ACI 318_2019_with comments & replies

Document: ACI 318: Building Code Requirements for Structural Concrete and Commentary Public Discussion Period: December 21, 2018 to February 4, 2019

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Public Commenter Name ACI Staff

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Public Comment

Committee Response

Please verify that all standards referenced in Chapter 3 are the latest appropriate standards for the 2019 version of 318.

All standards are being reviewed. Those that have been updated will be balloted with the responses responses to public comments. See separate file on ballot containing CA195, CB101, CB102, CX002, CX003, and CX004. Based on several accepted comments received from Lobo on this response, several changes were made to CA195: C496 should be deleted from standards list. Revise C42-18 to C42-18a – a note clarifies who is the specifier of the test consistent with ACI 318 Revise C94-17a to C94-18 – clarifies issues on delivery ticket Revise C595-17 to C595-18 – clarifies evaluation of blended cements for ASR Revise C618-17a to C618-19 – updates the basis for clas sification of fly ash consistent with ASTM C1178 for ASR Revise C989-18 to C989—18a – clarifies sampling and reporting requirements on mill cert Based on accepted and resolved negative from Wyllie, editorial change was made to list of ACI references in CX002 strike ACI on line 16 of CX002: ACI 437.2-13 – Code Requirements for Load Testing of Existing Concrete Structures and Commentary Sub H verified that CSA 23.3 2014 (Canadian concrete code) is the appropriate reference to be cited in ACI 318-19. There are two instances of CSA 23.3 in the reference list. The second reference in the list, Page 891, Line 8, is redundant and should be deleted. The date of the first reference should be 2014

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Public Commenter Name Dale C. Biggers, P.E. Chair of the PDCA Technical Committee and Voting member of ACI 543 Concrete Pile Committee

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Abbas Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee

Thomas Schaeffer

Public Comment

Committee Response

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This submission has too many inconsistencies and serious restrictions that should not be accepted without a great deal more input from other engineers and contractors. This should be tabled for at least a year or two. There is no reason to rush this.

Disagree. No specific code provisions are cited in the comment. Assuming this comment is related to the added foundation provisions; the foundation related Code change proposals originated in Subcommittee that contained several members from ACI 336 and 543, as well as members that are also members of ASCE-7 and IBC.

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I read these draft of ACI Standard and I had no comment, as far as I am concerned and according to my exact specialist. Through line 13: Section 1.4.7 states, “T his code does not apply to the design and installation of concrete piles, drilled piers, and caissons embedded in ground, except as provided in (a) through (d):” Code section 13.4 “Deep Foundations” is not referenced in entirety in any sections (a) through (d). Will section 13.4 be applicable if not specifically referenced in any subsection (a) through (d) of 1.4.7?

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13.4.4 should be 13.4 because Precast Pile provisions occur in 13.4.1, 13.4.2, 13.4.3, and 13.4.5

No change required. Thank you for your review. Agree, the references in 1.4.7 are too specific and may unintentionally exclude pertinent provisions. A reference to Ch. 13 will be added to (c), (18.13.5) will be revised to (18.13), and 1.4.7 (d) can be deleted, because 1.4.7(c) now includes all of Ch. 13. The provision will be revised to: 1.4.7 This Code does not apply to the design and installation of concrete piles, drilled piers, and caissons embedded in ground, except as provided in (a) through (dc): (a) For portions of deep foundation members in air or water, or in soil incapable of providing adequate lateral restraint to prevent buckling throughout their length (b) For precast concrete piles supporting structures assigned to Seismic Design Categories A and B (13.4.4) (c) For deep foundation elements supporting structures assigned to Seismic Design Categories C, D, E, and F (Ch. 13), (18.13.5) (d) For cast-in-place deep foundation elements according to 13.4.3.1 Agree. 1.4.7 will be revised as shown in Response to #4, page 2, line 12.

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Public Commenter Name Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee David L. Hartmann

Public Comment

Committee Response

Proposed code language states precast concrete piles assigned to SDC A and B shall be designed in accordance with 13.4.4. This section is “Cast -in-place deep foundations”. We believe the correct reference sh ould be 13.4.5 “Precast concrete piles”.

Agree, but should be 13.4

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Believe (13.4.4) should be (13.4.5)

Agree, but should be 13.4

8.

Thomas Schaeffer

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Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee David L. Hartmann

13.4.3.1 should be 13.4 because Cast-in-place Pile provisions occur in 13.4.1, 13.4.2, 13.4.3, and 13.4.4 Proposed code language states that cast-in-place deep foundation elements shall be designed in accordance with 13.4.3.1. This reference reference appears to be incorrect. incorrect. Correct reference should probably be 13.4.4 “Cast -in-place deep foundations” or more generally 13.4 “Deep foundations”.

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11.

Anthony Galterio

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David P. Gustafson

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13. 14.

David P. Gustafson David P. Gustafson

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22 24

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Believe 13.4.3.1. should be 13.4.1.2 Reference to 13.4.3.1 completely bypasses the Allowable axial strength section of 13.4.2. Please add a reference to the ACI 350 code document in section 1.4.9 for tanks and reservoirs. I come across projects every few years where someone has mistakenly designed a concrete tank to the 318 code and there is always discussion about the reference not being on the mandatory code side, just in the commentary. Should “computer programs” be replaced with “computer software”? The term “computer software program” occurs on Page 111, Lines 2-3. Replace “report” with “guide”. Should “design” be replaced with “design work”? Line 2 speaks of “design work”.

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1.4.7 will be revised as shown in Response to #4, page 2, line 12.

1.4.7 will be revised as shown in Response to #4, page 2, line 12. This comment is no longer applicable because 1.4.7 (d) is deleted in the revised 1.4.7 as shown in Response to #4, #4, page 2, line 12. This comment is no longer applicable because 1.4.7 (d) is deleted in the revised 1.4.7 as shown in Response to #4, #4, page 2, line 12.

This comment is no longer applicable because 1.4.7 (d) is deleted in the revised 1.4.7 as shown in Response to #4, page 2, line 12. Not accepted. Reasoning presented for adding ACI 350 to the code side is not persuasive.

Not accepted. Leave as “programs” throughout throughout code.

Accept. Editorial change. Accept. Editorial change.


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Public Commenter Name Brian Gerber

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David P. Gustafson

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Amin Ghali and Ramez B. Gayed

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18.

Allan Bommer

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19.

Robinson

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Reid W. Castrodale

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Public Comment

Committee Response

Given that a significant portion of the code refers to the “contractor” as the respo nsible party, the definition of “contractor” needs to be added as Section 1.8 and defined in Chapter 2. Since this party is significant, relying on other publications for a definition would not be appropriate. Should “a computer program” be replaced with “computer software”? Through page 26, all lines: Throughout Chapter 2, replace the words “centroidal axis” by the word “principal axis”.

To be considered as New business.

The revision is needed to avoid occasional confusion by beginners. The revision distinguishes distinguishes between infinite centroidal axes of which two are principal. The code or commentary should indicate what strain state (ultimate flexure? forces coinciding with ultimate shear?) d should be calculated for (centroid of longitudinal tension reinforcement varies per strain state). The resulting shear capacities can vary significantly (over 50%) depending upon the strain state used.

It should be noted that the engineer delegates the calculation of d to software almost all the time (and millions of times per project), so declaring that human “engineering judgment” should be used is ignoring the realities of design practice. With the removal of the option to specify fct when determining lambda, is this required? 2.2-Notation With the removal of the option to specify fct when determining lambda (with which I don’t agree), is this required? From a search on fct, it still appears in Table 25.4.9.3, but probably should not since it has been removed from a similar table (25.4.2.5). Other than that, there is no other occurrence of fct showing up in this document.

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Not accepted. Leave as “programs” throughout throughout code.



This is actually page page 15, line 17. Accepted. Editorial change. Delete fct from notation list. This is actually page 15, line 17. Comment accepted. Change response to read: read: Make the following code changes: 1. Delete fct from notation list, page 15, line 17. (CA111)


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Public Commenter Name

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Public Comment

Committee Response

2. Delete fct from definitions, definitions, page 40, line 10. 3. Delete row with fct from Table 25.4.9.3, page 721, line 13. This change was approved in CA111 but was not implemented. 4. Delete row 19.2.4.3, 19.2.4.3, page 951 (App C). C). This row is not needed needed given fct has been deleted from code. 21.

Carson Baker (CPL)

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In a coupled wall system, is it the intent of the committee that lw refers to the entire wall as the total length of both the wall piers and coupling beams, or to the length of the individual wall piers on either side of the coupling beams? If to the wall piers on either side, what aspect ratios of coupling beams are required to create this behavior? (This could perhaps be defined in terms of a “degree of coupling” of the wall system, which is the ratio of the moment resisted by the coupling system to the total overturning moment. Alternatively, any systems qualifying as a ductile coupled wall system per 18.10.9 could be considered to have lw defined as the length of the wall pier on each side of the coupling beam, and for all other systems lw is taken as the entire wall length)

22.

Reid W. Castrodale

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Through line 26 2.2-Notation I greatly prefer the definition of lambda given in the AASHTO LRFD Bridge Design Specifications {referred to in following as AASHTO LRFD], which makes no inference regarding the potential reduction in material properties. Such statements should be limited to the commentary, not the code. The AASHTO LRFD definition is: “concrete density modification factor,” although this seems to indicate that the density is being modified.

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Disagree. Subcommittee H studied extensively the possibility of using “degree of coupling” in the definition of a coupled wall. I t was found, however, that a more satisfactory method was to specify the length-to-height ratio of coupling beams that results in optimal energy dissipation, along with appropriate detailing requirements for the coupling beams. Regarding the definition of the length lw to be used for a coupled wall, the definition “Structural wall, ductile coupled” points to Section 18.10.9. In 18.10.9.2 the required aspect ratio Hwcs/lw is stated in terms of the individual walls on either side of the coupling beams. No change to code language, but will insert in the definition list in Chapter 2, Ductile coupled structural wall – see structural wall, ductile coupled See response to comment 312, page 539, line 12, Castrodale


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Public Comment

Committee Response

This definition, and the one that follows for lambda a, indicate that lightweight concrete has “reduced mechanical properties,” which may sometimes be true, but published test date demonstrate clearly that it is not always the case for tensile strength which is the real focus of this factor. I am surprised that ACI would consider publishing such a statement which is not only untrue but is also damaging to part of the concrete community.

Lambda has always been targeted for use with properties that are related to the potential tensile strength reduction of LWC for equations with a sqrt f’c term. Other mechanical properties are addressed in other ways, such as the unit weight, wc, being included in the equation for Ec. Possible modifications to the ACI definition:

23.

David Darwin

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29

1.

Lambda = modification factor to reflect a potentially reduced tensile strength for lightweight concrete.

2.

Insert “potentially” prior to “reduced”.

See also comment for p. 45, line 1. Because o applies only to the development of hooked and headed bars, it will be helpful to users of t he Code to modify the definition to “factor used to modify development length of hooked and headed bars based bars based side cover and confinement”

Agree. Reason: The proposed change improves the clarity of the definition.

Change the definition of o to “factor used to modify development length of hooked and headed bars based on side cover and confinement”

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No. 24.

Public Commenter Name John Cook

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Public Comment

Committee Response

Material other than water, aggregate, should not have a strike through

Accept. Editorial change. Approved as “material other “material other than water, aggregate, cementitious materials …

25.

James Getaz

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26

Why does 318 still mention hooked bolts , or at least without the kind of warning in AISC?

Disagree. AISC provides a recommendation in AISC Design Guide 1 “Base Plate and Anchor Ro d Design” to use headed anchors. Moreover, the AISC Steel Construction Manual (15th Ed), Chapter 14 notes hooked anchor rods should only be used for axially loaded members subject to compression only during erection.

ACI does not want to preclude the use of J- and L- bolts, as they are still used in the industry. We recognize these types of anchors have a smaller pullout capacity than headed anchors, however there is not a safety concern when they are designed in accordance with ACI 318. 26.

Robinson

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27.

Reid W. Castrodale

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28.

Daniel S. Stevenson, P.E. Representing DFI

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The definition of normalweight concrete should have a lower limit that corresponds with the new definition of lightweight concrete. 2.3-Terminology With a density range given in the definition for “concrete, lightweight” [line 15], it seems that the definition for normal weight concrete should also include at least a lower limit shown that corresponds to the upper limit for lightweight concrete. The AASHTO LRFD includes the lower limit of 135 pcf in its definition of normal weight concrete. The definition for a drilled pier states that it is filled with reinforcing and concrete. Current code allows for plain concrete drilled piers for structures assigned to SDC A and B.

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Accepted. Editorial change. Add: “and having a density greater than 135 lb/ft3” at end of current definition. See response to comment 26, page 30, line 21, Robinson.

According to 1.4.7c, the Code only applies to cast-in-place concrete deep foundation elements assigned to SDC C, D, E, and F; therefore, the term reinforcing in the definition is appropriate.


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Public Commenter Name Codes and Standards Committee

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Public Comment

Committee Response

Reinforcement is not a necessary necessary component. The proposed definition does not distinguish a drilled pier from other common cast-in-place deep foundation types (e.g. auger-cast piles). Consider using definition for drilled shaft in IBC 2018.

Cast-in-place concrete deep foundation elements in SDC A and B will be considered for New Business in the next Code cycle. For reference: this is the definition from IBC 2018 referenced in the Comment: DRILLED SHAFT. A cast-in-place deep foundation element, also referred to as a caisson, drilled pier or bored pile, constructed by drilling a hole (with or without permanent casing or drilling fluid) into oil or rock and filling it with fluid concrete after the drilling equipment is removed.

29.

Robinson

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30.

Reid W. Castrodale

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31.

Adam Lubell

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This definition appears to indicate that the only way equilibrium density can be determined is by actual environmental testing. This is not the intent of ASTM C567. 2.3-Terminology This definition for “equilibrium density” appears to indicate that the only way that it can be determined is by actual environmental testing. This is not the intent of C567, although the definition given is very close to the definition in ASTM C567. The sentence should end after “ASTM C567.” If the entire definition is retained as it stands, the last word should be changed from “density” to “mass” to agree with ASTM C567. The definition of “strut, boundary” is poor by referring to “..boundary of…discontinuity region”. The definition as written written leaves it ambiguous if this classification is also intended to apply to the boundary between the discontinuity region and any “b-region”. This could be clarified by adding a B-region to D-region transition figure as part (b) to Fig R23.2.1.

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No change required. Accepted. Substantive change. End the definition after “… in accordance with ASTM C567.” See response to comment 29, page 33, line 24, Robinson

Disagree. The commentary removes any ambiguity.


No.

32.

Public Commenter Name Mark W Cunningham

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Public Comment

Committee Response

The definition of tie implies a single bar or wire in a closed configuration. 1. Can’t each (closed) tie be provided using more than one bar? When I made this comment on the 318-14 update, part of the committee response was: “As new business, ACI Committee 318 will consider revision of this terminology to address that it could be made of multiple pieces (e.g., two overlapping rectangles)”. 2. The “Cap tie” sho wn in Fig. R9.7.7.1 (page 228), which is clearly labeled as a type of “tie”, doesn’t meet the definition since it’s not closed.

Agree

An individual tie is not always a loop, and ties can be comprised of multiple pieces, for example crossties through a column or a cap tie on a beam. We will change the definition definition of a tie to be: Code Change: tie—(a) loop of reinforcing bar or wire enclosing longitudinal reinforcement; a continuously wound transverse bar or wire in the form of a circle, rectangle, or other polygonal shape without reentrant corners enclosing longitudinal reinforcement; see also stirrup, hoop; (b) tension element in a strut-and-tie model.

Please note as new business, the committee will be revisiting the definition of a spiral, circular hoop, circular tie, etc. to achieve more consistency between the Code and common industry terminology for such reinforcement. 33.

34.

Dale C. Biggers, P.E.

Daniel S. Stevenson, P.E. Representing DFI Codes and

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Through line 30: Drill shafts and auger- cast piles “ driving a casing “ – this does not apply.

Through line 30: Definition for “uncased cast -in-place drilled or augered piles” states that piles may be installed b y driving a temporary casing. By definition “drilled or augered piles” are not inst alled by

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Agree with comment. The term “driving” will be replaced with “installing” because there are several methods to install the casing. The revised Code definition will be: uncased cast-in-place concrete drilled or augered piles – piles with or without an enlarged base (bell) that are constructed by either drilling a hole in the ground, or by driving installing a temporary casing in the ground and cleaning out the soil, and subsequently filling the hole with reinforcement and concrete. Agree with comment. The term “driving” will be replaced with “installing” because there are several methods to instal l the casing.


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35.

36.

Public Commenter Name Standards Committee

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Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee

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Reid W. Castrodale

45

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Public Comment

Committee Response

driving. Consider deleting the phrase “drilled or augered” from term defined or deleting reference to driving in the definition.

The revised Code definition will be: uncased cast-in-place concrete drilled or augered piles – piles with or without an enlarged base (bell) that are constructed by either drilling a hole in the ground, or by driving installing a temporary casing in the ground and cleaning out the soil, and subsequently filling the hole with reinforcement and concrete. According to 1.4.7c, the Code only applies to cast-in-place concrete deep foundation elements assigned to SDC C, D, E, and F; therefore, the term reinforcing in the definition is appropriate.

Definition for “uncased cast -in-place concrete drilled or augered piles” states that piles are formed by drilling a hole and filling with reinforcing and concrete. Current code allows for plain concrete cast-in-place piles for structures assigned to SDC A and B. Reinforcing is not a necessary component. component.

R2.2-Notation In 318-14, notations rarely appear on both the code and commentary side of the page, and when they d o, it appears that the notation in the commentary column is a different notation. However, with this entry, lambda would be in both columns. This statement does begin with the text “In most cases” which at least gives the impression that lightweight concrete may not always have reduced mechanical properties, contrary to the statement in the notation.

To address the second sentence: From a search of the ACI 31819 draft, and from the list of topics given in R19.2.4, it appears that the only instance in ACI 318 where the reduction from lambda is “not related directly to tensile strength” is the use of lambda to reduce the compressive resistance of a compression strut in the strut-and-tie model. If this is so, the last sentence, if

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The inclusion of cast-in-place concrete deep foundation elements in SDC A and B will be considered for New Business in the next Code cycle. No change required. See response to comment 312, page 538, line 12, Castrodale


No.

37.


Reid W. Castrodale

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47

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Public Comment

Committee Response

retained, needs to be singular. However, it appears that CA113 has removed lambda in the equation for the compressive strength of the strut, realizing that this was an inappropriate use of lambda. Therefore, it appears that there is no longer a reason to make the definition more general, and it should be revised to indicate its intent to account for the potential reduction in tensile strength of lightweight concrete. Through page 48 line 3: R2.3-Terminology This discussion of the term “sand -lightweight concrete” appears to indicate that the designer knows what the

See response to comment 312, page 538, line 12, Castrodale

concrete constituents and mix design will be during the design phase. This is very rarely the case. This is the impetus for introducing the new definition of lambda based on density, because during design, the designer almost always has no way of knowing the mix design and the volume fraction of the types of aggregate. Using the old approach places an unnecessary obstacle in the way of using lightweight concrete since it raises confusion in the minds of designers about how to use it. Who is to state the replacement limits as mentioned on p. 48, lines 2&3? I have seen that it is a requirement of submittals from the concrete supplier, but that is too late for design. This is not a reasonable expectation during design. Therefore, I think that retaining the old method of defining lambda based on “type of lightweight concrete” is a mistake, and that it should be removed from ACI 318. 38.

David P. Gustafson

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30

Replace “computations” with “calculations”.

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Agree.


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Public Comment

Committee Response Specific code change required: Change “computations” with “calculations”. Sentence should read “…for shear strength calculations is given in 18.8.4.3.”

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41.

David P. Gustafson

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2

Replace “the Code” with “this Code”. Consider replacing “Wind and Earthquake” with “ wind and earthquake”. Replace “the Code” with “this Code”.

Agree. Agree. This is written undercase in other areas areas of the code (for example, R6.6.4.6.2). Change made. made. Agree. Page 50, Line 2: “reinforcement specifications in the this Code. No other reinforcement qualifies. This definition”

42.

David P. Gustafson

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43.

James Getaz

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0

Should “earthquake loadings” be replaced with “earthquake effects”? For example, the term “earthquake effects” appears on preceding Page 20, Line 41, on Page 38, Line 30, and on Page, Line 16. Figure R2.1(A) Why does 318 still show L-bolts and J-Bolts, or at least without the kind of warning in AISC?

Disagree. Subcommittee H believes the term “earthquake loadings” is clearer in this context. Disagree. AISC provides a recommendation in AISC Design Guide 1 “Base Plate and Anchor Rod Design” to use headed anchors. Moreover, the AISC “Steel Construction Manual (15th Ed),” Chapter 14 notes hooked anchor rods should only be used for axially loaded members subject to compression only during erection. erection. Neither of these are Code provisions, per se.

ACI does not want to preclude the use of J- and L- bolts, as they are still used in the industry. We recognize these types of anchors have a smaller pullout capacity than headed anchors, however there is not a safety concern when they are designed in accordance with ACI 318.

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No.

44.


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Catherine French and Conrad Paulson

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3

Public Comment

Committee Response

This comment is also in relation to pg. 557 Line 24. ASTM A615/A615M-15a, which is the most recent edition of the standard, has no specified minimum requirement for the ratio of actual tensile strength strength to actual yield strength. ACI 318 should specify a minimum ratio of actual tensile strength to actual yield strength of at least 1.1. Additionally, the specified minimum tensile strength requirements for A615 should be reduced to match those of A706. Alternatively, if the ASTM standard is updated to reflect these changes, the updated ASTM standard should be referenced.

Agree. Reason statement: The ACI 318 Committee requested revisions to the ASTM A615/A615M standard appear unlikely to be published before ACI 318-19 is published. This leads to a structural safety concern, because current ASTM A615 tensile strength requirements result in excessive overstrength of reinforcement, leading to non-ductile behavior of members reinforced with overstrength reinforcement. The requirement for a minimum T/Y ratio also helps to mitigate unintended non-ductile behavior and should be implemented with the required adjustments to the tensile strength requirements. Specific Code/Commentary Change Proposal Required: The proposed Code/Commentary Change Proposal is written in combined response to address Public Comments 44-46 and affects Section 20.2.1.3 and R20.2.1.3. The requirements given in proposed Table 20.2.1.3a specifically address Public Comment 44 and are similar to those given in a resolution approved by Committee 318 at the Fall 2017 meeting. Remaining requirements are similar to those presently being balloted by ASTM. Language and format used is consistent with approach taken in the ASTM standards.

45.


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This comment is also in relation to pg. 557 line 25. ASTM A706/A706M-14, which is the most recent edition of the standard, does not include Grade 100. If A706 Grade 100 reinforcement is to be allowed by ACI 318, the required

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Due to space limits in this response column, the Code/Commentary Change Proposal Required to address the cumulative response to Public Comments 44-46 are given in a separate cell after comment 46. Agree. Reason statement: The ACI 318 Committee-requested Committee-requested revisions to the ASTM A706/A706M standard appear unlikely to be published


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Public Comment

Committee Response

mechanical properties must also also appear in ACI 318. The ACI 318 provisions also need to include a requirement to prevent premature fracture of bars under cyclic seismic loading, suc h as requiring a minimum r/h value for the ratio of the radius (r ) of the deformation at the transition to the barrel of the reinforcing bar to the height (h) of the deformation. Alternatively, if the ASTM standard is u pdated to reflect these changes, the updated ASTM standard should be referenced.

before ACI 318-19 is published. Because the current edition of ASTM A706 does not include requirements for Grade 100 reinforcement, it becomes necessary to include such requirements in ACI 318-19. Additionally, appropriate control of the r/h ratio to deter premature fracture of reinforcing bars under cyclic seismic loading addresses a safety concern. Specific Code/Commentary Change Proposal Required: The proposed Code/Commentary Change Proposal is written in combined response to address Public Comments 44-46 and affects Section 20.2.1.3 and R20.2.1.3. The proposed requirements given in 20.2.1.3b (i) and (iii) and proposed Table 20.2.1.3b specifically address Public Comment 45 and uses the ratio T/Y=1.17 from Resolution CR015 and bar deformation geometry requirements from Resolution CR031, which were approved by Committee 318 at the Spring 2017 and Fall 2018 meetings, respectively. Remaining requirements are similar to those presently being balloted by ASTM. Language and format used is consistent with approach taken in the ASTM standards.

46.


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This comment is also in relation to pg. 557 line 25. ASTM A706/A706M-14, which is the most recent edition of the standard, does not include minimum uniform elongation requirements. ACI 318 should include uniform elongation requirements in place of or in addition to the current requirements for minimum elongation across the fracture. Note that CALTRANS is also pushing ASTM for this change.

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Due to space limits in this response column, the Code/Commentary Change Proposal Required to address the cumulative response to Public Comments 44-46 are given in a separate cell after comment 46. Agree. Reason statement: The ACI 318 Committee-requested Committee-requested revisions to the ASTM A706/A706M standard appear unlikely to be published before ACI 318-19 is published. This i s a structural safety concern, because the lack of minimum uniform elongation requirements may lead to structures that lack adequate ductility under seismic


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Public Comment

Committee Response

Alternatively, if the ASTM standard is u pdated to reflect these changes, the updated ASTM standard should be referenced.

loading; this is a particular concern with higher grades of reinforcement. Specific Code/Commentary Change Proposal Required: The proposed Code/Commentary Change Proposal is written in combined response to address Public Comments 44-46 and affects Section 20.2.1.3, R20.2.1.3, and 20.2.2.5. The proposed requirements given in 20.2.1.3b (ii) and proposed Table 20.2.1.3c specifically address Public Comment 46 and are similar to those presently being balloted by ASTM. Language and format used is consistent with approach taken in the ASTM standards.

Due to space limits in this response column, the Code/Commentary Change Proposal Required Required to address the cumulative response to Public Comments 44-46 are given in the next cell.

Committee Response <> 20.2.1.3 Deformed bars shall conform to (a), (b), (c), (d), or (e), except bar sizes larger than No. 18 shall not be permitted: (a) ASTM A615 – carbon steel, including supplementary requirements specified in Table 20.2.1.3a (b) ASTM A706 – low-alloy steel, including supplementary requirements specified in (i), (ii), and (iii): (i) Tensile property requirements for ASTM A706 Grade 100 reinforcement shall be as specified in Table 20.1.2.3b20.2.1.3b, and bend test requirements for ASTM A706 Grade 100 reinforcement shall be the same as the bend test requirements for ASTM A706 Grade 80 reinforcement. (ii) Uniform elongation requirements for all grades of ASTM A706 reinforcement shall be as specified in Table 20.1.2.3c20.2.1.3c, and uniform elongation shall be determined as the elongation at the maximum force sustained by the reinforcing bar test piece just prior to necking or fracture, or both. (iii) For all grades of ASTM A706 reinforcement, the radius at the base of each the deformation shall be at least 1.5 times the height of the deformation., forThis requirement applies to all deformations on a bar, including transverse lugs, longitudinal ribs, grade ribs, grade marks, and intersections between deformations. Conformance shall be assessed by measurements taken on newly-machined rolls used to manufacture reinforcing bars, in lieu of measurements taken on samples of bar samples. (c) ASTM A996 – axle steel and rail steel; bars from rail steel shall be Type R

15 of 215


No.

Public Commenter Pg # Line # Public Comment Name (d) ASTM A955 – stainless steel (e) ASTM A1035 – low-carbon chromium steel

Committee Response

Table 20.2.1.3a - Supplementary Modified tensile strength and additional tensile property requirements for ASTM A615 reinforcement Grade 40

Grade 60

Grade 80

Grade 100

60 000

80 000

100 000

115 000

1.10

1.10

1.10

1.10

Tensile strength, minimum, psi Ratio of actual tensile strength to actual yield strength, minimum

Table 20.2.1.3b – Supplementary tTensile property requirements for ASTM A706 Grade 100 reinforcement Grade 100 Tensile strength, minimum, psi Ratio of actual tensile strength to actual yield strength, minimum

117 000 1.17

Yield strength, minimum, psi

100 000

Yield strength, maximum, psi

118 000

Fracture eElongation in 8 in., minimum, %

10

Table 20.2.1.3c - Supplementary uUniform elongation elongation requirements for ASTM A706 reinforcement Grade 60

Grade 80

Grade 100

3, 4, 5, 6, 7, 8, 9, 10

9

7

6

11, 14, 18

6

6

6

Uniform Elongation, minimum, % Bar Designation Nos.

16 of 215


No.

Public Commenter Pg # Line # Public Comment Committee Response Name R20.2.1.3 The supplementary requirements specified in 20.2.1.3(a) and ( b), and in Tables 20.2.1.3a through c, are necessary because the referenced standards in Chapter 3, ASTM A615-181 and ASTM A706-16, do not include these requirements. For project specifications, these requirements should be specified along with the corresponding ASTM requirements. The supplementary requirements provide for harmonization of minimum tensile strength requirements between ASTM A615 and AS TM A706, add new ductility requirements to both ASTM A615 and ASTM A706, and introduce Grade 100 reinforcement for ASTM A706. These requirements accommodate the introduction of higher strength reinforcement into the Code for special seismic applications and have been developed considering both structural safety and production of reinforcement. The method for determination of uniform elongation specified in 20.2.1.3(b)(ii) is taken from ASTM E8. Low-alloy steel deformed bars conforming to ASTM A706 are intended for applications where controlled tensile properties, are required. ASTM A706 also includes restrictions on chemical composition to enhance weldability for Grades 60 and 80, or both, are required. … … In 2015, ASTM A615 included bar sizes larger than No. 18, and in 2016, ASTM A1035 also included bar sizes larger than No. 18. Bar sizes larger than No. 18 which are not permitted by the this Code due to the lack of in formation on their performance including bar bends and development lengths.

20.2.2.5 Deformed nonprestressed longitudinal reinforcement resisting earthquake-induced moment, axial force, or both, in special moment framesseismic systems, special structural walls, and all components of special structural walls including coupling beams and wall piers and anchor reinforcement in Seismic Design Categories C, D, E, and F shall be in accordance with (a) or (b): (a) ASTM A706, Grade 60, Grade 80 or Grade 80100 for special structural walls and Grade 60 and Grade 80 for special moment fra mes. (b) ASTM A615 Grade 40 reinforcement if (i) and (ii) are satisfied and ASTM A615 Grade 60 reinforcement if (i) through (iii) (iv) are satisfied. ASTM A615 Grade 80 and Grade 100 are not permitted in special seismic systems. (i) Actual yield strength based on mill tests tests does not exceed f y y by by more than 18,000 psi (ii) Ratio of the actual tensile strength strength to the actual yield strength is at least least 1.25 (iii) Minimum fracture elongation in 8 in. shall be at least 14 percent for bar sizes No. 3 through No. 6, at least 12 percent for bar sizes No. 7 through No. 11, and at least 10 percent for bar sizes No. 14 and No. 18. (iv) Minimum uniform elongation shall be at least 9 percent for bar sizes No. 3 through No. 10, and at least 6 percent for bar sizes No. 1114, No.11 14, and No. 18.

<>

ASTM E8/E8M-16a - Standard Test Methods for Tension Testing of Metallic Materials 47.

Tennis

56

20

ASTM C150/C150M-18 is published and should be referenced. C150/C150M-19 has been approved and will be published in

17 of 215

Accepted.


No.


Pg #

Line #

48.

DAVID MANTE

56

28

49.

Tennis

57

5

50.

Tennis

57

20

51.

David P. Gustafson

66

34

52.

ACI Staff

70

6

Public Comment

Committee Response

April 2019; should be referenced depending on the publication schedule for ACI 318. Most recent version of ASTM C469 is C469-14 (not C469-10 as referenced in draft). draft). Was inclusion of updated version considered? ASTM C595/C595M-18 is published and should be referenced. C595/C595-19 has been approved and will be published in April 2019; should be referenced depending on the publication schedule for ACI 318. ASTM C1157/C1157M-17 is published and should be referenced. Should “seismic design category” be shown as “ Seismic Design Category”? Ditto on Line 35. And on Page 67, Lines 1, 3, and 5.

Should this section receive some re-wording now that there are specific one-way slab structural integrity provisions in 7.7.7?

Accepted.

Accepted.

Accepted. Disagree. The forms used consistently throughout the code are as follows. When “seismic design category” is used as a general term, it is not capitalized; when “Seismic Design Category” refers to a specific category, e.g. “Seismic Design Category D,” it is capitalized., No change. Agree. Delete last sentence. sentence. Make editorial changes as shown below. R4.10.2:…Minimum requirements for structural integrity – Structural members and their connections referred to in this section include only member types that h ave specific requirements for structural integrity. Notwithstanding, detailing requirements for other member types address structural integrity indirectly. Such is the case for detailing of one-way slabs as provided in 7.7.

53.

Ing. Hugo Juan Donini

72

12

Reason for addition: for the design of foundations it is relevant to check the flotation, sliding and overturning conditions.

18 of 215

The committee will consider the impact of flotation and uplift as New Business in coordination with ASCE 7.


5.2.4. FLOTATION 5.2.4.1. The effects of the pressure generated by the hydrostatic uplift force under service conditions should be considered in the design, in particular the uplift on foundations. Precautions should be taken to prevent failure by buoyancy effects, providing adequate self weight or ballast. It also must consider the likely effect of leakage can generate in evaluating the water table. 5.2.4.2. For design of flotation resistance should consider the weight of the empty structure according to the expression (5.2.4.2-1). D

1 .

Ar . . (d r r – d d w w ) .

w

(5.2.4.2-1)

where: D dead weight of the structure. flotation safety factor under article 5.2.4.3. 1 Ar foundation area of the structure. d r r depth of foundation. d w depth of water table level. w water density. w 5.2.4.3. The flotation safety factor 1 should reflect the risk associated with the hydrostatic loading condition. Commonly used safety factors are 1.10 for worst-case conditions, such as flood to the top of structure and using dead weight resistance only, or 1.25 for well-defined design flood conditions below the top of structure. A minimum safety factor of 1.25 is also recommended where high ground water conditions exist. Where maximum ground water or flood levels are not well

19 of 215


No.


Pg #

Line #

Public Comment

Committee Response

defined, or where soil friction is i ncluded in flotation resistance, higher safety factors should be used. 5.2.5. SLIDING AND OVERTURNING 5.2.5.1. There are situations to evaluate sliding and / or overturning in structures or components thereof due to soil conditions or unbalanced loads, wind actions, etc. The minimum values of the sliding safety factor stability, 2 and the minimum base area in compression is shown in Table 5.2.5.1. Table 5.2.5.1. Safety factors of stability*

Loading condition

Minimum safety Minimum base area in compression factor stability 2 Usual 1,5 100% Inusual 1,33 75% *Table is not intended to apply to structures that rely on anchorage devices, such as rock or soil anchors, for stability. Loads used to calculate safety factors should be service loads.

The usual load state corresponds to that expected in normal operation of the structure, while the unusual be likened to building situations. The safety factor to overturning, 3 must be greater than 1.5. For elevated structures, service charges that resist overturning are the self weight D when combined with wind W, D + F when combined with the earthquake E, and the self weight D combined with earthquake E. 54.

Mark W Cunningham

72

12

I provided a detailed comment on 5.3.7 during the 318-14 public comment period. The committee’s response was: “The treatment of fluids load F in 318-14 is consistent with ASCE/SEI

20 of 215

The Committee agrees that the definition of F should be revised as follows:


No.


Pg #

Line #

Public Comment

Committee Response

7-10. See ASCE/SEI 7-10 commentary section C2.3.2 for further information.”

“F = effect of service lateral load due to fluids with well-defined pressures and maximum heights”

However, the treatment of fluid loads in ACI 318-14 (and 31819) is not consistent with ASCE 7-10 for a few reasons, and this results in unintended consequences. To be consistent with ASCE 7-10, perhaps ACI 318 should r efer the user directly to ASCE 7-10 instead of providing a modified version of the ASCE 7-10 provisions. ACI 318 5.3.9 and 5.3.10 do reference ASCE 7 in this way and doing so would be akin to how IBC refers the user to ASCE 7. It would also eliminate similar issues if ACI 318 updates for consistency with a newer version of ASCE 7 in the future. (It is inferred that t he ACI 318 committee decided against updating the code with respect to ASCE 7-16 at this time.) 1.

2.

In ACI 318, F is defined as: “effect of service lateral load due to fluids with well-defined pressures and maximum heights”. In ASCE 7 -10, it is defined as: “load due to fluids with well -defined pressures and maximum heights”. Hence, in ASCE 7 it includes both lateral and vertical loads. This is also mentioned in C2.3.2 as follows. “Where F acts as a resistance to uplift forces, it should be included with dead load D.” and “To make it clear that the fluid weight in a tan k can be used to resist uplift, F was added to load combination 7, where it will be treated as a dead load only when F counteracts E.” ACI 318 separates lateral load, F, from the liquid weight. So, it isn’t clear how ACI 318 addresses the vertical load that is due to the liquid that causes F.

21 of 215


No.


Pg #

Line #

Public Comment

Committee Response

3.

55.


72

16

ACI 318 identifies the “Primary load” for each load combination in T5.3.1. Primary loads are not identified this way in ASCE 7-10. 4. Per T5.3.1, F and H aren’t the primary loads for any of the load combinations. But F and H could be the primary loads. (One example is if the effect of E adds to the effect of F, with F being the primary load.) 5. ACI 318 also doesn’t consider the case where F adds to E, when E is the primary load (Eq 5.3.11g). 6. Because H is not a primary load, it is not clear how ACI 318 treats F in adding to or counteracting H. This is not addressed in 5.3.7. 7. ACI 318, 5.3.8 addresses H acting alone, or adding to or counteracting the primary load effect. Since F is not a primary load for any load combination, it is not clear how the code treats H in relation to F. 8. In ACI 318, 5.3.7(c) and (d) address F being either permanent or not permanent. ASCE 7-10 does not consider F to be permanent. The corresponding commentary in C2.3.2 states: “However [F] is not permanent; emptying and filling causes fluctuating forces in the structure…” and “F is not included in combination 6 because the wind load can be present whether the tank is full or empty, so the governing load case in combination 6 is when F is zero.” Reason for change: consider the loads due to fluids with welldefined pressures and maximum heights and loads due to weight and pressure of soil, water in soil, or other materials, or related internal moments and forces in the load combinations. These cases may be relevant in the design of foundations.

Table 5.3.1 – Loads combinations

22 of 215

New Business


No.


Pg #

Line #

Public Comment

Committee Response

Load combination

Equation

U = 1.4 (D + F) U = 1.2 (D + F) + 1,6 (L + H) + 0,5 (L r or S or R) U = 1.2 D + 1,6 (L r or S or R) + (1.0 L or 0.5 W) U = 1.2 D + 1,0 W + 1.0 L + 0.5 (Lr or S or R) U = 1.2 D + 1,0 E + 1.0 (L + Lr) + 0.2 S U = 0.9 D + 1.0 W + 1.0 H U = 0.9 D + 1.0 E + 1.6 H

56.

David P. Gustafson

76

4

57.

John Gardner

76

10

(5.3.1a) (5.3.1b) (5.3.1c) (5.3.1d) (5.3.1e) (5.3.1b) (5.3.1b)

Primary load D and F L+H Lr or S or R W E W and H E and H

Consider replacing “earthquake loads” with “earthquake effects”. 5.3.1 Load Factor Factor for Loads due to construction process

(suggest 1.2) R5.3.1

Flat plates are usually constructed using a single

level of shores (forms) which support the freshly placed concrete, supported on the most recently cast plate which in turn is supported by reshores from earlier cast, but still immature, plates. Without further information, information, it is recommended that the upper supporting plate be assumed to carry its own self weight plus 0.55 of the weight of the the freshly cast plate plus 0.55 of the shore self weight plus 0.55 of the construction live load. Flat

23 of 215

Agreed. Accept as New Business. The committee will take up as new business clarification of the responsibility responsibility for the consideration of the effects of shoring and reshoring upon deflections.


No.


Pg #

Line #

Public Comment

Committee Response

plates have two areas of concern; punching shear, which can occur during construction when the developed strength of the immature concrete is low and large immediate and creep deflections during service.

(Reference - Monette Luc and Gardner N. J. , “Shored/Reshored Construction of Flat Plates Analyses of the effect of reshore stiffness on load distribution”, distribution”, ACI Concrete International, Sep t. 2015, pp 52 -60.)

58.


80

1

Reason for addition: it is important to generate loads combinations in service conditions that allow the designers to make decisions about phenomena such as deformations and cracking. 5.3.14. SERVICE LOADS COMBINATION 5.3.14.1. Group 1 In elevated structures, as elevated water tanks, the combinations designers must analyze at least when the effects of one or more acting simultaneously: D+F D+F+G+S+L+T D+G+W+L+S D + F + G + 0,7 E + L + S

(5.3.14.1a) (5.3.14.1b) (5.3.14.1c) (5.3.14.1d)

When: G = eccentric load effects due to dead load and water

24 of 215

Disagree. Elevated water tanks should be covered in ACI 350, not 318.


No.


Pg #

Line #

Public Comment

Committee Response

For serviceability limit states involving visually objectionable deformations, repairable cracking or other damage to interior finishes, and other short-term effects, the suggested load combinations are: D+L (5.3.14.1e) D + 0.5S (5.3.14.1f) For serviceability limit states involving creep, settlement, or similar long-term or permanent effects, the suggested load combination is: D + 0.5L (5.3.14.1g) The dead load effect, D, used in applying Eqs. 5.3.14.1e, 5.3.14.1f and 5.3.14.1g may be that portion of dead load that occurs after attachment of nonstructural elements. For example, in composite construction, the dead load effects frequently are taken as those imposed after the concrete has cured; in ceilings, the dead load effects may include only those loads placed after the ceiling structure is in place.

The following load combination, derived similarly to Eqs. 5.3.14.1e and 5.3.14.1f, can be used to check shortterm effects: D + 0.5L + W a (5.3.14.1h) in which Wa is wind load based on serviceability wind speeds.

5.3.14.3.2. Group 2

Combinations designers must analyze at least when D or F reduce the effects of W or E: 0,6 D + W (5.3.14.2a) 0,6 D + 0,7 E (5.3.14.2b)

25 of 215


No.


Pg #

Line #

Public Comment

Committee Response

0,6 (D + F) + 0,7 E (5.3.14.2c)

59.

60.

