16 types of steel and concrete failure modes for anchors are shown in Fig. RD.4.1(a) and RD.4.1(b). Comprehensive 17 discussions of anchor failure modes are included in References D.8 16 to D.1018, D.19 and D.20. Tension failure 18 modes related to concrete capacity include concrete breakout failure in D.5.2 (applicable to all anchor types), pullout 19 failure in D.5.3 (applicable to cast-in anchors and post-installed expansion and undercut anchors), side-face blowout 20 failure in D.5.4 (applicable to headed anchors), and bond failure in D.5.5 (applicable to adhesive anchors). Any 21 model that complies with the requirements of D.4.2 and D.4.3 can be used to establish the concrete-related strengths. 22 For anchors such as headed bolts, headed studs, and post-installed anchors, the concrete breakout design methods of 23 D.5.2 and D.6.2 are acceptable. The anchor strength is also dependent on the pullout strength of D.5.3, the side-face 24 blowout strength of D.5.4, and the minimum spacings and edge distances of D.8. Shear failure modes related to 25 concrete capacity include concrete breakout failure and concrete pryout in D.6.2 and D.6.3, respectively (applicable 26 to all anchor types). Any model that complies with the requirements of D.4.1.3 and D.4.2 can be used to establish 27 the concrete-related strengths. Additionally, anchor tensile and shear strengths are limited by the minimum spacings 28 and edge distances of D.8 as required to preclude splitting. The design of anchors for tension post-installed anchors 29 recognizes that the strength of anchors is sensitive to appropriate installation; installation requirements are included in 30 D.9. Some post-installed anchors are less sensitive to installation errors and tolerances. This is reflected in varied φ-31 factors, given in D.4.3 and D.4.4, based on the assessment criteria of ACI 355.2 and ACI 355.Y. [2,10,13] 32

Test procedures can also be used to determine the single-anchor breakout strength in tension and in shear. The test 33 results, however, are required to be evaluated on a basis statistically equivalent to that used to select the values for 34 the concrete breakout method “considered to satisfy” provisions of D.4.2. The basic strength cannot be taken 35 greater than the 5 percent fractile. The number of tests has to be sufficient for statistical validity and should be 36 considered in the determination of the 5 percent fractile. 37

Under combined tension and bending, individual anchors in a group are subjected to different magnitude tensile 38 forces. Similarly, under combined shear and torsion, individual anchors in a group are subjected to different 39 magnitude shear forces. Table D.4.1.1 includes requirements to design single anchors and individual anchors in a 40 group to safeguard against all potential failure modes. For steel and pullout failure modes, the most highly stressed 41 anchor in the group should be checked to ensure it has sufficient capacity to carry its required load, whereas for 42 concrete breakout, the anchors should be checked as a group. Elastic analysis or plastic analysis of ductile anchors 43 as described in D.3.1 may be used to determine the loads carried by each anchor. [10] 44

RD.4.1.2 — The 0.55 factor used for the additional calculation for sustained loads is correlated with ACI 355.Y test 45 requirements and provides satisfactory performance of adhesive anchors under sustained tension loads when used in 46 accordance with ACI 355.Y. Product evaluation according to ACI 355.Y is based on sustained tension loading being 47 present for a minimum of 50 years at a standard temperature of 70o F and a minimum of ten years at a temperature of 48 110o F. For longer life spans (i.e., for example, > 50 years) or higher temperatures, lower factors should be 49 considered. [2] 50

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RD.4.1.3 and RD.4.2 and RD.4.3 — D.4.1.3 and D.4.2 and D.4.3 establish the performance factors for which 1 anchor design models are required to be verified. Many possible design approaches exist and the user is always 2 permitted to “design by test” using D.4.2 as long as sufficient data are available to verify the model.[13] 3

The method for concrete breakout design included as “considered to satisfy” D.4.2 was developed from the Concrete 4 Capacity Design (CCD) Method,D.17, D.18 which was an adaptation of the κ MethodD.25, D.26 and is considered to be accurate, 5 relatively easy to apply, and capable of extension to irregular layouts. The CCD Method predicts the strength of an 6 anchor or group of anchors by using a basic equation for tension, or for shear for a single anchor in cracked concrete, 7 and multiplied by factors that account for the number of anchors, edge distance, spacing, eccentricity, and absence of 8 cracking. Experimental and numerical investigations have demonstrated the applicability of the CCD method to 9 adhesive anchors as well.D.19[2,35] 10

The breakout strength calculations are based on a model suggested in the κ Method. It is consistent with a breakout prism 11 angle of approximately 35 degrees [Fig. RD.4.2 (a) and (b)]. [35] 12

RD.4.2.1 — 13

References D.816, D.1121, D.1222, D.1323, and D.1424 provide information regarding the effect of reinforcement on the 14 behavior of anchors. The effect of reinforcement is not included in the ACI 355.2 and ACI 355.Y anchor acceptance 15 tests or in the concrete breakout calculation method of D.5.2 and D.6.2. The beneficial effect of supplementary 16 reinforcement is recognized by the Condition A φ-factors in D.4.4 3 and D.4.54. Anchor reinforcement may be provided 17 instead of calculating breakout strength using the provisions of Chapter 12 in conjunction with D.5.2.9 and D.6.2.9. [2] 18

