proposal it1-1 (y= 19, yr=4 , n= 0 , nv=1 --100%) · it1 response: nonpersuasive. “designated...

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COMMENTS AND RESPONSES ON 2nd MEMBER ORGANIZATION BALLOT

PROPOSALS

PART 1

Proposal IT1-1 (Y= 19, YR=4 , N= 0 , NV=1 --100%)

Johnson (NV): This proposal seems irrelevant.

IT 1 Response: No Comment

Line (YR): Revise line 20 and 21: Buildings and other structures required to have enhanced safety or functionality, such as Occupancy Categories III and IV of ASCE 7, are required to have more strength than normal buildings structures in other Occupancy Categories to reduce damage to the structural system. Reason: Remove implication that buildings in Occupancy Category III and IV are not “normal buildings”.

IT 1 Response: Persuasive. Change to: “…more strength than structures in Categories I and II to reduce…”

Aschheim (YR): Consider editorial suggestions and wordsmithing as follows:

1. Lines 4, 5, and 30 hedge the issue of expected performance and uncertainty. I think it would be clearer to state on Lines 4 and 5:

“…The intent of these Provisions is to provide reasonable assurance of seismic performance that will:” followed by the three bullets, and to change lines 28- 30 to read:

IT 1 Response: Nonpersuasive. Committee wordsmithed this to death.

IT-1 chair went through each comment and several were basically editorial (persuasive) and countered several other comments and found them nonpersuasive. A motion was made to accept IT 1’s responses as listed and the PUC approved (18,0,0). This proposal moves to Member Organization ballot with the accepted editorial changes.

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“…In addition, large uncertainties as to the intensity and duration of shaking in any earthquake and the possibility of unfavorable response of a small subset of buildings or other structures prevent precise prediction of performance may prevent full realization of the intent. IT 1 Response: Persuasive.

2. Line 9: change “minimize” to “reduce”; change “when” to “where”

IT 1 Response: Partially persuasive. Do not change “minimize”. Change “when” to “where”.

3. Line 16: need to maintain parallel structure, or change to “…anchoring and bracing, and accommodation of…”

IT 1 Response: Persuasive. Change “accommodations” to “accommodation”

4. Line 22: change “control” to “reduce” (even though it would now read “…are

reduced to reduce…”).

IT 1 Response: Nonpersuasive.

Manley (YR): Just a few comments: • Shouldn’t this section be written in mandatory language? If the intent

of Part 1 is to recommend exceptions or additions to ASCE 7-05, it might be a bit more appropriate to use mandatory language.

IT1 Response: Nonpersuasive. This is the intent of the Provisions and is not a proposed change to ASCE 7. It is written in similar language to previous similar sections.

• 1st paragraph, last sentence: Modify to read “...and guidance for

anchoring, bracing, and structural drift accommodations of structural drift for nonstructural systems.”

IT1 Response: Nonpersuasive.

• 2nd paragraph, 1st sentence: Modify to read “...are required to have

more strength than normal buildings to reduce damage to the structural system.” Reason: I’m not sure what constitutes a normal building (are we talking about only Occupancy Category II buildings?). Also, what about “other structures”? It would be easier to delete the phrase...

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IT1 Response: Persuasive. See Line comment above.

• 2nd paragraph, last sentence: Delete “extremely”. It is redundant with the designation of “important.”

IT1 Response: Persuasive.

Sprague (YR): RE: Page 1, Line 8, “avoid loss of function in critical facilities; “ The term “avoid” is also used in the previous line for loss of life and in the following paragraph for collapse prevention. This implies a similar probability. I do not believe we can imply the same level of assurance when it comes to loss of function. Currently we use importance factors to develop functionality. I think we have a long way to go to imply this level of functionality. It is more appropriate to use the term “minimize” in line 8.

IT1 Response: Nonpersuasive.(but interesting) The committee debated if this section should describe the intent of the Provisions or the results or the Provisions. Since the section is titled “intent,” we stuck with that. We think the intent is to avoid.

RE: Page 1, Line 24, Add: “Further, the performance of the components of a building will determine if a building can remain functional following an earthquake. If functionality of the facility is to be a requirement, the following characteristics should be clearly listed: The vertical and horizontal ground shaking for a given functionality performance level The criticality of the components The intended performance of components The in-structure shaking of the components at the performance level ground shaking”

IT 1 Response: Nonpersuasive. This is far too detailed for this section.