Adam Lubell

Restrepo J.I. and Rodriguez M.E.

83

97

5

8

61.


103

5

62.

David P. Gustafson

107

14

63.

ACI Staff

108

23

64. 65.


111 111

4 5

66.

David P. Gustafson

111

13

For Clause 6.2.5.3 and related commentary, consider providing a direct ex planation that justifies a limit of “1.4Mu” since that limit is not present in other international design codes. With clause renumbering, this check in Fig R6.2.5.3 is incorrect labelled. This line should read “…shear walls structural walls” The reason is that in ACI 318-19 the wording “structural walls” is used instead of “shear walls” This line should read “…shear walls structural walls” See reason given in comment on page 97, line 8. Line 2 in R6.6.4.6.4 – Simply an observation; note the terminology “computer analysis programs”. Ditto – Line 2 in R6.7.1.2. No line numbers in Chapter 6 commentary. Last paragraph of R6.6.5 – is there any way to reword the code in 6.4.3.3 to state that moment redistribution is not allowed using this loading pattern? If so, then the wording of the code provision 6.6.5.1 could be simplified to something along the lines of “Except where not permitted in 6.5, 6.8, and 6.4.3.3,…” Consider replacing “great” with “large”. In Section R6.9.2, Line 5, should “analysis” be replaced with th e plural “analyses In Section R6.9.3, Line 1, should “For inelastic finite element analysis, the rules . . .” be revised to: • “For an inelastic finite element analysis, the rules . . . “ • Or to: “For inelast ic finite element analyses, the rules . ..“

26 of 215

Disagree on first point. The last sentence in R6.2.5.3 provides reason for the 1.4 factor. Agree on second point. Changed reference reference in Figure R6.2.5.3 to 1.4Mu factor (change from 6.2.6 to 6.2.5.3). Agree. Change made.

Agree. Change made.

No change needed.

Disagree. No change needed.

Agree. Change made. Agree. Change made. Agree. Change made to“For an inelastic finite element analysis, the rules…”


No.

67.

68.

Public Commenter Name Reid W. Castrodale

Reid W. Castrodale

Pg #

Line #

116

4

116

10

Public Comment

Committee Response

7.3.1.1.2 The reference to a range of lightweight concrete from 90 to 115 pcf appears to be a carry over from the old definitions of lightweight concrete. However, the commentary for Article 9.3.1.1.2 explains why this range is shown.

Disagree.

Therefore, commentary should be added for this article that would be the same as Article R9.3.1.1.2. Through line 11 7.3.1.1.3 This sentence does not make sense t o me – I am not aware of situations where there is “a combination of lightweight and normalweight concrete.”

No change needed.

Perhaps this is intended to address situations where they are both present in a slab because of puddling of higher strength normalweight concrete around the column, but th e proper word for that situation would not be that the concretes are combined, which means to me that the types of concrete would actually be mixed. It seems that it would be better to say that they are present simultaneously in the slab.

The commentary of R7.3.1 refers refers to R9.3.1. It was decided not to repeat every single section for the commentary, but rather have the general section refer to commentary.

Disagree. This provision is referring to a composite slab where one part of the composite slab is made with normalweight concrete while another (such as a topping) is made with lightweight concrete. This provision has been worded as such for many years. No change needed.

Another possible intended meaning could be that this sentence is addressing a combination of lightweight and normal weight aggregate, not a combination of NW and LW concrete as stated.

69.

Adam Lubell

119

1

Please clarify. It appears that the code should be revised and a statement in the commentary added. In 7.6.3.1, minimum shear reinforcement in slabs is only required when Vu>Phi*Vc whereas for beams, 9.6.3 requires minimum shear reinforcement when Vu>Phi*1.0*root(fc’)*bw*d except for specific exemptions in

27 of 215

Disagree. This limit has been successfully used in the Code since 1971. For slabs, load sharing is recognized by ACI 318 due to variation in


No.


Pg #

Line #

Public Comment

Committee Response

Table 9.6.3.1. There are no exemptions exemptions listed in 7.6.3.1 and therefore designs utilizing Phi*Vc without providing shear reinforcement will occur, including slabs and footings with vary large thicknesses and/or with low reinforcement ratios due to member depth and/or use of high strength reinforcement.

loading as well as continuity of the slab system. In the 318-19 Code, a size effect factor account for member depth has been added which reduces the nominal shear strength for thicker slabs and increases safety of these thicker slab syst em. No change needed.

Lubell (2006) and Sherwood et al (2006) demonstrated through laboratory testing that member width does not influence the shear stress at failure for members detailed as slabs compared to members detailed as beams when the loading was approximately uniform across the width. Therefore, for the common slab or footing loading scenario of uniformly distributed loading on the entire slab, there is no justification to relax the minimum shear reinforcement requirement relative to that applying to beams and thus 7.6.3.1 should require minimum shear reinforcement with the same sectional shear limit criteria as 9.6.3.1. If the code committee believes believes the “load sharing” argume nt in R7.6.3.1 is justified in some cases, such as patch loading, the code committee should develop a new clause to guide a designer on the appropriate distribution width that can be used for 7.6.3.1 checks.

70.

Adam Lubell

124

22

References cited: [1] Lubell, A.S., “Shear in Wide Reinforced Concrete Members”, PhD Thesis, University of Toronto, 2006, 455 pp [2] Sherwood,E.G.; Lubell,A.S.; Bentz,E.C; and Collins,M.P. “One way shear strength of thick slabs and wide beams”, ACI Structural Journal, Vol 103, Nov 2006. R7.6.3.1 should also refer to Lubell (2006) and Sherwood et al (2006) where it was demonstrated that member width does not influence the shear stress at failure for slabs when approximately uniform loading across the width is present. This negates the argument in the first sentence of R7.6.3.1 that the

28 of 215

Disagree. Please see response to Comment 69, page 119, line 1 Lubell. The addition of these references is not considered needed.


No.


Pg #

Line #

71.

Dan Mullins

135

1

72.

Dan Mullins

135

2

73.


135

4

Public Comment

Committee Response

possibility of load sharing allows less stringent minimum shear requirements. See also comment submitted by Lubell Lubell at Page 119 Line 1. Should say “drop panel or shear cap” to be consistent with definitions and previous sentence. Should say “drop panel or shear cap” to be consistent with definitions and previous sentence.

No change needed.

Through line 10 and page 163 line 6 through 164 line 10 Subsequent to public discussion of ACI 318-14, studies confirm the position of ACI Committee 421 and the discussers regarding the permitted increase of  f and the corresponding reduction of v in 8.4.2.2.4 and R8.4.2.2.4. Shear and bending in two way slabs must comply with: “ 4.5.1 Analytical procedures shall satisfy co mpatibility of deformations and equilibrium of forces.” Removal of 8.4.2.2.4 and R8.4.2.2.4 is proposed, because they violate equilibrium. They permit replacing shear and bending parameters complying with 4.5.1 with emperical values that violate equilibrium. Table 8.4.2.2.4 is based on interpretation of test results without considering equilibrium. Shear in two-way slabs is equal to derivative of bending (Timpshenko and Krieger, 1959); this relationship applies in all load stages. The increase of  f , with equal reduction of v according to Table 8.4.2.2.4, underestimates the required shear reinforcement. Reduced or eliminated shear reinforcement cannot be replaced by additional flexural reinforcement. This is is not permited for frames; it should be disallowed in two-way slabs. Similarly, the minimum flexural reinforcement As,min, required in 8.6.1.2 and R8.6.1 to resist flexure-induced punching, does not justify reduction or elimination of required shear reinforcement. 8.6.1.2 and R8.6.1.2 are new in ACI 318-19.

29 of 215

Agree. Change made. Agree. Change made. Disagree. The noted procedures are effectively existing code language. We are not aware of any problems associated with as-built slabs related to application of these provisions. No change needed.


No.


Pg #

Line #

Public Comment

Committee Response

The suggested removal of optional 8.4.2.2.4 and R8.4.2.2.4 enhances safety without losing simplicity. T he optional reduction of v, introduced in 1980s to simplify design, is not needed in current practice. Design of shear reinforcement in slabs is routinely and easily done with computers, using v specified in 8.4.4.2 and R8.4.4.2, that are derived by finiteelement analyses (Elgabry and Ghali, 1996; Gayed and Ghali, 2008; Megally and Ghali, 1996).

74.


138

27

References: Timosheko, S. and Woinowsky- Krieger, S., 1959, “Theory of Plates and Shells, 2 nd Ed., McGraw Hill, New York. Elgabry, A.A., and Ghali, A., 1996, “Moment Transfer by Shear in Slab-Column Slab-Column Connections,” ACI Structural Journal, Vol. 93, No. 2, March-April, pp. 187-196. Gayed, R.B., and Ghali, A., 2008, “Unbalanced Moment Resistance in Slab-Column Slab-Column Joints: Analytical Assessment,” Journal of Structural Engineering, ASCE , Vol. 134, No. 5, May, pp. 859-864. Megally, S.H. and Ghali, A., 1996, “Nonlinear Analysis of Moment Transfer Between Columns and Slabs”, Proceedings, Canadian Society for Civil Engineering Annual Conference, Edmonton, Alberta, May, Vol. 2a, pp. 321-332. Through page 139, line 4 Calibration of test results was based on yield-line analysis with concentric and eccentric V u. The code should require As,min computed by yield-line analysis. Simplified analysis should be in R8.6.1.2; replace 8.6.1.2 on pages 138-139 by: cross- sectional area ≥ 8.6.1.2 Top 8.6.1.2 Top flexural reinforcement of cross-sectional As,min determined by yield-line analysis, shall be provided in two orthogonal directions over area of radius 0.2 lc, surrounding column or reaction area.

30 of 215

Disagree. In accordance with results of the test data calibration described in R8.6.1.2, the As,min required by Eq. 8.6.1.2 is greater than that required by yield line analysis. Further, if the wrong yield line mechanism is selected for a given loading condi tion, the design may be unsafe. In addition, because column spacings can be irregular, the use of a width bslab is more realistic than a radius of 0.2l c Editorial changes made: 1. Change v ug ug in Eq. 8.6.1.2 to v uv uv .


No.

75.



Pg #

141

Line #

7

Public Comment

Committee Response

Through line 9: Reason for change: in case of more demanding exposure categories (F2, F3, S2, S3, W2, C1 and C2), it is suggested to reduce maximum spacing s of deformed longitudinal reinforcement in order to verify the most demanding cracking criteria. 8.7.2.2. For nonprestressed solid slabs, maximum spacing s of deformed longitudinal reinforcement shall be the lesser of 2h and 18 in. at critical sections, and the lesser of 3h and 18 in. at other sections. 8.7.2.2.1 In slabs exposed to exposure categories F2, F3, S2, S3, W2, C1 and C2, the maximum spacing s of the bending and tension reinforcement must be less or equal to that shown in Figure 8.7.2.2.1. The values are plotted as a function of the minimum concrete cover to centroid of steel d c c at at the tensile face for plates with different supports, uniform loads and l min min / l max ratios of 0.5, 0.7 and 1.0. max ratios

31 of 215

2. Move heading R8.6.1.2 (Page 167, Line 2) to paragraph beginning on p.166 line 20 “Tests on interior …” Disagree. Existing code provisions have shown to provide adequate durability. No change needed.


No.


Pg #

Line #

Public Comment .

Committee Response

n

lmin/lmax = 0,5

11.00 in

10.00 in

lmin/lmax = 0,7

9.00 in s ( g 8.00 in n i c a p s 7.00 in m u m i x 6.00 in a M

lmin/lmax = 1

5.00 in

4.00 in

3.00 in

2.00 in 1.70 in

1 .8 0 in

1 .9 0 in

2 .0 0 in

2 .10 in

2.20 in

2.30 in

2.40 in

2 .5 0 in

2 .6 0 in

Minimum concrete cover to centroid of steel at the tensile face (d c )

Figure 8.7.2.2.1 — Variation of the maximum spacing s of deformed longitudinal reinforcement in two-way slabs with uniform loads (exposure categories F2, F3, S2, S3, W2, C1 y C2)

R 8.7.2.2.1 — The equations for crack control in beams or slabs in one direction may become unsuitable for those developed in the slabs and plates into two directions (ACI 224R). ACI 224R proposed expressions relating the service-load stress with the spacing of the reinforcement, maintaining a constant relationship with the concrete cover, as on slabs, such factor remains practically constant. From investigations developed by Nawy and Blair in 1971, the ACI 224R-01 discusses the use of the equation C 8.7.2.2.2-1 for the prediction of probable maximum crack width in slabs and plates in two directions:

wmáx

145.k..f s. = 0,145

GI (R 8.7.2.2.1-1)

32 of 215

2 .7 0 in

2 .80 in


No.


Pg #

Line #

Public Comment

Committee Response

with: w máx = crack width at face of concrete caused by flexure, in. máx = k = = fracture coefficient Table C 8.7.2.2.1. 8.7.2.2.1. Table R 8.7.2.2.1 — Fracture coefficients for slabs for slabs and plates

ading type

Slab shape

Boundary condition

Span ratio lmin/lma x

ncentrated

Square

ncentrated

Square

Uniformly istributed Uniformly istributed

Rectangular Rectangular

Uniformly istributed

Rectangular


Rectangular


Square


Square

4 edges restrained 4 edges simply supported 4 edges restrained 4 edges restrained 3 edges restrained y 1 hinged 2 edges restrained y 2 hinged 4 edges restrained 3 edges restrained y 1 hinged

Frac Fractu turr coe coeffic fficiie k (.10-5

1,0

2,1

1,0

2,1

0,5

1,6

0,7

2,2

0,7

2,3

0,7

2,7

1,0

2,8

1,0

2,9

33 of 215


No.


Pg #

Line #

Public Comment

Uniformly distributed

Committee Response

Square

2 edges restrained y 2 hinged

1,0

4,2

= 1.25 (chosen to simplify calculations, although it varies between 1.20 and 1.35). f s = actual average service-load stress level or 40% of the specified yield strength f y, ksi. Gl = grid index equation R 8.7.2.2.2-2. d .s s .s .d 8 R 8.7.2.2.1-2 GI = b1 2 = 1 2 c . db1  t1  d b1 b1 = diameter of the reinforcement in Direction 1 closest to the concrete outer fibers, in. s1 = spacing of the reinforcement in Direction 1, in.. s2 = spacing of the reinforcement in perpendicular Direction 2, in. t1 = active steel ratio, that is, the area of steel As per ft width/[12db1+ 2c1] c 1 = clear concrete cover measured from the tensile face of concrete to the nearest edge of the reinforcing bar in Direction 1. d c c = = concrete cover to centroid of reinforcement, in. From equation R 8.7.2.2.1-1, the maximum possible spacing of flexural reinforcement for a given condition of cracking is:

w máx máx

= 0,145.k..f s .





w máx GI  GI =   0,145 .k..f  s  

2

8.7.2.2.1-3 Assuming s1 = s2 = s:

sl



GI .db1. dc .8

R 8.7.2.2.1-4

34 of 215

R


No.


Pg #

Line #

Public Comment

Committee Response

From this expression, was drawn Figure 8.7.2.2.1, which raises spacing of flexural reinforcement in slabs and walls under more severe exposure categories. For the confection of Figure 8.7.2.2.1 is considered a maximum crack width of 0,01 in., an average service-load stress level f s of 24 ksi (0,4 (0,4 . 60 ksi), a minimum concrete cover of 1-1/2 in. (see Table 20.6.1.3.1), a coefficient equal to 1,25 and coefficient fracture for slabs with uniformly distributed for span ratios lmin / lmax of 0,5, 0,7 and and 1,0 with with different boundary condition. The rebar diameters ranges were considered No. 8 to to 18 . 76.

77.


John Gardner

145

160

12

23

Through line 13: The sentence on lines 12-13 12- 13 is: “Headed stud shear reinforcement shall be permitted if placed perpendicular to the plane of the slab”. Delete the words “if placed perpendicular to the plane of the slab”. The words to be deleted require placing the shear reinforcement in an orientation other than the most effective one. No basis is given for disallowing inclined headed studs in slabs, while allowing stirrups in all members without such restriction. Assemblies automatically maintain specified spacing and orientation of studs until concrete is cast; with stirrups, control of spacing and orientation is necessary, but is not as ea sy. The current comment proposes removing the restriction and insertion of commentary R7.7.1. Through line 27 8.3.1 Two-way slab minimum thickness requirements R8.3.1 The provisions suggested by Ofuso-Asamoah and Gardner take account of the construction cycle – age age and

35 of 215

Disagree: This issue was suggested as a topic for examination in the 318-19 cycle. However, no evidence could be found of tests where inclined headed stud shear reinforcement had been used in tests or in practice. Results of tests are desirable before such a change is made. It should be noted that alternate systems can be proposed under Code Section 1.10. No change needed.

New business. The minimum thickness requirements requirements were considered for updating in this code cycle, but further review is needed.


No.


Pg #

Line #

Public Comment

Committee Response

magnitude of first construction loading on the limiting span thickness ratios. Asamoah K. and Gardner N. J., “Flat Slab (Reference - Ofosu- Asamoah Thickness to Satisfy Serviceability including Early Age Construction Loads”. ACI Structural Journal, Nov-Dec 1997. Pp 700-707)

78.


164

26

8.4.4.2.3 is a key section for strength design of two-way slabs. R8.4.4.2.3 is revised below to give a general equation for vc that applies to critical sections of any shape, with eccentric force V u. Symbol J c is defined such that the equation of vc gives stress whose resultant = the eccentric force V u. On line 26 of page 164, remove the heading R8.4.4.2.3 and insert: R8.4.4.2.3 In R8.4.4.2.3 In general, eccentric force V u is equivalent to V u at the centroid of the shear critical section’s perimeter, combined with M sc sc. At point ( x, y) on the perimeter of a shear critical section of general shape, the shear stress due to eccentric shearing force V u is calculated by:

v u

=

   M +  d  J

V u bo

v

c

sc

  

x

   M  J 

y + 

v

c

sc

  

x y

(R8.4.4.2.3) J c = d multiplied by moment of inertia of shear critical section’s perimeter about its principal axis x or y. The subscripts x and y refer to the principal axes. Referring to the shear critical section in Fig. R8.4.4.2.3,

36 of 215

Disagree. This is textbook material and not needed. No change needed.


No.


Pg #

Line #

Public Comment

J c

=

d (c

+ d )

3

1

6

+

Committee Response

d (c

2

+ d ) (c + d )

2

1

2

---------------------End of insertion--------------------Delete lines 5-8 of page 165.

79.

Amin Ghali and Ramez Gayed

166

20

In R2.2, insert a definition of J c as given above. Through line 27: As,min to resist flexure-induced punching is necessary over an assumed pattern of yield lines. Lines 20-27 of page 166 should be more accurately replaced by: Tests show that yielding of the slab’s flexural tension reinforcement in the vicinity of interior column leads to increased local rotations and opening of any inclined crack existing within the slab (Hawkins and Ospina 2017; Widianto et al. 2009; Muttoni 2008). Peiris and Ghali 2012 and Gayed et al. 2017 show by tests and analysis that unless As,min is provided over potential yield-lines in the vicinity of columns, sliding along inclined crack can cause flexure-driven punching failure at a shear force less than the strength calculated by the two-way shear equations in Tables 22.6.5.2 and 22.6.6.2; this finding is calibrated with eccentric V u and with V u at the centroid of the shear critical section. Dam et al. 2017 calibrated tests using equivalent yield-line analysis. As,min is cross-sectional area of top reinforcement placed above column to resist flexure-induced punching. Unless As,min is provided over an assumed pattern of yield lines, sliding along inclined crack causes flexure-induced punching failure at a shear force less than the strength calculated by the two-way shear equations of Table 22.6.5.2 or 22.6.6.2.

37 of 215

Disagree. As worded, the commentary adequately supports the Code provisions. Please see response to Comment 74, page 138, line 27, Ghali. Further, the appropriate  factor to use is the  factor for shear because the proposed As,min provision is intended to prevent a brittle punching shear failure in a slab whose flexural capacity is less than that associated with a shear stress of 4 sqrt f’ c. and above that associated with the shear stress for a yield line analysis. As,min is defined such that the factored shear force on the critical section for shear in the slab equals the shear force associated with local yielding of the slab flexural reinforcement around the column.

No change needed.


No.


Pg #

Line #

Public Comment

Committee Response

As,min is required to control flexural cracks at yield lines. In calculating the flexural strength provided by As,min, the strength reduction factor is  for flexure.

80.


167

2

Reference: Gayed, R.B., Peiris, C. a nd Ghali, A., 2017, “Flexure-Induced “Flexure-Induced Punching of Concrete Flat Plates,” American Concrete Institute, fib Bulletin 81, March, pp. 73-100. Through line 10 Replace lines 2-10 on page 167 by R8.6.1.2 as given below. The equation for As,min is revised to give the minimum flexural reinforcement required over the area of yield-line pattern. As,min is not additional to the flexural flexural reinforcement required by other code equations. The total flexural reinforcement area required by the code for the governing V u includes As,min .These revisions are done in the proposed R8.6.1.2 given below. Equation 8.6.1.2 of ACI 318-19 draft, gives As,min required over bslab. Replace Eq. 8.6.1.2 by Eq. R8.6.1.2 (in the revised version) to give the flexural reinforcement required over area of potential yield-line pattern; use  for flexure. Equation 8.6.1.2 gives  min providing a strength less than the strength required in a column strip. This means that 8.6.1.2 in ACI 318-19 draft, does not govern the design of flexural reinforcement over interior columns. As example, consider an interior column with centre-to-centre span between columns in orthogonal directions, lc = 344 in. (8.7 m); ln = 323.8 in.; vug = 203 psi; square column = 20.7 in.; bslab = 50.2 in.; bo = 116.4 in.; s = 40; f y = 58 ksi;  (shear) = 0.75. Equation 8.6.1.2 gives: As,min = 5 vug bslab bo /( s f y) = 3.41 in. 2 (’= 0.80 percent over bslab), compared with ’= 0.66 percent required over column strip width = 172 in. ( As within column strip = 9.53 in. 2). This example shows that 8.6.1.2 has no effect on flexural

38 of 215

Disagree. Please see response to Comments 74, page 138, line 27, Ghali and 80, page 166, line 20-27, Ghali. No change needed.


No.


Pg #

Line #

Public Comment

Committee Response

reinforcement design. Similarly, 8.6.1.2 does not govern the design of flexural reinforcement in any of the four examples in the revised R8.6.1.2 (proposed below), or with any practical lc. For interior column, Eq. 8.6.1.2 of the ACI 318-19 draft and the proposed Eq. R8.6.1.2 are based on the the same yield-line equation: the required flexural strength per unit length is approximately equal to V u/8. Although the two equations should give approximately the same As,min per unit width (same ’), the total amounts of reinforcement are different because the of the difference in the zone to be covered. The parameter bslab , specifies location of flexural reinforcement associated with M sc sc. Both parameters: bslab and M sc sc, are irrelevant to the flexural reinforcement required to avoid premature development of a yield-line mechanism. As,min is required over the area of the potential yield-line pattern that can induce punching (with any M sc sc ≥ 0). Proposed R8.6.1.2: R8.6.1.2 An idealised yield-line pattern of isotropic slab, induced by shearing force, V u = vu,max bo d , is assumed. The force V u is located at the centroid of the shear critical section (Fig. R8.6.1.2). Actual column cross-sectional area = c2 is idealized as a circular column of equal a rea. Equilibrium of a typical slab segment gives (Ghali and Gayed, 2019):

(m + m ) =

v u ,max bo d



2  (1 − 2.8 c l c )



(

v u ,max bo d

8

)

2 m =  f y d 1 − 0.59  f y f c

min =   As ,min

(0.4 l ) =  c

min

b d

(R8.6.1.2)

39 of 215


No.


Pg #

Line #

Public Comment

Committee Response

where vu,max = maximum absolute value of vu calculated by Eq. R8.4.4.2.3 for the shear critical section at d /2 /2 from periphery of actual column; lc = larger center-to-center distance between columns in adjacent panels;  = flexural strength reduction factor; m and m = flexural strengths per unit length provided by top and bottom reinforcements, reinforcements, respectively; As,min = crosssectional area of top flexural reinforcement providing moment strength = m (0.4 lc ) ; b = unit length. Flexural strength, m = fraction of m = strength provided by bottom flexural reinforcement ≥ the minimum required for shrinkage and temperature in 24.4.3.2. Derivation of Eq. R8.6.1.2 conservatively substitutes ecce ntric forc V u by a force = vu,max bo d at at centroid of shear critical section. The flexural strength per unit length of prestressed reinforcement can be deducted from ( m + m). The calculated As,min provided to resist flexure-induced punching includes all reinforcement required for strength in 8.4. Thus, the design for As,min does not necessarily increase the total a mount required for flexural strength. Assuming, m = m 4 ,the above equations give: min = 0.53, 0.53, 0.56 and 0.60 percent, respectively for lc = 220, 276, 344 and 413 in. Data: uniform gravity load, qu = (106 h + 638)×10 -3 psi, with h in inch; d = = h – 1.4 1.4 in.; h = lc/35; V u = qu lc2 ; c = 0.06 3 lc; f c = 4350 p---si; f y y = 58×10 psi;  = 0.9.

Reference: Ghali, A. and Gayed, R.B., 2019,” Universal Design for Punching Resistant Concrete Slabs”, ACI AC I Structural Journal, January, Vol. 116, N0. 1, pp. 207-212.

40 of 215


No.


Pg #

Line #

Public Comment

) l a c i r i p m E (

Committee Response

4

c Segment isolated in part (b)

V flex

c

l

4 . 0

Cross-sectional Cross-sectional area of column = c2; c = side of square column (not shown)

(a)

Downward force=

V flex

0.4  lc

m 1

Support

m

m

1 (b)

81.


173

24

c

m Radius = 0.2 lc

Fig. R8.6.1.2 — Assumed Assumed yield-line pattern for derivation of Eq. R8.6.1.2. (a) Yield-line pattern (b) Forces and moments on isolated segment Immediately below line 24, insert commentary R7.7.1: R7.7.1 Experiments R7.7.1 Experiments show that shear reinforcement is more effective when placed perpendicular to shear cracks (Dilger, 2017). Inclined headed studs are permitted for beams; they should also be allowed for slabs. Tables 8.7.7.1.2, 22.6.6.1 and 22.6.6.3 recognize that headed stud shear reinforcement is more effective than stirrups. The incline of studs induces no

41 of 215

Disagree. Please see response to Comment 76, page 145, line 12, Ghali. No change needed.


No.


Pg #

Line #

Public Comment

Committee Response

difficulty: assemblies maintain the studs in specified orientation, spacing and cover until concrete is cast. Headed studs, placed in direction perpendicular to potential shear cracks, is used with vs calculated by Eq. 22.5.8.5.4, adjusted below for slabs: v s

=

Av f yt bo s

(sin  + cos )

with s measured in direction parallel to slab surface;  = inclination angle of studs with slab surface (Ghali and Gayed, 2017). References: Dilger, W.H., 2017, “Inclined Stirrups and Inclined Stud Shear

82.


173

31

Reinf orcement orcement in Zones of High Shear”, ACI SP -321 — 10. 10. Ghali, A. and Gayed R.B., 2017, “Inclined Headed Stud Shear Reinforcement: Design and Detailing”, ACI SP-321 SP -321 — 11. 11. The stud assemblies in Fig. R8.7.7 are placed perpendicular to column sides, with one assembly at each column corner. At a wide column side, it may be necessar y to provide more than two stud assemblies. To avoid ambiguity, insert at end of paragraph: The assemblies of headed studs in Fig. R8.7.7 are placed perpendicular to column sides with one one assembly close to each column corner, such that: number of assemblies within column side ≥ 1+[(width of column side – 3 – 3 times stud diameter (or width of rail))/2 d ]. ]. Rules for design and detailing of headed stud assemblies and flexural reinforcement apply with the crucifix layout in Fig. R8.7.7. Radial layout follows different rules; mingling the rules can cause interference of flexural a nd shear reinforcement (Ghali, and Gayed, 2017). Values of vc in Table 22.6.6.1(b) apply only with the crucifix layout of stud assemblies.

42 of 215

Disagree. Commentary figures are intended to indicate one possible configuration. Other configurations are possible. No change needed


No.

83.

84.

85.

86.



Robinson

Reid W. Castrodale

Allan Bommer

Pg #

187

193

193

196

Line #

2

21

27

27

Public Comment

Committee Response

Reference: Ghali, 2017 and Gayed, 2017, Discussions of Title 114-S19, “Behavior of Monotonically Loaded Slab-Column Connections Reinforced with Shear Studs”, Studs” , ACI Structural Journal, Vol. 114, No. 6, November-December. The spacing ≤ 2 d between between legs of stirrups needs to be shown in Figs. 8.7.6d and e. A relevant statement needs to be inserted at end of R8.7.6.

This line still has the density range of 90 to 115 pcf from the old definition of lightweight concrete. concrete. A sentence should be added to the commentary matching the one t hat appears in R7.3.1.1.2 that explains why the range does not extend for the full range of densities given in the definition of lightweight concrete. Through line 28 9.3.1.1.3 Same comment as for p. 116, lines 10-11.

9.6.1.2 can provide unsafe results when reinforcement is placed in odd locations (such as the centroid of a section). The cracking moment varies with h and the capacity varies with d. The following plot shows the relationship of d/h and the factor of safety ( φMn/Mcr).

Disagree. Detailing requirements for for stirrups are shown in Fig. R8.7.6b. In addition, spacing ≤ 2d is indicated in Figures 8.7.6d & 8.7.6e. No change needed. Disagree. No change needed. The explanation for densities greater than 115 pcf is provided in the commentary of R9.3.1.1.2.”

Disagree. Please see response to comment 67, page 116, line 4, Castrodale. No change needed. Not persuasive. The statement is correct; if the reinforcement is placed in the wrong face, it is not effective. At the same time, placing reinforcement in the correct location is the responsibility of the LDP. No change needed.

43 of 215


No.


Pg #

Line #

Public Comment

Committee Response

It can be see that the current equation ranges from unsafe to excessively conservative. 87.

Adam Lubell

197

18

9.6.3.1 requires that Av,min is provided if Vu>Phi*1.0*root(fc’)*bw*d except for specific exemptions in Table 9.6.3.1 in which case a limit of Vu>Phi*Vc applies. As one example, Vu > Phi*Vc applies for beams built integrally with slabs if h<24 inches. Laboratory tests for thicker beams beams with low amounts of high-strength longitudinal reinforcement have shown that these can fail at low shear stress that could be below Phi*Vc. For example, refer to tests by Desalegne and Lubell (ACI Structural, 2010) and Collins and Kuchma (ACI Structural 1999). It is recommended that 2 changes to 9.6.3.1 be implemented: (1) Change the basic check of Vu > Phi*1.0*root(fc’)*bw*d to be Vu > Phi*0.5*Vc where Vc is calculated in accordance accordance with 22.5.5.1. A

44 of 215

New business.


No.

88.


Dan Mullins

Pg #

197

Line #

20

Public Comment

Committee Response

designer needs to complete all of the 22.5.5.1 calcs as part of the overall design so this change does not add significant complexity and provides appropriate and more consistent safety for taller beams with low reinforcement ratios. This also keeps the check consistent with wording in 9.6.3.2. (2) Restrict the “Integral slab” limit in Table 9.6.3.1 to cases where fy < 60 ksi until sufficient test data is available to relax this. By doing so, a designer considering use of fy>60 would evaluate the recommended 0.5*Phi*Vc limit that would consider both size and reinforcement ratio influences. Only the exceptions are listed as cases where Av min is required if Vu>phiVc. Another case is where low rho and large d lead to a low value of Vc, which can be less than the limit in line 19. Does this need to be explicitly stated?

89.

David Darwin

197

22

Table 9.6.3.1: For steel fiber-reinforced concrete, the cited sections 26.4.2.2(d) and 26.12.5.1(a) should be changed to 26.4.2.2(i) and 26.12.7.1(a), respectively because of changes in section numbering.

90.

Dan Mullins

199

12

Suggested rewording: “Along development and lap splice lengths of longitudinal bars with fy>80,000 psi, transverse reinforcement shall be provided such that Ktr shall not be smaller than 0.5 db” It seems inconsistent to me that deep beams, a vast majority of which are designed by STM, are subject to a shear stress limit (Eq. 9.9.2.1), while other discontinuity regions (brackets, for example) are not, provided they rely on transverse reinforcement meeting the requirements of Section 23.5. Slender beams are also subject to a similar limit.

91.

Andrew Stam

205

21

45 of 215

Disagree. The restriction to 1 sqrtf’c is sufficient to address this case. No change needed. Agree. Change made.

Agree. Change made. Disagree. Discontinuity regions designed by the strut and tie method have additional restrictions on the compressive strut (including possible shear limits) as noted in the new sections 23.4.3 and 23.4.4. Brackets and corbels designed by section 16.5 have their own unique design checks (including shear).


No.


Pg #

Line #

92.

David Darwin

213

27

93.


219

10

Public Comment

Committee Response

Would it not be prudent (not to mention consistent) to require that all strut-and-tie models, including n on-deep beams that rely on transverse reinforcement, be checked for shear stress via Eq. 9.9.2.1 or something similar? The reasons given for the deep beam stress limit (crack control, preventing diagonal compression failure) are still valid concerns for other reinforced discontinuity regions. 26.4.2.2(d) should be changed to 26.4.2.2(i) because of changes in section numbering.

No change needed.

Reason for addition: It is necessary to indicate a calculation equation for the additional stirrups and the area in which should be arranged. R 9.7.6.2. Shear R 9.7.6.2.1. If a reinforced concrete beam is cast monolithically with a supporting beam and intersects one or both sides faces of a supporting beam may be subject to premature failure unless additional transverse reinforcement, commonly referred to as hanger reinforcement, is provided (Mattock and Shen, 1992). The hanger reinforcement (Figure 9.7.6), placed en addition to other transverse reinforcement, is provided to transfer shear from the end of the supported beam. Research indicates that if the bottom of the supported beam is at or above middepth of the supported beam or if the factored shear transferred from d , hanger reinforcement the supported beam is less than 3 f’ cbw d is not needed. The area of hanger reinforcement, Ai , should be determined f y from Ai  (1-hb/hg).V u/(. f y), ), where V u is the beam factored shear at the supported face; Ai is is the total area of the hanger stirrups; hg is the girder height; f yt is the stirrup specified yield strength; yt is and  = 0,75.

46 of 215

Agree. Revised cross reference as noted. Disagree. Committee 318 discussed various ways to design the hanger reinforcement and voted to leave the design method to the LDP. The proposed addition is overly prescriptive. No change needed.


No.

94.

95.

96.


Dan Mullins

ACI Staff

Dan Mullins

Pg #

231

243

245

Line #

21

2

23

Public Comment

Committee Response

At least two-thirds of Ai should should be evenly distributed within the supported beam width bw , plus hb at each side. The remaining area of hanger stirrups, not more than one-third of A i, should be evenly distributed within d/4 from the supporting girder face, where d is is the supported beam effective depth. Beam bottom longitudinal bars should be placed above the girder bottom longitudinal bars. Suggested rewording: “Along development and lap splice lengths of longitudinal bars with fy>80,000 psi, transverse reinforcement shall be provided such that Ktr shall not be smaller than 0.5 db” The reference to 11.5.4.3 is not correct. This appears to be a remnant of an errata correction from 318-14 and the new change proposal CE070. Please provide the correct reference. reference.

This section seems in conflict with new section 11.5.4.5. Does 11.5.4.5 take precedent over 11.5.4.2. If so, this needs to be stated. 11.5.4.1 doesn’t appear to give that flexibility.

Agree. Change made. Disagree. This comment refers to 11.6.2(a) 11.6.2(a) on page 248, line 2. The reference is correct. The wording, however, should be slightly adjusted: Change to: “… t required for strength in 11.5.4.3.” Agree. The upper limit of 10

f c Acv for an individual vertical wall

segment in 11.5.4.5 directly contradicts the limit of

8 f c Acv for

any horizontal section in 11.5.4.2. After review, 11.5.4.5 is not needed in Chapter 11. The limit in 11.5.4.2 is sufficient. Recommended Changes:

• • • 47 of 215

Delete 11.5.4.5 Delete R11.5.4.5 Editorial change to 11.5.4.1 to reflect the deletion of a subsection.


No.


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Public Comment

Committee Response

11.5.4.1 Vn shall be calculated in accordance with 11.5.4.2 through 11.5.4.5 11.5.4.4. 97.


248

16

Reason for change: in case of more demanding exposure categories (F2, F3, S2, S3, W2, C1 and C2), it is suggested to reduce maximum spacing s of deformed longitudinal reinforcement in order to verify the most demanding cracking criteria. 11.7.2.1.1 — Spacing, s, of longitudinal bars in cast-in-place walls shall not exceed the lesser of 3h and 18 in. If shear reinforcement is required for in-plane strength, spacing of / 3. longitudinal reinforcement shall not exceed l w w / 11.7.2.1.2 — In cast-in-place walls exposed to exposure categories F2, F3, S2, S3, W2, C1 and C2, the maximum spacing s of longitudinal bars must be less or equal to that shown in Figure 11.7.2.1.2. The values are plotted as a function of the minimum concrete cover dc to centroid of steel at the tensile face for plates with different supports, uniform loads and l min / lmax ratios of 0.5, 0.7 and 1.0.

48 of 215

Existing code provisions have been shown to provide adequate durability. No change needed.


No.


Pg #

Line #

Public Comment .

Committee Response

n

lmin/lmax = 0,5

11.00 in

10.00 in

lmin/lmax = 0,7

9.00 in s ( g 8.00 in n i c a p s 7.00 in m u m i x 6.00 in a M

lmin/lmax = 1

5.00 in

4.00 in

3.00 in

2.00 in 1.70 in

1 .8 0 in

1 .9 0 in

2 .0 0 in

2 .10 in

2.20 in

2.30 in

2.40 in

2 .5 0 in

2 .6 0 in

2 .7 0 in

2 .80 in

Minimum concrete cover to centroid of steel at the tensile face (d c )

Figure 11.7.2.1.2 — Variation of the maximum spacing s of deformed longitudinal reinforcement in cast-in-place walls with uniform loads (exposure categories F2, F3, S2, S3, W2, C1 y C2)

98.

James Lintz

248

42

Through line 43

See changes proposed in response to Viral Patel (Comment 99, page 248, line 42).

ACI 318-19 Section 11.7.4.1 “If longitudinal reinforcement is required for axial strength” is unclear. Does this mean that if the axial load, Pu , exceeds the axial strength for a plain concrete member, φPn , with Pn given by equation 14.5.3.1 that t he member needs transverse ties. Or does this mean that if the axial load, Pu , exceeds the axial strength for a plain concrete member, φPn , with Pn given by equation 14.5.4.2 that the member needs transverse ties. Or does it mean something else entirely. In any case I believe an explanation should at least be given in the commentary if this wording is to remain. Further, the wording of this section was

49 of 215

The 1% limit on longitudinal reinforcement has been in the Code for more than 30 years. No evidence has been presented that this needs to be changed for 318-19.


No.


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Committee Response

changed from the wording in the equivalent section of ACI 31811, Section 14.3.6, and no explanation was given in ACI 318-14. I believe an explanation for this change should be given in the commentary if the wording of this s ection is to remain the same. If one of the explanations above is correct, and transverse ties are required whenever P u exceeds φPn based on plain concrete design, then this creates an issue where (1 - lc/32h) will be negative for nearly all slender concrete walls, which would therefore require nearly all slender concrete walls to have transverse ties. This would seem to contradict my understanding of the testing that was done to provide the underpinning for the Alternative method for out-of-plane slender wall analysis since the tested walls did not include transverse ties around all of the bars, and no mention of transverse ties being required is given in Section 11.8. It would also contradict decades of design practice where slender walls have been designed and built successfully without transverse ties.

Why is the maximum amount of longitu dinal steel allowed without transverse ties set to 1% of the gross concr ete area? This number appears to be arbitrary, especially since no explanation is given in the commentary. Why n ot 1.5% or 2%? Why should the Ast/Ag ratio even be used to determine when transverse ties are required? The beam chapter of ACI 318-14 Section 9.5.2 requires transverse ties for axial load when Pu>0.1f c’Ag. Basing the requirement for transverse ties on the amount of axial load in the member, as is done in the beam

50 of 215


No.


Pg #

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Public Comment

Committee Response

chapter, would seem more logical than basing it on the Ast/Ag ratio. If the ACI wanted to be more conservative for walls than for beams, the axial load required could be lowered to 0.06f c’Ag to match Section 11.8.1.1(d). Since one of the main reasons to include transverse ties is to prevent buckling of the longitudinal bars in compression, a requirement for ties based on longitudinal bars being in compression would be logical. I believe this requirement should be that if t he distance from the extreme compression fiber to the neutral axis is greater than the distance from the extreme compression fiber to the inner most part of the steel nearest the compressive face of the wall then transverse ties should be required.

To conclude I believe ACI 318-19 Section 11.7.4.1 should be revised to read as follows; Longitudinal bars shall be laterally supported by transverse ties if Pu ≥ 0.10f c’Ag or if c ≥ d’ + db/2. 99.

Viral Patel

248

42

ACI 318-14 and 318 Public discussion draft section 11.7.4.1 indicates that “If longitudinal reinforcement is required for axial strength or if Ast exceeds exceeds 0.01 Ag, longitudinal reinforcement shall be laterally supported by transverse ties.” This provision was modified in ACI318-14 from from ACI318-11. ACI 318-11 provision 14.3.6 indicates that “Vertical reinforcement need not be enclosed by t ransverse ties if vertical reinforcement area is not greater than 0.01 times gross concrete area, or where vertical reinforcement is not required as compression reinforcement.”

51 of 215

Agree. Change made.


No.


Pg #

Line #

Public Comment

Committee Response

For non-seismic application, when reinforcement in wall is needed for tension, it should not require transverse reinforcement in form of ties regardless of amount of reinforcement. It is very common to use higher than 1% longitudinal reinforcement for tension resulting from moment. Such reinforcement (when not used for compressive strength) does not need lateral support and transverse reinforcement is not needed in form of ties. Providing transverse reinforcement reinforcement in such situation will not improve the performance and could add significant material and labor cost without adding value. Note that there are methods (also commercial software) that will allow use of reinforcement reinforcement only for tension. Therefore, designers can ascertain if reinforcement is needed for compressive strength or not. Additional information: ACI staff should investigate why this provision was changed from 318-11 318-11 to 318-14. It is possible that it was an oversight. At least preliminary investigation investigation does not support any reason for the change. Proposed change:

11.7.4.1 - If longitudinal reinforcement is required for axial strength compression or and if Ast exceeds exceeds 0.01 Ag, longitudinal reinforcement shall be laterally supported by transverse ties. 100.