RD.4.2.2 — The method for concrete breakout design included as “considered to satisfy” D.4.2 was developed from 19 the Concrete Capacity Design (CCD) Method,D.9,D.10which was an adaptation of the κ MethodD.15,D.16and is considered to 20 be accurate, relatively easy to apply, and capable of extension to irregular layouts. The CCD Method predicts the 21 strength of an anchor or group of anchors by using a basic equation for tension, or for shear for a single anchor in 22 cracked concrete, and multiplied by factors that account for the number of anchors, edge distance, spacing, eccentricity, 23 and absence of cracking. The limitations on anchor size and embedment length are diameter is based on the current 24 range of test data. In the 2002 through 2008 editions of the Code, there were limitations on the diameter and 25 embedment of anchors to compute the concrete breakout strength. These limitations were necessitated by the lack of 26 test results on anchors with diameter larger than 2 in. and embedment length longer than 24 inches. In 2011, limitations 27 on anchor diameter and embedment length were revised to limit the diameter to 4 in. diameter based on the results of 28 tension and shear tests on large diameter anchors with deep embedmentsD.27, D.28. These tests included 4.25 in. diameter 29 anchors embedded 45 in. in tension tests and 3.5 in. diameter anchors in shear tests. The reason for this 4 in. diameter 30 limit is that the largest diameter anchor in ASTM F1554 Standard Specification for Anchor Bolts, Steel, 36, 55, and 31 105-ksi Yield Strength is 4 in. while other ASTM specifications permit up to 8 in. diameter anchors that have not been 32 tested to ensure applicability of the D.5.2 and D.6.2 concrete breakout provisions. [35] 33

The breakout strength calculations are based on a model suggested in the κ Method. It is consistent with a breakout prism 34 angle of approximately 35 degrees [Fig. RD.4.2.2(a) and (b)]. [35] 35

RD.4.2.3 — ACI 355.Y limits the embedment depth of adhesive anchors to 4da ≤ hef ≤ 20da, which represents the 36 theoretical limits of the bond modelD.19. [2] 37

RD.4.4 3 — 38

The ACI 355.2 tests for sensitivity to installation procedures determine the reliability category appropriate for a 39 particular expansion or undercut anchoring device. In the ACI 355.2 tests for expansion and undercut anchors, the 40 effects of variability in anchor torque during installation, tolerance on drilled hole size, and energy level used in setting 41 anchors are considered;, and for expansion and undercut anchors approved for use in cracked concrete, increased crack 42 widths are considered. ACI 355.Y tests for sensitivity to installation procedures determine the category for a 43 particular adhesive anchor system considering the influence of adhesive mixing and the influence of hole 44 cleaning in dry, saturated and water-filled/underwater bore holes. The three categories of acceptable post-45 installed anchors are: [2] 46

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RD.5 — Design requirements for tensile loading 1

RD.5.1 — Steel strength of anchor in tension 2

RD.5.1.2 — The nominal strength of anchors in tension is best represented as a function of futa rather than fya 3 because the large majority of anchor materials do not exhibit a well-defined yield point. The American Institute of 4 Steel Construction (AISC) has based tension strength of anchors on Ase,Nfuta since the 1986 edition of their 5 specifications. The use of Eq. (D-32) with 9.2 load factors and the φ-factors of D.4.43 give design strengths 6 consistent with the AISC Load and Resistance Factor Design Specifications.D.1931 7

The limitation of 1.9fya on futa is to ensure that, under service load conditions, the anchor does not exceed fya. The 8 limit on futa of 1.9fya was determined by converting the LRFD provisions to corresponding service level conditions. 9 For Section 9.2, the average load factor of 1.4 (from 1.2D + 1.7L) divided by the highest φ-factor (0.75 for tension) 10 results in a limit of futa/fya of 1.4/0.75 = 1.87. For Appendix C, the average load factor of 1.55 (from 1.4D + 1.7L), 11 divided by the highest φ-factor (0.80 for tension), results in a limit of futa/fya of 1.55/0.8 = 1.94. For consistent 12 results, the serviceability limitation of futa was taken as 1.9fya. If the ratio of futa to fya exceeds this value, the 13 anchoring may be subjected to service loads above fya under service loads. Although not a concern for standard 14 structural steel anchors (maximum value of futa/fya is 1.6 for ASTM A307), the limitation is applicable to some 15 stainless steels. 16

For post-installed anchors having a reduced cross-sectional area anywhere along the anchor length, such as wedge-17 type anchors, Tthe effective cross-sectional area of an the anchor should be provided by the manufacturer of 18 expansion anchors with reduced cross-sectional area for the expansion mechanism. For threaded rods and headed 19 bolts, ANSI/ASME B1.1D.1 defines Ase,N as[2] 20

2

,

0.97434se N a

t

A dn

π ⎛ ⎞= −⎜ ⎟

⎝ ⎠ 21

where nt is the number of threads per inch.[13] 22

RD.5.2 — Concrete breakout strength of anchor in tension 23

RD.5.2.2 — The basic equation for the basic anchor concrete breakout strength was derivedD.917,-D.1118,D,21,D.1626 24 assuming a concrete failure prism with an angle of about 35 degrees, considering fracture mechanics concepts. [2] 25

The values of kc in Eq. (D-76) were determined from a large database of test results in uncracked concreteD.917 at the 5 26 percent fractile. The values were adjusted to corresponding kc values for cracked concrete.D.1018,D.2032 Tests have shown 27 that the values of kc applicable to adhesive anchors are approximately equal to those derived for expansion anchors.D.19, 28 D.33 Higher kc values for post-installed anchors may be permitted, provided they have been determined from product 29 approval testing in accordance with ACI 355.2 or ACI 355.Y. For anchors with a deeper embedment (hef > 11 in.), test 30 evidence indicates the use of hef

1.5 can be overly conservative for some cases. Often, such tests have been with selected 31 aggregates for special applications. An alternative expression (Eq. (D-87)) is provided using hef

5/3 for evaluation of 32 cast-in headed studs and headed bolts anchors with 11 in. ≤ hef ≤ 25 in. The limit of 25 in. corresponds to the upper 33 range of test data. This expression can also be appropriate for some undercut post-installed anchors. However, for such 34 anchors, the use of Eq. (D-87) should be justified by test results in accordance with D.4.2. Experimental and numerical 35 investigations indicate that Eq. (D-7) may be unconservative for hef > 25 in. where bearing pressure on the anchor head 36 is at or near the limit permitted by Eq. (D-14)D.34[2,35] 37