Proposal IT1-3 (Y=16 , YR= 2 , N=6 , NV=0 --75%)

IT 1 chair reviewed each comment and provided the PUC a revised proposal incorporating all editorial comments. A limited discussion on the acceptance of Nonlinear Static Procedures outlined in ASCE 41 was conducted and it was determined that additional commentary on this subject would be helpful. There was significant discussion on the reference to ATC 63 which is not yet published. IT 1 chair offered to change the wording to say the “75% draft of ATC 63” anticipating no substantive changes towards the 100% final version. This was modified to reverse the initial motion and the PUC was asked to vote on not including the words “75%”. This modified motion passed (18,1,1). A final motion was made to accept the IT 1 responses of persuasive and nonpersuasive as listed and this passed (17,1,2).

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Wood (No): Please correct the typographical error in the first sentence of 11.1.4.2.4 “a designated seismic systems” should be either “a designated seismic system” or “designated seismic systems.”


The second sentence in this paragraph seems out of place. The section is entitled “Nonstructural Seismic Design” but this sentence addresses “designated seismic systems.” This provision should be moved to a different section of the proposal. What provisions govern the design of structural components that are not designated as part of the seismic-force-resisting system?

IT1 Response: Nonpersuasive. “Designated seismic systems” is a term used in the nonstructural chapter (Section 13.2.2).

Thompson (No): Pending the finalization and availability of ATC 63, I do not believe it is appropriate to reference this document at this time.

IT1 Response: Partially persuasive. Whatever ATC 63 document is available will be referenced. ATC 63 will be used as an example of probabilistic methods. See the proposed rewrite at the end of these comments.

Johnson (No): It has not been clearly established that for all sizes and types of construction ASCE 41 or similar methods are suitable for use for new buildings, with no other provisions.

IT1 Response: Nonpersuasive. ASCE 41 is a standard that includes nonlinear response parameters for elements detailed according to the code for new buildings. Entire new seismic systems can be inserted into existing buildings and designed using this standard It is not clear what is not suitable. .

Line (No): YR on Section 11.1.4.1. 11.1.4 Alternate Materials and Methods of Construction. Alternate materials and methods of construction to those prescribed in the seismic requirements of this standard shall not be used unless approved by the authority having jurisdiction. Substantiating evidence shall be submitted demonstrating that the proposed alternate, for the purpose intended, will be at least equal in strength, durability, and seismic resistance.

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Reason: Section 11.1.4 in ASCE 7-05 is applicable to cases considered as alternatives to seismic requirements of the standard. While I prefer current 11.1.4 in ASCE 7-05 over 11.1.4.1, additional modification of 11.1.4 is proposed to remove ‘‘strength’’ and ‘‘durability’’. Strength is addressed by ‘‘seismic resistance’’ and ‘‘durability’’ is vague in the context of seismic resistance and addressed by general provisions of the building code alternative methods clause.

IT 1 Response: Nonpersuasive. New section 11.1.4.1 is the same as the existing section 11.1.4.

N on Section 11.1.4.2 --- 11.1.4.2.4. Reason: (a) Defaulting to required peer review and need for a ‘‘preliminary submittal’’ on a project by project basis is excessive for many structures where use of proprietary components is common place. Examples in wood-frame include proprietary engineered wood products, connectors including fasteners and straps, and preservative treated wood products. The list of proprietary products grows substantially if section 11.1.4 is not made specific to compliance with seismic requirements as done in current Section 11.1.4 of ASCE 7-05.

IT 1 Response: Nonpersuasive. The procedures of Section 11.1.4.2 are not necessarily intended to apply to all proprietary products. This section does not change current local or ICC product approval processes. Note the first sentence of Section 11.1.4.2 that allows the authority having jurisdiction to use other approval processes.

(b) Reference to requirements of the ICC Performance Code, procedures in ASCE/SEI 41-06, and ATC 63 is better placed in Commentary where approaches can be briefly described as guidance for the user. Other concerns include potential for a circular reference to ICC Performance Code, pre-mature reference to ATC 63 in this proposal, and whether proposed design criteria lead to similar results.

IT1 Response: Partially persuasive. See proposed rewording at end of comments. This proposal should either be in Part 1 or Part 3, not lost in the commentary. It is primarily for building officials who now have no guidance for alternate means submittals.