Robert Sculthorpe Chairman ACI Committee 560

251

11

Through line 13: ACI 560 Committee agreed on the following revised language: ”R11.1.6 Specific design recommendation s for cast-in-place walls constructed with insulating concrete forms are not provided in this code. Guidance on the design of cast-in-place

52 of 215

Agree. Change made.


No.

101.



Pg #

252

Line #

13

Public Comment

Committee Response

walls constructed with insulating concrete forms can be found in PCA 100 and background information on their use in ACI 560R. Guidance can be found in ACI 560R and PCA100.” This line should read “…shear walls structural walls” See reason given in comment on page 97, line 8.

Agree. Change made. Note: Restrepo and Rodriguez proposed similar changes in several places in 318. The proposed responses have been coordinated for consistency to accept the change to “structural walls”

102.

Dan Mullins

256

20

This line seems more appropriate as 12.2.1 (f)

Disagree. Items 12.2.1 (a) through (e) are forces. Section 12.2.2 addresses the effects of slab openings, which includes not only forces but also other influences of openings, so it would not be appropriate to add 12.2.2 to the list of forces in 12. 2.1 No change.

103.

David P. Gustafson

258

25

Through line 26: Re-evaluate Lines 25-26. Rho-sub-tee is a ratio. “ . . .shall not exceed 100 psi; and ρt is is the ratio of distributed reinforcement oriented parallel to the in-plane shear to gross concrete area perpendicular to that reinforcement.” In 2.2, rho-sub-tee is defined as:

Partially agree. Make the following change in line 25: “…and rho -t is refers to the distributed…”

104.

David P. Gustafson

268

31

105.

David P. Gustafson

269

2

106.


270

26

ρt = ratio of area of distributed transverse reinforcement to gross concrete area perpendicular to that reinforcement Consider replacing “seismic design requirements” with “requirements for earthquake -resistant design”. Consider replacing “seismic” with “earthquake -resistant”.

There are confusing words re: steel casings and their contributions to capacity.

53 of 215

Partially agree. Delete the words “seismic design” from line 31 of page 268 Partially agree. Delete the words “seismic design” from line 2 of page 269 On line 27, “Steel pile shells are” will be revised to “Steel pile casing is”.


No.


Pg #

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Public Comment

Committee Response

Revise to: R13.4.2.3 The basis for this allowable strength is the added strength provided to the concrete by the confining action of the steel casing. This strength applies only to non-axial load-bearing steel where the stress in the steel is taken in hoop tension instead of axial compression. Steel pile shells are casing is not to be considered in the design of the pile to carry a portion of the pile axial load. Potential corrosion of the metal casing should be considered; provision is based on a non-corrosive non-corrosive environment. 107.

108.

Thomas Schaeffer

David L. Hartmann

274

274

19

19

1.4.6 should be 1.4.7

Agree.

1.4.6 should be 1.4.7

Revise to: 13.1.2 Foundations excluded by 1.4.67 are excluded from this chapter. Agree.

109.

David L. Hartmann

275

23

“. . . induced reactions.” Should read “. . . induced reactions except as permitted by 13.4.2.”

110.

ACI Staff

279

12

Via member Schaeffer. Please verify the language “authority having jurisdiction”. Th is was changed in several other locations in the code, should this be changed as well?

Revise to: 13.1.2 Foundations excluded by 1.4.67 are excluded from this chapter. Agree. It will be revised to: 13.2.6.3 Foundation members shall be designed t o resist factored loads and corresponding induced reactions except as permitted by 13.4.2. Agree. Change will be made to be co nsistent with other provisions. The Code will be revised to: 13.4.1.1 Number and arrangement of deep foundation members shall be determined such that forces and moments applied to the foundation do not exceed the permissible deep foundation strength. Permissible deep foundation strength shall be

54 of 215


No.

111.

112.




Pg #

Line #

Public Comment

Committee Response

279

23

Limits unnecessarily allowable stress design – remove.

279

23

Code language states that allowable stress design can be used only when bending moments are less than that moment caused by an eccentricity of 5% of the pile diameter or width. The word “pile” should be replaced by “deep foundation member”. The 5% limit is very very restrictive. IBC 2018 section 1810.3.1.3 states that deep foundations be designed for mislocations (eccentricity) of at least 3”. Taken together, this will prohibit the allowable strength design of any single element deep foundation member (e.g. drilled piers) with a diameter of 60” or less. Current IBC code language contains a similar restriction, but uses the term “accidental eccentricities” instead of a specific limit. The IBC terminology prevents the use of ASD except when there are no applied design moments (typically from applied lateral loads or fixed base columns).

determined through principles of soil or rock mechanics in accordance with the general building code, o r other requirements as determined by the authority having jurisdiction building official. Disagree, the 5 percent eccentricity is supported by ACI 543 GUIDE TO DESIGN, MANUFACTURE, AND INSTALLATION OF CONCRETE PILES. No change required. Agree regar ding substitution for “pile” to member. The Code will be revised to: 13.4.2.1 It shall be permitted to design a deep foundation member using load combinations for allowable stress design in ASCE/SEI 7, Section 2.4, and the allowable strength specified in Table 13.4.2.1 if (a) and (b) are satisfied: [CF005] (a) The deep foundation member is laterally supported for its entire height. (b) The applied forces cause bending moments in the deep foundation member less than the moment due to an accidental eccentricity of 5 percent of the pile member diameter or width. Disagree regarding the 5 percent eccentricity, this is supported by ACI 543 - GUIDE TO DESIGN, MANUFACTURE, AND INSTALLATION OF CONCRETE PILES; and the Mislocation check of 1810.3.1.3 is a separate check with a permissible overload of 110 percent of the allowable. For reference, IBC 1810.3.1.3 states: 1810.3.1.3 Mislocation. The foundation or superstructure

55 of 215


No.


Pg #

Line #

Public Comment

Committee Response

shall be designed to resist the effect of the mislocation of any deep foundation element by not less than 3 inches (76 mm). To resist the effects of mislocation, compressive overload of deep foundation elements to 110 percent of the allowable design load shall be permitted.

113.

114.

Thomas Schaeffer


279

279

26

26

In the Table, the word “rock” in t he second row under the heading appears to be in the wrong place because it doesn’t make sense as it is written. It should be reworded to say “Cast in-place concrete pile in rock, a pipe, tube, or other permanent casing that does not satisfy 13.4.2.3”

Is it the intention that section 13.4 will apply to structural steel pipes and tubes filled with concrete and micropiles? Current proposed code language appears to apply to structural steel members filled with concrete, as stress levels are given for “Cast-in-place concrete pile in a pipe, tube… There is also a definition given for “concrete filled pipe piles”, that would make it appear that ACI 318 will apply to the design of these members. Consider deferring to the general general building code (IBC) and AISC 360 for these deep deep foundation types. Concrete filled structural steel pipe columns, which are similar members, are not covered by ACI 318-19 (see (see section R10.1.1). If it is not the intent of ACI that this section should apply to concrete filled structural steel sections and/or micropiles, this should be specifically stated in the commentary.

56 of 215

No change required. Agree. Revise the wording in the Third Row of the Table to: Cast-in-place concrete pile in rock or within, a pipe, tube, or other permanent metal casing or rock that does not satisfy 13.4.2.3. Micropiles are currently not included in the 318-19 Code provisions, and the term Micropile does not occur in the Code. The Code does include provisions for pile that consists of cast-inplace concrete in a steel pipe or metal casing. Also, the r eference to AISC 360 is given in R10.1.1 for composite columns which, where applicable, can be used for concrete filled steel pipe piles. Concrete filled pipe piles with a contribution from the steel pipe will be considered for New Business in the next Code cycle. Revise Commentary to: R1.4.7 The design and installation of concrete piles fully embedded in the ground is regulated by the general building code. The 2019 edition of the Code contains some provisions that previously were only available in the the general building code. In addition to the provisions in this Code, recommendations for concrete piles are given in ACI 543R, recommendations for drilled piers are given in ACI 336.3R, and recommendations for precast prestressed concrete piles are given in “Recommended Practice for


No.


Pg #

Line #

Public Comment

Committee Response Design, Manufacture, and Installation of Prestressed Concrete Piling” (PCI 1993). Requirements 1993). Requirements for the design and construction of micropiles are not specifically addressed by this Code.

115.


279

26

The footnote [2] given to allowable stress category (b) in the table states that the strength of steel casing, pipe, or tube shall not be included in the design. This is a major departure from current code and practice and will result in significant increased construction costs. Current IBC code requires that that the casing not be considered for axial load only for metal cased concrete piles (13.4.2.3). For micropiles and concrete filled filled structural steel members, IBC permits the steel to be considered as part of the capacity. capacity. Consider removing this footnote from stress category (b) and applying it instead to stress category (c), the latter which pertains to metal cased concrete piles. Leaving this note on (b) would in practicality eliminate the use of concrete filled structural steel piles, as these foundation members usually derive most of their capacity from the structural steel. steel. There are no provisions in ACI 318 for the strength design of concrete filled steel pipes and tubes. R10.1.1 refers to AISC 360 for concrete filled pipes and tubes. As AISC 360 already contains design design provisions for concrete filled steel pipes and tubes, it would be more appropriate for ACI 318 to defer to ASCE 360 for the design of these members rather than to duplicate these provisions.

In Table 13.4.2.1, the member type associated with the equation that has the footnote [2] is being revised to: Cast-in-place concrete pile in rock or within, a pipe, tube, or other permanent metal casing or rock that does not satisfy 13.4.2.3. In this case, as stated, the pipe is only serving as permanent casing, and the provision is not intended to include compositely designed concrete and steel pipe. Concrete filled pipe piles with a co ntribution from the steel pipe will be considered for New Business in the next Code cycle. In the case cited where the concrete filled structural steel pipe pile derives most of its capacity from the structural steel, the designer could utilize AISC specifications for the design of that pile. Sentence will be added to commentary clarifying composite action in concrete filled steel pipe piles. Revise to: R13.4.2.3 The basis for this allowable strength is the added strength provided to the concrete by the confining action of the steel casing. This strength applies only to non-axial load-bearing steel where the stress in the steel is taken in hoop tension instead of axial compression. In this Code steel pile shells are not to be considered in the design of the pile to carry a portion of the pile

57 of 215


No.


Pg #

Line #

Public Comment

Committee Response axial load. Provisions for members designed to be composite with steel pipe or casing are covered in AISC 360. Potential corrosion of the metal casing should be considered; provision is based on a non-corrosive non-corrosive environment.

116.

117.

Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee Dale C. Biggers, P.E.

280

6

“If 13.4.2.1 (a) and (b) are not satisfied…” should be “If 13.4.2.1 (a) or (b) is not satisfied…”, as both (a) and (b) need to be satisfied to use the allowable allowable stress design provisions. If either is not satisfied, strength design shall be used.

280

13

These comments apply only to “Raymond” mandrel -driven corrugated shell piles which have disappeared altogether. We drove our last corrugated-shell pile in 1988. They were generally 16-in diameter or smaller. Why limit pipe piles to that diameter ? Also the corrugated casing had had no axial strength; it was only for confinement. Do not limit the axial capacity of pipe – it has axial strength.

118.


280

13

Why must the element be mandrel driven? Would not the same allowable stress level apply if alternate installation methods, such as drilling, are used?

119.

Daniel S. Stevenson, P.E.

280

24

Note IBC section 1810.3.2.8 allows for increased allowable stress, but also requires a geotechnical investigation and that

58 of 215

Agree. Provision will be revised to: 13.4.2.2 If 13.4.2.1 (a) and or 13.4.2.1(b) are is not satisfied, a deep foundation member shall be designed using strength design in accordance with 13.4.3. Data supporting that there is an adequate amount of confinement for metal cased cast-in-place concrete deep foundation members with a diameter greater than 16-in. has not been made available to the committee. The maximum diameter of 16-in. has been in the general building code for some time and is current accepted practice. Since, as the commenter noted, this type of pile is not very common at the present, it is not considered worthwhile to study larger diameter piles of this type as New Business. No change required. This provision is almost verbatim to a provision contained in the current edition of the IBC. The intent of adding these new provisions was so that IBC can remove the concrete related pile provisions and reference ACI 318. If this type of pile is no longer being installed, the next Code cycle may consider removing the provision. No change required. Currently 13.4.2.4 states that the use of higher allowable strengths is allowed if accepted by the building official and


No.

Public Commenter Name Representing DFI Codes and Standards Committee

Pg #

Line #

Public Comment

Committee Response

the deep foundation members be installed under the direct supervision of a registered registered design professional. The ACI provisions for increasing allowable stress do not contain these extra provisions currently contained in IBC.

justified with load tests. IBC 1810.3.2.8 states that it is allowed where supporting data is filed with the building official and the supporting data shall include a geotechnical investigation and load tests. The Commentary will be revised to include Geotechnical requirements. There are no conflicts with IBC regarding inspection, 26.13.1.1 states that concrete construction shall be inspected as required by the general building code, and as a minimum with 26.13. 26.13.1.2 states that inspection of concrete construction shall be conducted by the licensed design professional responsible for the design…..; so the inspection aspects are currently covered. Revise Commentary to: R13.4.2.4 Geotechnical and Lload test requirements for deep foundation members can be found in the IBC.

120.


281

2

Through line 24: Sections 13.4.2.5 to 13.4.2.7 are concerned with the design of pile caps, which must be designed using strength design provisions. However, the title of section 13.4.2 is “Allowable “Allowable Axial Strength”. We suggest that the code sections in 13.4.2 that pertain to pile caps be moved to section 13.4.5 “Pile Caps”.

Agree. Lines 2 through 24, p. 281 are misplaced. They are part of the Pile Cap provisions which are in 13.4.6. All lines shall move to 13.4.6 at the end of the Chapter, thereby making what is shown on page 281 as 13.4.2.5 to 13.4.6.3, 13.4.2.6 to 13.4.6.4, and 13.4.2.7 to 13.4.6.5 Delete 13.4.2.5 through 13.4.2.7: 13.4.2.5 Except for pile caps designed in accordance with 13.2.6.3, the pile cap shall be designed such that (a) is satisfied for one-way foundations and (a) and (b) are satisfied for two-way foundations. (a) ϕV n ≥ V u, where V n shall be calculated in accordance with 22.5 for one-way shear, V u shall be calculated in accordance with 13.4.2.7, and ϕ shall be in accordance with 21.2

59 of 215


No.


Pg #

Line #

Public Comment

Committee Response (b) ϕv n ≥ vu, where v n shall be calculated in accordance with 22.6 for two-way shear, vu shall be calculated in accordance with 13.4.2.7, and ϕ shall be in accordance with 21.2 13.4.2.6 If 13.4.2.6 If the pile cap is designed in accordance with the strutand-tie method as permitted in 13.2.6.3, the effective concrete compressive strength of the struts, f ce, shall be calculated in accordance with 23.4.3, where β s = 0.60λ , and λ is is in accordance with 19.2.4. 13.4.2.7 Calculation 13.4.2.7 Calculation of factored shear on any section through a pile cap shall be in accordance with (a) through (c): (a) Entire reaction from any pile with its center located d pile /2 /2 or more outside the section shall be considered as producing shear on that section. (b) Reaction from any pile with its center located d pile /2 /2 or more inside the section shall be considered as producing no shear on that section. (c) For intermediate positions of pile center, the portion of the pile reaction to be considered as producing shear on the section shall be based on a linear interpolation between full value at d pile /2 outside /2 outside the section and zero value at d at d pile /2 inside /2 inside the section. Move the deleted sections to the section for Pile Caps, 13.4.6, and renumber: 13.4.26 Pile caps 13.4.26.1 Overall depth of pile cap shall be selected such that the effective depth of bottom reinforcement is at least 12 in. 13.4.26.2 Factored moments and shears shall be permitted to be calculated with the reaction from any pile assumed to be concentrated at the centroid of the pile section 13.4.2.56.3 Except for pile caps designed in accordance with 13.2.6.3, the pile cap shall be designed such that (a) is satisfied for

60 of 215


No.


Pg #

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Public Comment

Committee Response one-way foundations and (a) and (b) are satisfied for two-way foundations. (a) ϕV n ≥ V u, where V n shall be calculated in accordance with 22.5 for one-way shear, V u shall be calculated in accordance with 13.4.2.7, and ϕ shall be in accordance with 21.2 (b) ϕv n ≥ vu, where v n shall be calculated in accordance with 22.6 for two-way shear, vu shall be calculated in accordance with 13.4.2.7, and ϕ shall be in accordance with 21.2 13.4.2.66.4 13.4.2.66.4 If the pile cap is designed in accordance with the strut-and-tie method as permitted in 13.2.6.3, the effective concrete compressive strength of the struts, f ce, shall be calculated in accordance with 23.4.3, where β s = 0.60λ , and λ is is in accordance with 19.2.4. 13.4.2.76.5 Calculation 13.4.2.76.5 Calculation of factored shear on any section through a pile cap shall be in accordance with with (a) through through (c): (c): (a) Entire reaction from any pile with its center located d pile /2 /2 or more outside the section shall be considered as producing shear on that section. (b) Reaction from any pile with its center located d pile /2 /2 or more inside the section shall be considered as producing no shear on that section. (c) For intermediate positions of pile center, the portion of the pile reaction to be considered as producing shear on the section shall be based on a linear interpolation between full value at d pile /2 outside /2 outside the section and zero value at d at d pile /2 inside /2 inside the section.

121.

Thomas Schaeffer

281

2

122.

Thomas Schaeffer

281

2

Lines 2 through 24 are misplaced. They are part of the Pile Cap provisions which are in 13.4.6. All lines should move, thereby making what is shown as 13.4.2.5 to 13.4.6.3, 13.4.2.6 to 13.4.6.4, and 13.4.2.7 to 13.4.6.5 The reference to section 13.2.6.3 should be 13.2.6.5

Agree. All lines shall move to 13.4.6 at the end of the Chapter, thereby making what is shown on page 281 as 13.4.2.5 to 13.4.6.3, 13.4.2.6 to 13.4.6.4, and 13.4.2.7 to 13.4.6.5 Agree. It will be revised to: 13.4.2.56.3 Except for pile caps designed in accordance with 13.2.6.35, the pile cap shall be designed such that (a) is satisfied

61 of 215


No.

123.


Pg #

Line #

Public Comment

Committee Response

for one-way foundations and (a) and (b) are satisfied for two-way foundations. Agree.

281

2

Reference to 13.2.6.3 should be 13.2.6.5.

124.

Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee David L. Hartmann

281

2

125. 126.

Thomas Schaeffer Dale E. Biggers P.E.

281 281

12 30

Reference to 13.2.6.2 does not appear to make sense should it be 13.4.2? The reference to section 13.2.6.3 should be 13.2.6.5 Some non-prestressed members do not have ties for their full length, which is okay. This needs to be addressed.

127.


281

30

128.

Dan Mullins

281

30

Code language in 13.4.3.2 states that concrete deep foundation members shall be designed in accordance with 10.5. Section 10.5 refers to table 22.4.2.1 for for maximum axial strength for compression members. This table provides for allowable strengths for deep foundation members, and also stipulates that ties must conform to chapter chapter 13. However, chapter 13 does not contain any tie requirements for deep foundation members. What about deep foundation members, members, or portions of deep foundation members, that d o not contain any ties? It is very common that only the upper portions of deep foundation members members are reinforced. The unreinforced portions will not have any ties for confinement but may be confined by the surrounding soils. Based on the logic in this paragraph, the capacity of a deep foundation will increase if a nominal moment is applied, as the phi-factor for axial will increase from 0.55 to 0.65. This doesn’t seem like the intent.

62 of 215

Agree, the reference to section 13.2.6.3 should be 13.2.6.5 Agree Provision 13.4.3.2 states that the provisions of 22.4.2.4 and 22.4.2.5 shall not apply to deep foundation members. Tie requirements for these members are in 18.13.5.7. No change required. The tie requirements for deep foundation members are in 18.13.5. Provision 13.2.3.2 states that deep foundation members in SDC C, D, E, or F shall be designed in accordance with 18.13. And, according to 1.4.7(c), the Code only applies to cast-in-place concrete deep foundation members assigned to SDC C, D, E, and F. The requirements for precast piles in SDC A and B are in 13.4.5. Cast-in-place concrete deep foundation elements in SDC A and B will be considered for New Business in the next Code cycle. No change required.

The committee recognizes the possible inconsistency in the phi factor for columns and deep foundation members and this will be handled as New Business for the next Code cycle.


No.

Pg #

Line #

129.

Public Commenter Name David L. Hartmann

281

31

Add the word compressive to “using the (compressive) strength reduction factor . . .” to be consistent.

130.

David L. Hartmann

281

33

In section 13.4.3.2 the last sentence “The provisions of 22.4.2.4 and 22.4.2.5 shall not apply to deep foundations.” appears to create a gap in the provisions. provisions. It could be argued that omitting those sections and by extension the sections they reference, you do not need ties in cast in place deep foundations (seismic provisions not withstanding). The current provision does give necessary detailing relief; especially from 25.7.2.4.1 which would be a constructability disaster. I would suggest that deleting the noted sentence and adding a Section 13.4.4.3 “Ties for cast in place concrete deep foundations assigned to SDC A & B shall satisfy the requirements of 25.7.2.1 and 25.7.2.2, 25.7.3, or other means demonstrated to provide acceptable support to the longitudinal reinforcement. reinforcement. Ties for cast in place deep foundations assigned to SDC C, D, E, or F shall satisfy 18.13.5.” This would also clear up a somewhat awkward reference in Table 22.4.2.1 (e).

131.

Thomas Schaeffer

282

1

Public Comment

Committee Response

In the Table, the word “rock” in the second row under the heading ap pears to be in the wrong place because it doesn’t make sense as it is written. It should be reworded to say “Cast in-place concrete pile in rock, a pipe, tube, or other permanent casing that does not satisfy 13.4.2.3”

63 of 215

Agree. The word compressive will be added. The revised provision will be: 13.4.3.2 The strength design of deep foundation members shall be in accordance with 10.5 using the compressive strength reduction factors of Table 13.4.3.2 for axial load without moment, and the strength reduction factors of Table 21.2. 1 for tension, shear, and combined axial force and moment. The provisions of 22.4.2.4 and 22.4.2.5 shall not apply to deep foundations. According to 1.4.7(c), the Code only applies to cast-in-place concrete deep foundation elements assigned to SDC C, D, E, and F, and currently doesn’t include A and B for cast -in-place concrete deep foundations. Cast-in-place concrete deep foundation elements in SDC A and B will be considered for New Business in the next Code cycle. No change required.

Agree. Revise the 1st column, 3rd row in Table 13.4.3.2 to: Cast-in-place concrete pile in rock or within a pipe, tube, or other permanent metal casing or rock that does not satisfy 13.4.2.3.


No.

Pg #

Line #

282

1

133.

Public Commenter Name Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee Dan Mullins

282

1

134.

David L. Hartmann

282

1

132.

Public Comment

Committee Response

Table 13.4.3.2 gives phi factors for concrete filled pipes, but how does one design in ACI 318? R10.1.1 states that composite structural steel-concrete columns are not covered in ACI. Is the contribution of the structural steel supposed supposed to be neglected? We suggest the design of composite structural steel-concrete members be delegated to AISC 360. Its not clear what the soil conditions noted in the footnote have to do with the phi-factor for the strength of the concrete element. The phi-factor should be based on the concrete only. The phi-factor values seem low and cause problems with continuity with section 21.2.1

Agree. See response to Dolan #115.

For (b) “. . . other permanent casing or rock that does not . . .” words “or rock” should be removed.

Disagree. The soil conditions c an affect the quality of the concrete in the member. The phi factors in the Table are consistent with the recommended values in ACI 543. The continuity issue with the phi factors for combined axial force and moment will be considered for New Bu siness in the next Code cycle. No change required. Agree. Same response as Wood #131 Revise the 1st column, 3rd row in Table 13.4.3.2 to : Cast-in-place concrete pile in rock or within a pipe, tube, or other permanent metal casing or rock that does not satisfy 13.4.2.3.

135.

Thomas Schaeffer

284

3

Table 13.4.4.6(b) should be Table 13.4.5.6(b)

136. 137.

David L. Hartmann David L. Hartmann

284 284

3 5

Should read Table 13.4.5.6 (b) Through line 9: Section numbers of 13.4.2 are incorrect. 13.4.6?

64 of 215

Agree. It will be revised to: Table 13.4.4.613.4.5.6(b) Maximum transverse reinforcement spacing Agree Agree, 13.4.2 should be 13.4.6. It will be revised to: 13.4.26 Pile caps 13.4.26.1 Overall depth of pile cap shall be selected such that the effective depth of bottom reinforcement is at least 12 in. 13.4.26.2 Factored moments and shears shall be permitted to be calculated with the reaction from any pile assumed to be concentrated at the centroid of the pile section.


No.

Pg #

Line #

284 284

5 5

140. 141. 142. 143.

Public Commenter Name Thomas Schaeffer Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee Dan Mullins Thomas Schaeffer Thomas Schaeffer Thomas Schaeffer

Public Comment

Committee Response

13.4.2 should be 13.4.6 Section 13.4.2 (which follows 13.4.5.6) should be re-numbered 13.4.5, and following sections also renumbered.

Agree. Change made. Agree, but 13.4.2 should be 13.4.6

284 284 284 286

5 6 8 30

Section needs to be renumbered? 13.4.6? 13.4.2.1 should be 13.4.6.1 13.4.2.2 should be 13.4.6.2 Section number R13.2.6.2 should be R13.2.6.3

286

30

David L. Hartmann

286

30

146.

Thomas Schaeffer

287

13

Section R13.2.6.2 isn’t commentary on the same numbered code section. Need to move t his commentary to a different section and provide proper commentary on Code 13.2.6.2 R13.2.6.2 text does not apply to section. Might work for 13.2.6.3 Section number R13.2.6.3 should be R13.2.6.4

Agree, 13.4.2 should be 13.4.6 Agree. Change made. Agree. Change made. Agree. It will be revised to: R13.2.6.23To design a footing or pile cap for strength, the induced reactions due to factored………. Agree, Section number R13.2.6.2 should be R13.2.6.3

144.

Dan Mullins

145.

147.

Thomas Schaeffer

287

20

Section number R13.2.6.4 should be R13.2.6.5

148.

David L. Hartmann

288

4

149.

Thomas Schaeffer

288

4

138. 139.

Through line 8: Repeat of Page 287 Lines 25-29. Lines 4-8 are repeated from Page 287, lines 25-29; and should be deleted.

65 of 215

Agree, Section number R13.2.6.2 should be R13.2.6.3 Agree. It will be revised to: R13.2.6.34 Foundation design is permitted to be based directly on fundamental principles of………….. Agree. It will be revised to: R13.2.6.46.5 An example of the application of this provision is a pile cap supported on piles, similar to that Agree, lines 4-8 are repeated from Page 287, lines 25 -29; and should be deleted Agree. Change made.


No.

Pg #

Line #

150.

Public Commenter Name Dan Mullins

Public Comment

Committee Response

288

4

Figure referenced should be renamed Fig R13.2.6.5 to align with the code section

290

1

Section number R13.4.4.6 should be R13.4.5.6 and it should move to the correct location in the Chapter.

David P. Gustafson

290

27

Replace “carry” with “resist”.

153.

Dan Mullins

291

1

154.

Thomas Schaeffer

291

3

Section number seems incorrect or misplaced? Should be 13.4.5.6 and relocated to the proper position? Add Heading “R13.4.3 Strength Design” Design”

Agree, the Figure number on page 293 should be revised from R13.2.6.3 to R13.2.6.5 and line 25 on page 287 should be revised to: Figure R13.2.6.35. Agree. It will be moved to the correct numerological location and revised to: R13.4.4.65.6 The minimum transverse reinforcement required in this section is typically sufficient……….. Agree. It will be revised to: R13.4.2.3 The basis for this allowable strength is the added strength provided to the concrete by the confining action of the steel casing. This strength applies only to non-axial load-bearing steel where the stress in the steel is taken in hoop tension instead of axial compression. Steel pile shells are not to be considered in the design of the pile to carry resist a portion of the pile axial load. Potential corrosion of the metal casing should be considered; provision is based on a non-corrosive environment. Agree, Section number R13.4.5 should be R13.4.6

151.

Thomas Schaeffer

152.

155.

Dan Mullins

291

6

156.

David L. Hartmann

291

12

Thru line 9. This language seems in conflict with code section 13.4.3.2 pointing the user to section 21.2.1 for phi -factors

Through line 20: Section reference does not match Code

66 of 215

Agree. The heading will be added: R13.4.3 Strength design Disagree, this commentary is only in reference to the footnote in the Table that discusses possible adjustment to the phi factor based on soil conditions and quality control. No change required. Agree, Section number R13.4.5 should be R13.4.6. It will be revised to: R13.4.56 Pile caps


No.


Pg #

Line #

Public Comment

Committee Response R13.4.5.46.4It is required to take the effective concrete compressive strength from expression (c) in Table 23.4.3 because it is generally not feasible to provide confining reinforcement satisfying 23.5 in a pile cap. R13.4.5.56.5 If piles are located inside the critical sections d or or d /2 /2 from face of column, for one-way or two-way shear, respectively, an upper limit on the shear strength at a section adjacent to the face of the column should be considered. The CRSI Handbook (1984) (1984) offers guidance for this situation.

157. 158. 159.

Thomas Schaeffer Dan Mullins ACI Staff

291 291 291

12 12 12

160.

David L. Hartmann

291

13

161. 162.

Thomas Schaeffer ACI Staff

291 291

13 13

163.

ACI Staff

291

14

Section number R13.4.5 should be R13.4.6 Section needs to be renumbered? 13.4.6? Suggest revise “R13.4.5 Pile Caps” to “R13.4.2 Allowable axial strength” to coordinate with code language. Through line 15: Section does not address Code section Section number R13.4.5.4 should be R13.4.6.4 Possibly revise “R13.4.5.4 It is required ……… pile cap”. It does not coincide with provision 13.4.5.4. It looks like it refers to provision 13.4.2.6. Change Table 23.4.3 to Table 23.4.3(a). Should it be expression (f) instead of (c) also?

Agree. Change made. Agree, Section number R13.4.5 should be R13.4.6 Agree, Section number R13.4.5 should be R13.4.6 Agree, Section number R13.4.5 should be R13.4.6 Agree. Change made. Agree, Section number R13.4.5.4 should be R13.4.6.4

Agree a correction is needed for Table reference, plus the c urrent commentary is too Code like and too specific. There are more options. Therefore, additional changes are proposed. "R13.4.35.4 It is required typically typically necessary to take the effective effective concrete compressive strength from expression (c) (d) or ( f) in Table 23.4.3(a) because it is generally not feasible practical to provide confining reinforcement reinforcement satisfying 23.5 in a pile cap."

164. 165.

Thomas Schaeffer ACI Staff

291 291

16 16

Section number R13.4.5.5 should be R13.4.6.5 Possibly revise “R13.4.5.5 If piles are located ………… for this situation”. It does not coincide with provision 13.4.5.5. It looks like it refers to provision 13.4.2.7.

67 of 215

Agree. Change made. Agree, Section number R13.4.5.5 should be R13.4.6.5


No.

Pg #

Line #

166.

Public Commenter Name Thomas Schaeffer

Public Comment

Committee Response

293

8

Section number R13.2.6.3 should be R13.2.6.5

23

Re-evaluate the term “non-seismic areas”. Should the term be replaced with something like: • “low earthquake-risk areas” • “non-earthquake-risk area”

Agree, Figure number R13.2.6.3 should be R13.2.6.5. It will be revised to: Fig. R13.2.6.35 – One-way One-way shear design of a spread footing using the strut-and-tie method This comment is actually for line 33.

167.

David P. Gustafson

300

168.

David P. Gustafson

301

6

169.

Dr. Fariborz Tehrani, PE

307

15

The footnote on lambda = 0.75 is not aligned with recent research, cited in comment No. 4

170.

Robinson

307

15

Why is lambda 0.75 for any concrete mixture “containing lightweight aggregate” regardless of the concrete density or composition?

171.

Reid W. Castrodale

307

15

Table 15.4.2.3 The note following the table indicates that lambda = 0.75 for any concrete “containing lightweight aggregate,” and 1.0 for normalweight concrete.

Replace “computations” with “calculations”.

As the note stands, the density limit in the definition of lightweight concrete is not used, which means that just a handful of lightweight aggregate could be added, and the full reduction would be required. The reduction is excessive, and it

68 of 215

Agree. Reworded to “commercial buildings located in areas of low seismic risk.” Agree with editorial change for consistency with the rest of the Code. Changed “computations” to “calculations.” Disagree. There is not sufficient information available on the behavior of beam-column joints with various types of lightweight aggregates to support the use of a lambda factor other than 0.75.

Disagree. There is not sufficient information available on the behavior of beam-column joints with various types of lightweight aggregates to support the use of a lambda factor other than 0.75. Disagree. There is not sufficient information available on the behavior of beam-column joints with various types of lightweight aggregates to support the use of a lambda factor other than 0.75.


No.


Pg #

Line #

Public Comment

Committee Response

is also a step function, so as soon lightweight aggregate is added, the concrete has a reduced capacity. This reduction would also have to be applied to internal curing mixtures.

172.

173.

ACI Staff

ACI Staff

311

311

5

8

This requirement inhibits the use of light weight concrete in concrete frames. While the design code must be conservative, this appears overly conservative. There are test data indicating performance of lightweight concrete in joint shear that satisfies code requirements. I expect that this issue cannot be addressed in this code cycle, but it should be addressed in the next cycle. The reference to ACI 445A-18 needs to be removed/rescinded to an older reference as discussed during the development of this code with Klein. Please verify what the correct reference reference will be. Reason: this document is not finalized finalized – even if it was received by TAC immediately, there is little chance for it to be published before 318 as would be required. Possibly change “For joints in ……… strut -and-tie method of Chapter 23.” To “R15.2.5 For joints in ……… strut-and-tie method of Chapter 23 .”

Agree. Specific code change required: Replace “ACI 445A-18” with “Klein (2008)”. Reference is already included in the Code. New Business. Making such a change would also require moving other parts of R15.2 to commentary associated with subsections of R15.2. The subcommittee believes that at this point it is better to keep the commentary associated with 15.2 and subsections in a single commentary in R15.2. Specific code change required: For consistency with this intent for commentary section R15.2, R15.2.4 should be deleted and its first sentence moved to the beginning of the third paragraph of R15.2. Thus, this paragraph should read: “Corner joints occur where two non -colinear members transfer moment and terminate at the joint. A rooflevel exterior joint is an example of a corner joint between two members, also referred to as a knee joint. Corner joints are vulnerable…”

69 of 215


No.


Pg #

Line #

174.

ACI Staff

311

14

Public Comment

Committee Response

Possibly change “Transfer of bending …….. Chapter 8.” To “R15.2.9 Transfer of bending ………..Chapter 8.”

New Business. Making such a change would also require moving other parts of R15.2 to commentary associated with subsections of R15.2. The subcommittee believes that at this point it is better to keep the commentary associated with 15.2 and subsections in a single commentary in R15.2. A reorganization of some of the content in Chapter 15 was underway at the end of this Code Cycle. If this reorganization is continued during the next Code cycle, relocation o f some of the commentary will be considered.

175.

176.

Reid W. Castrodale


322

326

30

24

16.5.2.5 This article refers to “all -lightweight or sand-lightweight concrete.” It appears that the article shoul d be revised to simply refer to “lightweight concrete.” The definitions of all and sand-lightweight concrete may not be used by the designer with the new definition of lambda.

This line should read “…shear walls structural walls” See reason given in comment on page 97, line 8.

Agree. Specific code change required: Change “For all-lightweight concrete or sand-lightweight concrete” to “For lightweight concrete”. Thus, the sentence should read: “For lightweight concrete, the bracket or corbel dimensions…”

Agree. Specific code change required: Change “shear walls” to “structural walls”. Sentence should then read: “…in precast columns and wall panels, including structural walls, are designed to transfer…”

177.

Reid W. Castrodale

330

13

Through line 16: R16.5.2.5

Agree. Change made. Specific code change required:

70 of 215


No.


Pg #

Line #

Public Comment

Committee Response

If the change to Article 16.5.2.5 proposed in the previous item is made, this should also be revised.

178.

179.

Christopher Gamache, P.E.

Karl Pennings

336

338

23

17

Delete last two sentences of R16.5.2.5, starting with “No data are available for corbels…” Thus, R16.5.2.5 should read: “ Tests (Mattock et al. 1976a) have shown that the maximum shear friction strength of lightweight concrete brackets and corbels is a .” function of both f c′ and and av /d .”

The proposed embedment depth 5da ≤ hef ≤ 10da and hef ≥ 1.5 in. does not correspond to ICC-ES AC193 and upcoming revisions to ACI 355.2 where the minimum embedment depth hs) ≥ 1.5 in., where h nom is the for screw anchors will be (hnom – h nominal embedment depth and h s is the dimension from the end of the anchor to the first full thread of the s crew. Proposed revision to Line #23 would be: 17.3.4 For screw anchors with embedment depths h ef ≤ 10d a and (hnom – h hs ) ) ≥ 1.5in., concrete breakout strength… Additional notations in Chapter 2 will be needed as follows: hnom = distance between the embedded end of the concrete screw, the expansion or undercut anchor and the concrete surface, in. hs = length of the embedded end of the screw anchor without full height of thread, in.

Disagree

In section 17.5.2.1 are you allowed to take a reduction if excess reinforcement is provided according to 25.4.10.1 or is it all or nothing with the anchor reinforcement?

No. ACI 318 does not allow the excess excess reinforcement factor to be used for anchor reinforcement. reinforcement. This is an all or nothing provision. Presumably the reinforcement area is sized to closely correspond with the applied load. Having a slight “excess” is not detrimental to transferring load in the connection. connection. We have added commentary for clarification.

71 of 215

The text as given in ACI 318, 17.3.4 is correct. Please consider the following: a) The limitations given given in ACI 318 represent the range of experience and validity of the given design equations. The validity is given for hef ≥ 1.5in. considering reproducible concrete characteristics and hef ≥ 5da representing the lower bound of tested products considered in the derivation of the design equations. Therefore it is necessary necessary to keep both conditions. b) The value for hef to be used in design is given in the Evaluation Evaluation Report. Therefore the designer does not necessarily have to know about the definitions of hnom and hs. c) ICC-ES AC193 and ACI ACI 355.2 are test and evaluation evaluation provisions. They give information under which conditions practice is correctly simulated by the given tests. Therefore the range of applications for test and design provisions provisions do not have to agree. agree. ICC test and ACI 318 design provisions are two separate items.


No.


Pg #

Line #

Public Comment

Committee Response

Commentary Change to R17.5.2.1(b): To ensure development of anchor reinforcement for shear, the enclosing anchor reinforcement shown in Fig. R17.5.2.1(b)(i) should be in contact with the anchor and placed as close as practicable to the concrete surface. The research (Eligehausen et al. 2006b) on which the provisions for enclosing reinforcement are based was limited to anchor reinforcement with maximum diameter equivalent to a No. 5 bar. The larger bend radii associated with larger bar diameters may significantly reduce the effectiveness of the anchor reinforcement for shear; therefore, anchor reinforcement larger than a No. 6 bar is not recommended. Because development for full f y y is required, the use of excess reinforcement to reduce development length is not permitted for anchor reinforcement. 180.

ACI Staff

353

15

Increasing only E h by 0 was submitted as an erratum to ACI 318-11 and to the third printing of ACI 318-14. A justification or clarification for the change in the commentary was not provided. FEMA P750 referenced in R17.10.5.3 references ACI 318-11 Section D3.3 in Table 1 on page 277, where E is is increased by 0 and not only E h.

Disagree. As justification of the errata, the intent of omega is to increase the seismic force to elastic levels to provide additional protection against concrete breakout for anchors governed by this failure mode in tension. The Fp value is a reduced demand value that reflects component ductility. The vertical component is not adjusted for these effects since vertical response is typically unaffected by component ductility. Applying omega to the vertical component would have the effect of amplifying the vertical component beyond elastic response. In accordance with ASCE 7-10, Section 12.4.3. 1 Horizontal Seismic Load Effect with Overstrength Factor: E mh mh = Ω0 QE

72 of 215


No.


Pg #

Line #

Public Comment

Committee Response

Where QE = = effects of horizontal seismic seismic forces. It is not applied to the vertical component, where Fv = 0.2 QE = = 0.2 Fp. Page 353, Line 15: No Change. Code Change to 17.10.6.3 (Page 354, Line 14):

181.

James Getaz

358

21

“…accordance with 17.5.2.9…” 17.5.2 goes up to 17.5.2.6.

(c) Anchor or group of anchors shall be designed for the maximum shear obtained from factored load combinations that include E , with E E h increased by Ω0. Agree Page 358, Line 21 Should read: “reinforcement provided in accordance with 17.5.2.9 17.5.2.1 may be used, or the reinforcement should be” Also: Page 49, Line 30: “used for this purpose (refer to 17.4.2.9 and 17.5.2.9 17.5.2.1); however, other configurations that can be”

182.

183.

David P. Gustafson


382

385

15

22

Replace “seismic” with “earthquake”.

And on line 26: These lines should read “…shear walls structural walls” See reason given in comment on page 97, line 8.

Agree Page 382, Line 15: “Under seismic earthquake conditions, the direction of shear may not be predictable. The full shear force” Agree Page 385, Line 22: “on typical anchor bolt connections for wood -framed shear walls structural walls (Fennel et al. 2009) showed” Page 385, Line 26:

73 of 215


No.


Pg #

Line #

Public Comment

Committee Response “and toughness for the shear walls structural walls and limited the loads acting on the bolts. Procedures for”

184.

185.

186.

David P. Gustafson



387

408

410

2

8

5

Replace “carry” with “resist”.

Agree

“moment frames” should read “structural frames”

Page 387, Line 2: “carry resist a portion of the shear load because they displace the same as the shear lug. The portion of” Disagree. “moment frames” is the commonly used name for this structural system. “Structural frames” is too general and could include other types of frames, such as braced frames. No change.