RD.5.2.6 — Post-installed and cast-in anchors that have not met the requirements for use in cracked concrete 38 according to ACI 355.2 or ACI 355.Y should be used only in uncracked regions that will remain uncrackedonly. The 39 analysis for the determination of crack formation should include the effects of restrained shrinkage (see 7.12.1.2). 40 The anchor qualification tests of ACI 355.2 or ACI 355.Y require that anchors in cracked concrete zones perform 41 well in a crack that is 0.012 in. wide. If wider cracks are expected, confining reinforcement to control the crack 42 width to about 0.012 in. should be provided. [2] 43

RD.5.3 — Pullout strength of cast-in, and post-installed expansion and undercut anchors in tension[2] 44

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RD.5.3.1 — The design requirements for pullout are applicable to cast-in, post-installed expansion, and post-1 installed undercut anchors. They are not applicable to adhesive anchors, which are instead evaluated for bond failure 2 in accordance with D.5.5. [2] 3

RD.5.5 — Bond strength of adhesive anchor in tension[2] 4

RD.5.5.1 — Evaluation of bond strength applies only to adhesive anchors. Single anchors with small embedment 5 loaded to failure in tension may exhibit concrete breakout failures, while deeper embedments produce bond failures. 6 Adhesive anchors that exhibit bond failures when loaded individually may exhibit concrete failures when in a group 7 or in a near-edge condition. In all cases, the strength in tension of adhesive anchors is limited by the concrete 8 breakout strength as given by Eq. (D-3) and Eq. (D-4) D.19. The influences of anchor spacing and edge distance on 9 both bond strength and concrete breakout strength must be evaluated for adhesive anchors. The influences of anchor 10 spacing and edge distance on the nominal bond strength of adhesive anchors in tension are included in the modifi-11 cation factors Ana/ANao and ψed,Na

in Eq. (D-18) and (D-19). [2] 12

The influence of nearby edges and adjacent loaded anchors on bond strength is dependent on the volume of concrete 13 mobilized by a single adhesive anchor. In contrast to the projected concrete failure area concept used in Eq. (D-3) 14 and Eq. (D-4) to compute the breakout strength of an adhesive anchor, the influence area associated with the bond 15 strength of an adhesive anchor used in Eq. (D-18) and (D-19) is not a function of the embedment depth but rather a 16 function of the anchor diameter and the characteristic bond stress. The critical distance cNa is assumed the same 17 whether the concrete is cracked or uncracked; for simplicity the relationship for cNa in Eq. D-21 uses τuncr. This has 18 been verified by experimental and numerical studiesD.19. Figure RD.5.5.1(a) shows ANao

and the development of Eq. 19 (D-20). ANao is the projected influence area for the bond strength of a single adhesive anchor. Figure RD.5.5.1(b) 20 shows an example of the projected influence area for an anchor group. Because, in this case, ANa is the projected 21 influence area for a group of anchors, and ANao

is the projected influence area for a single anchor, there is no need to 22 include n, the number of anchors, in Eq. (D-19). If anchors in a group (anchors loaded by a common base plate or 23 attachment) are positioned in such a way that the projected influence areas of the individual anchors overlap, the 24 value of ANa is less than nANao.

[2] 25

The tensile strength of closely spaced adhesive anchors with low bond strength may significantly exceed the value 26 given by Eq. (D-19). A correction factor is given in the literatureD.19 to address this issue, but for simplicity this factor 27 is not included in the Code. [2] 28

RD.5.5.2 — The equation for basic bond strength of adhesive anchors as given in Eq. (D-22) represents a uniform 29 bond stress model which has been shown to provide the best prediction of adhesive anchor bond strength through 30 numerical studies and comparisons of different models to an international database of experimental resultsD.20. The 31 basic bond strength is valid for bond failures that occur between the concrete and the adhesive as well as between 32 the anchor and the adhesive. [2] 33

Characteristic bond stresses should be based on tests performed in accordance with ACI 355.Y and should reflect 34 the particular combination of installation and use conditions anticipated during construction and during the anchor 35 service life. For those cases where product-specific information is unavailable at the time of design, Table D.5.5.2 36 provides lower-bound default values. The characteristic bond stresses in Table D.5.5.2 are the minimum values 37 permitted for adhesive anchor systems qualified in accordance with ACI 355.Y for the tabulated installation and use 38 conditions. Use of these values is restricted to the combinations of specific conditions listed; values for other 39 combinations of installation and use conditions should not be inferred. Where both sustained loading and earthquake 40 loading are present, the applicable factors given in the footnotes of Table D.5.5.2 should be multiplied together. The 41 table assumes that all concrete has a minimum age of 21 days and a minimum concrete compressive strength of 42 2500 psi. See RD.2.2. [2] 43

The terms "indoor" and "outdoor" as used in Table D.5.5.2 refer to a specific set of installation and service 44 environments. Indoor conditions represent anchors installed in dry concrete with a rotary impact drill or rock drill 45 and subjected to limited concrete temperature variations over the service life of the anchor. Outdoor conditions are 46 assumed to occur, when at the time of anchor installation, the concrete is exposed to weather and may therefore be 47