(c) Is 11.1.4.2.4 repeating information for clarity? The intent of seismic provisions and requirements for alternative methods (Section 11.1.4) coupled with existing sections 13.2.5 and 13.2.6 provide the essence of the requirements for nonstructural components.

IT 1 Response: Nonpersuasive. 11.1.4.2.4 is giving a performance basis for nonprescriptive design of nonstructural systems.

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Aschheim (YR): My reservations have to do with 11.1.4.2.3. It seems to me that stated performance objectives in items 2 and 3 should vary with Importance.

IT1 Response: Persuasive. See rewording at end of comments

Also, I am unsure if ASCE/SEI 41-06 might be less restrictive in allowing NSP to be used more broadly than in our NSP Appendix. (A proposal to modify our NSP Appendix to limit its use for new design to heights less than 40 ft where detailed member evaluation is done recently passed TS-2 and will reach the PUC shortly).

IT 1 Response: Nonpersuasive. ASCE 41 has limitations on the use of NSP (although not limited to 40’ and the results of FEMA 440 are mentioned in the accompanying commentary. For the purposes of a format to establish design criteria for an alternate means criteria, ASCE 41 will be adequate.

Editorial: Line 18: insert comma to read “…description and, if applicable, design…” Line 23: insert hyphen to read “…performance-based…”


Gillengerten (No): The criteria in Section 11.1.4.2.3 are unsuitable for application to essential structures. For example, it would be inappropriate to design a hospital using ASCE 41 with a primary performance level of Collapse Prevention. I would change my negative vote to yes if the proposal was expanded to include Occupancy Category III and IV structures.

IT1 Response: Persuasive. See rewording at end of comments

Manley (No): I found the Reason statement to be very weak and would like the following questions answered before I consider changing my vote:

• What is the source of these requirements? • Have these been adopted and applied in any jurisdiction to date? • What is the need for this proposal? That is, how are ASCE and IBC

broken with respect to alternate means and methods? IT1 Response: Nonpersuasive. IT1 was given the charge by the PUC to develop guidance for alternate means and method proposal. As performance-based design becomes more common, more engineers and owners will see benefits in designs that may not meet the many prescriptive

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requirements in the general code. Local jurisdictions need guidance on how to review these proposals.

• Why is this being recommended for placement right up front in

Section 11 of ASCE 7? Couldn’t it be an appendix? IT1 Response: Nonpersuasive. Section 11.1.4 is existing and unchanged. Only details on possible approval processes have been added.

• What guidelines should be followed for the peer review?

IT1 Response: Peer review is now also required for Nonlinear Response History Analysis, Damping Systems, and Isolation Systems. Only the general areas of review are given. The specifics are determined on a case-by-case basis.

• In Section 11.1.4.2.3, are these the only appropriate documents? The

list doesn’t seem complete. For instance, what about the necessary resistance standards?

IT1 Response: The equivalent of resistance standards is included in ASCE 41 and ATC 63.

While, I initially believe that it is totally inappropriate to place this verbiage in Section 11.4 of ASCE 7 as the default requirement for alternate materials design and methods of construction, I think it might be something that would be appropriate for an appendix that could be independently adopted by jurisdictions.

IT1 Response: Nonpersuasive. The section allows the local jurisdiction to adopt its own acceptance criteria for alternate materials design and methods of construction. However, the wording has been softened in the proposed rewrite.

Cobeen (YR): Sec. 11.1.4.1 & 11.1.4.2. I generally support the proposal. I would like to see the intent of the word “complete” in Sec. 11.1.4.2.3 clarified (versus partial, isolated elements, incomplete systems).

IT1 Response: Persuasive. The sentence needs clarification. See proposed rewording.

I would also like to see some discussion of intent for items that do not fall under Sections 11.1.4.2.3 or 11.1.4.2.4. These issues might be handled in commentary discussion.

IT1 Response: Nonpersuasive.

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A performance basis is needed for nonstructural systems. Such a performance description is not available elsewhere. For example, an analytical design could be developed that meets the performance criteria (but does not have complete testing, experience data, or does not meet the prescriptive anchoring requirement of the code).