Reason: The reason is that since ACI 318-19 uses “structural walls”, then it would be app ropriate using “structural frames”. All cases in 318-19 that read now “moment frames” should be changed to “structural frames” With the changes that have occurred in the stress-strain relationship for nonprestressed deformed reinforcing bars over the time since the Type 2 mechanical splice provisions of Section 18.2.7.1(b) were developed in the 1990s, and also considering that higher grades of reinforcement have been introduced into ASTM A706 since the 1990s, the current requirements for Type 2 mechanical splices should be updated to develop a reasonable minimum strain requirement for the Type 2 mechanical splice. As a minimum, ACI 318 should adopt strain-based provisions for Grade 100 reinforcement and consider adding a commentary statement cautioning users about the lack of ability of the current Type 2 mechanical splice requirement to achieve ductility when splicing lower grades of reinforcement (Grades 60 and 80). It is preferable that ACI 318 adopt revised strain-based provisions to address all grades of reinforcement. Additionally, ACI 318 should clearly state seismic “toughness” requirements (inelastic cyclic strain

74 of 215

Agree. Reason statement: This is a st ructural safety concern, because as currently‐defined, Type 2 mechanical splices on high grades of reinforcement (e.g., Grade 80 and 100) might not develop reasonable levels of strain in the bars being connected, likely leading to non‐ductile behavior under earthquake loading. The graphic shown with the proposed code change illustrates that the current Type 2 requirements provide levels of tensile strain as low as 2 to 4 percent, which may not be adequate for some special seismic applications. Specific Code/Commentary Change Proposal Required: The proposed Code/Commentary Change keeps Type 1 and Type 2 mechanical splices and restricts application of Type 2 for Grade 80 and 100 bars in special seismic systems. A sentence will be deleted in Commentary of Chapter 25 (i.e., first s entence of R25.5.7.1). Requirements for seismic cyclic toughness, however,


No.


Pg #

Line #

Public Comment

Committee Response

endurance, including reversal of yield) for Type 2 spliced bar systems.

are proposed to be taken up as new business because of the complexity with defining appropriate requirements. Due to space limits in this response column, the Code/Commentary Changes required to address Public Comment 186 is given following Public Comment 186.

75 of 215


The following is the graphic mentioned in response to first comment by Frosch 186:

Splices Precisely Complying with Type 2 140

Type 2 on A706 Grade 100 120

Type 2 on A706 Grade 80

100 ) i s k ( s s e r t S

Type 2 on A706 Grade 60

80

Code does not require development development of strains above those associated with “Type 2” minimum strength

60

40

Representative actual stress-strain curves for reinforcing bars commercially produced in the U.S. during 2017-2019. Tests conducted at the structural laboratories of Wiss, Janney, Elstner Associates.

20

0 0

*A706 GR100 #11 A706 GR80 #9 A706 GR80 #14 A706/A615 GR60 #10 A706 GR60 #7

A706 GR80 #6 A706 GR80 #7 A706 GR80 #8 A706/A615 60 11 A706/A615 60 9

G R1 00 Ty Ty pe pe 2/ 2/ Ty Ty pe pe 1 M ec h S pl pl ic ic e

G R8 0 T yp yp e 2 /T yp yp e 1 Me Me ch ch Sp Sp lili ce ce

2

4

A706 GR80 #18 A706 GR80 #5 A706/A615 GR60 #14 A706 GR60 #11 A706/A615 60 5

6

G R6 0T yp yp e 2 Me Me ch ch Sp Sp li ce ce

8

10

Strain (percent)

Approved Code and Commentary Changes in Response to Public Comments 186 and 377:

CHAPTER 18 — EARTHQUAKE-RESISTANT EARTHQUAKE-RESISTANT STRUCTURES 18.2 — General General 18.2.7 Mechan 18.2.7 Mechanical ical splices in special special moment moment frames and special special structural structural walls 18.2.7.1 Mechanical splices shall be classified as (a) or (b):

76 of 215


No.


Pg #

Line #

Public Comment

Committee Response

(a) Type 1 – 1 – Mechanical Mechanical splice conforming to 25.5.7 (b) Type 2 – 2 – Mechanical Mechanical splice conforming to 25.5.7 and capable of developing the specified tensile strength of the spliced bars 18.2.7.2 Type 1 Except for Type 2 mechanical splices on Grade 60 reinforcement, mechanical splices shall not be located within a distance equal to

twice the member depth from the column or beam face for special moment frames or from critical sections where yielding of the reinforcement is likely to occur as a result of lateral displacements beyond the linear range of behavior. Type 2 mechanical splices on Grade 60 reinforcement shall be permitted at any location, except as noted in 18.9.2.1(c).

In a structure undergoing inelastic deformations during an R18.2.7 Mechanical Mechanical splices in special moment frames and special structural walls — In earthquake, the tensile stresses in reinforcement may approach the tensile strength of the reinforcement. The requirements for Type 2 mechanical splices are intended to avoid a splice failure when the reinforcement is subjected to expected stress levels in yielding regions. Type 1 mechanical mechanical splices on any grade of reinforcement and Type 2 mechanical splices on Grade 80 and Grade 100 reinforcement are not required to satisfy the more stringent requirements for Type 2 mechanical splices, and may not be capable of resisting the stress levels expected in yielding regions. The locations of Type 1 these mechanical splices are restricted because tensile stresses in reinforcement in yielding regions can exceed the strength requirements of 18.2.7.1 25.5.7. The restriction on all Type 1 mechanical splices and on Type 2 mechanical splices on Grade 80 and Grade 100 reinforcement applies to all reinforcement resisting earthquake effects, including transverse reinforcement. Recommended Recommended detailing practice would preclude the use of splices in regions of potential yielding in members resisting earthquake earthquake effects. If use of mechanical splices in regions of potential yielding cannot be avoided, there should be documentation on the actual strength characteristics of the bars to be spliced, spliced, on the the force-deformation force-deformation characteristics of the spliced spliced bar, and on the ability of the Type Type 2 mechanical mechanical splice splice to be be used to meet the the specified performance performance requirements. requirements. 77 of 215


No.


Pg #

Line #

Public Comment

Committee Response

Although mechanical splices as defined by 18.2.7 need not be staggered, staggering is encouraged and may be necessary for constructibility or provide enough space around the splice for installation or to meet the clear spacing requirements. R18.2.7.1 The additional requirement for a Type 2 mechanical splice is intended to result in a mechanical splice capable of sustaining inelastic strains

through multiple cycles.

R18.5 — Intermediate Intermediate precast structural walls Connections between precast wall panels or between wall panels and the foundation are required to resist forces induced by earthquake motions and

to provide for yielding in the vicinity of connections. When Type 2 mechanical splices are used to directly connect primary reinforcement, the probable strength of the splice should be at least 1.5 times the specified yield strength of the reinforcement.

R18.9 — Special Special moment frames constructed using precast concrete The detailing provisions in 18.9.2.1 and 18.9.2.2 are intended to produce frames that respond to design displacements essentially like monolithic

special moment frames. Precast frame systems composed of concrete elements with ductile connections are expected to experience flexural yielding in connection regions. Reinforcement in ductile connections can be made continuous by using Type 2 mechanical splices or any other technique that provides development in tension or compression of at least the specified tensile strength of bars (Yoshioka and Sekine 1991; Kurose et al. 1991; Restrepo et al. 1995a,b). Requirements for mechanical splices are in addition to those in 18.2.7 and are intended to avoid strain concentrations over a short length of reinforcement adjacent to a splice device. Additional requirements for shear strength are provided in 18.9.2.1 to prevent sliding on connection faces. Precast frames 78 of 215


No.


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Committee Response

composed of elements with ductile connections may be designed to promote yielding at locations not adjacent to the joints. Therefore, design shear V e, as calculated according to 18.6.5.1 or 18.7.6.1, may not be conservative.

18.12 — Diaphragms Diaphragms and trusses 18.12.7 Reinforceme 18.12.7 Reinforcement nt 18.12.7.4 Type 2 splices are required where mechanical splices on Grade 60 reinforcement are used to transfer forces between the diaphragm and the

vertical elements of the seismic-force-resisting system. Grade 80 and Grade 100 reinforcement shall not be mechanically spliced for this application.

CHAPTER 25 R25.5.7.1 The maximum reinforcement stress used in design under the Code is the specified yield strength. To ensure sufficient strength in splices so that yielding can be achieved in a member and thus brittle failure avoided, the 25 percent increase above the specified yield strength was selected as both an adequate minimum for safety and a practicable maximum for economy. 187.

David L. Hartmann

411

25

Through line 26: “. . . with E taken as twice that prescribed by the general building code.” Rather than Ω0 similar to 18.3.3 (b)?

188.

Ahmed M.Osman

411

26

18.4.2.3 (b) … Similar scenario for beams as above.

79 of 215

Disagree. The distinction between Omega-zero and the factor of 2 i s intentional. The factors are intended to be different for beams and col umns. Columns are more critical than beams, hence the higher multiplier on column shear. No change. Non responsive It is not clear what “similar scenario for beams as above” means, or what specific change is being proposed.


No.


Pg #

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Committee Response

189.

Ahmed M.Osman

412

12

190.

Joe Ferzli (CKC), Jerry Lee (CKC)

412

22

191.

Ricardo Gómez Serrano

416

5

Width bw shall be at least the GREATER of 0.3h and 10 in.

192.

Patricio Placencia

419

6

Provision 18.7.2: Column size at first story (at ground level) should be large enough such any Pu be smaller than Pb. In special moment frames, plastic hinges are supposed to be at beam edges, but the plastic mechanism is completed with plastic hinges at column bases too. If Pu is larger than Pb, the column cannot be ductile.

18.4.3.1 (b) … What if the columns are in a scenario where Ωo is required when calculating the factored load combination E (e.g. columns supporting discontinued members)? Does that mean for these Columns the maximum shear required per 18.4.3.1 (b) is obtained using twice Ωo (one from the factored load combination and the other from int ermediate frame requirement) or only one Ωo is sufficient? Through line 26: Is it intended to intraplate in the case where reinforcement is specified to a steel Grade between 60 ksi and 80ksi? Please clarify [This comment applies to many locations throughout CH 18]

The code recommendation may be either after the column design is made, to check that the maximum Pu < Pb, or before modelling the structure, as pre dimensioning step, for interior columns:

80 of 215

No change. Disagree. Omega-zero should only be applied once to the design of any structural member. No change.

Disagree. It is not intended to interpolate between steel grades. In any case, Grade 75 reinforcement will soon be dis continued, so the question of what to do with Grade 75 reinforcement will become moot. No change. Disagree. “lesser” is correct. No change. New business. Disagree. There is no requirement in ACI 318 that the axial load on columns of special moment frames must be less than the balanced axial load Pb. Therefore the proposed restrictions are not necessary. No change.


No.


Pg #

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Committee Response

Goal: Pu < Pb (it could be Pu< f Pb, where f is less than 1) Pu at base= 1.2 PD +1.6PL Assuming Pb is similar similar to Po/3

The concept is valid for exterior columns as well, but it is not recommended to have half of Ag of the interior column.

193.

Saman Abdullah

419

17

“load combination” should be “load combinations”

194.

Carson Baker (CPL)

420

8

195.


420

16

This provision restricts column longitudinal bar size based on the unbraced length of the column. At columns supporting mezzanines or ramps, or which frame into large beams and slab steps and have very short unbraced lengths, this provision leads to impractical designs, requiring the use of #4 bars or smaller. It is recommended either that an exception be introduced such that bars need not be taken as smaller than #6 bars, or that this provision need not apply if bars are continuous (eg. not lap spliced) within the unbraced length. 18.7.5.1 Transverse reinforcement required in 18.7.5.2 through 18.7.5.4 shall be provided over a length ℓo from each joint face and on both sides o f any section where flexural yielding is li kely to occur as a result of lateral displacements beyond the elastic

81 of 215

Agree. Editorial change. Change “combination” to “combinations” Disagree. This section is related to the reinforcement detailing of columns in special moment frames only. The examples cited are very unlikely to be designed as special moment frames, so no exception is needed. No change.

Agree that this proposal should be considered by Subcommittee H. However, there is insufficient time to evaluate a proposed change of this magnitude. magnitude. This proposal should be considered for new business in the next code cycle.


No.


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Committee Response

range of behavior. Length ℓo shall be at least t he greatest of (a) through (f) conform 18.7.5.1.1 or 18.7.5.1.2:

New business.

(a) The depth of the column at the joint face or at the section where flexural yielding is likely to occur (b) One-sixth of the clear span of the column (c) 18 in. 18.7.5.1.1 Columns confined with rectilinear hoops or crossties at least the greatest of (a) and (b): (a) 2h (b) 0.3 ℓu 18.7.5.1.2 Columns confined with with either single or overlapping spirals or circular hoops at least the greatest of (a) and (b): (a) 3h (b) 0.4 ℓu Reason: Recent work by Guerrini and Restrepo (2018) have shown that current provisions of ACI 318 may be liberal, and that columns reinforced with circular hoops or spirals are treated identically to those reinforced with rectilinear hoops and crossties. Analysis and testing have shown that the spread of plasticity in columns, where special transverse reinforcement needs to be detailed, is significantly longer than what is currently being recommended, particularly when the axial load ration in the column is moderate or high. Furthermore, in columns reinforced with circular hoop the extent of pl asticity is significantly greater than that in columns reinforced with

82 of 215


No.


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Committee Response

rectilinear hoops. The requirements proposed are a simplification of those recommended by Guerrini and Restrepo.

196.


420

28

Reference Guerrini, G. and Restrepo, J.I., 2018. Extent of Plasticity in Reinforced Concrete Columns. ACI Structural Journal, 115(5). In our opinion the following addition is necessary in 18.7.5.2: “(a) Transverse reinforcement shall comprise either single or overlapping spirals, circular hoops, or single or overlapping rectilinear hoops with or without crossties. Where crossties are used, seismic hooks shall be provided at each end.”

197.


421

6

Reason: The use of crossties with seismic hooks at each end is specified for walls in section 18.10.6.4 of ACI 318-19. The reason is that tests of RC walls have shown that crossties having alternating 90-degree and 135-degree hooks might not be as effective as crossties with seismic hooks at both ends. Considering the similarities in RC walls and RC columns, it seems appropriate to have comparable requirements in both RC elements. Incidentally, the use of crossties with seismic hooks in columns and walls is a co mmon practice throughout Latin America. The problem to address in earthquake resisting design of RC structures is not only confinement in cores, but it is also about longitudinal bar fracture after buckling after the loss of the concrete cover, which can occur in columns with low and moderate axial compression. Therefore 18.7.5.2(f) should specify seismic hooks not only for columns with high axial loads or high strength concrete but also for any column in structures resisting earthquakes.

83 of 215

Disagree. Subcommittee H has considered the need to provide seismic hooks at both ends of cross ties in columns of special moment frames with low axial loads and concluded this is not required. Cross ties with seismic hooks at both ends are required, though, for columns with high axial loads or high concrete strengths. No change.

Disagree. Subcommittee H has considered the need to provide seismic hooks at both ends of cross ties in columns of special moment frames with low axial loads and concluded this is not required. Cross ties with seismic hooks at both ends are required, though, for columns with high axial loads. No change.


No.

198.

Public Commenter Name Restrepo J.I. and Rodriguez M.E.

Pg #

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421

11

Public Comment

Committee Response

18.7.5.3 Spacing of transverse reinforcement shall conform 18.7.5.3.1 or 18.7.5.3.2 not exceed the smallest least of (a) through (ed):

Disagree. It is not clear why the commenters believe that circular hoops are less effective at restraining bar buckling than rectangular hoops. The commenters have not presented research or other evidence that the spacing for circular hoops and rectangular ties need to be different. No change.

18.7.5.3.1 Spacing of transverse reinforcement in columns confined with rectilinear hoops or crossties shall not exceed the least of (a) through (d): (a) One-fourth of the minimum column dimension (b) For Grade 60 longitudinal reinforcement, 6db of the smallest longitudinal bar (c) For Grade 80 longitudinal reinforcement, 5db of the smallest longitudinal bar (ed) so, as calculated by: so

 14 − h x  = 4+   3 

18.7.5.3.2 Spacing of transverse reinforcement in columns reinforced with either single or overlapping spirals or circular hoops shall not exceed: (a) One-fourth of the column diameter (b) For Grade 60 longitudinal reinforcement, 5db of the smallest longitudinal bar (c) For Grade 80 longitudinal reinforcement, 4db of the smallest longitudinal bar Reason: The possible tighter spacing limitation of the transverse reinforcement in circular columns reflects the fact that h oops, while being very efficient at confining the column concrete core, provide limited restraint against buckling of longitudinal

84 of 215


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bars, which generally buckle along various sets of hoops or spiral turns. Provision 18.7.6.1.1 Column shear forces based on top and bottom joint forces from beams Mpr , is okay for all columns, except for those at ground level, where a plastic hinge at their base is expected, and hence, shear forces should be b ased on column Mpr at base

199.

Patricio Placencia

423

9

200.

Patricio Placencia

423

16

201.


426

1

202.

Robinson

426

1

Why is lambda 0.75 for “concrete containing lightweight aggregate” regardless of the concrete density or composition?

Disagree. There is not sufficient information available on the behavior of beam-column joints with various types of lightweight aggregates to support the use of a lambda factor other than 0.75.

203.

Reid W. Castrodale

426

1

Table 18.8.4.3 Same note is used as for Table 15.4.2.3. See comments for that table (p. 307, line 15).


Provision 18.7.6.2.1 Vc=0 maybe is a better recommendation for those columns at ground level, where plastic hinges are expected. For other columns, the conditions for Vc= 0 sound not logic. Vc has its value for all levels of compression forces, starting with none. In upper stories, with less compression forces than in lower ones, but not likely of plastic hinges, Vc=0 The footnote on lambda = 0.75 is not aligned with recent research, cited in comment No. 4

85 of 215

Disagree. Section 18.7.6.1.1 states that the joint forces used to determine Ve “shall be calculated using the maximum probable flexural strengths, Mpr, at each end of the column associated with the range of factored axial forces, Pu, acting on the column.” At the top of a foundation, the maximum probable flexural strength is the Mpr of the column it self, which appears to address the concern of the commenter. No change. Disagree. The proposed change requires more justification. No change.



No.

Pg #

Line #

204.

Public Commenter Name Robinson

427

205.

Reid W. Castrodale

427

206.


429

Public Comment

Committee Response

3

Why is lambda 0.75 for lightweight concrete without consideration of the concrete density or composition?


3

18.8.5.1 This article requires an increase in required development length for bars in tension for “lightweight concrete” compared to bars in normalweight concrete. This reduction is for “lightweight concrete” rather than “concrete containing lightweight aggregate” as is used for the note to Table 18.8.4.3. Therefore, these requirements, which appear in adjacent provisions in the code, address lightweight concrete in different ways, so the requirements may apply differently for particular situations.

Agree.

10

I expect that this distinction is unintended, so it should be corrected to have uniform application of requirements to lightweight concrete. Comment on 18.10.2.3(a): This provision recommending an extension of 12 ft violates Buckingham’s π theorem of dimensional analysis. Such requirement will result unconservative in the design of rectangular walls when l w exceeds approximately 12 ft/ 0.6 = w exceeds 20 ft. (assuming a tension shift equal to 0.6 l w ) ; and in flanged w); walls (such as T, L, [, Z , U walls and the like], when reliance is made in the longitudinal reinforcement of the boundary element at one end of the flange to resist flexure, and the sum of the portion of the flange from the boundary element to the wall web plus l w exceeds 20 ft. Both cases described here are w exceeds commonly found in practice. The main issue here is that the shear lag causing the tension shift effect in the longitudinal

86 of 215

Specific code change required: Change line 3 of page 427 to: “The value of  shall be 0.75 for concrete containing lightweight aggregate and 1.0 otherwise.”

New business Subcommittee H and the main committee discussed and balloted this provision extensively and concluded that the recommended cutoff provisions incorporate an appropriate balance of adequacy and practicality. Provisions attempting to achieve greater accuracy are difficult to justify for earthquake loading for which ground motions and inelastic dynamic response cannot be predicted accurately. New Business related to the consideration of T-shaped walls. No change.


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Committee Response

reinforcement of a boundary element not only occurs in the plane where the wall resists the seismic shear, but also in the plane of the flanges. The following strut-and-tie sketch, Fig. A, clearly illustrates the load path through the web and flange in a T-section wall with the flange in tension.

(a) Elevation

(b) Side elevation showing flange Figure A. 3-D strut-and-tie model

The following change is suggested (a) Except at the top of a wall, longitudinal reinforcement participating in flexure at a section of the wall shall extend at least 12 ft a distance l sl above the point at sl above which it is no longer require to resist flexure but need not extend more than l d d above the next floor level, where l sl = 0.6 l w in rectangular walls sl = w in l sl – The greater of 0.6 l w,x and 0.6(l w,y + l fi ) in flanged sl – w,x and w,y + walls, where boundary reinforcement in the flanges participate in flexure.

87 of 215


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Suggested commentary R18.10.2.3 Figure B shows a T-section wall with seismic attack in x and y directions, respectively. Boundary element Bars “A” resist flexure in both directions of attack. To cut some of these bars off, the shear lag should be considered in each of the two directions. In the x-direction, the bars need to be extended a distance 0.6 l w,x from the section where w,x from the bars are not needed to resist flexure in such direction. In the y-direction, the bars need to be extended a distance 0.6(l w,y + l fi ) from the section w,y + where the bars are not needed to resist flexure in such direction. The structural engineer engineer should evaluate the worst of the two cases.

Figure B. T-section wall with seismic attack in x and y directions

88 of 215


No.

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207.

Public Commenter Name William Pollalis, Santiago Pujol, Robert Frosch

Public Comment

Committee Response

429

17

We would suggest that the Code should prevent the use of lap splices in longitudinal bars in all seismic applications regardless of classification of the wall, especially for grades higher than 60ksi in ordinary walls. Please refer to the appended file for documentation supporting this statement.

New business Subcommittee H is of the opinion that lap splices should be allowed in walls, but that certain restrictions should be placed on the allowable locations of lap splices. For example, in the cited section, lap splices have been prohibited near the base of slender, special walls and at other other critical sections. Further restrictions on the locations of lap splices in walls can be taken up as future business. No change. Future business.

208.

Carson Baker (CPL)

429

17

Disagree. The intention of this provision is intended to apply to any wall that has a critical section, and at every critical section. No change.

429

17

Is the intent that 18.10.2.3 (c) is required only for walls with aspect ratio h/l > 2 and designed to have a single critical section? If so, this language should be added to section (c), otherwise as written this would apply to any wall that has a critical section, and at every critical section. For walls with irregular openings, this could imply lap splices are not permitted across the entire wall. The language of item (c), lines 17-22, is cumbersome and should be improved.

209.

Saman Abdullah

Agree. The language of 18.10.2.3(c) is indeed confusing. A figure is to be added to the commentary to help explain (see response to Lepage). Replace 18.10.2.3(c) as follows: (c) Lap splices of longitudinal reinforcement within boundary regions shall not be permitted over a height equal to hsx above, and ℓd below, critical sections where yielding of longitudinal reinforcement is likely to occur as a result of lateral displacements. The value of hsx need not exceed 20 ft. Boundary regions include those within lengths specified in 18.10.6.4(a) and within a length equal to the wall thickness measured beyond the intersecting region(s) of connected walls.

89 of 215


No.


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Committee Response

Adjust/insert figure as shown below as well:

210.

Saman Abdullah

429

26

Page 429 lines 26-33 and page 430 lines 1-5 For item (a), it does not make sense that l_be is used because l_be is based on a compression check, whereas the minimum quantity of longitudinal reinforcement refers to boundary longitudinal reinforcement in tensions, which is at the other end of the wall (not compression boundary). Suggested revisions are provided below. Note that, if the suggested revisions are accepted, Fig. R18.10.2 and the caption for this figure are correct. However, if the suggested revisions

90 of 215

Agree Make the changes described by the commenter below the l ine “Suggested revised text (this would be much easier to apply):” apply) :”


No.


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Committee Response

are not accepted, then possibly a new figure (Fig. R18.10.2(a)) is need that shows l_be (and current figure could be retained as, e.g., Fig. R18.10.2(b)). Suggested revised text (this would be much easier to apply) : 18.10.2.4 Walls or wall piers with hw/lw ≥ 2.0 that are effectively continuous from the base of structure to top of wall and are designed to have a single critical section for flexure and axial loads shall have longitudinal reinforcement at the ends of a vertical wall segment section that satisfies (a) through (dc).

(a) Where boundary elements are required by 18.10.6, the longitudinal reinforcement ratio within the boundary element shall be at least 6 f ' f (ba) Where boundary elements are not required by 18.10.6, the lLongitudinal reinforcement ratio within 0.15lw from the end of a vertical wall segment, and over a width equal to the wall thickness, shall be at least 6√f’c/fy (cb) The longitudinal reinforcement required by 18.10.2.4(a) or 18.10.2.4(b) shall extend vertically above and below the critical section at least the greater of lw and Mu/3Vu. (dc) No more than 50% of the reinforcement required by 18.10.2.4(a) or 18.10.2.4(b) shall be terminated at any one section. 211.

Saman Abdullah

430

7

“Or Spliced” Should be removed, as splices should not be allowed in coupling beams.

91 of 215

Agree. Delete “or spliced” in line 7


No.

212.

Public Commenter Name Saman Abdullah

Pg #

430

Line #

14

213.

Zach Whitman (CPL)

430

20

214.

Zach Whitman (CPL)

430

26

215.

Zach Whitman (CPL)

430

26

Public Comment

Committee Response

“–Vu shall be obtained …. factored load combinations.” This sentence should be deleted. It is the same sentence on lines 20-21. CH09 as approved in Dallas.

Agree. Delete the sentence “ -Vu shall be obtained…factored load combinations.” From lines 14 and 15. Leave the words “Design forces” as an italicized heading in line 14.

In addition, modify commentary section R18.10.3 as follows: Design shears for structural walls are R18.10.3 Design forces — Design obtained from lateral load analysis with the appropriate load factors. However, tThe possibility of yielding in components of such structures structural walls should be considered, as in the portion of a wall between two window openings, in which case the actual shear may be in excess of the shear indicated by lateral load analysis based on factored design forces. Does the committee intend for the factored shear force to Agree. Add commentary to Section Section R18.10.3.1. “The application of ΩV to include the redundancy factor calculated per ASCE 7? In ASCE to V u does not preclude the application of 7-16 12.4.3.1, load combinations with overstrength included do a redundancy factor if required by the general building code.” not require the redundancy factor. It would be helpful for 31819 to discuss in the commentary if the committee believes the ACI overstrength factors should or should not be applied with the redundancy factor. As ACI references Vu and not the Qe used in the ASCE 7 equations, it is not necessarily clear what is intended. Is the intent for the value of Mu to include the redundancy Disagree. factor per ASCE 7-16 Section 12.4.3? This would be useful to The application of overstrength and redundancy factors used to clarify in the commentary. compute Vu is the province of ASCE 7. No change. In many cases, the ratio Mpr/Mu will be much greater than 1.5. Agree While 1.5 is a decent estimate of overstrength for non-coupled Change equation 18.10.3 by adding at the end “<= 3V u” planar walls, flanged walls are more commonly found in building design and are not well-approximated by planar wall overstrength. Consider the case of a simple core comprised of two coupled C-shapes. In this case, the flexure of one C-shape is controlled by the load combination associated with tension exerted on the shape by core coupling as well as the -0.2Sds D

92 of 215


No.


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Committee Response

contribution. The difference in factored design load between the "heavy" (compression due to coupling, +0.2SdsD) and "light" (tension due to coupling, -0.2Sds) axial loads can be extremely large. This could result in Mpr/Mu values up to 4 or 5. Is it the intent of the authors that values of 4 or 5 be used? The commentary states that "a value greater than 1.5 may b e appropriate if provided longitudinal reinforcement exceeds that required," but the axial load effect could create a very large overstrength factor even if the flexural reinforcement were designed at a DCR of 1.0.

216.

217.


Allen Adams

431

431

7

10

We propose that the “Greater of” in Table 18.10.3.1.2 is replaced by “Lesser of.” This would create an effective overstrength cap of 1.5*1.8 = 2.7. Factors derived from flexural overstrength calculations reaching the 4-5 range would make shear walls infeasible as a system for many buildings. A phi factor of 0.75 would be taken whenever the overstrength factor is taken as more than 1.0 18.10.3.1.3 reads: “Where ns shall not be taken less than 0.007 hwcs.”

This requirement needs to be revised since ns is the number of stories which has no units, and hwcs is a height with units in in. Section 18.10.4.1: It says that “Vn of structural walls shall not exceed…”, and then it gives Eq. (18.10.4.1). There is disagreement among engineers on whether Eq. (18.10.4.1) gives the design shear strength Vn of Special Walls, or is merely a limit on Vn for Special Walls. It doesn’t say “… shall be calculated by…”, which is the terminology used elsewhere throughout ACI 318. And the phrase “… shall not exceed…” is used extensively throughout the spec but only after some value

93 of 215

Agree. On page 431, line 7, make the following changes Where n Where n s shall not be taken less than the quantity 0.007 hwcs, in units of number of stories.

Agree. The revised provision appears below. 18.10.4.1 V n shall be calculated by: Vn

(

= c 

'

fc

+ t f yt

)A

where:

c = 3 for hw/ℓ w  1.5

cv cv

(18.10.4.1)


No.

218.


Allan Bommer

Pg #

431

Line #

10

Public Comment

Committee Response

is given, which is then limited by the “… shall not exceed…” value. It appears from outside sources that the intent of this Section is to provide the value Vn to be used, but it doesn’t explicitly say that. Note that even though Section 11.1.2 says that special walls shall be in accordance with Chapter 18, Section 18.2.1.2 says that all members shall satisfy Chapters 1 to 17. And Section 11.5.4.3 (see page 245 line 25) says that “Vn shall be calculated by…” and the n gives Eq (11.5.4.3). So this is the design value Vn, and then considering Section 18.10.4.1, that value is “not to exceed” Eq. (18.10.4.1). If the intent of Section 18.10.4.1 is to give the design value of Vn, please make the simple change: “Vn of structural walls shall be calculated by…”. (18.10.4.1) The code says “Vn of structural walls shall not exceed:”, but from discussions with Jack Moehle it appears the intent of the committee is that equation 18.10.4.1 is be used as a “shall be permitted to be taken as” value instead of a limiting “shall not exceed” value.

c = 2 for hw/ℓ w  2.0 It shall be permitted to linearly interpolate the value of c between 3 and 2 for 1.5 < hw/ℓ w < 2.0

Agree. The revised provision appears below. 18.10.4.1 V n shall be calculated by: Vn

(

= c 

fc'

+ t f yt

)A

cv cv

(18.10.4.1)

where:

Note also that NIST CGR 11-919-11 (Seismic Design of Cast-inPlace Concrete Special Structural Walls and Coupling Beams) references the equation with “defines the nominal shear strength as” in Section 5.4.

219.

Zach Whitman (CPL)

432

23

Is the intent here that 18.10.6.2 is now required for walls with a single critical section and h/l > 2? If so, this would be helpful to explain in the commentary.

220.

Saman Abdullah

432

26

Wrong font style of lw. Change it to “

w”.

Also, add “a” to

equation number (i.e., 18.10.6.2a) because the subsequent equations is 18.10.6.2b

94 of 215

c = 3 for hw/ℓ w  1.5 c = 2 for hw/ℓ w  2.0 It shall be permitted to linearly interpolate the value of c between 3 and 2 for 1.5 < hw/ℓ w < 2.0 Disagree. The committee believes that the applications of 18.10.6.2 and 18.10.6.3 are clear. No change. Agree. Change the style of lw, as indicated by yellow highlight. Also, change the number of equation 18.10.6.2 to 18.10.6.2a


No.

Pg #

Line #

432

26

222.

Public Commenter Name Restrepo J.I. and Rodriguez M.E. Saman Abdullah

433

3

223.

Saman Abdullah

433

7

Remove “except as permitted in 18.10.6.4(i)”. This is moved to item (i) in lines 7-8. Change font of lw.

224.

Saman Abdullah

433

8

Change 18.10.6.4(g) to 18.10.6.4(i)

225.

433

8

226.

Zach Whitman (CPL) Saman Abdullah

433

9

What is permitted in 18.10.6.4 (g)? I think may be intended to reference a different subsection, most likely 18.10.6.4 (i). Change font of lw.

227.

Saman Abdullah

433

11

Change font of lw.

228.

Saman Abdullah

433

11

I believe that Ve (amplified) should be used in this equation in lieu of Vu. This model i s derived based the maximum shear force developed in the wall tests.

221.

Public Comment

Committee Response

It reads (18.10.6.2) and it should read (18.10.6.2a)

Agree. Change the number of equation 18.10.6.2 to 18.10.6.2a Agree. Remove “except as permitted in 18.10.6.4(i)” Agree. Change font of lw Agree. Change 18.10.6.4(g) to 18.10.6.4(i) Agree. Change 18.10.6.4(g) to 18.10.6.4(i) Agree. Change font of lw Agree. Change font of lw Agree. In Equation 18.10.6.2b, change V u to V e.

There are other sections in the code and commentary where Vu is used as a criterion. The committee should consider using Ve as opposed to Vu. These sections are §18.10.2.1 (min web reinforcement), §18.10.2.2 (number of curtains), §18.10.6.5 (a) (development of web horizontal bars for OBE), and Table 18.10.6.5b (extending longitudinal reinforcements OBE). There are other sections such as 18.10.2.4(c) and 18.10.6.2(b)(i), where shear-moment ratios (Mu/3Vu or Mu/4Vu) are used to determine extending longitudinal reinforcements and boundary confinements, respectively. For these provisions, use of Vu is probably appropriate (otherwise, if Vu is changed to Ve, then Mu would also have to be changed, possibly to Mpr)

95 of 215

Regarding the remaining comments, the remainder of Chapter 18 was reviewed, and no other instances requiring a change from V u to V e were identified.


No.

Pg #

Line #

229.


433

11

230.

Saman Abdullah

433

23

231.

Saman Abdullah

434

9

232.

Andrew Taylor

434

11

Public Comment

Committee Response

In appendix C, an SI-unit version of equation 18.10.6.2b should be given, as the shear term of the equation changes (i.e., the factor in the denominator of the shear term changes from 8 for f'c in psi to 0.67 for MPa). Change (i) to (j) [this is because item (g) was added]

Agree. Added an SI version of this equation to Appendix C

Possibly, Table 18.10.6.5b should be placed in section 18.10.6.4e (special walls) rather than in 18.10.6.5 “ordinary walls”. Section 18.10.6.5 should refer to 18.10.6.4, not vice versa. section 18.10.6.3(f) is not clear about the lateral constraint of longitudinal bars in boundary elements elements of walls. One interpretation is that every longitudinal bar within a special boundary element is to be supported, but it does not quite say this. If the intent is to laterally support every every bar, I suggest the following revisions:

Agree. In Line 23 change (i) to (j) Consider as new business. No change.

Agree, clarification necessary. See below.

(f) Transverse reinforcement shall be arranged such that every longitudinal bars or bundles of bars around the perimeter of the boundary element are is laterally supported by a seismic hook of a crosstie or corner of a hoop….

Public comment No. 232, response to public comment (ik ) shall be satisfied: 18.10.6.4 If special boundary elements are required by 18.10.6.2 or 18.10.6.3, (a) through (ik ) (a) The boundary element shall extend horizontally from the extreme compression fiber a distance at least the greater of c – 0.1 0.1ℓ w and c /2, where c is the largest neutral axis depth calculated for the factored axial force and nominal moment strength consistent with δu. (b) Width of the flexural compression zone, b, over the horizontal distance calculated by 18.10.6.4(a), including including flange if present, shall be at least hu /16. (c) For walls or wall piers with hw / ℓ ℓw ≥ 2.0 that are effectively continuous from the base of structure to top of wall, designed to have a single critical section for flexure and axial loads, and with c / ℓ ℓw ≥ 3/8, width of the flexural compression zone b over the length calculated in 18.10.6.4(a) shall be greater than or equal to 12 in. (d) In flanged sections, the boundary element shall include the effective flange width in compression and shall extend at least 12 in. into the web. 96 of 215


No.


Pg #

Line #

Public Comment

Committee Response

(e) The boundary element transverse reinforcement shall satisfy 18.7.5.2(a) through (d) and 18.7.5.3, except the transverse reinforcement spacing limit of 18.7.5.3(a) shall be one-third of the least dimension of the boundary element. The vertical spacing of transverse reinforcement in the boundary element shall be in accordance with Table 18.10.6.5b. (f) Transverse reinforcement shall be arranged such that longitudinal bars or bundles of bars around the perimeter of the boundary element are laterally supported by a seismic hook of a crosstie or corner of a hoop. Tthe spacing hx between laterally supported longitudinal bars around the perimeter of the boundary element shall shall not exceed the lesser of 14 14 in. and two-thirds two-thirds of the boundary boundary element element thickness. thickness. Lateral support support shall be provided provided by a seismic hook of a crosstie or corner of a hoop. The length of a hoop leg shall not exceed two times the boundary element thickness, and adjacent hoops shall overlap at least the lesser of 6 in. and two-thirds the boundary element thickness. (g) The amount of transverse reinforcement shall be in accordance with Table 18.10.6.4(f g). 18.10.6.4(f g).

Table 18.10.6.4(fg)—Transverse reinforcement for special boundary elements Transverse Applicable reinforcement expressions

Ash/sbc for rectilinear Greater hoop of

 Ag  f c −1  Ach  f yt

0.3 

0.09

ρs for spiral or circular hoop

Greater of

f c f yt

(a)

(b )

 Ag  f c −1  Ach  f yt (c)

0.45 

0.12

f c f yt

(d )

97 of 215


No.


Pg #

Line #

Public Comment

Committee Response

(gh) Concrete within the thickness of the floor system at the special boundary element location shall have specified compressive strength at least 0.7 times f c' of the wall. (hi) For a distance above and below the critical section specified in 18.10.6.2(b), 18.10.6.2(b), web vertical reinforcement shall have lateral support provided by the corner of a hoop or by a crosstie with seismic hooks at each end. Transverse reinforcement shall have a vertical spacing not to exceed 12 in. and diameter satisfying 25.7.2.2. [CH011] (i j) j) Where the critical section occurs at the wall base, the boundary element transverse reinforcement at the wall base shall extend into the support at least ℓ d , in accordance with 18.10.2.3, of the largest longitudinal reinforcement in the special boundary element. Where the special boundary element terminates on a footing, mat, or pile cap, special boundary element transverse reinforcement reinforcement shall extend at least 12 in. int o the footing, mat, or pile cap, unless a greater extension is required by 18.13.2.3. (jk ) Horizontal reinforcement reinforcement in the wall web shall extend to within 6 in. of the end of the wall. Reinforcement shall be anchored to develop f y within the confined core of the boundary element using standard hooks or heads. Where the confined boundary element has sufficient length to develop the f y / s of the horizontal web reinforcement does not exceed A s f f yt / s of the boundary element transverse reinforcement horizontal web reinforcement, and A s f / / parallel to the horizontal web web reinforcement, reinforcement, it shall be permitted permitted to terminate terminate the horizontal horizontal web reinforcemen reinforcementt without a standard standard hook or head. head. Commentary changes: R10.10.6.4 R18.10.6.4 The horizontal dimension of the special boundary element is intended to extend at least over the length where the concrete compressive

strain exceeds the critical value. For flanged wall sections, including box shapes, L-shapes, and C-shapes, the calculation to determine the need for special boundary elements should include a direction of lateral load consistent with the orthogonal combinations defined in ASCE/SEI 7. The value of c /2 in 18.10.6.4(a) is to provide a minimum length of the special boundary element. Good detailing practice is to arrange the longitudinal reinforcement

and the confinement reinforcement such that all primary longitudinal reinforcement at the wall boundary is supported by transverse reinforcement.

98 of 215


No.


Pg #

Line #

Public Comment

Committee Response

A slenderness limit is introduced into the 2014 edition of this Code based on lateral instability failures of slender wall boundaries observed in recent earthquakes and tests ( Wallace 2012; Wallace et al. 2012 ). For walls with large cover, where spalling of cover concrete would lead to a significantly reduced section, increased boundary element thickness should be considered. A value of c / ℓ ℓ w ≥ 3/8 is used to define a wall critical section that is not tension-controlled according to 21.2.2. A minimum wall thickness of 12 in. is imposed to reduce the likelihood of lateral instability of the compression zone after spalling of cover concrete. Where flanges are highly stressed in compression, the web-to-flange interface is likely to be highly stressed and may sustain local crushing failure unless special boundary element reinforcement extends into the web. Required transverse reinforcement at wall boundaries is based on column provisions. Expression (a) of Table 18.10.6.4(fg) was applied to wall special boundary elements elements prior to the 1999 edition of this Code. It is reinstated in the 2014 edition of this Code due to concerns that expression (b) of Table 18.10.6.4(fg) by itself does not provide adequate transverse reinforcement for thin walls where concrete cover accounts for a significant portion of the wall thickness. For wall special boundary elements having rectangular cross section, A g and A ch in expressions (a) and (c) in Table 18.10.6.4(fg) are defined as A g = ℓ be b and A ch = b = b c1 c1 b c2 c2, where dimensions are shown in Fig. R18.10.6.4.1. This considers that concrete spalling is likely to occur only on the exposed faces of the confined boundary element. Tests (Thomsen and Wallace, 2004) show that adequate performance can be achieved using vertical spacing greater than that permitted by 18.7.5.3(a) . The limits on spacing between laterally supported longitudinal bars are intended to provide more uniform spacing of hoops and crossties for thin walls. 233.

Joe Ferzli (CKC), Jason Thome (CKC)

434

12

Consider allowing crossties in special boundary elements that are enclosed by hoops to have alternating 90-degree hooks and one end and seismic hooks. Requiring seismic hooks at all cross ties is feasible when special boundary elements are pretied. However, this becomes a constructability issue when crossties need to be field placed between boundary elements. It is also

99 of 215

Disagree. Subcommittee H discussed and balloted this change, and concluded that the provision of cross ties with 135 degree bends at both ends is necessary for improved seismic performance. No change.


No.


Pg #

Line #

Public Comment

Committee Response

234.


448

3

an issue when boundary ties need to be field adjusted/tied to accept diagonally reinforced coupling beams. Replace word “pile” with “deep foundation member”.