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wet. Anchors installed in outdoor conditions are also assumed to be subject to greater concrete temperature 1 variations such as might be associated with freeze-thaw or elevated temperatures resulting from direct sun exposure. 2 While the indoor/outdoor characterization is useful for many applications, there may be situations in which a literal 3 interpretation of the terms "indoor" and "outdoor" does not apply. For example, anchors installed before the building 4 envelope is completed may involve drilling in saturated concrete. As such, the minimum characteristic bond stress 5 associated with the outdoor condition in Table D.5.5.2 applies, regardless of whether the service environment is 6 "indoor" or "outdoor." Rotary impact drills and rock drills produce non-uniform hole geometries which are generally 7 favorable for bond. Installation of adhesive anchors in core drilled holes may result in substantially lower 8 characteristic bond stresses. Because this effect is highly product dependent, design of anchors to be installed in core 9 drilled holes should adhere to the product-specific characteristic bond stresses established through testing in 10 accordance with ACI 355.Y. [2] 11

The characteristic bond stresses associated with specific adhesive anchor systems are dependent on a number of 12 parameters. Consequently, care should be taken to include all parameters relevant to the value of characteristic bond 13 stress used in the design. These parameters include but are not limited to: [2] 14

1. Type and duration of loading – bond strength is reduced for sustained tension loading; [2] 15 2. Concrete cracking – bond is higher in uncracked concrete; [2] 16 3. Anchor size – bond is generally inversely proportional to anchor diameter; [2] 17 4. Drilling method – bond is lower for anchors installed in core drilled holes; [2] 18 5. Degree of concrete saturation at time of hole drilling and anchor installation – bond may be reduced due to 19

concrete saturation; [2] 20 6. Concrete temperature at time of installation – installation of anchors in cold conditions may result in retarded 21

adhesive cure and reduced bond; [2] 22 7. Concrete age at time of installation – installation in early-age concrete may result in reduced bond; [2] 23 8. Peak concrete temperatures during anchor service life – under specific conditions (for example, anchors in thin 24

concrete members exposed to direct sunlight) elevated concrete temperatures can result in reduced bond; and[2] 25 9. Chemical exposure – anchors used in industrial environments may be exposed to increased levels of 26

contaminants that can reduce bond over time. [2] 27

Anchors tested and assessed under ACI 355.Y may in some cases not be qualified for all of the installation and 28 service environments represented in Table D.5.5.2. Therefore, even where the minimum values given in Table 29 D.5.5.2 are used for design, the relevant installation and service environments should be specified in accordance 30 with D.9.2.1 and only anchors which have been qualified under ACI 355.Y for the installation and service 31 environments corresponding to the characteristic bond stress taken from Table D.5.5.2 should be specified. [2] 32

Characteristic bond stresses associated with qualified adhesive anchor systems for a specific set of installation and 33 use conditions may substantially exceed the minimum values provided in Table D.5.5.2. For example, 1/2-in. to 3/4-34 in. diameter anchors installed in impact-drilled holes in dry concrete where use is limited to indoor conditions in 35 uncracked concrete as described above may exhibit characteristic bond stresses, τuncr, in the range of 2000 to 2500 36 psi. [2] 37

RD.5.5.3 — Refer to RD.5.2.4. [2] 38

RD.5.5.4 — If anchors are located close to an edge, their strength is further reduced beyond that reflected in 39 ANa/ANao. If the smallest side cover distance is greater than or equal to cNa, there is no reduction (ψed,Na = 1). If the 40 side cover is less than cNa, the factor ψed,Na accounts for the edge effect.D.17,D.19[2] 41

RD.6 — Design requirements for shear loading 42

RD.6.1 — Steel strength of anchor in shear 43

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RD.6.1.1 —The shear load applied to each anchor in a group may vary depending on assumptions for the concrete 1 breakout surface and load redistribution. See RD.6.2.1. [12] 2

RD.6.1.2 — The nominal shear strength of anchors is best represented as a function of futa rather than fya because 3 the large majority of anchor materials do not exhibit a well-defined yield point. Welded studs develop a higher steel 4 shear strength than headed anchors due to the fixity provided by the weld between the studs and the base plate. The 5 use of Eq. (D-1928) and (D-2029) with 9.2 load factors and the φ-factors of D.4.43 give design strengths consistent 6 with the AISC Load and Resistance Factor Design Specifications.D.1931 7

The limitation of 1.9fya on futa is to ensure that, under service load conditions, the anchor stress does not exceed fya. 8 The limit on futa of 1.9fya was determined by converting the LRFD provisions to corresponding service level conditions 9 as discussed in RD.5.1.2. 10

For post-installed anchors having a reduced cross-sectional area anywhere along the anchor length, Tthe effective 11 cross-sectional area of anthe anchor should be provided by the manufacturer of expansion anchors with reduced 12 cross-sectional area for the expansion mechanism. For threaded rods and headed bolts, ANSI/ASME B1.1D.1 defines 13 Ase,V as[2] 14

π ⎛ ⎞= −⎜ ⎟

⎝ ⎠

2

,

0.97434V ase

t

A dn

[2] 15

where nt is the number of threads per inch. 16

RD.6.2 — Concrete breakout strength of anchor in shear 17

RD.6.2.1 — The shear strength equations were developed from the CCD Method. They assume a breakout cone 18 angle of approximately 35 degrees (see Fig. RD.4.2 .2(b)), and consider fracture mechanics theory. The effects of 19 multiple anchors, spacing of anchors, edge distance, and thickness of the concrete member on nominal concrete 20 breakout strength in shear are included by applying the reduction factor of AVc/AVco in Eq. (D-2130) and (D-2231), 21 and ψec,V in Eq. (D-2236). For anchors far from the edge, D.6.2 usually will not govern. For these cases, D.6.1 and 22 D.6.3 often govern. 23

Figure RD.6.2.1(a) shows AVco and the development of Eq. (D-2332). AVco is the maximum projected area for a 24 single anchor that approximates the surface area of the full breakout prism or cone for an anchor unaffected by edge 25 distance, spacing, or depth of member. Figure RD.6.2.1(b) shows examples of the projected areas for various single-26 anchor and multiple-anchor arrangements. AVc approximates the full surface area of the breakout cone for the 27 particular arrangement of anchors. Because AVc is the total projected area for a group of anchors, and AVco is the area 28 for a single anchor, there is no need to include the number of anchors in the equation. 29