Proposal 2- 2(Y= 14 , YR= 3 , N=2, NV=3 --89%)

Hamburger (No): My negative is with respect to the proposal to change the trigger for dynamic analysis for regular structures in seismic design categories D, E, and F from a period-trigger to a height trigger. This is conceptually the wrong thing to do. While I do not dispute the author’s study, I believe that it did not adequately cover the full range of structures that engineers, in their cleverness will conceive, and which though less than 160 feet in height, should be analyzed using the more realistic modal response approach. Further, I do not find the fact that some structures will be forced by the current provisions to use dynamic analysis rather than ELF to be a persuasive reason for change. The fact is that is not burdensome to perform modal analysis. No engineer designs multi-story structures today without the aid of analysis software such as ETABs, SAP, RAM, STAAD, etc. All of these have the capability at no extra cost or effort to perform modal analysis. I do however, support the simplifications proposed for the table. Bachman (YR): : I still don’t like Table 12.6-2 as revised. I would suggest rather than a table a new section that would read something like this. New Section: Modal Response Spectra Analysis and Seismic Response History Analysis is permitted for all structures assigned to any Seismic Design Category. Equivalent Lateral Force Analysis is permitted for all structures assigned to Seismic Design Category A or B. Equivalent Static Analysis is permitted for structures assigned to Seismic Design Category D, E or F unless one or more of the following conditions

The Hamburger comment was based on the belief that TS 2 was trying to modify an existing trigger for analysis. Discussion by TS 2 members pointed out that they were not adjusting the trigger, but were in fact adding an additional trigger. Hamburger withdrew his negative. The Bachman comment was discussed and TS 2 pointed out a similar discussion was conducted within TS 2 during proposal development. TS 2 found the use of the table much more advantageous then text. A motion was offered to find the Bachman comment nonpersuasive and the PUC agreed (10,3,4). The other comments, even Manley’s No vote, were found to be editorial and TS 2 agreed to modify the proposal. The proposal passed without vote, as modified by edits, and will be forwarded to the Member Organizations for ballot.

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exist in which case Modal Response Spectra Analysis or Seismic Response History Analysis must instead be used:

1. The structure is regular, has a height greater than 160 feet of height and has a period of the structure T is equal to or greater than 3.5 Ts.

2. The structure is irregular and is greater than 160 feet in height. 3. The structure is irregular with horizontal irregularity type 1. 4. The structure is irregular with vertical irregularity type 1, 2 or 3.

Wood (YR): Suggest changing “less than or equal to” to “not exceeding” in two locations in Table 12.6-1. Gillengerten (YR): Since all but one entry in the table is “P”, do we need a table? The table lists structures with different attributes, but they are all treated the same. Manley (No): I’d like a simple clarification. The change to Table 12.6-1 shows “and all structures of light frame construction” in the third row under SDC D, E, F as deleted; however, in the Reason for Proposal, the table without markup shows the language as remaining in the first row under SDC D, E, F. If the language regarding light frame construction is meant to remain in the table, I will remove my negative.

Proposal 2-4 (Y=20, YR=1 , N=2, NV=3 --91%)

Hamburger (No): There are several reasons for my negative:

1. Design review is not required when elastic-plastic hysteretic assumptions are made in the pushover analysis. As indicated by TS2 this is most likely to be done in lower seismic design categories where designers generally have poor understanding of nonlinear seismic response. Elasto-plastic assumptions are totally inappropriate for the types of semi-ductile elements commonly used in such seismic design categories. Thus, persons using this provision could perform a pushover analysis of a structure with brittle or semi-ductile elements, neglect

The PUC was first briefed on what the proposal was attempting to accomplish. This Proposal revises the section on P-delta limits. The PUC took exception to adopting P-delta currently specified in ASCE 7-05. Consequently, the PUC kept the 2003 NEHRP Provisions position on P-delta as a place holder. Proposal 2-4 is a new proposal on P-delta to replace the original exception. Mark Aschheim of TS 2 defended this proposal on the PUC comments and found several of the YR comments persuasive. The Wood No vote was found nonpersuasive and the PUC voted (21,0,0) to approve this proposal as amended to be forwarded for member organization b ll

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their loss of strength at amplified displacement, demonstrate that their structure is stable, but completely overlook brittle or strength degrading behaviors that would lead to greater strength degradation and propensity for p-delta instability. If anything more design review should be provided if elasto-plastic assumptions are utilized.

TS 2 response: Persuasive. We have removed the exemption from Design Review.

2. In my opinion it is not enough to say that “compliance with the provisions of the nonlinear response history procedures of Chapter 16 are followed.” I believe the requirement should indicate that the shaking should use MCE ground motions and that a maximum permissible number of collapses (or failure to converge) per analysis suite should be specified, probably not more than 1 in 7, or 0 in 3.