235.


448

10

Replace word “pile” with “deep foundation member”.

236.

ACI Staff

448

10

Change Table 18.7.5.4(e) to Table 18.7.5.4. Please confirm.

Agree. It will be revised to: 18.13.5.3 For structures assigned to SDC C, D, E, or F, the minimum longitudinal and transverse reinforcement required by 18.13.5.7 through 18.3.5.10 s hall be extended over the entire unsupported length for the portion of pile deep foundation member in air or water, or in soil that is not capable of providing adequate lateral restraint to prevent buckling throughout this length. Agree. It will be revised to: 18.13.5.5 For structures assigned to SDC D, E, or F or located in Site Class E or F, concrete piles deep foundation members shall have transverse reinforcement in accordance with 18.7.5.2, 18.7.5.3, and Table 18.7.5.4(e) within seven pile member diameters above and below the interfaces between strata that are hard or stiff and strata that are liquefiable or soft. Agree. Provision will be revised to include Item (e) Revise to: 18.13.5.5 For 18.13.5.5 For structures assigned to SDC D, E, or F or located in Site Class E or F, concrete deep foundation members shall have transverse reinforcement in accordance with 18.7.5.2, 18.7.5.3, and Table 18.7.5.4 Item (e) within seven pile diameters above and below the interfaces between strata that are hard or stiff and strata that are liquefiable or soft.

237.

Daniel S. Stevenson, P.E. Representing DFI Codes and

448

18

Does 18.13.5.7 apply to drilled piers? Suggest changing “Uncased cast-in-place drilled or augered piles or piers” to “Cast-in-place deep foundations”, so it is clear these provisions

100 of 215

Yes it applies to drilled piers (without casing), as that would be an “uncased cast-in-place drilled pier”. Disagree with changing the terminology as this is consistent with what is currently in ASCE/


No.

238.

239.

Public Commenter Name Standards Committee

Pg #


449


449

Line #

0

0

Public Comment

Committee Response

apply to all cast-in-place concrete deep foundation members. This will match current IBC language.

SEI-7, and this terminology is used in several places throughout the Code.

The Table requires full-length cages. This is both unnecessary and very costly in many soil and loading situations. Usually cages are only necessary in the upper section of the pile where soils are weaker.

Table 18.13.5.7.1 requires full length cages for piles in SDC D through F, site classes E and F. This is a significant change from the current IBC requirements (IBC 1810.3.9.4.2) and will result in a significant increase in the cost of construction on some projects. Commentary states that full full length cages are required because soils are either liquefiable or not capable of providing confinement. However, the suspect soils are often only present in the upper regions regions of a pile shaft. Consider the case of a pile 100 feet long, where soft/liquefiable soils are only present in the upper 20 feet. feet. The remaining 80 feet feet of the pile shaft is founded in dense/hard dense/hard soils. The rationale for full length piles given in the commentary would not be applicable in this circumstance. Proposed code section 18.13.5.5 requires transverse reinforcing (and therefore vertical reinforcing) to extend at least 7 pile diameters above and below t he interface between strata that are hard/stiff and strata that is soft/liquefiable. This section (which matches IBC 2018 section 1810.3.9.4.2.2) will ensure piles h ave adequate reinforcement/confinement reinforcement/confineme nt and d uctility where soft/liquefiable soils are present. present. Full length cages should not

101 of 215

No change required. Disagree. No change to Code or Commentary Required. Full length cages are only required in SDC D, E, F; Site Class E, F and that is consistent with the current IBC requirements. In addition, the row is titled “Minimum Reinforced Pile Length”, so it is not felt that further clarification is needed. No change required. The requirement that longitudinal and transverse reinforcement extend full length of the pile for piles in SDC D-F that occur in Site Classes E or F is consistent with the current requirement in ASCE/SEI-7 [14.2.3.2.3 Reinforcement for Uncased Concrete Piles (SDC D through F)]; therefore, there is no change from current requirements. For reference, the following is an excerpt from ASCE -7 [14.2.3.2.3]: In addition, for piles located in Site Classes E or F, longitudinal reinforcement and transverse confinement reinforcement, as described above, shall extend the full length of the pile. No change required.


No.

240.


ACI Staff

Pg #

449

Line #

0

Public Comment

Committee Response

be required for every project assigned to SDC D through F with site class E and F. Note 1 to the table does allow for for a small reduction in cage lengths, but the 5% limit from total pile length is not significant. For the example given given above, a cage length of 95 feet will be required, whereas current IBC code would require a cage length of only 50 feet. Removal of the requirement for minimum number of bars (per 10.7.3.1) in this table for sections of deep foundation members not required to have transverse reinforcement per 18.13.5.5 would allow for piles to be reinforced with a cage in the upper section where soils are liquefiable or soft, and a single center bar in the lower section where soils are firm. This would match current practice and IBC requirements. Change Table 18.7.5.4(e) to Table 18.7.5.4 in two places. Please confirm.

Agree. Provision will be revised to include Item (e)

241.

Thomas Schaeffer

451

23

Delete “(b)”, it does not belong on this line

242.

Thomas Schaeffer

451

24

243.

Thomas Schaeffer

451

28

“(c)” should be “(b)”; it appears that this is mislabeled due to automatic numbering “(d)” should be “(c)”

244.

Thomas Schaeffer

452

1

“(e)” should be “(d)”

245.

Thomas Schaeffer

454

2

“(f)” should be “(e)”

246.

Thomas Schaeffer

454

8

In the Equation, the variables “sb “ sbc” is missing after “0.3”

247.


457

7

Add the exception to 18.4.3.3(c) that equations (c) and (f) in Table 18.7.5.4 are not required to be satisfied for columns that falls under the category of “Members not designated as part of

102 of 215

Revise “Table 18.7.5.4 Item (e)” in two places in the Table 18.13.5.7.1 Agree. Delete “(b)” in front of “[CF001]” on line 23 Agree. Change (c) to (b) on line 24 Agree. Change (d) to (c) on line 28 Agree. Change (e) to (d) on line 1 Agree. Change (f) to (e) on line 2 Agree. Add the variables “sb “ sbc” after “0.3” in the equation. Agree. During the ACI 318-14 code cycle, the addition of equations (c) and (f) in Table 18.7.5.4 Table 18.7.5.4 was intended to apply to special moment


No.


Pg #

Line #

Public Comment

Committee Response

the seismic-force-resisting system” such as gravity columns even when induced moments and shear are not checked/satisfied.

frame columns. If one does not check the moments and shears induced by design drift or if the moments and shears are above the capacities, then it is appropriate to detail the column per full seismic frame column provisions including new equations (c) and (f). So, there should be no change to 18.14.3.3(c). However, if one does check induced moments and shears under design drift, and they are less than capacities, then equations (c) and (f) should not apply as these are only needed to obtain drift capacities of up to 0.03 – (see commentary to 18.7.5.4). Therefore, 18.14.3.2 (c) should be adjusted with the yellow highlights below (Note, the non -yellow strikeout and underline were part of ballot CH 014): (c) Columns with factored gravity axial forces exceeding and 18.7.5.7. The The minimum 0.35 P o shall satisfy 18.14.3.2(b) and 18.7.5.7. amount of transverse reinforcement provided shall be, for rectilinear hoops, at least one-half the greater of Table 18.7.5.4 parts (a) and (b) and, for spiral or circular hoops, one half the greater of Table 18.7.5.4 parts (d) and (e ). of that required by Table 18.7.5.4 Table 18.7.5.4 (a), (b), (d), and (e) and spacing shall not exceed s exceed s o for the full column length and This transverse reinforcement shall be provided over a length l o, as defined in 18.7.5.1, in 18.7.5.1, from from each joint face.

248.


458

18

To resist flexure-induced punching in an earthquake, verify As,min according to 8.6.1.2. On page 458, line 18, insert a new 18.14.5.4: 18.14.5.4 Verify As,min requirement in 8.6.1.2 to resist flexureinduced punching.

103 of 215

Disagree. 8.6.1.2, if applicable, needs to be satisfied when designing the slab for gravity loads. The provisions of Chapter 18 are in addition to those in Chapter 8. Thus, no change is needed.


No.

249.

Public Commenter Name Andres Lepage

Pg #

Line #

466

4

Public Comment

Committee Response

A reference to tests of coupling beams (Weber-Kamin (Weber-Kamin et al. 2019) is missing on Page 466, Line 4. In addition, the reference to Kabeyasawa needs to be deleted (as indicated on Page 900, Line 25). Rewrite sentence in Lines 1 through 4 using:

Agree. 1)

“The increases to 80,000 psi and 100,000 psi f or shear design of

2)

Modify the language of page 466. Lines 1 to 4 as shown in the paragraph at the left that appears in quotes. Add the correct citation to the references list, as indicated by the comments to page 919, Line 9.

some special seismic system members is based on research indicating the design shear strength can be developed (Sokoli and Ghannoum 2016; Kabeyasawa and Hiraishi, 1998; Aoyama, 2001; Budek et al. 2002; Cheng et al. 2016, ; Huq et al. 2018; WeberKamin et al. 2019 ).” The proper citation to Weber-Kamin et al. (2019) is included in Comments to Page 919, Line 9. 250.

ACI Staff

480

16

251.

Saman Abdullah

486

18

252.

Karl Pennings

488

7

Through line 22: Delete section R18.8.3.4 This paragraph, lines 18-22, should be deleted. See CH09 approved in Dallas.

In section R18.10.4 the definition of coupling beam is vague in the commentary and not addressed addressed in the body of the code. code. It is my understanding that the requirements of 18.10.7 apply to coupling beams but not horizontal wall segments. For instance, what would be required if you have an isolated door

104 of 215

Agree. Delete all lines of section R18.8.3.4 Agree. Delete the sentence “ -Vu shall be obtained…factored load combinations.” From lines 14 and 15. Leave the words “Design forces” as an italicized heading in line 14. In addition, modify commentary section R18.10.3 as follows: Design shears for structural walls are R18.10.3 Design forces — Design obtained from lateral load analysis with the appropriate load factors. However, tThe possibility of yielding in components of such structures structural walls should be considered, as in the portion of a wall between two window openings, in which case the actual shear may be in excess of the shear indicated by lateral load analysis based on factored design forces. Partially agree. This comment should be considered as new business in the next code cycle.


No.


Pg #

Line #

253.

Saman Abdullah

489

22

254.

Saman Abdullah

490

5

255.


490

7

Public Comment

Committee Response

opening in a wall with several stories of shear wall above the door, such that it is very deep with low shear shear values. It is impractical to reinforce that wall segment as a special moment frame and it is impractical to add diagonal bar groups. Add subscript “cs” to hw. Also, on page 489 line 24. Change year to 2019 (i.e., Abdullah and Wallace (2019)). It will be published in the January 2019 issue of ACI St. Journal. This was confirmed with ACI St. Journal. We suggest: “…. and δu /hwcs δc /h /hwcs of approximately 1.0 and 0.015 0.0225, respectively” Reason: The reason is that R18.10.6.2 in line 7 reads that parameter b was derived from Equation (18.10.6.2b) and this Equation uses /hwcs not δu /hwcs. δc /h

Agree. Make the changes indicated. Agree. Change year to 2019. Disagree. The introduction to this equation clearly states the relationship between delta_c and dulta_u (capacity must be greater than 1.5 x demand). It would not be appropriate to use a displacement capacity here; instead, it should be based based on demand. The following change clarifies this intention. Change lines 6 to 8 as follows (changes from “Public Comment Draft” are highlighted in yellow: The expression for b for b in in (ii) is derived from 18.10.6.2(b)(iii) (Equation 18.10.6.2b), assuming values of V u /(8A cv√f’ c ) and ) and δu /hwcs of approximately 1.0 and 0.015, respectively.

256.

Andrew Taylor

491

21

257.

Saman Abdullah

491

27

258.

Andrew Taylor

491

28

I believe the figure reference should be to Fig. R18.10.6.4.2. This is because the variables used in this sentence are defined in that figure. This sentence “Requirements for vertical extensions of boundary elements are summarized in Fig. R.18.10.6.4.3 (Moehle et al., 2011)” should not be removed. It should be added back in page 492 after line 11 (See CH011). (This comment relates to Wallace’s public comment number 16). If lines 27 and 28 are reinstated, reinstated, I believe the figure reference should be changed to Fig. R18.10.6.4.3

105 of 215

Agree. Change figure reference to R18.10.6.4.2. Agree. Replace the sentence “Requirements for vertical extensions of boundary elements are summarized in Fig. R.18.10.6.4.3 (M oehle et al., 2011)” and move it to page 492 after line 11 (See CH011). Agree. Change the figure reference to Fig. R18.10.6.4.3


No.

Pg #

Line #

259.


Public Comment

Committee Response

491

31

Agree. Change “vertical” to “longitudinal”

31

“web vertical bars” is used on Fig. R18.10.6.4.1, but the figure caption uses “web longitudinal bars”. Should Vertical be changed to longitudinal to be consistent, which would also be consistent with use of rho_l. The word “vertical” should be changed to “longitudinal”

260.

Andrew Taylor

491

261.

Saman Abdullah

492

1

Change to year to 2018 (i.e., Segura and Wallace, 2018)

262.

David P. Gustafson

492

6

Replace “carrying capacity” with “strength”.

263.

Saman Abdullah

492

20

Change Fig. R18.10.6.4.1 to Fig. R18.10.6.4.2

264.

492

20

492

30

266.

Restrepo J.I. and Rodriguez M.E. Restrepo J.I. and Rodriguez M.E. Andrew Taylor

492

31

Please consider this change: …illustrated in Fig. R18.10.6.4. 12 Please consider this change: “… summarized in Fig. R18.10.6.4.23” I believe the figure reference should be to Fig. R18.10.6.4.3

267.

Thomas Schaeffer

502

15

265.

Need to add the heading for the section “R18.13.4 Foundation Seismic Ties”

Agree. Change “vertical” to “longitudinal” Agree. Change made. Change year to 2018. Disagree. The committee feels “carrying capacity” is clearer. No change. Agree. Change Fig. R18.10.6.4.1 to Fig. R18.10.6.4.2 Agree. Change Fig. R18.10.6.4.1 to Fig. R18.10.6.4.2 Agree. However, line reference reference is 31, not 30. Change figure reference to R18.10.6.4.3 in line 31 Agree. Change figure reference to R18.10.6.4.3 Agree. Add the heading for the section “R18.13.4 Foundation Seismic Ties”

268.

Thomas Schaeffer

503

19

R1.4.5 should be R1.4.7

269.

Thomas Schaeffer

504

20

Add Heading “R18.13.5.8 Metal-cased concrete piles” piles”

270.

Thomas Schaeffer

504

24

Add Heading “R18.13.5.9 Concrete filled pipe piles”

271.

Thomas Schaeffer

505

0

Add Heading “R18.13.5.10 Precast concrete piles”

272.

Thomas Schaeffer

505

22

Add Heading “R18.13.6 Anchorage of piles, piers, and caissons”

106 of 215

Agree. The commentary will be revised to: …..guidelines (refer to R1.4.57) Agree. Add Heading “R18.13.5.8 Metal-cased concrete piles” piles” Agree. Add Heading “R18.13.5.9 Concrete filled pipe piles” Agree. Add Heading “R18.13.5.10 Precast concrete piles” Agree. Add Heading “R18.13.6 Anchorage of piles, piers, and caissons”


No. 273.

Public Commenter Name Amin Ghali and Ramez Gayed

Pg #

Line #

507

27

Public Comment

Committee Response

To design for flexure-induced punching in an earthquake, calculate As,min based on vu,max corresponding to the design story drift ratio; this applies to all components moving through the same drift. On page 507, line 27, insert R18.14.5.4.

Disagree. 8.6.1.2, if applicable, needs to be satisfied when designing the slab for gravity loads. The provisions of Chapter 18 are in addition to those in Chapter 8. Thus, no change is needed

R18.14.5.4 To R18.14.5.4 To design for flexure-induced punching in an earthquake, calculate As,min based on vu,max corresponding to the design story drift ratio. Fig. R18.7.5.2 should show seismic hooks for consistency with suggested change given in this discussion regarding 18.7.5.2 in page 420, line 28, suggesting the use of seismic hooks in building columns designated as part of t he seismic-resisting system.

274.


514

6

275.

Saman Abdullah

518

1

Fig. R18.10.6.4.1(a) shows l1<2bc, whereas (b) shows l1≤2bc. They should use the same symbol (probably use “≤” for both).

276.

Saman Abdullah

518

1

Change to “(b) Overlapping hoops…”. Since there is more than one hoop, the word hoop should be plural.

277.

Andrew Taylor

518

1

278.

Reid W. Castrodale

527

16

The version of Fig. R18.10.6.4.1 that appears in the public comment version of the Chapter 18 commentary was revised at the 318 Main Committee Committee Dallas meeting. The horizontal web bars (green) should have hooks at the left end in both figures (a) and (b), and the horizontal web bars in figure (a) should be located inside the l ongitudinal web reinforcement, as in figure (b). 19.2.1.1 Part (a) of this section states “Limits apply to both normalweight and lightweight concrete.” This is understood. Therefore, the statement is unnecessary and just draws attention to an unneeded distinction between normalweight and lightweight concrete.

107 of 215

Disagree. Subcommittee H has considered the need to provide seismic hooks at both ends of cross ties in columns of special moment frames with low axial loads and concluded this is not required. Cross ties with seismic hooks at both ends are required, though, for columns with high axial loads. No change Agree. In Fig. R18.10.6.4.1(a) change l1<2bc, to l1≤2bc Agree. In Figure R18.10.6.4.1(b) change “Overlapping hoop” to “Overlapping hoops” Agree. Replace the figure in the “Public Comment” draft with the revised figure approved at the December 2018 meeting in Dallas.

Disagree. Since the terms “normalweight” and “lightweight” appeared in the Table in 318-14 and are removed from the Table in 318-19, the statement in the provision that the “Limits apply to both normalweight and lightweight concrete” is warranted.

No change required.


No.


Pg #

Line #

279.


527

22

280.

Reid W. Castrodale

527

22

Public Comment

Committee Response

Therefore, it is proposed that the sentence be deleted. The toughness criteria for lightweight concrete with strengths exceeding 5 ksi is not clear.

Agree This should be taken up as new business..

19.2.1.1 Part (d) of this section indicates that lightweight concrete strengths exceeding 5 ksi can be used if “demonstrated by experimental evidence that members … provide strength and toughness equal to or exceeding those of comparable members made with normalweight concrete of the same strength.” Where are toughness criteria given? The goal for lightweight concrete is to provide strength equal to or greater than the strength expected in the code for a normalweight concrete with the same compressive strength, not just the strength of some normalweight concrete. This is a significant difference. Furthermore, some normalweight concrete will not meet the standards of strength expected in the code, but use of those materials is not restricted, nor is their capacity reduced in design. Concrete simply needs to meet the specified performance regardless of material designation. The problem is to define the required performance criteria that can be measured in simple ways rather than from large-scale component testing. Therefore, the text in (d) needs to be revised as proposed: “… toughness equal to or exceeding the code requirements for comparable members made with normalweight concrete of the same compressive strength.”

108 of 215

Agree This should be taken up as new business..


No.

281.

Public Commenter Name Dan Mullins

Pg #

Line #

528

1

Public Comment

Committee Response

Lines 3 and 4 of table. “utility” is not defined. What does this mean? Does this refer to IBC “Utility and Miscellaneous Group U”? Is a reference needed for clarity?

Agree with comment. In order to eliminate the ambiguity and to be consistent with the latest edition of the IBC, the IBC terms “use and occupancy classification” will be added in Table after “residential and utility”

In the 3rd row under the heading of Table 19.2.1.1 revise the application to: Foundations for rResidential and uUtility use and occupancy classification with stud bearing wall construction two stories or less assigned to SDC D, E, or F

In the 4th row under the heading of Table 19.2.1.1, there is also a typo repeating the SDC’s. Revise the application to: Foundations for structures assigned to SDC D, E, or F other than rResidential and uUtility use and occupancy classification with stud bearing wall construction two stories or less., assigned to SDC D, E, or F

282.

HOLCIM MEXICO

528

6

Through line 13 and page 529 lines 1 through 10 Currently, in section 19.2.2 Elasticity Module says: 19.2.2.1 It is allowed to calculate the modulus of elasticity, Ec, for the concrete by means of (a) or (b): a) For values of wc between 90 and 160 lb/ft³ (in psi) (19.2.2.1.a) b) For normalweight concrete (in psi) (19.2.2.1.b)

109 of 215

Not accepted. accepted. No changes. 1. The changes in 19.2.2 allow the LDP to test for MOE with project materials, if desired. 2. This recommendation should be referred to ACI 363 for review and possible action.


No.


Pg #

Line #

Public Comment

Committee Response

Therefore, we suggest the following consideration as a criterion of acceptance of the Elasticity Module, since the regional availability of the different aggregates used in the concrete, has become critical in the current era as well the transfer of the same at great distances is complex and very expensive, so we propose that you take the example of the characteristic base values of the “NTC 2017 (Complementary Techn ical Standards 2017) Design and Construction of Concrete Structures of the Construction Regulations of Mexico City” . A proposal is described below: 19.2.2 Elasticity Module

The static elastic modulus of the structural concrete will be determined according to the coarse aggregates available in the region. The modulus of elasticity is allowed to be calculated with the following expressions, for concrete of normal weight (Wc ≥ 140 lb / ft³). For concrete with nominal compressive strength f'c ≤ 35 Mpa: Ec = 4 400 (in MPa) for coarse aggregate of limestone

(19.2.2.1.a) Ec = 3 500

(in MPa) for coarse basaltic aggregate

(19.2.2.1.b) For concrete with nominal compressive strength f'c > 35 Mpa: Ec = 2 500 (in MPa) 19.2.2.1.c Other values of Ec that are sufficiently supported by laboratory results can be used. In problems of structural revision of existing constructions, the modulus of elasticity determined in concrete specimens extracted from the structure can be applied, which form a representative sample of the same.

110 of 215


No.

283.

Public Commenter Name Dr. Fariborz Tehrani, PE

Pg #

Line #

529

18

Public Comment

Committee Response

Numerous publications have found values in Table 19.2.4.1 and Table 19.2.4.2 to be conservative (Fang et al. Int J Concr Struct Mater 2018, 12:55 https://doi.org/10.1186/s40069-018-02743; and many others).

Not accepted. accepted. No change.

Further, there are evidences from recent research that performance of lightweight concrete in respect to str ength, drift, and absorbed energy can be higher than normal weight concrete (Carrillo et al. Engrg Struct 2015, 93:61-69 https://doi.org/10.1016/j.engstruct.2015.03.022; Øverli Engrg Struct 2017, 151:821-838 https://doi.org/10.1016/j.engstruct.2017.08.063; and many others). These findings indicate that performance of concrete is not just a function of the density, as proposed in historic publications (Ivey and Buth 1967; Hanson 1961; Mattock 1977 and others), and thus, there is a need for revising lambda values for both lightweight and normal weight concrete.

284.

Reid W. Castrodale

529

21

19.2.4.1 The proposed text related to Table 19.2.4.2 indicates that the value of lambda is “… based on the composition of the aggregate in the concrete mixture assumed in design.” I question use of the “composition”, which seems to imply the material composition of the aggregate itself, where what is actually intended is the type of mixture which depends on the proportions of the aggregate materials in the concrete mixture (which, as already stated, the designer will very rarely ever know).

111 of 215

There is no argument that the estimated value of lambda will, in many cases, be conservative using either Table 19.2.4.1 or Table 19.2.4.2. Both techniques for estimating lambda are provided as generally conservative methods for selecting a value of lambda for a given mixture proportion. If the LDP wishes to determine determine a more accurate value of lambda, the commentary in Section R19.2.4 offers guidance. The new method for determining lambda specified in 19.2.4.1, while based on equilibrium density, is rooted in the testing of 1249 different specimens using multiple mixture proportions incorporating 14 different lightweight aggregates. Thus, the new method considers far more than just equilibrium density. Lambda does not apply to normalweight concrete as is implied in the comment. This comment should be referred to ACI 213 for review and possible action. Not accepted. accepted. No changes. While "composition" may not the best word, its meaning is evident when considering the entries in Table 19.2.4.2.


No.


Pg #

Line #

285.

Reid W. Castrodale

529

26

286.

Colin Lobo

530

6

287.

Robinson

530

6

288.

Reid W. Castrodale

530

6

289.

Reid W. Castrodale

530

6

Public Comment

Committee Response

The use of “type” rather than “composition” is recomm ended. Table 19.2.4.1 Each line in the table has a letter associated with it in the rightmost column, which would appear to indicate a note would follow that would define these letters. However, no such note is given.

This should be corrected as appropriate. The Committee has provided a rational method for the designer to assume a value of λ when designing lightweight structural members based on the equilibrium density. Retaining Table 19.2.4.2 is not necessary. The commentary acknowledges that the designer does not have any idea of using this table as they do not know the composition of aggregates that will be used at this stage in the design. The only possible outcome is to use a conservative value of 0.75 that impacts the cost of lightweight concrete construction. This table for selecting the value of λ should be removed so that its use can be avoided. This table wrongly assumes the designer will know the mixture proportions to achieve the specified density. Table 19.2.4.2 As mentioned in earlier comment (p. 529 line 21), use of “composition” in the caption and a heading for Table 19.2.4.2 is misleading. Please revise as discussed previously. Table 19.2.4.2 In my opinion, inclusion of this table is misguided. The designer does not know, except in very rare cases, what the proportions of aggregate volumes in the concrete will be to achieve the

112 of 215

Discussed extensively at Steering Committee Meeting. No changes for this cycle. New Business.

Not accepted. accepted. No change. After significant discussion, Committee 318 adopted CA111 based upon keeping this approach in the code.

See response to comment 286, page 530, line 6, Lobo See response to comment 284, page 529, line 21, Castrodale

See response to comment 286, page 530, line 6, Lobo


No.


Pg #

Line #

Public Comment

Committee Response

specified density. And to think that interpolation could be used effectively is also misguided.

290.

Reid W. Castrodale

530

11

291.

Reid W. Castrodale

530

13

I strongly recommend that defining lambda based on th e proportions of aggregate in concrete be removed from the specifications. Table 19.2.4.2 The text in Note 2 is incomplete. 19.2.4.3 In ACI 318-11 and prior issues, an option was allowed to specify the splitting tensile strength of lightweight concrete to define the value of lambda. This recognized the very real po ssibility that the tensile strength of lightweight concrete could have a tensile strength greater than the reduced values that were provided as a simplified lower bound for the behavior of lightweight concrete. The provision in Article 8.6.1 read: If average splitting tensile strength of lightweight concr ete, fct, is specified, lambda = fct / (6.7 sqrt f’c) <= 1.0. In ACI 318-14, the wording in the renumbered article 19.2.4.3 was changed to something much less understandable and useful: If the measured average splitting tensile strength of lightweight concrete, fct, is used to calculate lambda, laboratory tests shall be conducted in accordance with ASTM C330 to establish the value of fct and the corresponding value of fcm and lambda shall be calculated by: Lambda = fct / (6.7 sqrt f’cm) <= 1.0 The concrete mixture tested in order to calculate lambda shall be representative of that to be used in the Work.

113 of 215

Change code last line in Note 2 to read: “…as a fraction of the total absolute volume of aggregate.” Editorial change. Not accepted. accepted. No changes. 1. The equation in 318-11 was not correct because the use of f’c is not reasonable. Any such testing should be done on project specific materials. To say that this approach is more accurate accurate is not correct. 2. If the LDP wishes to determine a more accurate value value of lambda for a given mixture proportion by means of laboratory testing, the commentary in Section R19.2.4 offers guidance on how to do so. As a matter of record, during the eight years it took to bring this ballot item to pass 318 Main, only one engineer indicated he had ever used this technique—and the project was never built! 3. it is preferred that the designer not specify splitting tensile strength (as per 318-11) as there are no criteria or detailed requirements on how and where to test this.


No.


Pg #

Line #

Public Comment

Committee Response

This approach is very confusing and unclear when compared to the simply stated requirement of earlier editions. If the designer desired, the effect of lambda could be eliminated (set equal to one) by simply specifying the tensile strength of the lightweight concrete to be greater than the tensile strength expected in the code for normalweight concrete. In the proposed ACI 318-19, this option is removed entirely. Therefore, this eliminates any option to allow use of a larger value of lambda, even when the tensile strength can be demonstrated to be equal to or greater than the expected tensile strength of lightweight concrete of 6.7 sqrt f’c.

292.

Eric Koehler

532

7

My recommendation is to return to the provisions of ACI 31811, which are supported by considerable data that indicate that lightweight concrete can indeed have tensile strengths equal to or exceeding the strength expected for normalweight concrete, and allow the designer the freedom to modify the lambda factor accordingly. In Table 19.3.2.1, for S3 Option 2, permissible ASTM C595 cements should be “Types with (HS) designation” and not “IP, IS or IT” to be consistent consistent with other S exposures. As written, the Table does not allow Type IL cement in S3 Option 2. In addition, the commentary on page 550 line 8 indicates that all ASTM C595 blends are suitable, including Type IL, so the table is not consistent with the commentary. Type IL cement under ASTM C595 can be demonstrated to achieve HS d esignation in accordance with ASTM C1012 and, therefore, provide necessary durability. Type IL with (HS) could pass as an ASTM C1157 cement or based on Note 4. The commentary is correct and the table should be revised.

114 of 215

Partially accepted. Editorial change to Code. Change Table for S3, option 2 to read: “Types with (HS) Designation” Portion of comment regarding Commentary is New Business.


No.

293.

Public Commenter Name Colin Lobo

Pg #

Line #

532

7

294.

Mark W Cunningham

533

0

295.

Tennis

533

0

296. 297. 298. 299. 300. 301.

Eric Koehler Colin Lobo John Gajda Mark W Cunningham Tennis Robinson

533 533 533 533

1 1 1 1

533

1

533

3

Public Comment

Committee Response

This revision refers the designer to consider alkali aggregate reactions for structural members assigned to exposure class W1 and W2. The designer is directed to consider using ASTM C1778. This guide is rather co mplicated and arriving at a single reasonable approach applicable to a local region will be elusive. ACI 301 has proposed requirements for AAR based on ASTM C1778. Consider including a reference to ACI 301 in the commentary either here or in Ch 26. T19.3.2.1: Suggest adding brief commentary as to why admixtures containing calcium chloride are prohibited for S2 and S3. Committee response to similar comment made on the 318-14 update was: “The restrict ion to the use of calcium chloride admixture is based on research performed by the USBR documenting that these admixtures had an adverse effect on sulfate resistance.” Can this or similar statement be included in the commentary? Table 19.3.2.1, S3 Option 1 under ASTM C595: For S3 conditions, Option 1, for ASTM C595 cements, it appears that Footnote [7] should be referenced, rather than Footnote [6] The word “basefallowd” is a typo. Correct typo in footnote 1 There is a typo: “basefallowed” should be changed to “based”. Fix typo: “basefallowd”.

Not accepted. accepted. No changes. If ACI 301 wants to have a simplified approach, that is fine for that document.

The word “basefallowd” in footnote [1] needs to be edited. It appears that it should be “based” Note 2 of Table 19.3.2.1 is not justified. If the free moisture of the (lightweight and/or normalweight) aggregates is determined and the mix water is adjusted to compensate, any water absorbed by any aggregate during mixing and delivery reduces the w/cm ratio. It does not increase it. The commentary states the mixing water absorbed by the

115 of 215

Editorial change: The additional requirements requirements for W1 and W2 should reference 26.4.2.2(d).

New business.

Accept. Editorial change. Correct footnote references for C150 and C595 to [7] Accept. Change to read: “The w/cm is based …” See response to comment 296. Page 533, line 1, Koehler See response to comment 296. Page 533, line 1, Koehler See response to comment 296. Page 533, line 1, Koehler

See response to comment 296. Page 533, line 1, Koehler New business.


No.


Pg #

Line #

302.

Reid W. Castrodale

533

3

303.

John Cook

533

3

304.

Colin Lobo

534

10

305.

Reid W. Castrodale

534

16

306.

Colin Lobo

534

24

307.

John Cook

535

17

Public Comment

Committee Response

lightweight aggregate “makes calculation of w/cm uncertain”, and ignores the fact that this only decreases the w/cm ratio, providing assurance that the maximum w/cm ratio has not been exceeded. Making specifying maximum w/cm ratio limits for lightweight concrete possible. Maximum w/cm ratio limits are routinely specified for lightweight concrete used in transportation structures by State DOT’s and their consultants across the US. Why can’t they be specified for building structures? Table 19.3.2.1 See comment for p. 547, lines 23-26. Table 19.3.2.1 Since It is mentioned that w/cm is difficult to accurately verify in the field so f'c is speci fied (page 547 line 9-10), Why is lightweight singled out in note 2 in relation to w/cm. Shouldn't normal weight and lightweight be treated the same in this table? In footnote 9, “mass of cement” is unclear as “cement” is not defined or used in ACI 318. It could be misunderstood to mean C595 blended cement. The intent should be mass of portland cement. Consider revising the footnote. 19.3.3.1 Recommended revision: “ Normalweight and lightweight concrete Concrete subject …” There is no reason to mention the two types. Concrete subject to cycles of freezing and thawing will be impacted by this exposure and it doesn’t seem appropriate that structural members constructed using dry -mix shotcrete does not have to be air entrained for exposure class F1 and F2, which can be an exterior wall or slab. Consider limiting the use of dry-mix shotcrete to repair type applications where it is typically used. 19.3.3.6 States for f'c greater than 5000 reduction of air content indicated in Table 19.3.3.1 and 19.3.3.3 by 1.0 percentage point is

116 of 215

See response to comment 318, page 547, line 23, Castrodale New business.

Accept. Editorial change. Change to read “ the mass of the portland cement.” This was approved as CA170. “portland” was somehow omitted since approval Accept. Editorial change. Delete ”Normalweight and lightweight”. Start provision with: “Concrete subject…” Not accepted. See commentary for discussion of why why dry-mix shotcrete is treated differently.

Accept. Substantive change. 1. There is currently currently no gray area. area.


No.

308.


John Gajda

Pg #

535

Line #

21

Public Comment

Committee Response

permitted. This leaves gray area. Greater than or equal to 5000 would clarify.

2. Most designers probably assume that concrete with f’c of 5000 psi is eligible for the 1% reduction, which is incorrect. 3. Rewrite as: “For f’c ≥ 5000 5000 psi…” While we do not agree that ASTM C672 should be used as a basis for accepting or qualifying concrete, we do agree that provisions for limits on SCM’s should be reviewed as New Business.

Add that running and passing a deicer scaling test can be used to permit SCMs higher than in the referenced table. Reference ASTM C672. In the commentary, the findings of research by Doug Hooton should be discussed (see PDF link below), and reference other deicer scaling methods. Alternatively, discuss allowing the use 28 or 56 days of curing under Section 7.3 of the 2012 version of C672, which is appropriate for higher SCM content concretes as they tend to gain strength more slowly than plain cement concretes for which C672 was developed. This change also needs to be added to: 1) page 548, Line 7 2) page 786, Line 22 3) page 788, line 24 The rationale is: 1) Many agencies use the referenced table (Table 26.4.2.2.b) as if it were gospel, and do not allow greater SCM that in the tables. tables. They say ACI 318 is the building code and cannot be violated. 2) Many projects with a specified long service life period, such as the TappanZee bridge have shown, through deicer scaling testing that concrete with higher SCM levels do not have issues in the F3 exposure condition. While ACI 318 may not be intended to apply to such projects, it is still used on such projects. 3) Research by ACI 318 subcommittee member, Dr. Doug Hooton, have showed that concretes with higher SCM

117 of 215


No.


Pg #

Line #

309.

Holland

536

7

310.

Reid W. Castrodale

537

22

311.

Colin Lobo

538

8

312.

Reid W. Castrodale

539

12

Public Comment

Committee Response

levels do not have issues in deicer scaling tests (or in the real world), and that certain d eicer scaling tests are more harsh than real world conditions. Here is an overview of his research (on the ACI website): https://www.concrete.org/portals/0/files/pdf/webina rs/Hooton-Doug.pdf 4) Language for the S3 sulfate exposure condition allow specific test results to p ermit deviations from the requirements. This is in the new discussion on page 548 and in the footnotes of Table 19.3.2.1. 5) Added language for the modulus of elasticity requirements allows deviation based on testing of the concrete. Test permits deviation from the standard 57,000 multiplier in the equation relating compressive strength to modulus. 19.4.1 At the end of the provision: provision: …”measured …”measured by mass of chloride ion to mass mass of cement.” Chloride limits were changed changed to mass of cementitious materials by CA070. This provision was apparently missed. R19.2.1 Editorial: add a space between 80,000 and psi. I am not sure if these values of properties stated can actually be “observed”. Suggest simplifying this to “differences between measured and calculated values of E c c . This is more relevant to the discussion regarding the accuracy o f assuming a value of E c c. Some of this seems to be redundant with the next paragraph – lines 19 – 25. Through page 541 line 6: R19.2.4 Every lightweight concrete mixture does not have “reduced mechanical properties” when co mpared with normal weight concrete of the same compressive strength as i s communicated by the statement in the commentary. The second sentence continues: “For design using lightweight concrete, shear

118 of 215

Accept. Editorial change. Change to read “…mass of cement cementitious materials.”

Accept as editorial change. Partially accepted. Editorial change. Change “observed” to “measured.” Comment on redundancy is not accepted. accepted. Redundancy to be looked at as new business. This definition was revised multiple times on multiple ballots before being accepted by 318. Recommend these comments be submitted to ACI 213 for review and recommendation to ACI 318.


No.


Pg #

Line #

Public Comment

Committee Response

strength, [etc.] are not taken as equivalent to normalweight concrete of the same compressive strength.” There are several issues that must be addressed here, so me of which are not new to the revisions in the current edition of ACI 318, but have been long-standing problems with how lightweight concrete is treated by the code. The first is that the factor should apply only to tensile properties, not mechanical properties in general. The list provided later in the paragraph only lists tensile-related properties. The factor certainly does not apply to compressive strength, or to the modulus of elasticity which is treated separately with the density appearing as a variable in the equation. The second is that this flatly states that the mechanical properties of normal of lightweight concrete are reduced compared to normal weight concrete. This is not a true statement. In fact, the statement is made in the 2nd edition of Mark Fintel’s Handbook of Concrete Engineering (1985) that “the tensile strengths of continuously moist -cured lightweight and normal-weight concretes of equal compressive strength are equal.” That discussion continues to mention that even with drying, lightweight concrete can still achieve tensile strengths equal to normal weight concrete. More current information also shows this as discussed below. The third issue is that the comparison being made should be to what is expected for normalweight concrete, that is, the tensile strength used or expected in t he design of the member, not just any comparison of lightweight lightweight concrete properties to some normalweight concrete. This distinction is very important

119 of 215


No.


Pg #

Line #

Public Comment

Committee Response

because the properties of normalweight concrete mixtures vary widely. Tests by Byard and Schindler (2010) report that the normalweight concrete mixture tested had a reduced tensile strength compared to both what was expected for a normalweight concrete mixture and to the lightweight concrete mixtures tested, which used three different lightweight aggregates. In this case, the lightweight concrete mixtures had tensile strengths very close to or exceeding the tensile strength expected for a normalweight concrete with the same compressive strength (6.7 sqrt f’c). However, while the tensile strength of the normalweight concrete mixture tested was about 15% less than what is expected for normalweight concrete, a reduction factor would not be considered appropriate for design using that concrete, even though its tensile strength is “deficient” according to the specifications. Another example appears in Chapman and Castrodale (2016) where the lightweight concrete mixture discussed did indeed have a tensile strength that was significantly less than the normalweight concrete; in fact, the reduction was clos e to the usual reduction factor for sand lightweight concrete of 0.85. However, upon closer examination, it was realized that the normalweight concrete mixture had a very high tensile strength, well above what is expected of normalweight concrete. It was then found that the lightweight concrete actually comfortably exceeded the expected tensile strength for normalweight concrete. A proposed revision is: The modification factor lambda is used to account for the potentially reduced tensile strength of lightweight concrete compared to the expected tensile strength of normalweight

120 of 215


No.


Pg #

Line #

Public Comment

Committee Response

concrete. For design using lightweight concrete, the lambda factor provides the means to reduce shear strength, [etc.] t o account for the possible reduction in the tensile strength of lightweight compared to the expected tensile strength of normalweight concrete of the same compressive strength.

313.

Reid W. Castrodale

539

22

References: Byard, B., Schindler, A.: “Cracking tendency of lightweight concrete,” Highway Research Center, Auburn, Alabama. (2010) Chapman, D., Castrodale, R. “Sand lightweight concrete for prestressed concrete girders in three Washington State bridges,” Proceedings, National Bridge Conference, Precast/Prestressed Concrete Institute, Chicago. (2016) R19.2.4 Recommend revising sentence: “…if the designer desires to determine a more precise accurate value of [lambda] …” However, I think that this sentence should probably be removed if the option to determine a more accurate value of lambda is removed as is currently proposed.

314.

Reid W. Castrodale

539

23

R19.2.4 The proposed commentary states “Table 19.2.4 .1 is based on data from tests …” I do not think that this is an accurate statement of the situation. The expression was developed based on limits of concrete density (100 pcf for all lightweight concrete and 135 pcf for the bottom of t he range for normalweight concrete) and the existing factors of 0.75 and 1.0 at these limits. The

121 of 215

Accept. Editorial change. The definition of accurate is “closer to the correct value” which is more appropriate in this situation. Change “precise” to “accurate.”

Second part of this comment is not accepted. accepted. The sentence provides guidance should the designer choose to pursue laboratory testing to determine a more “accurate” value of lambda. New business.


No.


Pg #

Line #

Public Comment

Committee Response

expression thus established was then compared to the data to see if it adequately represented the data, which it did.

315.

Reid W. Castrodale

539

28

316.

Reid W. Castrodale

540

9

317.

Reid W. Castrodale

540

17

318.

Reid W. Castrodale

547

23

Recommended revision: “The limits and expression shown i n Table 19.2.4.1 was developed based on the accepted range of the modification factor and corresponding densities. The expression was then compared to data from tests …” R19.2.4 Recommend revising sentence: “…[la mbda] which remains is retained from the previous code,” R19.2.4 Recommend revising sentence: “… was removed from the Code in 2019. However, this method is what would be used to determine a more accurate value for [lambda], as noted previously.”