As shown in the examples in Fig. RD.6.2.1(b) of two-anchor groups loaded in shear, Wwhen using Eq. (D-2231) for 30 cases anchor groups loaded in shear, where the anchor spacing s is greater than the edge distance to the near edge 31 anchor ca1,1, both assumptions for load distribution illustrated in Cases 1 and 2 examples on the right side of Fig. 32 RD.6.2.1(b) should be considered. This is because the anchors nearest to the free edge could fail first or the whole 33 group could fail as a unit with the failure surface originating from the anchors farthest from the edge. For Case 1, the 34 steel shear strength is provided by both anchors. For Case 2, the steel shear strength is provided entirely by the 35 anchor farthest from the edge. No contribution of the anchor near the edge is then considered. In addition, checking 36 the near-edge anchor for concrete breakout under service loads is advisable to preclude undesirable cracking at 37 service conditions. If the anchor spacing s is less than the edge distance to the near edge anchor, then the failure 38 surfaces may mergeD.24 and Case 3 of Fig. RD.6.2.1(b) may be taken as a conservative approach. [12] 39

If the anchors are welded to a common plate (regardless of anchor spacing s), when the anchor nearest the front edge 40 begins to form a failure cone, shear load would beis transferred to the stiffer and stronger rear anchor. For this 41 reason, only Case 2 need be consideredanchors welded to a common plate do not need to consider the failure mode 42 shown in the upper right figure of Fig. RD.6.2.1(b). which is consistent with The PCI Design Handbook 43 approachD.18 6.5.5D.30.suggests in Section 6.5.2.2 that the strength of the anchors away from the edge be considered. 44 Because this is a reasonable approach, assuming that the anchors are spaced far enough apart so that the shear failure 45

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surfaces do not intersect,D.11D.6.2 allows such a procedure. For determination of steel shear strength, it is 1 conservative to consider only the anchor farthest from the edge. However, for anchors having a ratio of s/ca,1,1 less 2 than 0.6, both the front and rear anchors may be assumed to resist the shearD.40. For ratios of s/ca,1,1 greater than one, 3 it is advisable to check concrete breakout of the near-edge anchor to preclude undesirable cracking at service 4 conditions. [12] 5

Further discussion of design for multiple anchors is giving in Reference D.16. [12] 6

If the failure surfaces do not intersect, as would generally occur if the anchor spacing s is equal to or greater than 7 1.5ca1, then after formation of the near-edge failure surface, the higher strength of the farther anchor would resist 8 most of the load. As shown in the bottom right example in Fig. RD.6.2.1(b), it would be appropriate to consider the 9 shear strength to be provided entirely by this anchor with its much larger resisting failure surface. No contribution of 10 the anchor near the edge is then considered. Checking the near-edge anchor condition is advisable to preclude 11 undesirable cracking at service load conditions. Further discussion of design for multiple anchors is given in 12 Reference D.8. [12] 13

The case of shear force parallel to an edge is shown in Fig. RD.6.2.1(c). The maximum shear force that can be 14 applied parallel to the edge, V||, as governed by concrete breakout, is twice the maximum shear force that can be 15 applied perpendicular to the edge, V⊥ . A special case can arise with shear force parallel to the edge near a corner. In 16

the example of a single anchor near a corner (see Fig. RD.6.2.1(d)), the provisions for shear force applied 17 perpendicular to the edge should be checked in addition to the provisions for shear force applied parallel to the edge. [12] 18

RD.6.2.2 — Like the concrete breakout tensile strength, the concrete breakout shear strength does not increase 19 with the failure surface, which is proportional to (ca1)2. Instead, the strength increases proportionally to (ca1)1.5 due to 20 size effect. The strength is also influenced by the anchor stiffness and the anchor diameter.D.917,D.18,,-D.1121,D.1626 The influence 21 of anchor stiffness and diameter is not apparent in large diameter anchorsD.28 resulting in a limitation on the shear 22 breakout strength provided by Eq. (D-34). [35] 23

RD.6.2.3 — For the case of cast-in headed bolts continuously welded to an attachment, test dataD.2539 show that 24 somewhat higher shear strength exists, possibly due to the stiff welding connection clamping the bolt more 25 effectively than an attachment with an anchor gap. Because of this, the basic shear value for such anchors is 26 increased but the upper limit of Eq. (D-34) is imposed because tests on large diameter anchors welded to steel 27 attachments are not available to justify any higher value than Eq. (D-34). Limits are imposed to ensure sufficient 28 rigidity. The design of supplementary reinforcement is discussed in References D.816, D.1121, and D.1222. [35] 29

RD.6.2.4 — For the case of anchors influenced by three or more edges located in narrow sections of limited 30 thickness where any the edge distances perpendicular to the direction of load and the member thickness are is less 31 than 1.5ca1, the shear breakout strength computed by the basic CCD Method, which is the basis for Eq. (D-21) 32 through (D-29), gives safe but overly conservative results. These cases were studied for the κ MethodD.1626 and the 33 problem was pointed out by Lutz.D.2135 Similarly, to the approach used for concrete breakout strength in tension 34 tensile breakouts in D.5.2.3, the concrete breakout strength in shear for this case is correctly more accurately 35 evaluated if the value of ca1 used in Eq. (D-2130) to (D-2939) and in the calculation of Avc is limited to the 36 maximum of two-thirds of the larger of the two edge distances perpendicular to the direction of shear, two-thirds of 37 the member thickness, ca2/1.5 in each direction, ha/1.5, and one-third of the maximum spacing between anchors 38 within the group, measured perpendicular to the direction of shear. The limit on ca1 of at least one-third of the 39 maximum spacing between anchors within the group prevents the use of a calculated strength based on individual 40 breakout prisms for a group anchor configuration. [36] 41