TS 2 Response: Persuasive. We agree, and have made changes in the proposal to reflect this. The new proposed language may need to be updated if revisions to Chapter 16 are approved.

3. The format is editorially poor. If two exceptions are permitted, it should be reformatted to read: Exception. The stability coefficient, θ shall be permitted to exceed 0.10 if either of the following apply: 1. – pushover language 2. – nonlinear dynamic language

TS 2 Response: Persuasive. The suggested format has been followed.

I would vote in support of this, if the editorial wording of the exception is cleaned up, if the proposal to move pushover analysis into part 1 is adopted and the permissive language on elasto-plastic assumptions is removed.

Malley (YR): I am concerned about saying that design review is not required in Exception 1. My expectation is that engineers designing using pushover type approaches in SDC B and C may be in more need of design review than those in SDC D and E. I don’t think it is a good precedent to use SDC as the sole trigger for design review.

TS 2 Response: Persuasive. In response to the concerns of several voters, the exception to the requirement for design review has been eliminated from the proposal.

Wood (No): This proposal sets a huge analysis hurdle for buildings in lower Seismic Design Categories that do not satisfy the P-delta limit. I think that additional justification is necessary before requiring nonlinear static analysis for buildings that are permitted using ASCE 7-05.

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TS 2 Response: Non-Persuasive. The use of nonlinear static analysis to justify acceptability of buildings currently permitted using ASCE 7-05 is not the subject of this proposal; it is existing language previously approved by the PUC.

Harris (Yes): In the “Reason” add more description about just which items from proposal 2-3 must come forward to make this proposal successful.

TS 2 Response: Persuasive. The requirement that the Appendix move into Part I and that section references be updated has been added to the Reason statement.

Proposal 2-9 (Y=24, YR=1 , N=0, NV=1 --100%)

Harris (YR): Under the reason for proposal, modify the first paragraph (line 8) as follows: “…indicate that tall Special Reinforced Concrete Moment Frame buildings may fail…”

TS 2 Response: Persuasive. The reason statement will be modified accordingly.

Proposal 3-1 (Y=20 , YR= 2 , N=1 , NV=1 --96%)

Hamburger (No): In the table, it is not clear how the column headings Vs/Vso and G/Go are to be used. My vote will change to Y if The proposal is revised to capture this.

TS 3 Response: Persuasive. In the “Reason for Proposal” section, add the following paragraph:

TS 2 chair explained the purpose of the proposal was to reinsert the calculation of the minimum Seismic Response Coefficient ( Cs ) that was omitted from ASCE 7 Supplement No. 2. The only comment was found persuasive and the PUC approved this proposal by a vote of (25,0,0).

TS 3 reviewed each comment. Hamburger withdrew his comment and No vote when TS 2 described the use of each column heading. Likewise, Johnson withdrew his comment when TS 2 described the use of each method that the column data depicts. Other comments were considered editorial. Consequently, there was no need for a PUC vote and this proposal moves forward to a Member Organization ballot.

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The application of the vs/vs0 and G/G0 values is the same as in previous versions of the Provisions. The table is used to evaluate vs and G from site data that consists of vs0 and G0. In most cases, these factors enter through Eq. 19.2-3, which in turn utilizes Eq. C19-2 to C19-7, which have G as a parameter. The term vs enters for the alternative (simplified) approach represented by Eq. 19.2-5.

Wood (Yes w/comment): Please correct the typographical error, “FEME” should be “FEMA.”

TS 3 Response: Persuasive. I will correct the type-o in the “Reason for Proposal” section,

Johnson (YR): This proposal still does not answer the question of what value to use when each method provides a different answer. Can either method be used, with no consideration of the alternative?

TS 3 Response: Nonpersuasive. Not sure I understand the point being raised. The vs corrections are the square root of the G corrections, and hence both are equivalent since G0=ρvs0

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Aschheim (YR): Line 11: change “FEME” to “FEMA”

TS 3 Response: Persuasive. I will correct the type-o in the “Reason for Proposal” section,

Proposal 3-2 (Y=22, YR=1 , N=0, NV=1 --100%)

Line (YR): Show curve labels as SDS/2.5 = 0.2 and SDS/2.5 = 0.1 to clearly define the basis of the curves for linear interpolation (Section 19.2.1.2).