A new paragraph should also begin following this sentence. Through line 22: R19.2.4 Much of the content of this paragraph is already presented in previous paragraphs. Therefore, it appears that it could b e deleted. Through line 26 R19.3.2 The footnote to the table and this discussion which contend that w/cm limits do not apply to lightweight concrete do not reflect current common practice, where lightweight aggregate is prewetted prior to batching so there is little loss of mix water into the aggregate. As a result, the w/cm can be reliably used for proportioning lightweight concrete mixtures. Therefore, it is recommended that the footnote be removed. The commentary could state that the use of the w/cm values in

122 of 215

Accept this comment. Change Commentary to read: “…which is retained…”

Not accepted. accepted. No change. This wording is already in the commentary on page 539, line 21

Delete lines 17 through 22 on page 540 of the commentary to eliminate redundancy.

New business.


No.


Pg #

Line #

319.

ACI Staff – Via Holland

556

1

320.

Todd Hawkinson, PE

558

4

Public Comment

Committee Response

the table for proportioning lightweight concrete mixtures assumes prewetting of the lightweight aggregate prior to batching. Through line 4: Something is amiss. There are no corresponding Code requirements (19.3.4 was deleted in CA190). Please verify what what should be done with these commentary sections from 318-14. 318-14. Should they be deleted or moved to another part of the commentary? Revise the lowest deformed wire size to D1.4 as wires as small as D1.4 are being manufactured now.

Accept. Editorial change. R19.3.4 should have been omitted as part part of CA190. Delete as a substantive change.

Disagree No change. Test data providing the basis for the development and lap splice provisions as included in Chapter 25 do not include wire diameters as small small as D1.4. Provisions cannot be extended extended to include wire sizes outside of the range used to calibrate them.

321.

Paul Aubee

558

8

New business.

20.2.1.7.3 Comment and Rationale: ACI 318 indicates that bond/development of welded deformed wire reinforcement (WDWR) can be quantified as a combination of (a) contribution from deformed wire surface and (b) the presence of strategically positioned welded intersections. But it also allows for a sole reliance on the former in the event there exists a misalignment/absence of the latter.

At issue is the prescriptive spacing provision for WDWR in Section 20.2.1.7.3(a). In a flexural or direct axial tension application, this section effectively discourages designer reliance on deformed wire surface only when said wires are part of a WDWR mat, as it prescriptively dictates that welded intersecting “crosswires”

123 of 215


No.


Pg #

Line #

Public Comment

Committee Response

perpendicular to the direction of stress/development must be present on the mat in an arrangement not exceeding 16-inch spacing. This despite the designer’s intent that these crossing wires be non-contributing from a structural perspective in the direction under consideration. ACI 318 provides throughout its text for a broad range of s izes of non-welded, “loose” deformed wire (i.e., the constituent component of WDWR) to be treated in a manner identical to that of conventional loose deformed reinforcing bar from a bond/development/lap splice standpoint. This equivalent treatment is further supported by Sections 25.4.6.4 and 25.5.3.1.1, where a WDWR mat itself is permitted to default to the use of “no contribution from welded intersection” tension development lengths and lap splice lengths when the positioning of welded intersecting wires on the mat does not align with conditions described in Sections 25.4.6.3 and 25.5.3.1 (a), respectively. ACI even illustrates in Figure R25.5.3.1(b) the overhanging exterior lengths of two WDWR mats o verlapping in a manner identical to loose deformed bar bar or wire. So, if deformed wire surface alone is sufficient in a region as critical as a tension lap splice, why then would the interior “fie ld region” of the WDWR mat need to have the 16” crosswire spacing requirement invoked? As currently worded, Section 20.2.1.7.3(a) suggests that structural wires on a WDWR mat that are in the direction of stress are inextricably reliant on prescriptively-spaced intersecting welded wire intersections in order to be considered structural viability. viability. Yet conceptually, when when those intersecting welded wires are removed and all that remains are

124 of 215


No.


Pg #

Line #

Public Comment

Committee Response

loose deformed wires in the direction of stress, the condition is perfectly viable. In light of the above information, the technical basis for a 16inch prescriptive maximum spacing of welded wire on a WDWR mat seems tenuous, and the requirement presents as unnecessarily restrictive for WDWR material that itself would theoretically trend towards the behavior of loose deformed wire/bar in those scenarios where positioning of its welded intersecting wires begins to deviate from the stated 20.2.1.7.3(a) maximum spacing. There are numerous instances as a designer where one would want to rely upon deformed wires in the direction of stress. This same designer might prefer there to be intersecting “ nonstructural” welded wires (perpendicular to the direction of stress) spaced at larger intervals than 16” as a means of on -site placement expedience and tolerance control. Proposal: Section 20.2.1.7.3(a) should be deleted.

The wording of Section 20.2.1. 7.3(a) currently mandates inclusion of prescriptively-spaced wires for WDWR, even in those instances where a structural design is otherwise apparently permitted by the same code to disregard such a contribution. In the absence of a specific design need (as in item #2 below), the spacing and positioning of welded intersecting wires on a WDWR mat should simply be a manufacturer detailing attribute that must satisfy the production tolerances

125 of 215


No.


Pg #

Line #

Public Comment

Committee Response

established by ASTM A1064 and t he means and methods considerations of the installer. Notes: 1. The welded plain wire reinforcement provision of Section 20.2.1.7.3 remains unchanged.

2.

322.

Todd Hawkinson, PE

558

12

Explicitly defined arrangements in ACI 318 where the presence of welded intersections is relied upon to contribute to development or anchorage would remain unchanged (for example, Section 25.7.1.4 related to non-hooked U-stirrups).

PREFERRED: Delete subparagraph (a)., 16 in. for welded deformed wire reinforcement. Reason, Deformed wire without any spacing criteria is allowed per ACI 318. There should be no limit set for Deformed Welded Wire. OR Add and Revise 16 in. in subparagraph (a) as follows re-write “(a) 18 in. for welded wire reinforcement except where holding wires are utilized.” Reason, this rule is conflicting with other sections of the code for deformed welded wire. Specifically, Sections 7.7.2.4 and 24.4.3.3. These sections allow 18 inch spacing of deformed reinforcement. Deformed wire reinforcement is allowed by this 318-19 and previous codes. An Overall Reason: It is the desire of many wire/welded wire manufacturers to place deformed wire with only minimal holding wires spaced at greater distances, than 16 or 18 inches. These holding wires would be in accordance with the requirements of ASTM A106415, Section 8.3.2, where applicable. The holding wire spacing

126 of 215

New business.


No.


Pg #

Line #

Public Comment

Committee Response

would be dependent on placement of that type o f reinforcement.

323.

324.

Ted Mize

Eamonn Connolly

558

558

12

25

Request: Delete “(a) 16 in. for welded welded deformed wire reinforcement” in its entire ty. Deformed wires used for

reinforcement in the direction of calculated stress, when not welded into welded deformed wire reinforcement, are permitted throughout the Code and do not have a 16 in. spacing limitation. Often, these wires are welded using “holding” wires simply to hold the spacing and position of the deformed wires in the direction of the calculated stress. They are now considered “welded deformed wire reinforcement” and therefore are subject to the 16 in. spacing limitation of 20.2.1.7.3 (a). Removing this limitation simply eliminates this inconsistency in the Code. All other limitations on rebar or deformed wire spacing still apply elsewhere in the Code and no other sections are affected by this change. Through page 560 line 16, and page 573, lines 6 through 7: In table20.2.2.4a on page558-559 the longitudinal reinforcement yield strength (fy) limit has changed from 80ksi to 100ksi. The shear and torsional reinforcement yield strength (fy) limit has remained unchanged unchanged at 60ksi. This means that for normal shear walls (non-seismic) resisting wind induced lateral loads (like typically here in Chicago) horizontal reinforcement with fy>60ksi is not permissible. I noticed that there is a note in section R20.2.2.4 on page 573 line 6 & 7 that states “ The limit of 60,000 psi on the values of fy and fyt used in design for most shear and torsional reinforcement is intended to control the width of inclined cracks under service-level gravity loads.”

127 of 215

New business.

New Business


No.


Pg #

Line #

Public Comment

Committee Response

Arguably shear wall horizontal reinforcement that is designed primarily to resist forces due to wind induced induced lateral loads could be exempted from the fy=60ski limit since it is not likely likely to crack under service level loads and the loads are non-gravity and transient. Is it possible to allow fy=80ksi for shear wall horizontal reinforcement resisting non-gravity loads? There are economic, constructibility and environmental benefits to this suggestion.

325.

Greg Deierlein

558

25

I find the proposed changes to Table 20.2.2.4a a bit awkward/misleading in that it implies that Gr. 80 and 100 are permitted for A615 in SMF and Special Special walls, but then the footnote indicates that Gr. 80/100 are not not permitted for A615. I realize it’s tough to squeeze things into a table, but this is confusing, especially given the significance of the change.

Agreed. This is confusing and can be fixed easily. Table 20.2.2.4a will be modified to delete A615[2] from the body of the table. The footnote on A706[2] points to 20.2.2.5 that clarifies where that A615 reinforcement may be used. Updated Table 20.2.2.4a includes revisions resolving comments 325, 326, 328, and 329.

Usage Flexure; axial force; shrinkage and temperature;

Application Special moment frames

Special seismic systems Special structural walls[1]

Maximum value Applicable ASTM specification of f of f y or f or f yt permitted for design Deformed Deformed calculations, psi bars wires

Welded wire reinforcement

Welded deformed bar mats

80,000 A615[2], A706[2]

Not permitted

100,000

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Not permitted

Not permitted


No.


Pg #

Line #

Committee Response

Other

100,000 [3] [4]

A615, A706, A955, A996, A1035

A1064, A1022

A1064, A1022

A184 [5]

Special seismic systems

100,000

A615, A706, A955, A996, A1035

A1064, A1022

A1064[6], A1022[6]

Not permitted

100,000

A615, A706, A955, A996, A1035

A1064, A1022

Not permitted

Not permitted

80,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted

A615, A706, A955, A996

A1064, A1022

A1064[6], A1022[6]

Not permitted

Lateral support of longitudinal bars; or Spirals concrete confinement Other

Special moment Special [8] seismic frames systems[ Special 7] structural walls[19]

Shear

Public Comment

80,000

100,000

Spirals

60,000

A615, A706, A955, A996

A1064, A1022

Not permitted

Not permitted

Shear friction

60,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted

60,000

A615, A706, A955, A996, A1035

A1064, A1022

A1064 and Not A1022 permitted welded plain wire

80,000

Not permitted

Not permitted

A1064 and A1022 Not welded deformed permitted wire

60,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted

Not permitted

Not permitted

Not permitted

Stirrups, ties, hoops

Torsion

Longitudinal and transverse

Special seismic systems 80,000

A615[2], A706[2]

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No.


Anchor reinforcement

Pg #

Line #

Other

Regions Ties used to transfer designed using shear Longitudinal strut-and-tie ties method Other

Public Comment

Committee Response

80,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

A184

60,00080,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted

80,00060,000

[1] All components of special structural walls, including coupling beams and wall piers. [2] ASTM A615 Grade 60 shall be permitted if requirements of 20.2.2.5(b) are satisfied. [3]In slabs and beams not part of a special seismic system, bars that pass through or extend from Special Structural Walls shall satisfy 20.2.2.5 [4] Longitudinal reinforcement with f y>80,000 psi is not permitted for intermediate moment frames and ordinary moment frames resist ing earthquake demands E . [5]Welded deformed bar mats shall be permitted to be assembled using A615 or A706 deformed bars of Grade 60 or Grade 80. [6] ASTM A1064 and A1022 are not permitted in special seismic systems if the weld is required to resist stresses in response to confinement, lateral support of longitudinal bars, shear, or other actions. [7] This application also includes shear reinforcement with a maximum value of 80,000 psi f y or f yt permitted permitted for design calculations for diaphragms and foundations for load combinations including earthquake forces if part of a building with a special seismic system. [8] Shear reinforcement in this application includes all transverse reinforcement stirrups, ties, hoops, and spirals in special moment frames. [9] Shear [9] Shear reinforcement in this application includes all transverse reinforcement in special structural walls, coupling beams, and wall piers. Diagonal bars in coupling beams shall comply with ASTM A706 or footnote 2.

326.

Dr. N. Subramanian (M 024902)

559

0

Through page 560 line 16, example table is pasted at the bottom of comment file: For shear design of "special moment frame" code allows f yt yt=80000 psi (550 Mpa) for all transverse reinforcement as mentioned in footnote 8 of table 20.2.2.4a. At the same time it allows only f yt yt=60000 psi (420 Mpa) for "stirrups,ties,hoops". It is somewhat confusing. Also, for lateral support to longitudinal bars/concrete confinement in "special moment frame" it allows f yt yt=10000 psi (690 MPa).

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Agreed. Footnote 8 referring to all transverse transverse reinforcement as as compared to stirrups, ties, and hoops for general shear is confusing. Modify footnote 8 of Table 20.3.3.4a w ith the following editorial change: “[8] Shear reinforcement in this application includes all transverse reinforcement stirrups, ties, and hoops, and spirals in special moment frames.” Agree. Regarding concrete confinement, confinement, Table 20.2.2.4a indicates that grade 100 reinforcement is allowed as transverse


No.


Pg #

Line #

Public Comment

Committee Response

Does it mean that we can take different value of f yt yt for the analysis of shear, capacity shear and to decide spacing and arrangement of hoops in confined zone based on formula given?

reinforcement is allowed as transverse reinforcement in Special f yt Moment Frames with the value of f limited to 80,000 psi in the yt limited design calculations for shear strength. In design calculations for required amount of confining reinforcement, f yt =100,000 psi is yt =100,000 permitted. No change required regarding this portion of the comment. Updated Table 20.2.2.4a includes revisions resolving comments 325, 326, 328, and 329.

327.

Dr. N. Subramanian (M 024902)

559

0

328.

Adam Lubell

560

25

Through page 560 line 16, example table is pasted at the bottom of the comment file: I have summarized the provisions of high strength rebars-See Table below. Such a table table may be added for better better clarity In Table 20.2.4a, A1035 is permitted for “Flexure” ->”Other” but is not listed under “Shear” ->”Stirrup ties hoops”. Given that the shear case limits fyt to 60ksi, exclusion of A1035 is not justified. The 60ksi limit for fyt is near the proportional limit for A1035 Grade 100 steel. Member designed with A1035 shear reinforcement limited to fyt=60ksi are expected to have similar performance to members designed with A615 or A706 shear reinforcement reinforcement with the same fyt limit. As written, this table prevents a d esigner from using the combination of A1035 longitudinal reinforcement and A1035 transverse reinforcement that might be desired in members subjected to aggressive environments.

New business. Adding such a table would add clarity.

Agreed. A1035 can be used as s hear reinforcement if the design yield strength is taken as 60 ksi. Refer to the portion of the table added in the next cell.

This is part of Comment 328. Modify Table 20.2.2.4a as follows:

Shear

Special seismic

Special moment frames[8]

80,000

A615, A706, A955, A996

A1064, A1022

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A1064[6], A1022[6]

Not permitted


No.


Pg #

Line #

systems[ Special 7] structural walls[19]

Public Comment

Committee Response

100,000

Spirals

60,000

A615, A706, A955, A996

A1064, A1022

Not permitted

Not permitted

Shear friction

60,000

A615, A706, A955, A996

A1064, A1022

A1064, A1022

Not permitted

60,000

A615, A706, A955, A996, A1035

A1064, A1022

A1064 and Not A1022 permitted welded plain wire

Not permitted

Not permitted

A1064 and A1022 Not welded deformed permitted wire

Stirrups, ties, hoops 80,000

329.

330.

Adam Lubell

David P. Gustafson

560

560

25

27

In the last line of Table 20.2.4a, the terminology “Ties used to transfer shear” is problematic since a strut and tie model represents a complete load path that does not distinguish between flexure and and shear. Is this wording trying to capture “Ties that cross inclined struts”?

The current ASTM A706/A706M-16 does not cover Grade 100; The specification covers only Grades 60 and 80. Thus: 1. Page 560, Line 27, delete “or Grade 100”. 2. Page 572, Line 23, delete “and Grade 100”. And replace “are” with “is”. Same comment on Lines 28 -29. 3. Page 573, Lines 18-19, delete “ASTM A706 Grade 100 for . . .”

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Agree. The nomenclature for “Application” has been better delineated in the strut-and-tie section to allow 80,000 psi for longitudinal reinforcement only. Reference to “transfer shear” in relation to STM has been removed. Updated Table 20.2.2.4a includes revisions resolving comments 325, 326, 328, and 329. Partially Agree. Reason statement: The ACI 318 Committee-requested revisions to the ASTM A706/A706M standard appear unlikely to be published before ACI 318-19 is published. Therefore coordination of ACI 318-19 with current edition of the ASTM standard is necessary to avoid inconsistencies between the two documents.


No.


Pg #

Line #

Public Comment

Committee Response

4. Page 800, Line 15 - There is no “ductility designation” in the current ASTM A706/A706M-16. Delete “or ductility designation”. Or consider deleting Line 15 in its entirety 5. Page 803, Line 15 - There is no “Type W” in the current ASTM A706/A706M-16. Delete “Type “W”. 6. Page 843 - Delete “Type W” in Lines 5, 6, 9 -10, 12, 20 and 22.

Items 1-3 of the six items proposed by commenter: As opposed to deleting the reference to ASTM A706/A706M Grade 100 reinforcement as suggested by the commenter’s Items 1-3, proposed changes in response to Public Comments 45 and 46 facilitate inclusion of Grade 100. Therefore the commenter’s suggested changes for these items are not taken up. The commenter’s items 4-6 remain relevant. Specific Code/Commentary Change Proposal Required: The following page and line numbers are with respect to the Public Comment draft of ACI 318-19. Items 4-6 of the six items proposed by commenter: Commenter’s Item 4: Page 800, Line 15 - Delete Line 15 in its entirety and re-letter the items that follow at Lines 17-24. Commenter’s Item 5: Page 803, Line 15, delete “Type “W” Commenter’s Item 6: Page 843, Lines 5, 6, 9 -10, 12, 20 and 22, delete “Type W”

Due to space limits in this response column, the Code/Commentary Change Proposal Required to address Public Comment 330 Items 4-6 are given in the next cell.

Subcommittee B Comment Response Public Comment No. 330 <> 26.6.1.1 Design information: (a) ASTM designation and grade of reinforcement, including applicable requirements for special seismic systems in accordance with 20.2.2. 5. (b) Weldability or ductility designation for ASTM ASTM A706 reinforcement. <>

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No.

Public Commenter Pg # Name (bc) (b) Type, size, location….

Line #

Public Comment

Committee Response

… <> <>

26.6.4.12 Compliance requirements: (a) Welding of all nonprestressed bars shall conform to the requirements requirements of AWS D1.4. ASTM specifications for bar reinforcement, reinforcement, except for ASTM A706, Type W, shall be supplemented to require a mill test report of material properties that demonstrate conformance to the requirements in AWS D1. 4. <> <>

Welding—If welding of reinforcing…..welding procedures. R26.6.4 Welding— Weldability of the steel… The expression considering only the elements carbon and manganese is to be used for bars other than ASTM A706 Type W. A more comprehensive CE expression is given for ASTM A706 Type W bars, which is identical to the CE formula presented in ASTM A706. … ASTM A706 covers low-alloy steel reinforcing bars intended for applications that require controlled tensile properties, welding, or both. Weldability is accomplished in ASTM A706 Type W by requiring the CE not to exceed 0.55 percent and controlling the chemical composition. The manufacturer is required by ASTM A706 to report the chemical analysis and carbon equivalent (Gustafson and Felder 1991). When welding reinforcing bars other than ASTM A706 Type W, th e construction documents should specifically require that the mill test report include chemical analysis results to permit calculation of the carbon equivalent. … …requires a minimum preheat. For bars other than ASTM A706 Type W, the minimum preheat required is 300°F for No. 6 bars or smaller, and 500°F for No. 7 bars or larger. The required preheat for all sizes of ASTM A706 Type W bars is to be the temperature given in the Welding Code’s table for minimum preheat corresponding to the range of CE “o ver 0.45 percent to 0.55 percent.”

<>

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No.


Pg #

Line #

Public Comment

Committee Response

331.


567

6

Concrete cover of 2.5 inches is standard. The requirement of 3inch cover is difficult to obtain in smaller piles and should be revised.

Disagree. The 3-in. cover requirement for this Concrete Exposure is consistent with Table 4.5.3.6 in ACI 543R-12.

332.


567

6

The change from 1-inch cover to 1.5-inch causes the same problems as the comment above.

Minimum concrete cover given in table 20.5.1.3.4 for cast-inplace deep foundation members cast against ground is given as 3”. This is a change from current IBC 2018 Table 1808.2, which specifies a minimum cover of 2.5”. The 3” cover requirement can be difficult to meet for small pile shafts, including micropiles. For a 12” pile, the tie will need to be 6” diameter. It is difficult for most fabricators to bend a #4 tie into a 6” diameter circle, but most can bend into a 7” circle. For a 12” pile with 3” clear cover, the amount of concrete within the confined core is structurally insignificant. If 2.5” of clear cover is allowed, the area of the con fined core is 36% greater than for the same pile with 3” clear cover. Consider allowing the same 2.5” clear cover that has been permitted by IBC for many code cycles. We know of no corrosion issues resulting from from the IBC 2.5” minimum clear cover. Part of the reasoning for the ACI 3” cover requirement for concrete cast against earth is that the excavations for footings are often uneven, so the actual cover can often be less than than the specified cover. Deep foundations are usually drilled, with the inside of the drill shaft relatively smooth. Spacers are used to ensure proper proper cover. Under such conditions, the 2.5” clear cover required by IBC is more appropriate. Minimum clear cover for deep foundation elements enclosed by steel casing, pipe, tube, or stable rock socket is given as

333.


567

6

334.

Daniel S. Stevenson, P.E.

567

6

135 of 215

No change required. Disagree. The 1.5-in. cover requirement for this Concrete Exposure is consistent with Table 4.5.3.6 in ACI 543R-12. No change required. The cover of 2.5-in will be considered for New Business in the next Code Cycle. Agree with comment regarding composite piles. Clarification added to Commentary, see response to public comment #115. No change required.

Disagree. The 1.5-in. cover requirement for this Concrete Exposure is consistent with Table 4.5.3.6 in ACI 543R-12.


No.

335.

336.

Public Commenter Name Representing DFI Codes and Standards Committee Daniel S. Stevenson, P.E. Representing DFI Codes and Standards Committee

Pg #

David P. Gustafson

573

567

Line #

6

15

Public Comment

Committee Response

1.5”. This is currently 1” in IBC. The increased 1.5” minimum cover in ACI will result in detailing difficulties for smaller piles, particularly micropiles. Increased pipe/casing size will be required in some circumstances, increasing construction costs. Table 20.5.1.3.4 is not referenced by section 1.4.7, or any of the referenced sections in 1.4.7. Section 1.4.7 states “This code does not apply to the design of concrete piles, drilled piers, and caissons embedded into the ground, except as provided in (a) through (d). If none of the sections (a) through (d) reference this table (directly or indirectly through other referenced sections), then it would not apply. Consider replacing “earthquake loads” with “earthquake load effects”.

Also, currently micropiles are not included in 318-19. No change required. Agree. 1.4.7(c) is revised as response to Comment #9 to include all of Ch. 13., and 13.2.1.2 references all of Ch. 20. No change required (see response to #4, page 2, line 12)

Agree. The suggested language revision revision creates consistency with ASCE 7 usage of terms. Page 573 – Line 15: “For strength -level earthquake loads effects, tests of members using higher strength reinforcement have…”

337.

Andres Lepage

573

17

A reference to tests of coupling beams (Weber-Kamin (Weber-Kamin et al. 2019) needs to be added on Page 573, Line 17. Modify Lines 15 through 17 using: “For strength -level earthquake loads, tests of members using

higher strength reinforcement have shown acceptable behavior (Wallace 1998, Aoyama 2001, Budek et al. 2002, Sokoli and Ghannoum 2016, Cheng et al. 2016, Huq et al. 2018, WeberKamin et al. 2019 ), leading…” The proper citation to Weber-Kamin et al. (2019) is included in Comments to Page 919, Line 9.

136 of 215

Agreed. Add reference as indicated. Change as follows: R20.2.2.5 R20.2.2.4… For strength-level earthquake loads, tests of members using higher strength reinforcement have shown acceptable behavior (Wallace 1998, Aoyama 2001, Budek et al. 2002, Sokoli and Ghannoum 2016, Cheng et al. 2016, Huq et al. 2018, WeberKamin et al. 2019)***, leading…”


No.

338.

339.

Public Commenter Name Joe Ferzli (CKC), Jason Thome (CKC)

Andrew Ayling (CPL)

Pg #

Line #

595

6

597

12

Public Comment

Committee Response

The one way shear equation limit stated in section 22.5.1.2 is not in line with behavior of deep beams with high strength concrete. This is reported in several test results. ACI Structural Journal Technical Paper “Maximum Shear Capacity of Reinforced Concrete Members” by Proestos, Bentz & Collings (Sep 2018) summarizes the outcome of 131 experiments and recommend a maximum shear upper limit as a linear function instead of a root function of the specified compressive strength of concrete (f’c).

New Business, the limit in 22.5.1.2 is current code language. During the next Code cycle an examination of the limit can be conducted.

Request code change to equation 22.5.1.2 for deep beams with concrete strength greater than 4000 psi to have an upper limit of 0.2 f’c. A directly proportional shear limit to f’c, similar to AASHTO, is more appropriate than one related to the square root of f’c for deep beams with high strength concrete. This section has a substantial effect on basement walls loaded in out-of-plane bending and appears to be solving a problem that does not exist. A 12” basement wall with 4,500 psi concrete that was sized to be shear controlled under ACI 31814 would now need to be approximately 18” thick under ACI 318-19 if no other capacity increasing measures like us ing a higher concrete strength or adding shear reinforcing were implemented. If you increased the concrete strength strength to 8,000 psi the wall would still need to be 14” thick. Either way this will result in large cost increases. As a practicing engineer for for over 16 years I am not aware of any shear related basement wall failures. This is likely due to overly conservative design pressures from the Geotechnical Geotechnical Engineer. The design loads are not likely to get smaller anytime soon so what we are l eft with is rising costs for basement walls when the status quo has been more than adequate. adequate. I suggest that an exception be added to 25.5.5 for structural out-of-plane walls that allows 2

137 of 215

Disagree with the impact, therefore no changes in the code or commentary. A 12” thick wall would have a ‘d’ no more than 11” which would result in a worst case size effect factor (s) of 0.976 (only a 2.5% increase). If the longitudinal steel ratio () is: 0.33% than 8()^(1/3) = 1.19 (40% reduction over using 2sqrt(f’c).) 1% than 8()^(1/3) = 1.72 (14% reduction over using 2sqrt(f’c).) 1.5% than 8 )^(1/3) = 1.97 (1.4% reduction over using 2sqrt(f’c).) Adding

longitudinal reinforcement in the zone of high shear is a solution over increasing wall thickness or increasing concrete strength.


No.


Pg #

Line #

Public Comment

Committee Response

roots f’c to be used. Or as an alternative you could still impose the size effect but start with 2 roots f’c.

Note: the engineer can also take advantage of the axial compressive force occurring simultaneously with the shear at the base of the wall. The intent is to take into account the observed low shear capacity test results for the case of no shear reinforcement, very low longitudinal steel ratio ( ) and no axial force (refer to figure): (above figure is an excerpt from the upcoming ACI Journal article)

340.

Zdenek P. Bazant Abdullah Dönmez

598

9

On p. 598, Eq. 22.5.5.1.3, the round parentheses “( )” in the denominator should be removed. They are superfluous, clutter the view of the equation. If anything, some might want to move the “(“ just before “d”, but this is also not necessary.

This formula (size effect factor) appears also at several other places, and the same revisions need to be made (for 23.4.4.1).

341.

Brian Gerber

608

1

342.


608

1

Agree, change size effect equation throughout the Code to:

s =

2 < 1 (1 + d / 10)

λ =  + ≤ 1

Through line 2: Neither Chapter 18 nor 22.6.6.1 mention the value of vc should be reduced to vc = 1.5(f´c)0.5 as given by Eq. 7-1a of ACI 421.1R for earthquake resistant applications. This needs to included. Through line 2: Removal of parts (c) and (d) of Table 22.6.6.1 is necessary. Also, it is necessary to require (e) for stirrups and studs at the outer shear critical sections.

Disagree. Experimental evidence from laboratory tests does not support that requirement provided the proposed 8.6.1.2 i s satisfied .

Applying reduction factors for v c when studs are used cannot be justified by tests or analysis. The permitted values of v c depend upon control of potential cracking by shear reinforcement; this is irrelevant to parameters parameters in parts (c) and (d) of Table 22.6.6.1

Part (e) refers to 22.6.4.2 which defines the location of the outer critical section mentioned by the respondents.

138 of 215

Disagree Parts (c) and (d) in Table 22.6.6.1 cannot be removed. They ma y govern even for slabs with headed shear stud reinforcement.


No.

343.



Pg #

608

Line #

6

Public Comment

Committee Response

(s, , and bo/d ). ).

The language proposed by commenters for cruciform layouts is fine but note the layout is already shown in Figs. R22.6.4.2a, b and c in the code; therefore no change.

Control of potential shear cracks depends upon shear reinforcement details. A statement should be inserted in R22.6.6.1, page 631 to state that parts (a) and (b) of Table 22.6.6.1 are intended for crucifix layouts with spacings specified in R8.7.6 and R8.7.7 (see comment relevant to page 631, line 11). Through line 7: Removal of the words “with stud shaft length not exceeding 10 in.” is necessary. Also, it is necessary to insert in R22.6.6.2, page 608: Mechanically anchored smooth bars, with or without prestressing are widely used in concrete industry without without length restriction. Restriction of length of shank to to 10 in. has no basis. With smooth shank, the heads exert confining confining force equal to the tension in the bar (≤ yield stregth). Unintended force exerted on the concrete by the shank , reduces the confining force; thus smooth shank enhances the confinement. Effectiveness of headed studs, with perfectly smooth shanks, has been calibrated by non-linear finite element analysis (Megally and Ghali, 1996). Short smooth studs with forged heads are economically produced at fast speed. Two short studs make one long stud by stacking (piggybacking, Fig. R22.6.6.2). Tests of beams with studs having smooth shanks taller than 10 in., produced by piggybacking, show that that the strenth is not adversely affected by the length of the shanks (Lubell et al., 2009). Unintended force exerted on the concrete by the intermediate head has no benificial effect; economy is the only reason that it exists. Similarly, economy is the only reason to use ordinary deformed bars to produce headed stud shear reinforcement.

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Disagree The restriction on the stud shank length was added because of concerns that long smooth studs may not be able to arrest the growth of the shear crack inside the slab and hence mitigate the size effect in a deep slab. The shear reinforcement in the 3 beams te sted by Lubbell et al (2009) indeed consisted of piggybacked shear studs along their length (with the lower stud being longer than 10 in.). However, no control specimen with single shank studs was tested to be able to compare the responses and confirm what the respondents are stating.


No.


Pg #

Line #

344.

Reid W. Castrodale

618

1

345.

Allan Bommer

622

36

Public Comment

Committee Response

References: Megally, S. and Ghali, A., 1996, “Nonlinear Analysis of Moment Transfer Between Columns and Sla bs”, Proceedings, Canadian Society for Civil Engineering Annual Conference, Edmonton, Alberta, May, Vol. 2a, pp. 321-332. Lubell, A.S.,Bentz, E. and Collins, M., 2009, “Headed Shear Reinforcement Assemblies for One-Way One-Way Shear”, ACI Structural Journal, Vol. 106, No. 6, November-December, pp. 878-886. Through line 3: Table 22.9.4.2 While the use of lambda in the table is reasonable, no reason is given here and no commentary is provided regarding the maximum limit of 0.85. Please provide guidance on the calculation of d (or dx and dy) in biaxial shear conditions. For any Vx and Vy shear forces, the neutral axis may be at any orientation; it has no fixed relationship to the shear force vector (sh ear is related to the derivative of moment and not directly to moment). The neutral axis can even be parallel to the shear vector.

A possible resolution to this problem is to define d for these biaxial cases as the maximum depth of all reinforcement on the appropriate face.

346.

Zdenek P. Bazant Abdullah Dönmez

624

15

It should be noted that the engineer delegates the calculation of shear capacity to software almost all the time (and millions of times per project), so declaring that human “engineering judgment” should be used is ignoring the realities of design practice. Page 624, [CE025], R22.5.5.1 line 15. The references cited, except Bazant, did indeed demonstrate that size effect exists and is significant, which ought to be referenced. But it needs to be also mentioned that these studies recommended

140 of 215

Disagree, the limit of 0.85 is existing code language (no change from ACI 318-14), therefore no justification is provided.

Disagree, the definition of dx and dy is sufficient. dx or dy (as defined by the commenter) is calculated as it is done currently without the consideration of biaxial shear, that is, strength is estimated in each direction independently (following the indications for uniaxial shear strength for the estimation of d) before checking that the capacity is adequate with the interaction curve (equation). Thus, dx or dy does not require special attention given that it is indicated in the commentary that strength should be calculated in each direction.

Disagree, the statement after the references states “has shown that the shear stress at failure is lower for beams with increased depth”. The number of references suggested by the reviewer is not necessary to provide a reason for the size effect. If a designer


No.


Pg #

Line #

Public Comment

Committee Response

equations different from the size effect factor adopted for the 2019 code, or else the readers would be confused. Among these references, only the reference to Bazant et al. 2007 gives the size effect factor used in the 2019 code. This reference represents a proposal by ACI-446, which justifies the size effect factor by nonlinear statistical regression of a very large database. However, this reference does not give full derivation and explanation. In the interest of reader’s understanding, clarity and fairness, the references listed below should be added. The first proposal of the size effect factor used in the 2019 code was made in 1984 in [A], and its simplified derivation was also given. The first proposal to apply this size effect factor to beam shear was made in 1984 in [B]. This paper was the first to assemble a large database (of 292 beam shear tests), and this database was then used in [B] to justify the size effect factor now in the code. Ref. [Ba] provided a more fundamental derivation and also presented for the first time test results with perfect geometric scaling, very small coefficient of variation of scatter and the biggest size range ever, 1 : 16, although the tests were made on reduced scale beams with reduced aggregate size and reduced steel bar diameters. Several other derivations, more complete discussions and explanations, and experimental and theoretical demonstrations that the same size effect factor applies to all quasibrittle materials, were presented in book [Bb] (Sec. 10.1), and later more extensively in book [C]. Reference [D] showed why and how the size effect factor could be applied to t he strut-and-tie model. Reference [E1, E2] presented the complete formula which included the effects of steel ratio and aggregate size, and

wants a more in depth justification, they can easily find the references.

141 of 215

With regards to comment referring to CF007, this should be CE021. We disagree on the 30% reduction to the shear strength of a footing due to size effect proposed by the commenters in absence of a formal provision for size effect on shear strength of footings. This proposed reduction seems rather arbitrary. For the record, ACI 318 had the opportunity to evaluate a proposal from 318F on the subject of size effect on s hear strength of footings near the end of the code cycle. No c onsensus on the subject was reached based mainly on the fact that i) no footing shear failures due to size effects have been reported let alone documented in detail, and, ii) the available experimental evidence is rather limited.

The introduction of a size effect in the formulation for the shear strength of footings will be treated as new business.


No.


Pg #

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Public Comment

Committee Response

presented for the first-time a properly weighted unbiased nonlinear regression of the database to optimize the size effect equation with the size effect factor. Reference [F] showed the method how to eliminate statistical bias from the database, the bias being inevitably caused by data crowding or sparsity in different ranges of the variables. Ref. [G] provided the most up-to-date arguments and optimization of the size effect, and for the first time analyzed test data documenting the geometrical similarity of shear failure modes of properly scaled beams of different sizes. ---------------Page 625, line 2: [CE075] R22.5.5.1.3 Add references, mainly [C], but also [A], [A], [Ba], [Bb] --------------Page 629, line 27: [CE065] R22.6.5.2 line 33 Reference [H] should be added. It showed, using reduced-scale model tests with reduced aggregate size, that the same size effect factor was also approximately applicable to two-way shear in slab punching. This was also discussed in [Ba, Bb]. -----------------------------Page 275, line 18: [CF007] 13.2.6.2 p. 275 This code article means that the size effect factor may, but need not, be applied to footings. But the difference can be quite large. This arbitrary choice seems to us a strange approach for a design code. If you want to allow omission of size effect, better write that, if the size effect factor is ignored, the shear strength of footing should be reduced by, e.g., 30%. REFERENCES TO ADD: [A] Bazant, Z.P. (1984). "Size effect in blunt fracture: Concrete, rock, metal." J. of Engrg. Mechanics, ASCE, 110 (4), 518--535.

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No.


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Public Comment

Committee Response

[B] Bazant, Z.P., and Kim, Jenn-Keun (1984). "Size effect in shear failure of longitudinally reinforced beams." Am. Concrete Institute Journal, 81, 456--468; Disc. & Closure 82 (1985), 579--583. [Ba] Bazant, Z.P., and Kazemi, M.T. (1991). “Size effect on diagonal shear failure of beams without stirrups." ACI Structural Journal 88 (3), 268--276. [Bb] Bazant, Z.P., and Planas, J. (1998). Fracture and Size Effect in Concrete and Other Quasibrittle Materials. CRC Press, Boca Raton and London (Sec. 10.1). [C] Bazant, Z.P. (2005). Scaling of Structural Strength, 2nd ed., Elsevier, London 2005. [D] Bazant, Z.P. (1997). "Fracturing truss model: model: Size effect in shear failure of reinforced concrete." J. of Engrg. Mechanics ASCE 123 (12), 1276--1288. [E1] Bazant, Z.P., and Yu, Q. (2005). "Designing against size effect on shear strength of reinforced concrete beams without stirrups: I. Formulation" J. of Structural Engineering ASCE 131 (12), 1877--1885. [E2] Bazant, Z.P., and Yu, Q. (2005). "Designing against size effect on shear strength of reinforced concrete beams without stirrups: II. Verification and calibration" J. of Structural Engineering ASCE 131 (12), 1885--1897. [F] Bazant, Z.P., and Yu, Qiang (2008). "Minimizing statistical bias to identify size effect from beam shear database." ACI Structural Journal 105 (6, Nov.-Dec.), 685--691. [G] Yu, Qiang, Le, Jia-Liang, Hubler, H.H., Wendner, R., Cusatis, G., and Bazant, Z.P. (2016). "Comparison of main models for size effect on shear strength of reinforced and

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No.


Pg #

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Public Comment

Committee Response

prestressed concrete beams." Structural Concrete (fib) 17 (5) Dec., 778--789. [H] Bazant, Z.P., and Cao, Z. (1987). “Size effect in punching shear failure of slabs." ACI Structural Journal 84, 44-53.

347.

Antoni Cladera antoni.cladera@ui b.es

624

17

1/3 No information regarding the new term  w w is included in the commentaries. In my opinion, it would be important for practising engineers, students and researchers to understand the physical meaning of this parameter. For this reason the following additional commentary is proposed, to be included in 22.5.5.1:

Research (Cladera et al. 2017, Frosch et al. 2017, Park and Choi 2017) has shown that most of the shear force due to the concrete at maximum load is carried by an inclined compression strut above the diagonal crack, transmitted across the non-cracked concrete above the tip of the diagonal crack 1/3 d is almost (Yu et al. 2016, Marí et al. 2015). The term (  w w ) proportional to the neutral axis depth, c, obtained using the standard analysis of cracked RC sections under pure flexure (Cladera et al. 2016).

Justification Four out of the six shear proposal summarized in the September 2017 Issue of Concrete International (published after the hot topic session celebrated at the ACI Spring Convention in Milwaukee, 2016) recognized the concrete compression chord as the main transfer action for the shear forces at the maximum load (Cladera et al. 2017, Frosch et al. 2017, Li et al. 2017, Park et al. 2017). I fully understand that to use c, the neutral axis depth as a design parameter could be

144 of 215

Disagree that additional references and justification is needed. Topic is covered in more detail in the referenced ACI Journal paper on the new one-way shear equations


No.


Pg #

Line #

Public Comment

Committee Response

1/3 complicate for practicing engineers, and the term  w w is much more convenient.

Research (Cladera et al. 2016, Cladera et al 2017) has shown 1/3 that c/d is is proportional to the term (  w . Consequently, the w ) proposed shear equations take indirectly into account the neutral axis depth. In Cladera et al. (2016) it’s shown that:

 =  −1 −1  1  2 ≈ 0.755/3

/E c, and it must be simplified being n the modular ratio, n =E s /E taken as a constant. The similitude between the two terms of previous equation is shown in the next figure, where the simplified solution (dashed black line) refers to the

0.755/3  1  ) :

and the exact value (red line) to

 (−1

145 of 215


No.


Pg #

Line #

Public Comment

Committee Response

 ∝ /3

Therefore, c is almost proportional to . We really think it’s important for practising engineers, rese archers and students to understand the physical meaning of t his parameter 1/3 and why this new term, (  w w ) , fits well with the experimental test results. References Cladera, A., Marí, A., Bairán, J. M., Oller, E., & Ribas, C. (2017). One-Way Shear Design Method Based on a Multi-Action Model. Concrete International, 39(9), 40-46. Cladera, A., Marí, A., Bairán, J. M., Ribas, C., Oller, E., & Duarte, N. (2016). The compression chord capacity model for the shear design and assessment of reinforced and prestressed concrete beams. Structural Concrete, 17(6), 1017-1032. Frosch, R. J., Yu, Q., Cusatis, G., & Bažant, Z. P. (2017). A unified approach to shear design. Concrete International, 39(9), 4752. Marí, A., Bairán, J., Cladera, A., Oller, E., & Ribas, C. (2015). Shear-flexural strength mechanical model for the design

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No.


Pg #

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Public Comment

Committee Response

and assessment of reinforced concrete beams. Structure and Infrastructure Engineering, 11(11), 1399-1419. Park, H. G., & Choi, K. K. (2017). Unified Shear Design Method of Concrete Beams Based on Compression Zone Failure Mechanism. Concrete International, 39(9), 59-63. Yu, Q., Le, J. L., Hubler, M. H., Wendner, R., Cusatis, G., & Bažant, Z. P. (2016). Comparison of main models for size effect on shear strength of reinforced and prestressed concrete beams. Structural Concrete, 17(5), 778-789. 348.