This approach is illustrated in Fig. RD.6.2.4. In this example, the limiting on the value of ca1 is the largest of ca2/1.5 in 42 either direction, ha/1.5, and one-third the maximum spacing between anchors for anchor groups results in denoted as 43 ca1′ and is used for the calculation of Avc, AVco, ψed,V and ψh,V as well as for Vb (not shown). = 5.33 in. For this 44 example, this would be the proper value to be used for ca1 in computing Vcb or Vcbg, even if the actual edge distance 45 that the shear is directed toward is larger. The requirement of D.6.2.4 may be visualized by moving the actual 46 concrete breakout surface originating at the actual ca1 toward the surface of the concrete in the direction of the 47 applied shear load. The value of ca1 used for the calculation of AVc and in Eq. (D-2130) to (D-2939) is determined 48 when either: (a) the an outer boundaryies of the failure surface first intersects the concrete surface a free edge; or (b) 49 the intersection of the breakout surface between anchors within the group first intersects the concrete surface of the 50

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concrete. For the example shown in Fig. RD.6.2.4, Point “A” shows the intersection of the assumed failure 1 surface for limiting ca1 with the concrete surface. [36] 2

RD.6.2.7 — Torque-controlled and displacement-controlled expansion anchors are permitted in cracked concrete 3 under pure shear loadings.[13] 4

RD.6.3 — Concrete pryout strength of anchor in shear 5

RD.6.3.1 — Reference D.917 indicates that the pryout shear resistance can be approximated as one to two times 6 the anchor tensile resistance with the lower value appropriate for hef less than 2.5 in. Because it is possible that the 7 bond strength of adhesive anchors could be less than the concrete breakout strength, it is necessary to consider both 8 D.5.2.1 and D.5.5.1 for determination of the pryout strength. [2] 9

RD.8 — Required edge distances, spacings, and thicknesses to preclude splitting failure 10

The minimum spacings, edge distances, and thicknesses are very dependent on the anchor characteristics. 11 Installation forces and torques in post-installed anchors can cause splitting of the surrounding concrete. Such 12 splitting also can be produced in subsequent torquing during connection of attachments to anchors including cast-in 13 anchors. The primary source of values for minimum spacings, edge distances, and thicknesses of post-installed 14 anchors should be the product-specific tests of ACI 355.2 and ACI 355.Y. In some cases, however, specific products 15 are not known in the design stage. Approximate values are provided for use in design.[13] 16

RD.8.5 — This minimum thickness requirement is not applicable to through-bolts because they are outside the 17 scope of Appendix D. In addition, sSplitting failures are caused by the load transfer between the bolt and the 18 concrete. Because through-bolts transfer their load differently than cast-in or The limitations on the value of hef do 19 not apply to cast-in and adhesive anchors because the splitting forces associated with these anchor types are less 20 than for expansion and undercut anchors, they would not be subject to the same member thickness requirements. 21 Post-installed anchors should not be embedded deeper than 2/3 of the member thickness. [2] 22

For all post-installed anchors, the maximum embedment depth for a given member thickness should be limited as 23 required to avoid back-face blowout on the opposite side of the concrete member during hole drilling and anchor 24 setting. This is dependent on many variables such as the anchor type, drilling method, drilling technique, type and 25 size of drilling equipment, presence of reinforcement, and strength and condition of the concrete. [2] 26

RD.8.6 — The critical edge distance cac is determined by the corner test in ACI 355.2 or ACI 355.Y, and is only 27 applicable to designs for uncracked concrete. To permit the design of these types of anchors when product-specific 28 information is not available, conservative default values for cac are provided. Research has indicated that the corner-29 test requirements are not met with ca,min = 1.5hef for many expansion anchors and some undercut anchors because 30 installation of these types of anchors introduces splitting tensile stresses in the concrete that are increased during 31 load application, potentially resulting in a premature splitting failure. Similarly, adhesive anchors that meet the 32 maximum embedment depth requirement of D.8.5 may not fulfill the corner test requirements with ca,min = cNa due 33 to the additional flexural stresses induced in the member by the anchor.To permit the design of these types of 34 anchors when product-specific information is not available, conservative default values for cac are provided. [2] 35

RD.9 — Installation and inspection of anchors 36

RD.9.1 — Many anchor performance characteristics depend on proper installation of the anchor. Installation of 37 adhesive anchors should be performed by personnel qualified for the adhesive anchor system and installation 38 procedures being used. Construction personnel can establish qualifications by becoming certified through 39 certification programs. For cast-in anchors, care must be taken that the anchors are securely positioned in the 40 formwork and oriented in accordance with the contract documents. Furthermore, it should be ensured that the 41 concrete around the anchors is properly consolidated. Inspection is particularly important for post-installed anchors 42 to make certain that the manufacturer's printed installation instructions are followed. For adhesive anchors, 43 continuous monitoring of installations by qualified inspectors is recommended to ensure required installation 44 procedures are followed. Post-installed anchor strength and deformation capacity are assessed by acceptance testing 45 under ACI 355.2 or ACI 355.Y. These tests are carried out assuming installation in accordance with the 46

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manufacturer’s printed installation instructions. Certain types of anchors can be sensitive to variations in hole 1 diameter, cleaning conditions, orientation of the axis, magnitude of the installation torque, crack width, and other 2 variables. Some of this sensitivity is indirectly accounted for in the assigned φ values for the different anchor 3 categories, which depend in part on the results of the installation safety tests. Gross deviations from the ACI 355.2 4 or ACI 355.Y acceptance testing results could occur if anchor components are altered, or if anchor installation 5 criteria or procedures vary from those specified in the manufacturer's printed installation instructions. [2] 6