TS 3 Response: Nonpersuasive. The recommended suggestion would imply that the curves are only valid at those specific acceleration levels, which is incorrect and misleading.

Proposal 3-3 (Y=12, YR=6 , N=5, NV=1 --78%)

Line stated that he was satisfied with TS 3’s response and withdrew his comment. The proposal passes and moves on to Member Organization ballot.

TS 3 pointed out that several of the comments would be satisfied by the Campbell and Bozorgnia paper attached to this document. The other PUC comments centered around when and where this vertical ground motion spectra would be used. TS 3 agreed to add additional language in the Reason for Proposal to satisfy these various concerns. A motion was made to accept TS 3 responses and to support the revised proposal . TS 3 will revise and submit a proposal to be voted on by the Member O i i Th PUC d h i d l ((18 0 1)

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Kircher (YR): I have both technical and administrative reservations. Technical Reservation – Consistency of horizontal and vertical spectrum shapes – I trust the formulas have been vetted by the committee and are technically sound, but they seem overly complex (vertical spectrum shape is more complex than horizontal spectrum shape). Complexity implies a level of precision missing form the much simpler, horizontal spectrum shape. In general, only horizontal ground motions are used for building design and are, with rare exception, more important to building performance than vertical ground motions – why are we introducing such a complex spectrum shape for vertical ground motions (that really don’t matter 99 percent of the time) when we are using a simpler shape for horizontal ground motions (that do matter 99 percent of the time)?

TS 3 Response: Persuasive & Nonpersuasive. See summary paper by Campbell & Bozorgnia at the end of this document. Note the simple shape of the vertical spectrum that is being proposed in Fig. 7 (last page of summary paper).

Technical Reservation - Reason for Proposal – Requests by TS-2 and TS-8 to develop vertical ground motions is not an adequate reason for this proposal – reason should state why we really need these new ground motions in the Provisions.

TS 3 Response: Persuasive. The reason is there are many structures, especially nonbuilding structures, where the effect of vertical ground motions is very significant to the response of the structure. For example, suspended boilers, long span roof structures (stadiums and high bay aircraft assembly plants) are very sensitive to vertical ground motion effects. For this reason, it was determined to be very important to provide vertical spectra in the NEHRP Recommended Provisions in addition to horizontal spectra.

Administrative Reservation – We already have a Chapter 23 (Seismic Design Reference Documents) in the Provisions which I assume we are not proposing to eliminate (??). Further, this new material should probably be a section (in Chapter 11), rather than a new whole chapter.

TS 3 Response: Nonpersuasive. It was considered more appropriate to have it as a separate chapter; other chapters that need the vertical spectrum can refer to it.

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Bachman (YR): Comment: I would suggest changing the definition of Tv to Tv = the vertical period of vibration Reason: I expect the vertical spectra will be used for other modes besides the fundamental period. Also I would suggest that the Chapter numbering be noted as just convenience for NEHRP voting. Please leave it to the ASCE 7 Scope and Format Committee to decide where this section belongs.

TS 3 Response: Persuasive. TS-3 has no position on these matters and will accept whatever is deemed appropriate.

Wood (No): I am voting no on this proposal for four reasons: (a) insufficient information was provided to understand the context of the proposed changes (Observation correct), (b) no technical justification for the proposed changes were given (Observation correct),, (c) in my opinion, the provisions are overly complex (perhaps it is because they are new - TS-3 considers them simple), and (d) the provisions for calculating the period in the vertical direction are not defined (Structural engineers who use vertical motion should know how to compute the vertical period),. Each issue is discussed below.

(a) The vertical component of the ground motion is included in the design process in12.4.2.2, which defines Ev as 0.2SDSD. There is no discussion in this section about calculating a design vertical response spectrum. Please define where a design vertical response spectrum is required. If this provision will apply to all building structures, I strongly object. The reason for proposal will be expanded to describe what building apply, if any.

TS 3 Response: Nonpersuasive. Provisions are not to be used for all buildings, and they do not have to be used for any buildings. The reason for introducing vertical provisions is there are many structures, especially nonbuilding structures, where the effect of vertical ground motions is very significant to the response of the structure. For example, suspended boilers, long span roof structures (stadiums and high bay aircraft assembly plants) are very sensitive to vertical ground motion effects. For this reason, it was determined to be very important to provide vertical spectra in the NEHRP Recommended Provisions in addition to horizontal spectra.