630

24

349.

David P. Gustafson

631

8

350.


631

11

351.

Amin Ghali and Ramez. B. Gayed

631

12

This line should read “…shear walls structural walls” See reason given in comment on page 97, line 8. Replace “carry” with “resist”. Immediately below line 11, insert: The rules for design and detailing of stirrups as shear reinforcement apply with the crucifix layout in Figs. R8.7.6d and e. Values of vc in Table 22.6.6.1(a) apply only with the crucifix layout of stirrups in Figs. R8.7.6d and e. The values in Table 22.6.6.1(b) are intended for the crucifix layout of headed stud assemblies in Fig. R8.7.7. Through line 13: In R22.6.6.2, retain only the first sentence; delete the words: “The ability of ordinary (smooth) headed shear stud … anchor the stacked stud.” The first sentence of R22.6.6.2 recognizes that minimum amount of shear reinforcement in slabs with d > > 10 in. mitigates the size effect. Further testing is not needed or expected in foreseeable future. Subsequent sentences of R22.6.6.2 disallow headed studs. Stirrups and headed studs are most effective when they are perpendicular to potential shear cracks. But R22.6.6.2,

147 of 215

Agree. Change made.

Agree, change “the stirrups carry all the shear” to “the stirrups resist all the shear”, this is more consist with the rest of the Code. Disagree: The proposed change is not needed. Reference to 8.7.6 (stirrup shear reinforcement) and 8.7.7 (headed shear stud reinforcements) is clearly noted in 22.6.6.2.

Disagree. See response to Comment 343 Page 608, lines 6-7, Ghali for reason.


No.


Pg #

Line #

Public Comment

Committee Response

or the restriction of inclined headed studs in 8.7.7.1, effectively permits inclined stirrups, but disallows smooth headed studs in slabs whose thickness , h ≥ 9.8 in. or d ≥ 8.4 in. (assuming 45degree incline and 0.75 in. complete cover of stud heads); note the contradiction with d > > 10 in. Any of the two restrictions, practically, disallows using the most effective type of shear reinforcement to mitigate size effect. Both re strictions need to be removed.

352.

Roshan A D

639

9

With the geometry of stud head and rail specified in ASTM 1044/1044M-05 (2010), no further anchorage is required or desired. Two stacked short studs make one longer stud (piggybacking). Deformation on shank surface of headed stud, or intermediate head in a stud produced by piggy-backing does not exert beneficial force on concrete; if such force exist, it would be small, would not contribute to end anchorage and would reduce the confining force exerted by end anchors. For accuracy, R22.6.6.2 should consist of its first sentence; the remainder is not needed. Through line 13: In Clause R 22.9.4.6, it is not clear whether whether the reinforcement required for shear friction, Avf, at a cross section is in addition to that has been already provided in that cross section to resist bending moment (flexure) and axial force .

Clause 22.9.4.2 is also not explicitly clarifying this issue as it states Avf is the reinforcement crossing the shear plane to resist shear. As the flexural flexural reinforcement provided in that cross section also crosses the shear plane where shear friction calculations are applied, this reinforcement reinforcement can also be also ‘argued’ to be counted as resisting shear friction. In view of the above, following additional line may be introduced in Clause R22.9.4.2 after line 22, stating

148 of 215

Disagree, 22.9.4.6 states explicitly that reinforcement requirements for net axial tension and shear friction are additive. The first paragraph of R22.9.4.6 provides complementary information about common sources of net axial tension, and the second paragraph then separately makes the point that flexural tension and net axial tension are treated differently when considering shear friction. friction. No change is required. required.


No.


Pg #

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Public Comment

Committee Response

“ Avf thus calculated is in addition to reinforcement already provided in the cross section to resist flexure or combined effect of tension and flexure or compression and flexure, as the case may be.”

353.

Khattab Saleem

651

0

There is some change in Strut and Tie chapter in the new ACI ACI 318-19. So, please accept my point of view for discussion through the paper below:

Thank you for your article. The Code permits the reinforcing of struts and ties with longitudinal reinforcement. No change is recommended and therefore no change has been made.

Suggesting alternatives for reinforced concrete deep beams by reinforcing struts and ties

Khattab Saleem Abdul-Razzaq1* and Sarah Farhan Jebur2 1 2

Department of Civil Engineering, Diyala University, Iraq. Department of Civil Engineering, Diyala University, Iraq.

Available: https://www.matecconferences.org/articles/matecconf/abs/2017/34/matecconf_asc m2017_01004/matecconf_ascm2017_01004.html 354.


655

3

The one way shear equation limit stated in section 23.4.4 is not in line with behavior of deep beams with high strength concrete. This is reported in several test results. ACI Structural Journal Technical Paper “Maximum Shear Capacity of Reinforced Concrete Members” by Proestos, Bentz & Collings (Sep 2018) summarizes the outcome of 131 experiments and recommend a maximum shear upper limit as a linear function instead of a root function of the specified compressive strength of concrete (f’c). Request code change to equation 23.4.4 for deep beams with concrete strength greater than 4000 psi to have an upper limit of 0.2 f’c. A directly proportional shear limit to f’c, similar to

149 of 215

New business. The cited research paper applies to sectional shear design of members with and without transverse reinforcement,

10√ 10√ ′

and the paper is critical of the shear stress limit on slender and deep beams in ACI ACI 318-19. The change proposal that included Equation 23.4.4 removed the 10 roots limit on shear stress in transfer girders designed using the strut-and-tie method and was shown to be conservative with respect to all tests of members (without transverse reinforcement and an a/d ratio less than 2) reported in the referenced ACI database — which included specimens with concrete strengths up to 14,000 psi. Note that strut compression, which is proportional to f’c must also be checked when Equation 23.4.4 is used. However, based on this comment, the committee agrees to re -examine shear


No.

355.

356. 357.


Adam Lubell

David P. Gustafson ACI Staff

Pg #

655

664 682

Line #

30

4 4

Public Comment

Committee Response

AASHTO, is more appropriate than one related to the square root of f’c for deep beams with high strength concrete. 23.5. In wide planar-type members designed by the strut and tie method, it is desirable to ensure the stress distribution over the member width is uniform. uniform. Consideration should be given to requiring that the spacing of curtains of distributed reinforcement from 23.5 through the member width should be limited similar to those specified for beam shear reinforcement in 9.7.6.2.2 either as a Clause in 23.5 or as Commentary.

stress limits in ACI 318, giving due consideration to the recommended approach. New business. The committee agrees that minimum reinforcement should be distributed in wide members. The commentary to 23.5 briefly mentions interior layers placed in wide members.

Where the member width is wider than the width used for the strut and tie model (for example, to obtain a restrained strut based on 23.5.3(b)), Clause 23.5 should require distributed reinforcement calculated based on the gross section of t he member rather than the analysis width of the s trut and tie model. Consider replacing “compute” with “calculate”. The figure refers to hairpin reinforcement which is typically small bars used for confinement. confinement. This appears to be a more more substantial bar in some or many many cases. Could this be reworded to “Tension ties anchored with 180 degree bend” or similar?

150 of 215

The committee disagrees that distributed reinforcement should be required where struts are laterally restrained in members like pile caps and beam ledges supporting concentrated loads. Nevertheless, the apparent confusion justifies revisiting both comments as new business.

Agree, change compute to calculate Agree. “’ Hairpin’ reinforcement” is unnecessary and will be deleted. Also remove pointers from “Hairpin reinforcement”. Adjust figure as shown below.


No.


Pg #

Line #

358.

Peter Bischoff

687

3

359.

ACI Staff

687

3

360.

Peter Bischoff

687

6

361.

Peter Bischoff

687

9

362.


689

19

363.

Peter Bischoff

697

1

Public Comment

Committee Response

For Table 24.2.3.5, in the denominator of the Ie equation, there should be a space between “2/3” and “Mcr” to avoid any confusion that it is not 2 divided by 3Mcr. Via member Kreger. Please change the equations so that it is more clear that it is (2/3)Mcr and cannot be misinterpreted as 2/(3Mcr). Change all 2/3Mcr to (2/3)Mcr in Table Table 24.2.3.5. Clause 24.2.3.6 refers to Eq. (24.2.3.5a) which is now part of Table 24.2.3.5. Suggest changing “Eq. (24.2.3.5a)” to “Table 24.2.3.5” unless wording needs to be changed as well. Clause 24.2.3.7 refers to Eq. (24.2.3.5a) which is now part of Table 24.2.3.5. Suggest changing “Eq. (24.2.3.5a)” to “Table 24.2.3.5” unless wording needs to be changed as well. 24.2.3.5 should state that it applies to members subjected to bending moment without normal normal force. Replace the words “For nonprestressed members" by: “For members subjected to bending without normal force …”.

Agree there will be confusion. confusion. Use Kreger suggestion suggestion from comment 359 page 687, line 3, change all 2/3Mcr to (2/3)Mcr.

Through line 12: R24.2.3.5:

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Agree there will be confusion. confusion. Use Kreger suggestion suggestion from comment 359 page 687 line 3, change all 2/3Mcr to (2/3)Mcr. Agree. Change made.

Agree. Change made.

This is page 686 Line 19. Disagree. Prefer to refer to nonprestressed nonprestressed members as it is difficult to show that there is absolutely no normal force in most design situations. Agree with changes in references as listed below.


No.


Pg #

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Public Comment

Committee Response

References provided in R24.2.3.5 are not all correct. The effective moment of inertia equation was developed by Bischoff (2005) and the reduced cracking moment 2/3 Mcr was proposed by Scanlon and Bischoff (2008). (2008). If necessary, the ACI publication by Bischoff and and Scanlon (2007) could be used in lieu of Bischoff (2005). The publication by Bischoff and Scanlon (2007) shows the range of applicability for Bischoff’s equation over a wide range of reinforcing ratios.

The committee will take up as new business the consideration of construction loads in the calculation of deflections.

Bischoff, P.H., 2005, “Revaluation of Deflection Prediction for Concrete Beams Reinforced with Steel and Fiber Reinforced Polymer Bars, Bars,” Journal of Structural Engineeri ng, ASCE, Vol. 131, No. 5, May, pp. 752-767. Bischoff, P.H., and Scanlon, A., 2007, “Effective Moment of Inertia for Calculating Deflections of Concrete Members Containing Steel Reinforcement and Fiber-Reinforced Polymer Reinforcement,” ACI Structural Journal , Vol. 104, No. 1, Jan-Feb, pp. 68-75.

Suggest the following, “R24.2.3.5 The effective moment of inertia approximation, developed by Bischoff (2005) Bischoff and Scanlon (2008), has been shown to result in calculated deflections that have sufficient accuracy for a wide range of reinforcement ratios (Bischoff and Scanlon 2007). Mcr is multiplied by 2/3 to consider restraint that can reduce the effective cracking moment as well as to account for reduced tensile strength of concrete during construction that can lead to cracking that later affects service deflections ( Bischoff and Scanlon and Bischoff 2008). Before 2019, ACI 318 used a different equation (Branson 1965) to calculate Ie. The previous equation has subsequently been shown to underestimate deflections for members with low reinforcement ratios, which often occur in slabs, and does not consider the effects of restraint. For

152 of 215

“R24.2.3.5 The effective moment of inertia approximation, developed by Bischoff (2005) Bischoff and Scanlon (2008), has been shown to result in calculated deflections that have sufficient accuracy for a wide range of reinforcement ratios (Bischoff and Scanlon 2007). Mcr is multiplied by 2/3 to consider restraint that can reduce the effective cracking moment a s well as to account for reduced tensile strength of concrete during construction that can lead to cracking that later affects service deflections (Bischoff and Scanlon and Bischoff 2008). Before 2019, ACI 318 used a different equation (Branson 1965) to calculate Ie. The previous equation has subsequently subsequently been shown to underestimate deflections for members with low reinforcement ratios, which often occur in slabs, and does not consider the effects of re straint. For members with greater than 1% reinforcement and a se rvice moment at least twice the cracking moment, there is little difference between deflections calculated using the former and current code provisions.”


No.


Pg #

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Public Comment

Committee Response

members with greater than 1% reinforcement and a service moment at least twice the cracking moment, there is little difference between deflections calculated using the former and current code provisions.” Note that the paper by Scanlon and Bischoff (2008) also recommends that immediate deflection be calculated using Ie corresponding to the full dead plus live load for all deflection calculations (ie. for immediate deflection under sustained load and immediate deflection under the full dead plus live service load. This accounts for preloading during construction and gives the most conservative estimate of incremental deflection. Suggest the committee consider adding an additional sentence at the end of the first paragraph to read as

364.

ACI Staff

697

7

365.


697

12

“Preloading from construction loads can be taken into account using an effective moment of inertia corresponding to the full dead plus live service load when calculating immediate deflection from sustained loads for incremental deflection calculations.” In the committee approved CC004, this sentence read “Prior to 2019, ACI 318…” During editorial review, ACI editors changed this to “Before 2019, ACI 318…” based on ACI style. Please provide direction to staff regarding preferred language. Through line 13 Members subjected to normal force due to prestressing or other cause need to be considered. At beginning of R24.2.3.5 insert: R24.2.3.5 I e is an interpolated parameter between I g and I cr cr ; where I e and I cr = moments of inertia about principal axes of cr = gross concrete section and transformed cracked section ignoring concrete in tension, respectively. The interpolation is based on immediate deflection of prismatic simple beams, having vertical and horizontal principal axes, subjected to maximum moment

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Change made. It is appropriate to use “Code” when referring to 318, and “code” when referring to general codes. Change made. New Business. These provisions must be reviewed and voted voted by the full committee.


No.


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Public Comment

Committee Response

M a at mid-span. Extending the analysis to other cases is based mainly on intuition. ACI 435R-95 (Appendix B added 2003) and Ghali et al., 2012 give a procedure applicable to frames (with non-prismatic members) subjected to bending and normal force induced by prestressing or other cause; cracking, creep, shrinkage and prestress relaxation are considered.

366. 367.

David P. Gustafson Dan Mullins

701 712

20 26

References: ACI Committee 435, 2003, Control of Deflection in Concrete Structures, ACI 435R-95 (Appendix B added 2003). Ghali, A., Favre, R. and Elbadry, M., 2012, Concrete Structures, Stresses and Deformations, CRC Press, 4th Edition, 637 pp. Consider replacing “compaction” with “consolidation” Suggested rewording: “For bars with fy>80,000 psi spaced closer than 6 in. on center, transverse reinforcement shall be provided such that Ktr shall not be smaller than 0.5 db”

Agree. Change made. Agree. Reason: the proposed language is clearer. Revise text (by adding “transverse reinforcement… such that”) as follows: 25.4.4.2 For bars with fy>80,000 psi spaced closer than 6 in. on center, transverse reinforcement shall be provided such that K tr tr shall not be smaller than 0.5d b b.

368.

369.

William Pollalis, Santiago Pujol, Robert Frosch

714

David Darwin

715

1

13

Comment regarding lap splices in ordinary walls: Lap splices meeting proposed design provisions are likely to result in a brittle response in ordinary walls resisting seismic demands in regions of moderate seismicity. Tests including Gr 60 lap splices show that structural members may fail at drift ratios as low as ½% to 1%. This brittle response is likely to be aggravated aggravated by the use of Gr 80 or Gr 100 reinforcement. Please refer to the appended file for documentation supporting this statement. Because 25.4.3.3 only defines what constitutes the total crosssectional area of ties or stirrups confining hooked bars Ath and

154 of 215

Agreed. The test data does indicate a potential issue, but the committee needs time to thoroughly vet this concern. New Business

Agree


No.


Pg #

Line #

Public Comment

Committee Response

contains no requirements, the presumption is that the wrong section has been cited. Therefore, “...25.4.3.3 (a) through (b)...” should be “...25.4.3. 4 (a) and (b)...”

The referen ce is ambiguous. A more appropriate change is “For fy ≥ 80,000 psi, confining reinforcement indicated in 25.4.3.3 (a) and (b) shall be provided”. But this line should be deleted. Reason: See response to comment 370, page 715 line 13. Change: 25.4.3.2 25.4.3.2 For...apply. For f y ≥ 80,000 psi, 25.4.3.3 25.4.3.3 (a) through (b) shall be satisfied.

370.

David Darwin

715

13

Assuming that the first (Darwin) comment on page 715, line 13 is correct, this change, requiring that extra confining reinforcing be provided at hooks in accordance with 25.4.3.4 25.4.3.4 (a) and (b) for f y ≥ 80,000 psi, is technically problematic for two reasons: (1) 25.4.3.4 (a) and (b) cover hooked bars anchored at the discontinuous ends of members with both low side cover and low top cover. It is written with cantilevered flexural members in mind, but it could also apply to the top of cantilevered columns. It was retained in the 2019 Code to maintain the current conservative approach to members of this type, although no members with this geometry have ever been tes ted. 25.4.3.4 (a) requires that dh be enclosed within “...ties or stirrups perpendicular to dh...” Thus, if retained, it will require bea m and slab flexural reinforcement anchored with hooks in beamcolumn joints, slab-column joints, beam-wall joints, slab-wall joints, and two-way slabs within the slab to be enclosed by reinforcement that is perpendicular to dh if f y ≥ 80,000 psi. The required orientation of the confining reinforcement is highly impracticable and will effectively prevent the use of Grade 80 and stronger flexural reinforcement in these cases. T here is nothing in the research on which the new hook provisions are

155 of 215

Agree. Delete as shown: Reason: Research does not support different confinement requirements for Grade 80 hooked bars. 25.4.3.1 is easily good for up to Grade 120 bars. Change: 25.4.3.2 For...apply. For f y ≥ 80,000 psi, 25.4.3.3 (a) through (b) shall be satisfied.


No.


Pg #

Line #

Public Comment

Committee Response

based (references cited in new Commentary) that justifies this requirement. It should be dropped. (2) To follow up on the last part of reason (1), there is nothing in the research on which the new hook provisions are based (references cited in new Commentary) that would indicate that the development of Grade 80 and stronger hooked bars needs to be treated differently than the development of lower lower strength hooked bars. The new development length provisions are based on test results with bar stresses a t anchorage failure up to 142 ksi. The provisions were formulated for hooked bars with f y up to 120 ksi. The new provisions appropriately include the effects of confining reinforcement and low side cover. The requirement to satisfy 25.4.3.4 (a) and (b) for f y ≥ 80,000 psi is not justified based on the research and should be dropped.

371.

Reid W. Castrodale

715

15

Table 25.4.2.5 Here and in a number of other tables (Tables 25.4.3.2 & 25.4.9.3), an entry appears for “lightweight concrete”. In some tables, however, a note indicates that a modification was required if lightweight aggregate was used. This needs t o be consistently treated throughout, because there are instances where a reduced density concrete, or an in ternally cured concrete, is used which includes lightweight aggregate, but may not have a density below 135 pcf.

Agree. Reason: Removing reference to “aggregate will improve clarity. Note: In 318-19, lightweight concrete is defined as having an equilibrium density between 90 and 135 lb/ft 3. Lightweight aggregate is not addressed in Code Chapter 25. This is an issue, however, in footnotes of Tables 15.4.2.3 and 18.8.4.3 where it states that “ shall be 0.75 for concrete containing lightweight aggregate and 1.0 for concrete containing all normalweight aggregate."

This must be clarified throughout the document. The term also appears in R25.4.2.4. Change footnotes of Tables 15.4.2.3 and 18.8.4.3: “  shall be 0.75 for concrete containing lightweight concrete aggregate and 1.0 for concrete containing all normalweight aggregate concrete. "

Change the first sentence of in R25.4.2.4 as follows:

156 of 215


No.


Pg #

Line #

Public Comment

Committee Response “R25.4.2.4 R25.4.2.4 The lightweight factor λ for calculating development length of deformed bars and deformed wire in tension is the same for all types of lightweight aggregate concrete. ”

372.

373.

Reid W. Castrodale

David Darwin

715

718

15

13

Table 25.4.2.5 Since the option of computing lambda where fct is specified has been proposed to be removed from the code, a factor of 0.75 must now be used all types of lightweight concrete. Since the other option was in the table, it must be appropriate for use. Therefore, this is a significant limitation. I find no commentary addressing this change. In Table 25.4.4.3 for modification factor  p, under Condition, “0.3 Ats” should be “0.3 Ahs”.

Disagree. Reason: Commentary on the change appears in R19.2.4.

Agree. Reason: This is a typo.

374.

375.

376.

Reid W. Castrodale

Mark W Cunningham

Dan Mullins

721

722

722

13

25

31

Table 25.4.9.3 This table still includes the provision to determine lambda based on specifying fct which has been removed from other similar tables. I expect that it was intended to be removed.

The reference to 25.2.1 was correct – don’t change to 25.5.2.1. Line 26 indicates “[Errata]” – presumably to 318-14. However, such errata to 318-14 is incorrect. 25.2.1 addresses minimum spacing, whereas 25.5.2.1 addresses the splice lengths.

Suggested rewording: “For bar s with fy>80,000 psi spaced closer than 6 in. on center, transverse reinforcement shall be provided such that Ktr shall not be smaller than 0.5 db”

157 of 215

Change: Make the suggested change under Condition, “0.3 Ats A Ahs”. Agree. Reason: This was missed. Reference to fct must be removed. Change: Modify Table 25.4.9.3 as shown: “Lightweight concrete, if f ct is specified ” and “In accordance with ct is 19.2.4.3” 19.2.4.3” Agree. Change Page 722, Line 25: “shall be in accordance with the requirements for individual bars in 25.5. 2.1.” Agree. Reason: the proposed language is clearer.


No.


Pg #

Line #

Public Comment

Committee Response Revise text (by adding “transverse reinforcement… such that”) as follows: 25.5.1.5 For bars with fy≥80,000 psi spaced closer than 6 in. on center, transverse reinforcement shall be provided such that K tr tr shall not be smaller than 0.5d b b.

377.


725

19

378.

Jason Kilgore, PE, SE

728

13

The requirements for mechanical and welded splices in 25.5.7 (i.e., Type 1 mechanical splices) should be based on actual yield strength or preferably be strain-based provisions. The present mechanical splice requirement may not ensure adequate ductility of spliced bars with high overstrength or short or nonexistent yield plateaus. The revised provisions should take into account the changes that have occurred in the stress-strain relationship for nonprestressed deformed reinforcing bars since the time that the requirements of 25. 5.7 were developed in the 1960s and 1970s, including the introduction of higher grades of reinforcement. In paragraph 25.7.2.4.1, please clarify the intent, even if only in the commentary, that hook closures on circular ties are only required for seismic categories D, E, and F.

New business.

Alternately, please add an exception to 25.7.2.4.1 for deep foundations similar to the exception in 25.7.3.3 (page 728, line 33)

Cast-in-place concrete deep foundation elements in SDC A and B will be considered for New Business in the next Code cycle.

Paragraph 18.13.5.4 (page 448, line 6) specifically requires t ie hooks for deep foundations in SDC D, E, or F, but doesn’t indicate a closure method for SDC A, B, or C.

18.13.5.4 actually applies to SDC C -F (see below). And according to 1.4.7(c), 318-19 does not apply to ca st-in-place concrete deep foundations in SDC A and B.

18.13.5.4 For structures assigned to SDC C, D, E, or F, hoops, spirals, and ties in deep foundation members shall be terminated with seismic hooks. No change required.

Justification: This is needed for drilled shafts supporting power transmission structures in low seismic areas.

158 of 215


No.


Pg #

Line #

Public Comment

Committee Response

The standard design for engineered poles has a cir cular ring of #18-Jumbo anchor rods held with steel ring templates. The bolt circle diameter is determined by the pole size, which in turn is based on wind and very high wire tensions. The outer pier reinforcing cage is located just outside the bolt template and determines the diameter of footing. Adding space for closure hooks to the ties in the outer pier reinforcing cage requires greatly increasing the pier diameter. Currently, as the codes governing power transmission lines don’t specifically reference the ACI 318, most power utilities in low-seismic areas simply ignore the hook requirement and use the old lap-splice details. But the IBC does reference ACI 318. These footings typically have high moments from wind loads but low shear and very low axial. Minimum shear steel almost always works, and the soil strength always controls over concrete/steel bending stress. Replace “reinforcing steel” with “reinfiorcent”.

379.

David P. Gustafson

739

3

380.

Reid W. Castrodale

739

19

R25.4.2.5 It appears that commentary sections were not renumbered with the articles. This should be R25.4.2.5

381.

Reid W. Castrodale

739

20

R25.4.2.4 Research is mentioned as being the reason for the general application of a limit to lightweight concrete. However, no reference is given to the research. This i s needed.

159 of 215

Agreed. R25.4.2.3 … Ѱg is the reinforcement grade factor accounting for th e yield strength of the reinforcing steel reinforcement. Accept, editorial. Renumber: R25.4.2.23 R25.4.2.34 R25.4.2.45 Agree. Page 739, Line 20, add reference: “variations of this factor in Codes prior to 1989 for all -lightweight and sand-lightweight concrete (ACI 408R-03(12)).”


No.

382.

383.


David Darwin

David Darwin

Pg #

739

743

Line #

25

9

Public Comment

Committee Response

The sentence in this article that indicates that the option to specify the splitting tensile strength was permitted has now been removed. As noted above, this makes removes the opt ion to make the factor less restrictive. This does not appear to be appropriate since the option was deemed appropriate in the past. The statement, “The reinforcement grade factor ψ g accounts for the yield strength of the reinforcement because development length is not linearly related to the yield strength (Canbay and Frosch 2005).” should be replaced because it misstates the Code change and does not cite the original research. Orangun et al. (1977) first observed that the bar stress is not proportional to development and splice length when bars undergo a bond failure. Their representation indicated that, while not proportional, the relationship between between bar stress and development length was close to linear. Other researchers a nd Committee 408 have reached a similar conclusion. In fact, the relationship between ψ g and f y is linear. The statement would be improved and be more useful to users of the Code if it were replaced by: “The reinforcement grade factor ψ g accounts for the yield strength of the reinforcement because increases in bond strength are not proportional proportional to increases in bonded length length (Orangun et al. 1977).”

Add commentary reference: ACI 408R-03(12) Bond and Development of Straight R einforcing Bars in Tension

“Ishao” should be “(Shao”

Agree. Reason: Although the effect of using ψg results in a nonlinear relationship between d and f y y , the consensus (ACI Committee 408 and other researchers) is that the relationship is close to linear, but non-proportional. The change proposed describes the reason for adding ψg without tying down the committee to a specific approach in future editions. Delete: “The reinforcement grade factor ψg accounts for the yield strength of the reinforcement because development length is not linearly related to the yield strength (Canbay and Frosch 2005) Replace with: The reinforcement grade factor ψg accounts for the effect of reinforcement yield strength on required development length. Research has shown that required development length increases disproportionately with increases in yield strength (Orangun et al. 1977; Canbay and Frosch 2005). Agree. Reason: This is a typo. IsShao” Make this change: “IsShao”

384.

Reid W. Castrodale

747

33

R25.4.9.2

Disagree.

160 of 215


No.

385.


ACI Staff

Pg #

748

Line #

23

Public Comment

Committee Response

Is not splitting also more likely in high strength concrete? So should a reduction factor also be considered for high strength concrete?

Reason: These are very old provisions. Little research has been done in this area, and there is not enough information available

Should this list include 7.7.7 now? Or consider rewording this to say “…or for development of structural integrity reinforcement.”

Agree.

to make a change. Note that

c is limited to 100 psi. f 

Change: Add 7.7.7 to the list. Page 748, Line 23: “provided according to 7.7.7, 8.7.4.2, 8.8.1.6, 9.7.7, and 9.8.1.6.”

386.

David P. Gustafson

751

9

387.

ACI Staff

757

13

Consider replacing “carrying” with “transferring”.

Verify (Fig R25.9.1.1b) applies here rather than (Fig. 25.9.1.1a). There is no local zone called out in Fig. 25.9.1.1b. Also, what does immediately ahead of the local zone mean? Possibly show meaning on graphic.

161 of 215

Disagree. These elements do carry the load also. Suggest showing a local zone in Fig. 25.9.1.1b similar to Fig. “…stresses 25.9.1.1a and changing the reference in R25.9.4 to “…stresses immediately ahead of the local zone should be checked (Figs. 25.9.1.1a and R25.9.1.1b).” R25.9.1.1b).” Also change title to “Fig. “Fig. R25.9.1.1b— Local and gGeneral zones for anchorage device located away from the end of a member.” member. ” See also page 776, line 1, an d sketch below (changes shown in red).


No.


Pg #

Line #

388.

Reid W. Castrodale

760

7

Public Comment

Committee Response

Through line 10: R25.9.4.5.2 The commentary states that “the lambda factor for lightweight concrete reflects its lower tensile strength … as well as the wide scatter and brittleness exhibited in some lightweight concrete anchorage zone test.”

Partially Agree.

Again, LWC is stated as having lower tensile strength. The brittleness and scatter observed in some LWC anchorage zone test are used to justify a reduction to be applied to all

162 of 215

Change the section to read: R25.9.4.5.2 Some inelastic deformation of concrete within general zones is expected because anchorage zone design is based on a strength approach. The inclusion of Unless shown by tests, the λ factor for lightweight concrete reflects its should be applied to reflect a lower tensile strength, which is an indirect factor in limiting compressive stresses, as well as the wide scatter


No.


Pg #

Line #

Public Comment

Committee Response

lightweight concrete. There are also some normalweight concretes that are brittle and have scatter, but that does not result in all NWC being penalized for it.

and brittleness exhibited in some lightweight concrete anchorage zone tests.

Again – the code needs to define performance standards and allow lightweight concrete to meet them without penalty when the material is capable of doing so.

389.

ACI Staff

762

13

Finally, although tests are mentioned, no references are given. Ties and stirrups not identified on drawing or title. What is confining reinforcement? Is it ties and stirrups? Suggest adding explanation to figure.

Agree: Reason: An explanation is needed to improve clarity of the figure. Note that confining reinforcement could consist of ties or stirrup depending if the hooked bars are anchored horizontally within a beam (as shown) or vertically within a column. Modified the figure shown in the response to Comment 389 modified to clearly show the 15d b dimension. The figure title will be as shown in CB601.

Placed figures a and b adjacent to each other and change the figure title to ” Fig. ” Fig. R25.4.3.3a —Confining reinforcement placed

163 of 215


No.


Pg #

Line #

Public Comment

Committee Response parallel to the bar being developed t hat contributes to anchorage strength of both 90- and 180-degree hooked bars.

390.

391.

ACI Staff

ACI Staff

763

767

3

4

Ties and stirrups not identified on drawing or title. What is confining reinforcement? Is it ties and s tirrups? Suggest adding explanation to figure.

Suggest calling out “potential failure surface” in busy figures similar to 318-14 Fig. R25.4.4.2e.

164 of 215

Agree. An explanation is needed to improve clarity of the figure. Note that confining reinforcement could consist of ties or stirrup depending if the hooked bars are anchored horizontally within a beam (as shown) or vertically within a column. Change: Figure will be as shown in the Committee response to Comment 389 (shown again below). The figure title will be as shown in CB601.

Fig. R25.4.3.3b—Confining reinforcement placed perpendicular to the bar being developed, spaced along the development length l dh , that contributes to anchorage strength of both 90- and 180-degree hooked bars. Agree.


No.


Pg #

Line #

Public Comment

Committee Response

Reason: The proposed change will improve the clarity of the figures. Added “Potential failure surface” to figure (twice), as shown. Note in figure on “parallel reinforcement within 8d 8 d b...” moved. Please use new crack and compression strut locations indicated in red.

165 of 215


No.


Pg #

Line #

Public Comment

Committee Response

Labeled the individual drawings as: “(a) horizontal headed bars” and “(b) vertical headed bars”. In figure (b) the dark region at the upper right should be removed.

166 of 215


No.


Pg #

Line #

392.

ACI Staff

769

9

393.

ACI Staff

775

8

Public Comment

Committee Response

Suggest changing title of (a) and (b). Possibly change from “(a) Section 25.5.3.1a” to “(a) Lap splice satisfies 25.5.3.1a”. Possibly change “(b) Section 25.5.3.1.1” to “(b) Lap splice satisfies 25.5.3.1.1”. Current figure subtitles leave no explanation unlike rest of Chapter 25 figure subtitles.

Agree.

Suggest calling out and showing “anchorage device” locations similar to Fig. R25.9.1.1b.

167 of 215

Reason; Changing the titles will improve the clarity of the figures. Change title of Fig. R25.5.3.1(a): R25.5.3.1(a): “(a) Section 25.5.3.1a Lap splice satisfies 25.5.3.1a”. Change title of Fig. R25.5.3.1(b): “(b) Section 25.5.3.1.1 Lap splice satisfies 25.5.3.1.1”. Agree, see sketch of Fig. R25.9.1.1a below, revisions in red.


No.


Pg #

Line #

Public Comment

Committee Response

168 of 215


No.


Pg #

Line #

Public Comment

Committee Response

Fig. R25.9.1.1a — Local and and general zones. zones. 394.

ACI Staff

776

6

Suggest calling out and showing “anchorage device” locations on similar to Fig. R25.9.1.1b. Also suggest calling out zones similar to Fig. R25.9.1.1a to explain “general zone”.

169 of 215

Disagree, Figs. R25.9.1.1a and R25.9.1.1b make that clear enough and inclusion here would make the figure too busy. Changed “Bursting forces” to “Bursting stresses” and “Spalling forces” to “Spalling stresses” to better match title of figure.


No.


Pg #

Line #

Public Comment

Committee Response

stresses

stresses

Fig. R25.9.4— Tensile Tensile stress zones within the general zone.

170 of 215


No.

395.

Public Commenter Name Asit Baxi

Pg #

Line #

779

0

Public Comment

Committee Response

Agree, see the attached revised Fig. R25.9.4.4.6. Also on page 759, line 12, change “loaded face” to “bearing face”.

This is detail (b) in Fig R25.9.4.4.6 – Anchorage zone reinforcement for groups of ½” or smaller d iameter tendons in slabs Show a thicker slab in the figure to highlight one of the important reasons for this code change which was how to detail the anchorage zone bars in thicker slabs. By showing the thicker slab and larger full slab depth hairpins it will highlight that a) the hairpins have to be full depth minus cover, b) the bars at the corners of the hairpins are different from the backup bars and c) the backup bars are to be placed within the confines of the anchor

171 of 215


No.


Pg #

Line #

396.

ACI Staff

779

2

Public Comment

Committee Response

Hairpin is a term not included in Chapter 2 notation. Suggest adding this term which is used in more than one place.

The term “hairpin” is currently def ined ined in the ACI CT and has a number of definitions. The usage here is clear since it is shown in a figure. Defining it in Chapter 2 will involve all usages in the Code, which may be different than the usage here. No change.

172 of 215


No.

397.

Public Commenter Name Eric Koehler

Pg #

Line #

783

17

Public Comment

Committee Response

Mineral filler should be in its own sub-section under 26.4.1 and not listed under aggregate. aggregate. This is consistent with approved changes for ACI 301 and ASTM C94. ACI 318 has specific requirements that apply to “aggregate” that are not relevant to and for which there are not suitable test methods for mineral filler. For example, alkali-aggregate requirements requirements are not applicable. Meanwhile 26.4.1.2.1(b) requires “aggregate” to conform to ASTM C33 or C330 or to have demonstrated performance and be approved by the building official. This would require “aggregates” fully meeting ASTM C1797 to be approved further by the building official as they do not conform to C33 or C330. This conflict can be resolved by moving mineral filler to it own subsection under 26.4.1.

Make change as recommended. This is an editorial change to the commentary.

Response to Comment 397 As is in draft 318-19: 26.4.1.2 Aggregate 26.4.1.2 Aggregatess 26.4.1.2.1 Compliance requirements:

Aggregates shall conform to (1), (2), or (3) (1) or (2): (a) Aggregates (1) Normalweight aggregate: ASTM C33. (2) Lightweight aggregate: ASTM C330. (3) Mineral fillers: ASTM C1797. C179 7.

26.4.1.3 Mineral fillers

173 of 215

See edits in next cell.


No.


Pg #

Line #

Public Comment

Committee Response

requirements: 26.4.1.3.1 Compliance requirements:

(a) Shall comply with ASTM C1797. [CA181]

Renumber subsequent provisions.

For Commentary: Renumber and move provision to correct location. location.

fillers… R26.4.1.2.1(a)(3) Mineral fillers… 398.

Ken Harmon

784

9

Please remove the sentence: (d) Crushed hydraulic-cement lightweight concrete shall not be permitted [CA167]

Delete referenced sentence.

Rational:

(d) Crushed hydraulic-cement lightweight concrete shall not be permitted.

Any aggregate derived from crushed concrete (whether normalweight or lightweight) should be permitted as long as it meets the requirements for gradation, Lo s Angeles abrasion loss, sulfate soundness, contaminates, etc. Further, this requirement is not realistic or practical to enforce. Recycling operations accept containers and dump truck loads of concrete rubble from many different sites. This demolished concrete contains aggregates from many different sources and there is no way to easily

174 of 215


No.


Pg #

Line #

Public Comment

Committee Response

identify the concrete as lightweight versus normalweight before it goes into the system where it is broken down to remove rebar, pvc, etc. and then crushed and screened. 399.

Robinson

784

9

400.

Reid W. Castrodale

784

9

What is the basis for not allowing the use of crushed recycled lightweight concrete if it meets the s pecified requirements for the application in its re-use? 26.4.1.1.1(d) This article prohibits the use of recycled lightweight concrete.

See response to Comment 398, page 784, line 9, Harmon

See response to Comment 398, page 784, line 9, Harmon

What is the basis for not allowing the use of crushed recycled lightweight concrete to be used? Recycled concrete is such an unknown combination of various sources of concr ete that including lightweight concrete cannot be much different. I could find no reference to a commentary section that would explain this prohibition. Making such statements without apparently justification is problematic.

401.

Reid W. Castrodale

787

16

This may not affect new construction but could affect life-cycle assessments of a project if the concrete cannot be reused. Through line 18: 26.4.2.1(a) (15) I find this requirement very interesting. So after the project has been designed, the concrete supplier is required to supply the volumetric fractions of aggregate. How is the supplier going to know that Table 10.2.4.2 was used for designing the structure so he would know to make this submittal?

175 of 215

Not accepted. Think you mean Table 19.2.4. The provision is written to the LDP who will know how lambda was determined. The intent is for the concrete supplier to provide aggregate info so the LDP can confirm assumptions made during design. See response to comment 286. Page 530, line 6, Lobo.


No.


Pg #

Line #

Public Comment

Committee Response

And what is the designer going to do with that information – redesign the structure if his assumptions did not match those of the concrete supplied?

402.

Reid W. Castrodale

787

17

403.

Colin Lobo

789

7

404.

Colin Lobo

790

4

405.

Greg Moody

790

21

406.

Greg Moody

790

24

407.

Reid W. Castrodale

791

1

Using this approach to define lambda just seems ludicrous to me. It should be removed. 26.4.2.1(a) (15) Remove space after “19.” The title of this table seems incorrect without a percentage indicated. Suggest “expansion strain” be revised to “length change” to b e consistent with the terminology used in ASTM C1012 and in the specifications for cementitious materials that refer to this test method. Also consider stating “,%” in the title rather in the requirements section. Exposure Class W1 and W2 refer to concrete in contact with water. This differs from exposed to “moisture in service”. Consider changing this to “in contact with water” to be consistent. What about admixtures with a trace amount of calcium chloride? Is “cement” referring to portland only, or all cementitious material? Through line 4 26.4.2.2 This provision is not clear.

Accept as editorial change. Accept comment. 1. Change title of table to: “Maximum expansion strain length change for tests in accordance with ASTM C1012, %.” 2. Delete “percent” in the cells of the table. These are editorial changes to the code.” Accept comment. Change “moisture” to “water”.

Note: Sub A will look at these definitions as as new business to ensure that definitions for exposure classes are consistent. New business. Accept. Editorial change. Change to “cementitious materials” This change approved by CA070 but got missed here. Partially accepted. accepted. Editorial change. See below for proposed changes.

Possible revision: For lightweight concrete, a fresh density corresponding to the specified equilibrium density shall be established by t he concrete supplier. The fresh density shall be used as the basis of acceptance.

176 of 215

See also response to comment 426. Page 814, line 6, Castrodale.


No.


Pg #

Line #

Public Comment

Committee Response

Response to Comment 407

For lightweight concrete, the fresh density shall be determined in accordance with ASTM C138 and correlated that corresponds with the specified equilibrium density determined in accordance with ASTM ASTM C567. The fresh density correlated corresponding corresponding to the specified equilibrium density shall be used as the basis of acceptance. acceptance. 408.

Greg Moody

791

3

409.

Eric Koehler

792

27

410.

Mostafa Gad Alla

795

24

411.

James Baty, FACI

796

1

Through line 4: This acceptance criteria conflicts with the acceptance criteria found in 26.12.5.1(d) (page 814, lines 5-7) Section 26.4.3.1(b) states that concrete mixtures shall be established based on Article 4.2.3 of ACI 301; however, 26.4.4.1(a) states that strength shall be based on field records of the “same concrete mixture” or laboratory batches of “the proposed mixture”. This is more stringent than ACI 301, 301, which allows interpolation between similar mixtures (e.g. 4.2.3.4(b) and 4.2.3.4(c)(c) of ACI 301-16). 301-16). Modern, large concrete operations can have thousands of mixtures and interpolation between mixtures to establish a new mixture is completely acceptable. This conflict can be resolved by changing changing 26.4.4.1(1) to be consistent with ACI 301. Through page 797 line 15, clause 26.5.3: In 26.5.3 Curing, membrane – forming curing compound is mentioned in curing methods and it is mentioned only in curing of shotcrete. Please refer to ACI 308R-16 clause 3.4.2.3 page 18. Through line 3:

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Not accepted. This statement is only explaining why the correlation procedure is carried out. The acceptance criteria are in 26.12.5.1 as the comment points out. New business.

Comment is not entirely clear. clear. Think the commenter is asking asking for a list of curing methods for concrete placed by other than shotcrete. Will be considered as new business. S ee comment comment 411. Page 796, line 1-3, Baty New business. Will seek input from ACI 308 on this comment.


No.