Anchor strength and deformation capacity can be assessed by acceptance testing under ACI 355.2. These tests are 7 carried out assuming that the manufacturer’s installation directions will be followed. Certain types of anchors can be 8 sensitive to variations in hole diameter, cleaning conditions, orientation of the axis, magnitude of the installation 9 torque, crack width, and other variables. Some of this sensitivity is indirectly reflected in the assigned φ values for 10 the different anchor categories, which depend in part on the results of the installation safety tests. Gross deviations 11 from the ACI 355.2 acceptance testing results could occur if anchor components are incorrectly exchanged, or if 12 anchor installation criteria and procedures vary from those recommended. Project specifications should require that 13 anchors be installed according to the manufacturer’s recommendations. [2] 14

RD.9.2.1 — Due to the sensitivity of bond strength to installation, on-site quality control is important for adhesive 15 anchors. Where appropriate, a proof loading program should be specified in the contract documents. For adhesive 16 anchors, the contract documents must also provide all parameters relevant to the characteristic bond stress used in 17 the design. These parameters may include, but are not limited to: [2] 18

1. Acceptable anchor installation environment (dry or saturated concrete; concrete temperature range); [2] 19 2. Acceptable drilling methods; [2] 20 3. Required hole cleaning procedures; and[2] 21 4. Anchor type and size range (threaded rod or reinforcing bar). [2] 22

23 Hole cleaning is intended to ensure that drilling debris and dust do not impair bond. Depending on the on-site 24 conditions, hole cleaning may involve operations to remove drilling debris from the hole with vacuum or 25 compressed air, mechanical brushing of the hole wall to remove surface dust, and a final step to evacuate any 26 remaining dust or debris, usually with compressed air. Where wet core drilling is used, holes may be flushed with 27 water and then dried with compressed air. If anchors are installed in locations where the concrete is saturated (for 28 example, outdoor locations exposed to rainfall), the resulting drilling mud must be removed by other means. In all 29 cases, the procedures used should be clearly described by the manufacturer in printed installation instructions 30 accompanying the product. These printed installation instructions, which also describe the limits on concrete 31 temperature and the presence of water during installation as well as the procedures necessary for void-free adhesive 32 injection and adhesive cure requirements, constitute an integral part of the adhesive anchor system and are part of 33 the assessment performed in accordance with ACI 355.Y. [2] 34

RD.9.2.2 -----The sensitivity of adhesive anchors to installation orientation combined with sustained tension 35 loading warrants installer certification. Certification may also be appropriate for other safety-related applications. 36 Certification is established through an independent assessment such as the ACI/CRSI Adhesive Anchor Installation 37 Certification Program, or similar program with equivalent requirements. In addition, installers should obtain 38 instruction through product-specific training offered by manufacturers of qualified adhesive anchor systems. [2] 39

RD.9.2.3 — For the purposes of satisfying D.9.2.3, an equivalent certified installer program should test the 40 adhesive anchor installer’s knowledge and skill by an objectively fair and unbiased administration and grading of a 41 written and performance exam. Programs should reflect the knowledge and skill required to install available 42 commercial anchor systems. The effectiveness of a written exam should be verified through statistical analysis of the 43 questions and answers. An equivalent program should provide a responsive and accurate mechanism to verify 44 credentials, which are renewed on a periodic basis. [2] 45

RD.9.2.4 — The IBCD.41 requires special inspection of all post-installed anchors. The installation of adhesive 46 anchors in horizontal and upwardly inclined orientations poses special challenges to the installer and requires 47 particular attention to execution quality as well as an enhanced level of oversight. It is expected that these anchor 48

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installations will be inspected by a certified special inspector who is continuously present when and where the 1 installations are being performed. [2] 2

3

4

Fig. RD.1—Types of anchors. [2] 5 6

7

8

9

A. Cast-in anchors: (a) hex head bolt with washer (b) L-bolt (c) J-bolt (d) welded headed stud.[2]

hef

(a) (b) (c) (d)

hef

(a) (b) (c) (d)

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B. Post-installed anchors: (a) adhesive anchor (b) undercut anchor (c) torque-controlled expansion anchors: (c1) sleeve-type (c2) stud-type (d) drop-in type displacement-controlled expansion anchor.[2]

Fig. RD.1.1—Types of anchors. [2]

Fig. RD.1.2—Possible orientations of horizontal and upwardly inclined anchors. [2]

[13]

Fig. RD.1.3––Illustrations of stretch length (see D.3.3.4.3).

1

(a) (b) (c1) (c2) (d)

hef

hef

(a) (b) (c1) (c2) (d)

hef

hef

hef

3787

[2] 1

2

3788

[2] 1

2

3 4

5

6

Fig. RD.5.2.3 — Example of Ttension where anchors are located in narrow members. [36] 7 8

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a) Single adhesive anchor away from edges and other anchors[2]

b) Four adhesive anchor group located near a corner[2]

Fig. RD.5.5.1—Calculation of influence areas ANao and ANa.[2]

1

2 3

( )=2

Nao NaA 2c

ANao

N

cNa cNa

c Na

c Na

ANa

cNa

c Na

ca1

c a2

s1

s 2

N

( )( )= + + + +Na Na 1 a1 Na 2 a2A c s c c s c if

a1c and <a2 Nac c

1s and <2 Nas 2c

Plan view

Section through anchor showing principal stress trajectories Section through anchor group showing

principal stress trajectories

Plan view

change in stress pattern with increasing embedment

3790

1

3791

1

Fig. RD.6.2.1(b)—Calculation of AVc for single anchors and groups of anchors. [12] 2