(b) What was the basis for (23.1-1) through (23.1-4)? I am willing to accept that

the peak vertical ground acceleration is not always equal to one-half the peak horizontal ground acceleration and that the structure does not always act as a rigid body in the vertical direction, but additional information is needed.

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TS 3 Response: Persuasive. See summary paper by Campbell & Bozorgnia at the end of this document.

(c) The proposed vertical response spectrum is more complicated that the current horizontal response spectrum used for design. Is this level of complexity necessary? A simplification might be to assume that Sav = SDS for Tv < 0.2 sec, and that Sav = 0.5SDS for Tv > To. A linear interpolation could be used between the 0.2 sec and To.

TS 3 Response: Nonpersuasive. Note the simple shape of the vertical spectrum that is being proposed in Fig. 7 (last page of summary paper).

(d) ASCE 7-05 includes a description of the modeling assumptions that must be made when calculating T and approximate values, Ta. This type of information is also required for Tv.

TS 3 Response: Nonpersuasive. Structural engineers who use vertical motion should know how to compute the vertical period. If guidance is needed, then other TS committees can provide it.

Without addressing these issues, it is premature to consider this proposal.

Line (YR): Line 6 and 7: To match format used in 12.4.2 of ASCE 7, replace ‘‘shall be taken as given by Eq. 23.1-1’’ with ‘‘shall be determined in accordance with Eq. 23.1-1 as follows’’. Make similar revisions elsewhere. To match format in 11.4.5, group definition of ‘‘CV’’ with other terms defined following step 4.

TS 3 Response: Editorial. TS-3 has no preference; let’s let PUC decide.

Holmes (YR): Editorial: Suggest “For vertical periods” at line 6, 10, 13, 16, 25, be changed to “For response of building components in the vertical directions at periods…..”

TS 3 Response: Nonpersuasive. The vertical provisions apply to non-building structures also, but lets let PUC decide wording.

Only 2 committee members voted. Please explain.

Explanation: BSSC incorrectly reported vote. B. Murphy sent two emails to PUC members correcting the error. Vote was 11 Yes and 2 Not Voting.

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Large attached package of numbers and spectra not described (or referenced).

TS 3 Response: Persuasive. See summary paper by Campbell & Bozorgnia at the end of this document.

Johnson (No): While the determination of vertical spectra may be terrific (I can’t say), the propsal leads to the question of how to calculate, or even determine, the period of the fundamental vertical vibration mode of buildinhgs. As a result, the propsal creates more and larger questions than it answers.

TS 3 Response: Nonpersuasive. Structural engineers who use vertical motion should know how to compute the vertical period. If guidance is needed, then other TS committees can provide it.

Ghosh (No): I do not understand how an important proposal such as this can be offered without any explanation whatsoever. A big bunch of papers is provided following the proposal. There isn’t a single line of text in it. The figures tell me how the horizontal and vertical ground motion spectra compare – that certainly is no explanation. I do not find the tables understandable without help.

TS 3 Response: Persuasive. See summary paper by Campbell & Bozorgnia at the end of this document for background on development of the vertical spectrum. The reason for introducing vertical provisions is there are many structures, especially nonbuilding structures, where the effect of vertical ground motions is very significant to the response of the structure. For example, suspended boilers, long span roof structures (stadiums and high bay aircraft assembly plants) are very sensitive to vertical ground motion effects. For this reason, it was determined to be very important to provide vertical spectra in the NEHRP Recommended Provisions in addition to horizontal spectra.

Aschheim (YR): I have strong reservations about the precision expressed in Equations 23.1-1 and 23.1-2 and the precision and complication implied by defining so many segments to the response spectrum. As a starting point, the coefficients in these equations could be changed from 0.32 to 0.3 and from 19.2 to 20 with no loss of piecewise continuity. Perhaps it would be preferable to replace these two equations with a straight line from 0.3CVSDS at T=0 to 0.8CVSDS at T=0.05 sec.

TS 3 Response: Persuasive. (PUC recommended, change to .3 and 20 (rounding)). Equations should not be changed since they were in part based on statistical analysis of numerous ground-motion records. See summary paper by Campbell & Bozorgnia at the end of this document for background on development of the vertical spectrum.