Pg #

Line #

Public Comment

Committee Response

This section has not seen appreciable language change for decades, based on versions I have reviewed. This is now an excessively-restrictive provision that interferes with means and methods by professional contractors and producers. ACI 318 has broad application across the landscape of concrete construction and limiting statements like this handcuff quality installations when LDPs do not care to take the time or do not feel they are paid to take the time to understand proposals in accordance with item (c) found in lines lines 6-14. It also does not allow a construction team to interrupt protection in accordance with ACI 306 or 308. Proposed language to be: (a) Concrete shall be maintained at a temperature of at least 50˚F and in a moist condition for at least the first 7 days after placement unless a protection plan conducive to the specific nature of the element and environment is approved.

412.

Mostafa Gad Alla

796

4

413.

Mostafa Gad Alla

797

31

414.

Mostafa Gad Alla

798

3

415.

Robbie Hall Chair, ACI 117-B

801

19

The commentary statement is o ften never engaged because LDPs do not wish to take the liability or the time to understand the variety of methods that are not available to demonstrate sufficient strength gain for concrete in conditions less than 50˚F/moist. Please provide clear definition for high early strength concrete, as there is a clear definition for high strength concrete. Please specify the concrete temperature limits in hot weather Through line 4: Please specify the concrete temperature limits in hot weather or at lease mention compliance with ACI 305 to avoid big confusion with Engineer (consultants) especially in GCC area. Through line 21 and page 802 lines 1 through 2 and page 841 lines 13 through 15:

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New business. Will seek input from ACI 308 on this comment. New business. Comments 413 and 414 should be linked to be addressed. Will seek input from ACI 305 on this comment. comment. New business. Comments 413 and 414 should be linked to be addressed. Will seek input from ACI 305 on this comment. comment.

Agreed. The tolerance has been been revised to the following:


No.

Public Commenter Name Voting Member, CRSI Placing Committee Chair, CRSI Detailing Committee Vice Chair, CRSI Manual of Standard Practice Committee

Pg #

Line #

Public Comment

Committee Response

The introduction of this more restrictive tolerance is likely going to create situations where the tolerance is not achievable. After discussing this issue with a number of contractors, rebar fabricators and rebar placers, my main areas of concern are as follows:

NEW CODE 26.6.2.1 Design information: (c) Tolerance for spacing of hoops and spirals over one-half the distance from the joint face given in 18.4.2.4, 18.6.4.1(a); one-half the distance above and below the criti cal section given in 18.10.6.2(b)(i), and over the distance given in 18.4.3.3 and 18.7.5.1 in members of intermediate and special seismic systems: (1) +1/2 in. increase of larger of longitudinal bar diameter diameter and 1 in. Lesser of +1.5 +1.5 in. and +1.5 db of the smallest longitudinal bar. (2) Lesser smaller of -1 in. per ft of least side dimension of member and -3 in. (3) Spacing adjustments shall result in no more than two hoops being in contact with each other.

1)

Many times, these elements are pre-tied in a shop/yard and are flown into place upon arrival at the jobsite. Pre-assembly provides the best opportunity to control uniform spacing at the specified value, but it can still be difficult to maintain. 2) Beyond pre-tying cages, the only way to improve the uniformity is to use a cage assembly/ welding machine, which uses a thin wire that is welded between hoops to fix them in their correct locations before the longitudinal bars bars are installed. The proposed +1/2” tolerance has a good chance of being achieved using this method, but many engineers do not approve the use of this machine. 3) Commonly, ties/hoops in these elements are detailed/fabricated/tied detailed/fabricated/tie d using serpentine ties (continuously wrapped/overlapped ties) that are a single piece of rebar vs. numerous i ndividual (outer/inner/cross) ties placed as a set. set. Either way this is done, an offset of one bar diameter between adjacent individual ties or adjacent legs on a serpentine tie is created. created. This alone could result in exceeding the new tolerance, making this fabrication and placement method prohibited. 4) Over the last 8-10 years, the fundamental characteristics of these types of reinforced concrete elements has changed….moving to smaller diameter longitudinal bars. This change has a drastic affect affect on

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No.


Pg #

Line #

Public Comment

Committee Response

the rigidity of the cage and has caused an increase is confinement reinforcing. reinforcing. This added congestion makes installing the reinforcing difficult and makes installing other items (horizontal reinforcing, cross ties, intersecting slab/beam bars, inserts/embeds, etc.) very time consuming and in some cases impractical. Commonly the spacing of the ties/hoops needs to be adjusted to accommodate these items, but under the new tolerance, even a small adjustment would exceed the allowable value. 5) The way the tolerance is currently s etup, in many cases, a tie/hoop being moved towards another by ½” to 1”, it would exceed the allowable tolerance and cause the succeeding ties to be moved, which may or may not be possible depending on what else is already installed. This becomes impractical and unachievable. unachievable. Recommendation: ACI 318 committee should consider removing this new tolerance from the 318-19 code cycle, and leaving this section as written in 318-14 until further discussion can take place. Since this is important for both design, construction, rebar fabrication, and rebar installation professionals, this should be discussed with representatives from ACI 117 Committee and CRSI (specifically the Fabrication and Placing Committees) to discuss concerns and come up with a solution that works for all affected parties involved.

416.

Jim Tkach – Largo Concrete, Inc

801

19

Through line 21: Request the new tolerance shown in 26.6.2.1 (c) NOT be adopted at this time. A number of practical reasons warrant a thorough discussion, including those listed here: The change, as drafted…

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See response to Comment 415, page 801 line 19, Hall.


No.


Pg #

Line #

Public Comment

Committee Response

-

417.

Eric Peterson – Webcor Concrete

801

19

Significantly impacts production on standard concrete elements. Affords the designer a false sense of precision. Ignores the practical reality of current construction methods. Is not based on known industry research. Through line 21 and page 802 lines 1 through 2: Comments below are with respect to 26.6.2.1(c): As Chair of ACI Committee 117, Tolerances for Concrete Construction and Materials, I have been in contact with a number of representatives of reinforcing steel subcontractors who install reinforcing for members of intermediate and special seismic systems. This said, the comments below are mine, and do not necessarily represent those of the entire ACI 117 Committee. In most cases what is stated below is based upon my own experience with the structures we build. The installers I have been in contact with are very concerned with the proposed new tolerances 26.6.2.1(c)(1, 2 & 3) as either being impracticable or unachievable. Here are some of the difficulties as I have experienced or understand them: 1.

2.

Hoops are placed for the referenced element types mostly in a shop setting. Often times, the hoops are fabricated into what is referred to as serpentine ties. They are continuously wrapped and overlapped rather than being discrete hoops. This facilitates the production process, and eliminates numerous cross ties, but also can initiate an offset of one hoop diameter between adjacent wraps. This could result in exceeding the new tolerance. While the practice of assembling the hoops around the longitudinal bars, in a fabrication facility provides

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No.


Pg #

Line #

Public Comment

3.

a. b. c. d. e. f.

Committee Response

the best opportunity for uniform spacing, it is still a difficult tolerance to maintain. maintain. The best means available today involves using a cage assembly machine which uses a thin wire which is welded between hoops to fix them in their correct locations before the longitudinal bars bars are installed. Using this method the new +1 /2” tolerance has a good chance of being achieved. Many engineers do not approve the use of this machine, machine, however. Achieving this tolerance consistently through manual assembly, even in a shop would be difficult and costly. Since approximately 2012, the fundamental character of the reinforced elements for intermediate and special seismic systems has changed. In the past the longitudinal bars were heavier sections providing rigidity to the assembled reinforcing. reinforcing. Now, relatively small diameter longitudinal bars are in use accompanied by in an increase in confinement reinforcing. This added congestion has made the installation of all other reinforcing and other items which must be integrally part of the shear wall systems more difficult. After the assembled cages and and longitudinal reinforced elements are installed, in their physical locations in the struc ture, there are subsequent operations which must be completed prior to closing the formwork and placing concrete. Some of these are: Installing horizontal reinforcing; Installing cross ties; Installing link beam reinforcing; Installing slab and beam bars; Installing inserts; Installing formwork anchors and ties;

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No.


Pg #

Line #

Public Comment

Committee Response

g. Installing embedments and their anchors. Any of these operations can necessitate the adjustment of the pre-fabricated assembly. assembly. Even a small adjustment of hoop spacing under these circumstances can exceed the tolerance which ACI 318-19 has balloted. Again, maintaining hoop spacing with these new tolerances, I believe, will be impracticable if not unachievable. 4. The minus side tolerance is defined as being -1” per width of the element in feet up to a maximum of - 3”. In reality, anytime a hoop is adjusted, it has a plus side tolerance effect on one adjacent hoop and a concurrent minus side tolerance effect on the other. Therefore the +1/2” tolerance always governs, unless multiple hoops are adjusted to reduce the effect of exceeding the plus side tolerance. tolerance. Moving a succession of hoops may or may not be possible because of the transverse, horizontal reinforcing, cross ties and all other items described above (in 3.). 5. This is a question – What specific research was carried out to determine the value of to lerance 26.6.2.1(c)(1)? There are a lot of people I’ve discussed this with who would like to know where this came from. 6. This is also a question – Was there discussion within the Committee to assess the achievability of these tolerances within our Industry? If so, what was the determination and reasoning? 7. Please review the photo below. It depicts three wraps of a serpentine tie for for a single hoop layer. This method is common in Industry practice now. now. With respect to tolerances 26.6.2.1(c)(1 & 2) what would be the method of t olerance evaluation (measuring points). With respect to requirement 26.6.2.1(c)(3),

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No.


Pg #

Line #

Public Comment

Committee Response

does this condition comply or does it not comply? Clarity for both of these conditions would be helpful.

8.

Finally, it concerns me, having been involved in our Industry for over forty years that a ½” difference in spacing of hoops can be the cause of a buckling failure. What does this say about the robustness of the structural system itself? Why would an installer be the final link in the safety of this system with so little room for dimensional deviation?

Since I am not a rebar installer, I may not have represented all of the conditions which make t his tolerance impracticable, as well as they could be expressed expressed by an installer. I would ask Committee 318 to please reconsider these new tolerances prior to the publication of ACI 318-19, and to allow time on

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No.


Pg #

Line #

Public Comment

Committee Response

your Agenda for an open discussion of this matter in Quebec City, Quebec at the next next Convention. Perhaps a special breakbreakout session could be provided to determine a better path forward.

418.

Mike Mota

801

19

Thank you. Through line 21: I have been in contact with a number of our member companies who place reinforcing bars for structural members in intermediate and special seismic systems, and the following comments are based on these these conversations. These placers are very concerned with the proposed new tol erances; in short, the message that has been conveyed to me i s that the proposed tolerances are either impracticable or unachievable. Below is a summary of the issues: 9. Hoops for beams and columns in intermediate and special moment frames are often fabricated in the shop as serpentine ties, which are continuously wrapped and overlapped (rather than fabricated as individual hoops). This facilitates the production process and eliminates the need for numerous crossties. This method initiates an offset of one hoop diameter between adjacent wraps, which could result in exceeding the new tolerance, thereby making this fabrication process prohibited. 10.One of the best ways to achieve uniform spacing of hoops in a fabrication shop is to use a cage assembly machine, which uses a thin wire that is welded between hoops to fix them in their correct locations before the longitudinal bars are installed. The proposed +1/2” tolerance has a good good chance of being achieved using this method, but many engineers do not approve the use of this machine.

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No.


Pg #

Line #

Public Comment

Committee Response

11.The modern design trend in in termediate and special moment frame members is to use relatively small diameter longitudinal bars with relatively heavier amounts of confinement reinforcement. This results in congestion and makes installing all other reinforcing and other items much more difficult. Maintaining hoop spacing under these revised tolerances will exacerbate this condition and will make it virtually impossible to install the reinforcement. Furthermore, installing other items─including reinforcement (such as for slabs, beams, crossties, and link beams between shear walls), inserts, formwork anchors and ties, and embedment anchors─necessitates the adjustment of the prefabricated cages. The proposed tolerances can easily be exceeded where these small adjustments need to be made. 12.The proposed minus side tolerance of -1” per width of the element in feet up to a maximum of -3” is highly impractical and cannot be achieved achieved under typical conditions. For example, if the plus side of the tolerance is ½”, and a hoop is being adjusted in one direction, moving one hoop towards the adjacent hoop by 1” exceeds the minus tolerance from the adjacent hoop. This would require moving succeeding hoops, which may or may not be possible because of the transverse reinforcement, horizontal reinforcement, and crossties, to name a few. It is proposed that the existing tolerances for this reinforcement remain as is until further discussion or research can warrant a change.

419.

Michael Sipes – Regional Vice

801

19

Thank you. Through line 21 and page 802 lines 1 through 2: As Regional Vice President of a Furnish & Installation contractor in Northern California - a region widely known for

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No.

Public Commenter Name President, Pacific Steel Group

Pg #

Line #

Public Comment

Committee Response

the most demanding seismic engineering conditions - the proposed tolerance language language is impractible. The placing of reinforcing steel bars being our primary business, t olerance(s) appropriate with the work are paramount to a successful assembly of special seismic systems. systems. If only assembling boundary columns or frame beams were in question, the proposed tolerance would be difficult difficult to impossible, at best. In consideration that the reinforcing steel must also share space with embeds, inserts, electrical connections, plumbing penetrations and forming systems, the balloted tolerances houses restrictions such that constructing seismic elements will be set up for failure before a single bar is placed. The current code provides tolerances that allow the aforementioned items to cohabitate with the reinforcing steel designed. Structural Engineers of Record have the ability to prescribe more stringent tolerances in critical components o f the work where deemed deemed necessary/appropriate. necessary/appropriate. With knowledge that the proposed tolerance changes come from a need to restrict buckling, it would be my assertion that the SEOR can design special seismic systems such that the size of the primary members will eliminate buckling concerns and allow constructible containment tie spacings. The SEOR always has the ability to review conditions where inserts, penetrations or construction methods require modifications to the final position of containment reinforcing (often larger than t he detailed spacing but less than the detailed spacing plus allowable tolerance). Up to this point, I have commented on only the seismic system components themselves, but it is just as important to consider that these components typically work together with adjacent members such as shear walls, header beams, beams and more.

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No.


Pg #

Line #

Public Comment

Committee Response

In the case of a boundary element, wall reinforcing must be placed adjacent to and connect the wall to the boundary element with horizontal reinforcing. reinforcing. This horizontal reinforcing is typically detailed with a standard right angle that does not fit into the detailed tie spacing in conjunction with the detailed vertical reinforcing without adjustments. adjustments. Another example is when two seismic system members join together; a frame beam and frame column for example. Equally important is an accurate interpretation of the code and SEOR’s requirements as it relates to 3rd Party Inspections. Over the course of 20+ years in the Reinforcing Steel industry, I have first-hand experience with Inspectors holding tolerance concerns to an impractical level creating an environment where installation failure is guaranteed. Tolerances with minuscule tolerances will mandate that mechanical assembly by use of technology, welding etc. are the only option to reinforcing steel installers. Often times, the equipment required to perform this are either a) not approved on seismic elements or b) not accessible to all installers. This will create an environment where installers are precluded from an opportunity to construct projects simply due to their lack of technology. In an effort to not only speak to reasons for not approving the currently balloted tolerance changes, I would like t o propose that the current language not be modified, but encourage SEOR’s to design the primary components such that seismic system confinement can be detailed such that these cu rrent tolerances work. SEOR’s can also direct installers or constructors when conditions exist where tighter tolerances are required.

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No.

420.

Public Commenter Name Owen Brizgys, Construction Manager

Pg #

Line #

Public Comment

Committee Response

801

19

Through line 21: 26.6.2.1.c


The change to a more stringent tolerance on spacing of confinement ties seems like an overreach that will significantly impact the economy of Reinforced Concrete Structures in my area (California). What is the reason or research behind this? Is buckling bars the concern? I would like to see research. If tie spacing is 5.5” and goes to 8.5” (old 3” rule) on a #10 bar because of constructability (ties, embeds, fabrication) would result in a negligible reduction in buckling capacity when compared to the ultimate strength of the bar. This is typical confinement spacing for vertical elements in my area. When spacing is increased on one tie spacing, the spacing on the one above or below is decreased and the buckling capacity of this bar is at best, very hard to understand. Now put this in an array of vertical core wall steel and the problem becomes extremely complex and from the looks of it robust and redundant. Spalling Concrete – wouldn’t this be a function of thickness? Research needs to show that given the spacing that is currently in place, this creates a situation of unnecessary risk of concrete that needs addressing. Could an alternative be: None more than +3” on any hoop Not more than 25% more than +1/2”

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No.


Pg #

Line #

Public Comment

Committee Response

Somehow we need to not look at each tie/vertical as a single, fragile element but as a robust and redundant system that has resiliency when a few ties are more largely spaces.

The ACI should work to create research and methods to simplify, reduce and better understand the requirements on confinement reinforcing. It has become a driving force on the economy of these systems and the intuition of the contractor says compared to other structural types there seems adequate overstrength in these elements. How can we help!? Some photos that show typical seismic systems and tie spacing.:

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191 of 215


No.


Pg #

Line #

421.

Catherine French

804

16

Public Comment

Committee Response

In 26.7.1(h), the reference to 17.6 and 17.7 does not seem to be correct.

Agree Code Change: 26.7—Anchoring to concrete 26.7.1 Design information (h) For post-installed anchors, parameters associated with the design strength in accordance with 17.5 17.6 and 17.7, including anchor category, concrete strength, aggregate type, required installation torque, and requirements for hole drilling preparation.

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No.

422.


Pg #

Line #

804

22

Public Comment

Committee Response

26.7.1(i) For adhesive anchors, the type of lightweight concrete is listed as information that is needed. This is reasonable (if it is possible to determine the type or density if the anchor is to be post-installed) since Article 17.6.4 includes type of lightweight concrete.

Agree Page 804, Line 17 & 18: “with 17.6 and 17.7 17.4 and 17.5 including anchor category, concrete strength, aggregate type, type of lightweight concrete, required installation torque, and requirements for hole drilling preparation.”

However, the type of lightweight concrete (or its density) is also required for other conditions listed in Table 17.2.4.1.

423.

Greg Moody

811

12

424.

Greg Moody

813

1

425.

Greg Moody

814

6

426.

Reid W. Castrodale

814

6

427.

David P. Gustafson

817

26

428.

Catherine French

821

10

Therefore, the type of lightweight concrete (or its density) must also be required for Article 26.7.1 (h), and possibly for other articles, if it is indeed appropriate for this article. Is “at least” referring to the number of cores or to the diameter of the core? Is the 3-inch diameter actual actual diameter or nominal diameter? ASTM C1140 refers to ASTM C42, C42, which requires cores to have a diameter at of at least 3.70 inches. (6.1) Reference to 26.12.4 (acceptance criteria for shotcrete) does not make sense. I believe the reference reference should be to 26.12.6 Change “4” to “4.0” to correspond with the reporting accuracy of ASTM C138. 26.12.5.1(d) Recommended revision: “… fresh density correlated corresponding to …” Replace “reinforcing steel” with “reinforcement”.

I think that the compliance and inspection requirements have now all moved into Chapter 26. Please review and update to reflect the changes that have been made.

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Editorial change. At least refers to the number number of cores. Change to code to read: “…at least three 3‐in. nominal diameter cores…” Accepted. Editorial change. Accepted. Editorial change. Accept. Editorial change. See also response to comment 407. Page 791, line 1, Castrodale Agree Page 817, Line 26: “26.13.2.4 Verify Test reports shall be verified to confirm for weldability of reinforcing steel reinforcement . . “ Agree Delete R26.1.1 in its entirety.


No.


Pg #

Line #

Public Comment

Committee Response

R26.1.1 Chapter 17, Anchoring to Concrete, also contains design information, compliance requirements, and inspection requirements for anchoring to concrete 429.

430.

431.

ACI Staff

Eric Koehler

Reid W. Castrodale

827

827

828

13

22

11

Suggest decoupling statement “This same tolerance is acceptable for shotcrete”. 26.4.2. 1(a)(6) does not reference shotcrete air entrainment requirements. Suggest adding shotcrete air entrainments tolerance provision elsewhere.

The requirement for “calcium carbonate content” is unclear. The commentary allows up to 15% calcium carbonate from cement and mineral filler, but many mineral filler sources complying with ASTM C1797 are not pure calcium carbonate, so there could be more than 15% limestone added (e.g. 20% of a material that is 75% calcium carbonate). ASTM C595 requires 70% calcium carbonate for limestone used in blended c ements and the limit of 15% is not on calcium carbonate but on limestone (15% of a limestone with 70% calcium carbonate would be 10.5% calcium carbonate). The 15% requirement in ASTM C595 is based on mass of total blended cement, but the 15% requirement in 318 is based o n cementitious material not including mineral filler, which is correct because mineral filler is often used to not replace cement. So, the last sentence of R26.4.2.1(a)(8) stating that the criteria is the same as ASTM C595 is not accurate and should be removed. Through line 13: R26.4.2.1(a) Recommended revision to third sentence: “Acceptance of lightweight concrete at the time of delivery is based on a fresh density determined by the concrete supplier that has been correlated with the equilibrium density.”

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Stated comment not accepted. No change. 26.4.2.1(a) applies to all concrete regardless of how it is placed. Additional editorial change: 26.4.2.1(a)(6) should be modified to read “…from 19.3.3.1 or 19.3.3.3.” The commentary points out where the tolerance for air is specified. Accepted. Delete last sentence in R26.4.2.1(a)(8), page 827, line 22.” These same criteria are used to permit the use of blended cements conforming to ASTM C595 that contain up to 15% limestone in concrete exposed to sulfates.

Accept. Editorial change.


No.

Pg #

Line #

432.


828

17

433.

Eric Koehler

832

3

434.

435.

Catherine French

Catherine French

844

844

25

32

Public Comment

Committee Response

R26.4.2.1(a) Editorial – some characters are not displaying correctly. The commentary states that the code does not address AAR, but provisions were added to 26.4.2.1(a)(12) of the Code in this version.

Change made. Delete “alkali-aggregate reactions” on page 832, line 3.”

There are a number of issues with the Code and Commentary sections not corresponding. Please review. I have identified some examples. The commentary listed under R26.7.1(f) does not seem to go with the code section 26.7.1(f). In ACI 318 -14, this is commentary to 17.8.1. Please revisit where this should be located in ACI 318-19.

The following changes should be made for proper Commentary alignment:

The commentary listed under R26.7.1(g) does not seem to go with the code section 26.7.1(g). It is about adhesive anchors and should be changed to R26.7.1(i):

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The Code does not include provisions for especially severe exposures, such as chemical contact, high temperatures, temporary freezing-and-thawing freezing-and-thawing conditions during construction, abrasive conditions, alkali-aggregate reactions, or other unique durability considerations pertinent to the structure. Agree

Changed: R26.7.1(f) to R26.7.1(h) R26.7.1(g) to R26.7.1(i) R26.7.1(j) to R26.7.1(l) Deleted R26.7.2(a) R26.7.2(b) to R26.7.2(c) R26.7.2(d) to R26.7.2(e) R26.7.2(e) to R26.7.2(f) Agree See response to French Comment 434 page 844 line 25.


No.


Pg #

Line #

436.

Catherine French

846

8

Public Comment

Committee Response

The commentary listed under R26.7.2(b) does not seem to go with the code section 26.7.2(b)—it should be changed to R26.7.2(c):

Agree 26.7.1(h) For post-installed anchors, parameters associated with the design strength in accordance with 17.6 and 17.7, including anchor category, concrete strength, aggregate type, required installation torque, and requirements for hole drilling and preparation. R26.7.2(b) The Manufacturer’s Printed Installation Instructions (MPII) contain information required for the proper installation of post-installed anchors. Additional requirements may apply for specific cases in accordance with 26.7.1(f) and 26.7.1(g). For adhesive anchors, application dependent requirements for qualification of installers and inspection requirements may apply.

437.

Catherine French

846

13

The commentary listed under R26.7.2(d) does not seem to go with the code section 26.7.2(d)—it should be changed to

196 of 215

Agree


No.


Pg #

Line #

Public Comment

Committee Response

R26.7.2(e) AND the reference within R26.7.2(d) should be to 26.7.1(l) NOT 26.7.1(j):

Part 1 – See response to Comment #434 where “R26.7.2(d) should be R26.7.2(e).” Part 2 – See below: Commentary Change R26.7.2(de) Many anchor performance characteristics depend on proper installation of the anchor. Horizontally or upwardly inclined adhesive anchors resisting sustained tension load are required to be installed by personnel certified for the adhesive anchor system and installation procedures procedures being used. Construction personnel can establish qualifications by becoming certified through certification programs. Refer to R26.7.1(j).

438.

Catherine French

846

19

439.

Reid W. Castrodale

854

4

440.

Reid W. Castrodale

854

5

441.

Reid W. Castrodale

854

7

442.

David P. Gustafson

870

5

The commentary listed under R26.7.2(e) does not seem to go with the code section 26.7.2(e)—it should be changed to R26.7.2(f):

R26.12.5 Recommended revision to first sentence: “… equilibrium density, wc, should account for variations …” R26.12.5 Recommended revision to second sentence: “The impact of the tolerance in density on the value of lambda …” R26.12.5 Recommend adding this sentence at end of paragraph: “Reducing the tolerance on fresh density is not recommended.” Consider replacing “carry” with “support”.

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Agree See response to French Comment 434 page 844 line 25.

Partially accepted. Editorial change. Change to read: “… is intended to account…” Accept. Editorial change.

Not accepted. Proposed change does not make make an improvement.

Change “carry” to “resist”:


No.


Pg #

Line #

443.

Reid W. Castrodale

870

23

444.

Salem Faza

879

26

445.

Tennis

880

21

446.

Tennis

881

3

447.

Tennis

881

26

448.

Tennis

882

27

449.

Thomas Sputo Steel Deck Institute [email protected] m

883

24

Public Comment

Committee Response

R27.4.6.5 The term “unit weight” is used instead of density. Perhaps this is the preferred term when describing loads. I had not noticed that whether the term had been used elsewhere in the code. The referenced standard is an old one. The latest ASTM A1035 Specification reference is 2016b, ASTM A1035M-16b ASTM C150/C150M-18 is published and should be referenced. C150/C150M-19 has been approved and will be published in April 2019; should be referenced depending on the publication schedule for ACI 318. ASTM C595/C595M-18 is published and should be referenced. C595/C595-19 has been approved and will be published in April 2019; should be referenced depending on the publication schedule for ACI 318. ASTM C1157/C1157M-17 is published and should be referenced. Design and Control of Concrete Mixtures 16th edition has been published and is referenced on page 902. Recommend this citation be updated. Change date of Standard from C-2011 to C-2017. The 2017 edition is referenced in IBC 2017 and will be retained into IBC 2020

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“R27.4.6.1 It is important to apply the load at locations so the effects on the suspected deficiency are a maximum and sharing of the applied load with unloaded unloaded members is minimized. minimized. In cases where it is shown by analysis that adjoining unloaded member will help carry resist some of the load, the test load should be adjusted to produce appropriate load effects in the critical region of the members being evaluated. “ Disagree. The term “unit weight” weight” is typically used. Leave as is.

Accepted. Standards are being updated. Change to 2019 edition.

Change to 2019 edition.

Accepted. Standards are being updated. Accept as editorial change.

Accepted. Standards are being updated.


No.

450.

451.

452.

Public Commenter Name Thomas Sputo Steel Deck Institute [email protected] m Saman Abdullah

Fiorato

Pg #

Line #

883

883

887

Public Comment

Committee Response

25

Change date of Standard from C-2010 to C-2017. The 2017 edition is referenced in IBC 2017 and will be retained into IBC 2020

Accepted. Standards are being updated.

28

Change year to 2019. It will be published in the January 2019 issue of ACI St. Journal. This was confirmed with ACI St. Journal.

Agreed. Change date of publication from 2018 to 2019

Abdullah S, Wallace JW, “Drift Capacity of Structural Walls with Special Boundary Elements (2018),” ACI Structural Journal, accepted for publication (May 7, 2018), Bibliographic information is not complete and format is not correct.

Accepted. Editorial change to what is shown in red in previous column.

9

Bezerra-Cabral, Antonio Eduardo; Schalch, Valdir; Carpena Coitinho; DalMolin, Denise; Duarte-Ribeiro, José Luis, 2010, “Mechanical properties modeling of recycled aggregate concrete,” Construction concrete,” Construction and Building Materials, V. 24, No. 4, April, pp. 421- 430.

453.

454.

David Darwin

Andres Lepage

894

897

29

28

The reference by Ghimire, Darwin and O’Reilly is not cited in the commentary and should be deleted.

Delete reference to Huq et al. (2018) on Page 897 Lines 28-30. This reference is already on Page 898 Lines 16-18.

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Agree. Reason: This reference is not cited. Change: Ghimire, K.; Darwin, D.; and O’Reilly, M., 2018, “Anchorage of Headed Reinforcing Bars,” SM Report No. 127, University of Kansas Center for Research, Lawrence, KS, Jan., 278 pp. Delete the redundant reference.


No.


Pg #

Line #

Public Comment

Committee Response

Huq M. S.: Burgos, E. A.: Lequesne, R. D.: and Lepage, A., 2018, “High-Strength Steel Bars in T-shaped Concrete Walls,” Eleventh U.S. National Conference on Earthquake Engineering, Los Angeles, CA. 455.

456.

Andres Lepage

Tennis

898

14

The list of references show a few items out of alphabetical order, for example: Hwang and Moehle (2000) Page 898 Lines 14-15, Ichinose (1995) Page 898 Line 1. The overall list needs to be checked.

Change made.

911

30

Through line 31: Design and Control of Concrete Mixtures 16 th edition has been published. Recommend this citation be updated. Change to “Segura, CL and Wallace JW (2018a), “Seismic performance limitations and detailing of slender RC walls,” ACI walls,” ACI Structural Journal , 115(3), pp. 849-859. doi: 10.14359/51701918” The last author is missing for this reference. It should be changed as follows: Sperry, J., Yasso, S., Searle, N., DeRubeis, M., Darwin, D., O’Reilly, M., Matamoros, A., Feldman, L., Lepage, A., Lepage, A., and Lequesne, R., and Ajaam, A., 2017a, “Conventional and HighHigh Strength Hooked Bars —Part Bars —Part 1: Anchorage Tests,” ACI Structural Journal, V. 114, No. 1, Jan.-Feb. 2017, pp. 255-266.

Accept as editorial change. Coordinate with comment 448 page 882 line 27.

To support above comments (to Page 466 Line 4 and Page 573 573 Line 17), add new reference:

Change made.

457.

Saman Abdullah

915

2

458.

David Darwin

916

1

459.

Andres Lepage

919

9

Weber-Kamin, A. S., Lequesne, Lequesne, R. D., and Lepage, A., A., (2019). “RC Coupling Beams with High -Strength Steel Bars: Summary of Test Results,” SL Report 19 -1, The University of Kansas Center for Research, Inc., Lawrence, Kansas, September, 132 pp. The reference is available (free download) at https://iri.ku.edu/reports

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Agreed. Change reference as shown in the comment.

Agree. Sperry, J., Yasso, S., Searle, N., DeRubeis, M., Darwin, D., O’R eilly, M., Matamoros, A., Feldman, L., Lepage, A., and Lequesne, R., and Ajaam, A., 2017a, “Conventional and High -Strength Hooked Tests,” ACI Structural Journal , V. 114, Bars—Part 1: Anchorage Tests,” ACI No. 1, Jan.-Feb. 2017, pp. 255-266.

Weber-Kamin, A. S., Lequesne, R. D., and Lepage, A., (2019). “RC Coupling Beams with High-Strength Steel Bars: Summary of Test Results,” SL Report 19 -1, The University of Kansas Center for Research, Inc., Lawrence, Kansas, September, 132 pp.


No.


Pg #

Line #

460.

Carson Baker (CPL)

932

15

Public Comment

Committee Response

Line number is estimate, Table A.9.1: Grade 80 and Grade 100 bars provisions have now been introduced throughout ACI 318-19. However expected strengths have not been provided for A615 Grade 80 bars, A615 Grade 100 bars, or A1035 Grade 100 bars. Specification of expected strengths is required for modeling expected response in NLRHA procedures, and would be helpful if provided.

At the time Appendix X was drafted and approved by Committee 318 there was not available test data that would have supported the inclusion of the values requested. Based on statistical information collected by Subcommittee R, which provided information to modify Table A.9.1 of Appendix A, Subcommittee N approved the inclusion of the aforementioned information as a response to the comments received. Subcommittee N requests to approve the modification shown of Table A.9.1 as a substantive c hange: Table A.9.1 Expected material strengths Material Concrete

Expected strength

fce = 1.3 f c 1

Reinforcing Steel

A615

A706 A1035 1

Expected Yield Strength, f ye , psi

Expected Tensile Strength, f ue , psi

Grade 60

70,000

106,000

Grade 80

90,000

120,000

Grade 100

108,000

138,000

Grade 60 Grade 80 Grade 100 Grade 100

69,000 85,000 105,000 131,000

95,000 112,000 133,000 165,000

Expectedstrength

 f  ce is strength expected at

approximately one year or longer.

461.

David P. Gustafson

934

6

Line number is estimate, fourth line of RA.10.2: Sixth line from the top of the page - Consider replacing “carrying capacity” with “strength”.

The 318 Committee thanks the commenter for the suggestion. Loss of gravity load carrying capacity depends on several factors and is not limited to just strength. The test data to be used to establish the ultimate deformation capacity is related to the Collapse Prevention Acceptance Criteria in ACI 369.1 and ASCE/SEI 41. The Committee prefers the way it is written and the direct link to the referred documents. No change made.

462.

Carson Baker (CPL)

936

6

Line number is estimate, A.11.3: Per TBI and LATBSDC provisions, the Bias factor is taken as 1.0 unless explicitly computed per the equation p rovided. However in ACI 318-19 only equation A.11.3 is provided. Is it the intent of the committee that the Bias factor i s always to be computed, and could even be required to be taken as less than

The 318 Committee unlinked the approach implemented in ASCE 7 of modifying the strength reduction factors, clearly within the domain of Committee 318, and combining them into the Bias factor. Notwithstanding, a default value of 1.0 is set. It shall be permitted, to compute the Bias factor through equation (A.11.3)

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No.


Pg #

Line #

Public Comment

Committee Response

1.0? If not, language should be added such that the bias factor need not be taken as less than 1.0.

but a lower limit of 1.0 is added to equation A.11.3. The corresponding section A.11.3 has been modified to: Section A.11.3 shall be modified to the following, as a substantive change: Original section A.11.3 as balloted and approved was: A.11.3 Bias A.11.3 Bias factor, B factor, B , shall be calculated by:

B = 0.9Rne Rn

(A.11.3)

New proposed section is: A.11.3 Bias A.11.3 Bias factor, B factor, B , shall be taken as 1.0. Alternatively, it shall be permitted to calculate B u si si n equation(A.11.3).

B = 0.9Rne Rn  1.0

463.

Subcommittee B

A/C

The original language of 26.7.2 was correct before a change proposal caused it to be struck. Reinsert language as as shown in 26.7.2.

(A.11.3)

Public Comment Version Language: 26.7.2 Compliance requirements: (ac) Post-installed anchors shall be installed in accordance with the manufacturer’s instructions. Post-installed adhesive anchors shall be installed in accordance with the Manufacturer’s Printed Installation Instructions (MPII). Should actually be: (c) Post-installed anchors shall be installed i n accordance with the manufacturer’s instructions. Post-installed adhesive anchors shall be installed in accordance with the Manufacturer’s Printed Installation Instructions (MPII).

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I have just summarized the requirements requirements of Draft ACI 318-19 for the use of high strength rebar in tabular form.

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Comment on lap splices in ordinary walls - William Pollalis, Santiago Pujol, Robert Frosch The figure below shows drift capacities measured in the tests described in the appendix to this note. In all test specimens, lap splices meeting the new ACI 318 code 1 were subjected to tension in areas with either constant or varying moment. Cross sections and bar configurations resembled what may be found near boundaries of structural walls with rectangular cross sections and no special confining hoops. 2 In all tests3, failure has been abrupt and has been caused by bursting stresses related to bond along lap splices in longitudinal bars. The test results suggest that the code, as it stands, would produce lap splices leading to bar stresses equal or higher than the yield stress. Yielding, however, does not always result in adequate deformation capacity. Deformation capacity depends not only on bar bar stress but also on how pronounced pronounced strain hardening is 4, 5 how curvature is distributed along the length of the element, and the effect of load cycles. Code provisions for bond have focused on bar force or stress almost exclusively, with little attention to deformability. This note deals with seismic applications, and in those, deformability (strain instead of stress in the bar) is the key factor to ensure adequate performance. From the figure below, a simple linear projection of the measured drifts suggests that (for minimal detailing and cover, and for cyclic loads) the proposed 318-19 code may produce structural walls with drift capacities as low as ½ to 1%. The new provisions ban the use of lap splices near bases of special structural walls. That is likely to address our concern in such walls. But ‘ordinary walls,’ although not addressed for seismic applications in the ACI318 code, can still be used in regions of moderate seismicity. In those walls, lap splices can be used near wall bases for grades as high as 100 ksi. Given: 1) 2) 3) 4) 5)

The great uncertainty related to the prediction of ground motion, The need to rely on ductile response to produce structures that can survive earthquakes, The catastrophic nature of splice failure, That bar stress and strain do not increase linearly with increases in development length, The introduction of higher steel grades that may require developing stresses nearly twice as high as those reached in Grade-60 bars,

we are convinced ACI 318 should prevent the use of lap splices in longitudinal bars near bases of structural walls in

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Appendix Tables 1 and 2 and Figures 1 to 7 describe the specimens discussed in the public comment. All specimens were fabricated using normal-weight concrete with the nominal proportions listed in Table 2. All specimens were cured under wet burlap for 3 to 21 days to control concrete strength. Dimension tolerances did not exceed ¼”. All specimens use #8 longitudinal reinforcing bars. Steel reinforcing bars were reported to meet ASTM A615 and additionally meet ASTM A706 mechanical requirements. Values of concrete strength f' c (at age of testing) and f y reported in Table 1 were averages of at least 3 tested samples. Beams denoted with the letter T were cast “upside down”, with the lap splices located near the bottom of the formwork. Other specimens specimens were cast “on their sides” to limit the casting depth to less than 12 in. Casting positions were selected to minimize “top casting effects”. Beams were tested under four-point bending, subjecting lap splices to tension in a constant moment region between the intermediate forces. Test wall W-60-U W-60-U was “fixed” at its base while subjected to uniaxial cyclic uniaxial cyclic lateral forces (along its plane) and axial loading of 400 kips (equivalent to approximately 0.1P n). Lap splices in the test wall were located at the base of the wall. Applied forces were measured with transducers with accuracies of up to 200 lbf. Displacements were measured with devices reliable to 0.01 in. Reported drift ratios are the maximum lateral displacement (midspan for the beam and top of specimen for the wall) divided by half the span of the constant moment region in beams and divided by the wall height in structural wall test.

Table 1 - Specimen Properties b

fy

Nominal

(in)

(ksi)

f y (ksi)

(in)

(in )

30

8

65

60

4.3

1.3

0.22

5

60

41

1.5

1.3%

10

30

8

66

60

4.1

0.8

0.22

5

60

54

1.1

0.6%

Minimal

10

30

8

63

60

5.9

1.3

0.22

10

60

44

1.4

1.0%

Minimal

10

30

8

63

60

5.2

1.3

0.22

10

60

47

1.3

1.0%

Constant

Minimal

10

30

8

63

60

6.3

1.3

0.22

10

60

42

1.4

0.9%

WB-60-U0

Constant

Minimal

14

48

10

60

60

5.4

1.6

0.22

6

60

34

1.8

2.2%

WB-60-U1

Constant

Improved

14

48

10

72

60

5.8

1.6

0.22

6

50

33

1.5

3.0%

WB-60-U2

Constant

Improved

14

48

10

72

60

6.0

1

0.22

6

60

44

1.4

3.3%

WB-60-U3

Constant

Improved

14

48

10

72

60

6.2

1

0.22

6

60

43

1.4

3.2%

WB-60-U4

Constant

Improved

14

48

10

72

60

5.6

1

0.22

6

60

45

1.3

2.5%

WB-60-U5

Constant

Minimal

14

48

10

72

60

5.7

1

0.22

6

60

45

1.3

1.4%

WB-80-U1

Constant

Improved

14

48

10

90

80

5.3

1

0.4

12

80

74

1.1

1.7%

WB-80-U2

Constant

Improved

14

48

10

90

80

5.2

1

0.4

12

80

75

1.1

1.3%

W-60-U

Varying

Improved

33

84

10

72

60

5.3

1

0.22

6

60

46

1.3

1.9%

Moment

Transverse

Span

Gradient

Reinf. Detail

(ft)

T-60-8-A

Constant

Minimal

10

T-60-8-B

Constant

Minimal

T-60-8-D

Constant

T-60-8-E

Constant

T-60-8-F

Seri Series es

Spec Specim imen en ID

Richter (2012) Hardisty (2015)

Pollalis (2018)

h (in)

f'c (ksi)

Table 2 - Nominal concrete mix proportions

Series

Cement (lb)

Sand (lb)

#8 crushed

pea

stone (lb)

gravel (lb)

water (lb)

w/c

Richter (2012) Hardisty (2015)

430 430

1600 1600

0 0

1800 1800

220 220

0.512 0.512

Pollalis (2018)

460

1500

1800

0

250

0.543

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cb

Atr 2

s (i (in) ls (db)

ls required by 318-19 (db)

Tested/

Drift

Required Ratio (%)

Figure 1 - ‘Minimum’ reinforcement detailing (Richter 2012, Hardisty 2015, Pollalis 2018)

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Figure 2 - ‘Improved’ reinforcement detailing (Pollalis 2018)

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Figure 3 - Beam (constant moment) test setup

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Figure 4 - Beam test splice failure

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Figure 5 - Structural wall (varying moment) test setup

Figure 6 - Structural wall splice failure

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Figure 7 - Structural wall load vs displacement

References Hardisty, J. N., Villalobos, E., Richter, B. P., and Pujol, S. (2015). “Lap splices in unconfined boundary elements.” Concrete International, 37(1), 51 – 58 – 58 Richter, 2012, 2012, “A New Perspective on the the Tensile Strength of Lap Splices in Reinforced Concrete Concrete

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Members.” Master’s thesis, Purdue Purdue Univ., West Lafayette, IN

ACI 318_2019_with comments & replies

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