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1

2

Fig. RD.6.2.1(c)—Shear force parallel to an edge. [12] 3 4

5

[2] 6

7

8

Fig. RD.6.2.1(d)—Shear force near a corner. [12] 9 10

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1 [36] 2

3

4

3794

1

2

1. The actual ca1 = 12 in. but two orthogonal edges ca2 and ha are ≤ 1.5ca1 3 therefore the limiting value of ca1 (shown as c'a1 in the figure) is the larger of 4 ca2,max/1.5, ha/1.5 and one-third of the maximum spacing for an anchor group. [36] 5

2. The two edge distances ca2 as well as ha are all less than 1.5ca1. [36] 6

3. The limiting value of ca1 (shown as c'a1 in the figure) to be used for the 7 calculation of AVc and in Eq. (D-30) to (D-39) is determined as the largest of the 8 following: [36] 9

c'a1 = max (7/1.5, 8/1.5, 9/3) = 5.33 in. [36] 10

Therefore, use c'a1 = 5.33 in. in Eq. (D-21) to (D-28) including the calculation of 11 AVc:

[36] 12

(ca2,max)/1.5 = (7) /1.5 = 4.67 in. [36] 13

(ha)/1.5 = (8) /1.5 = 5.33 in. (controls) [36] 14

s/3 = 1/3(9) = 3 in. [36] 15

4. For this case, AVc, AVco, ψed,V, and ψh,V are determined as follows: [36] 16

AVc = (5 + 9 + 7)(1.5 x 5.33) = 168 in.2 17

AVco = 4.5(5.33)2 = 128 in.2[36] 18

ψed,V = 0.7 + 0.3(5)/5.33 = 0.98[36] 19

ψh,V = 1.0 because ca1 = (ha) /1.5. Point A shows the intersection of the assumed 20 failure surface for limiting ca1 with the concrete surface that establishes the limiting 21 value of ca1.

[36] 22

23 Fig. RD.6.2.4—Example of shear where when anchors are located in narrow members of limited 24

thicknessinfluenced by three or more edges. [36] 25

Actual failure surface

Assumed failure surface for limiting c a1

Point Aha = 8 in.

c'a1

Actual failure surface

Assumedfailure surface for limiting ca1c ' a 1

c a 1 = 12 in.

s = 9 in. ca2,1 = 7 in.

Plan Side section

VV

c a 2,2 = 5 in.

11.5

11.5

Actual failure surface

Assumed failure surface for limiting c a1

Point Aha = 8 in.

c'a1

Actual failure surface

Assumedfailure surface for limiting ca1c ' a1

c a1 = 12 in.

s = 9 in. ca2,1 = 7 in.

Plan Side section

VV

c a 2,2 = 5 in.

Actual failure surface

Assumed failure surface for limiting c a1

Point Aha = 8 in.

c'a1

Actual failure surface

Assumedfailure surface for limiting ca1c ' a1

c a1 = 12 in.

s = 9 in. ca2,1 = 7 in.

Plan Side section

VV

c a 2,2 = 5 in.

11.5

11.5

11.5

3795

Change No.

Reason Statement

1 Update ASTM standards.

2Provide provisions for adhesive anchors in Appendix D and correct unconservative values associated with anchors in lightweight concrete.

3 Update referenced standards for cast‐in‐place slabs on steel deck.4 Provide provisions to prevent premature shear failures in wall piers.

5Move R19.1.1 to R1.1.10 and add a reference on cylindrical and spherical shells used in prestressed concrete tanks.

6 Update ACI 318 load combinations for consistency with ASCE/SEI 7‐10.

7Remove unnecessary code material that is more appropriate for industry manuals or manufacturer's literature.

8 Clarify that Nc includes the effects of the axial prestressing force and all service loads.

9Update provisions for anchor design for earthquake forces and compatibility between ACI 318 and the general building code.

10 Correct calculation of single anchor strength in tension and shear or group of anchors.

11 Update provisions to reduce the risk of column shear failures in intermediate moment frames.

12 Clarify "s" in RD.6.2.1(b) and Figures RD.6.2.1(c) and (d).13 Clarify language.14 Refer to ASTM A970 for acceptable head dimensions for headed bars.15 Update provisions to reflect revisions in ASTM specifications for reinforcing bars.16 Add provisions to include another type of corrosion‐resistant reinforcing bar.

17Provide provisions to require laboratories to meet ASTM C1077, and require distribution of test reports to all parties.

18Prescribe a standardized test to determine the amount of water‐soluble sulfates in soil and water for use in Table 4.2.1

19 Update AWS standard.20 Update provisions from 12 to 24 months.21 Clarify provision is not intended for use in strength evaluation of existing structures.22 Add provision for circular ties.

23Update requirements for prestressed shrinkage and temperature reinforcement in cast‐in‐place, monolithic beam and slab construction.

24 Update splicing requirements for integrity reinforcement.25 Clarify minimum reinforcement requirements for deep beams.

26Provide guidance on evaluation of slenderness effects for compression members that are loaded in biaxial bending.

27 Remove excess reinforcement factor for reduction of development length of headed bars.

28 Eliminate code criteria based on practical experience with post‐tensioned concrete members.

29 Provide guidance on the value of f py for various types of prestressing steel.

30Exclude the use of ASTM A706 Grade 80 reinforcement to resist flexural and axial forces in member of special moment frames and special structural walls.

31 Improve confinement of yielding regions in beams of special moment frames.

3796

Change No.

Reason Statement

32Clarify use of words beam, column, and member when establishing the degree of confinement in joints.

33 Clarify development of wall shear reinforcement where special boundary elements are required.

34 Document the availability of a design standard for one type of special precast structural wall.

35Increase anchor diameter limit to 4 in., and remove anchor embedment length limit for concrete breakout in tension and shear.

36 Clarify intent of provision.37 Clarify minimum edge distance applies to all cast‐in anchors.38 Updated reference.

3797