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I have some reservations about the structure of the proposal (although this structure just continues what already is in ASCE 7). It is possible to get the impression from the first sentence of 23.1 that 23.1 addresses cases where site-specific procedures are not used, but later in 23.1 it becomes apparent that this section also has relevance where site-specific procedures are used. It might be better to restructure as follows:

23.1 could state that the design vertical response spectrum may be developed according to a prescriptive method described in 23.2 or according to site specific procedures subject to the limits of 23.3. A clause here would state that for vertical periods greater than 2.0 sec, site-specific procedures must be used. 23.2 would present the relevant equations and limits on Sav. 23.3 would present the limits for vertical periods less than 2.0 sec and for vertical periods greater than 2.0 sec. 23.4 would be the currently proposed 23.2. TS 3 Response: Nonpersuasive. Prefer to keep structure and wording as is.

Gillengerten (No): The Reason for Proposal gives no indication of the source or derivation of proposed provision. The tables are confusing – the formatting makes it difficult to follow and they are offered without explanation of what they are supposed to be showing. I would change my negative to yes if the reason for proposal was amended to explain the source or derivation of the proposed provisions, and the tables were clarified.


Manley (YR): Shouldn’t there be charging language up in Chapter 11? Otherwise, I wonder how the user is going to get to this chapter. Additionally, the charging language needs to specify the restrictions on this method as well. That is, Chapter 23 is only appropriate for vertical periods less and or equal to 2.0 sec. and that a site-specific procedure is required for vertical periods greater than 2.0 sec.

18

TS 3 Response: Persuasive. PUC members of TS-2 and TS-8 that wanted vertical proposal can decide.

Additionally, the paragraph that begins “In lieu of using the above procedure...” should

probably be moved up to the beginning of the section – it strikes me as buried.

TS 3 Response: Nonpersuasive. Prefer to keep sentence in its present location.

Klingner (No): I am voting Negative on this proposal because it has not been justified technically by TS-3, and because TS-3 has not shown a convincing degree of support for it. My Negative can be satisfied by the generation of convincing technical reasons why the proposal is better than the current situation, and by a convincing degree of technical support within TS-3 and the technical subcommittees that have requested this.


BSSC incorrectly reported vote. B. Murphy sent two emails to PUC members correcting the error. Vote was 11 Yes and 2 Not Voting.

19

Background Information on the Proposed Procedure for Developing Vertical Design

Response Spectrum Kenneth W. Campbell and Yousef Bozorgnia

Supporting Studies In the last three decades several investigators studied the characteristics of vertical

ground motion and their relationship with those of horizontal components (see, e.g., Niazi and Bozorgnia, 1989, 1990, 1991, 1992; Bozorgnia et al. 1993, 1995, 1996; Watabe et al., 1990; Silva, 1997; Amirbekian and Bolt, 1998; Bozorgnia and Campbell, 2004; among others). These studies showed that:

Vertical ground motion has richer high frequency contents than horizontal motion;

Vertical ground motion attenuates faster than horizontal motion, especially in the near-source areas;

Vertical-to-horizontal (V/H) spectral ratio is sensitive to the spectral period, the distance from the fault, and the local site conditions; and

V/H spectral ratio has a distinct peak at short periods that exceeds a value of 2/3 in the near-source region.

Some recent studies have focused on the shape of the vertical response spectrum. For example, a simple spectral shape for the vertical ground motion was proposed by Elnashai (1997) and Elnashai and Papazoglou (1997). They proposed a vertical acceleration response spectrum that consisted of a flat portion at short periods (0.05–0.15 sec) and a decaying spectral acceleration portion for periods longer than 0.15 sec.

Bozorgnia and Campbell (2004) extensively studied the shape of the vertical response spectrum and the V/H spectral ratio and proposed a simplified vertical response spectrum. They used a comprehensive database of near-source worldwide accelerograms that had been recorded since 1957. The list of earthquakes along with the number of recordings used in that study is provided in Table 1. After extensive analyses of the shape of the vertical and horizontal response spectrum and the V/H spectral shape, they proposed a vertical response spectrum that is relatively simple yet captures the key seismological characteristics of the vertical response spectra. Their simplified vertical response spectrum, which they considered to be suitable as a design spectrum, is shown in Figure 1. The amplitude of the flat portion of spectrum, vsA , is equal to the value of the vertical spectral acceleration at a vertical spectral period ( VT ) of 0.1 sec (i.e., 0.1VT = sec), as explained next. The flat portion extends to a corner period at 0.15VT = sec. For

0.15VT > sec, the preliminary vertical design response spectrum decays as

20

0.75(0.15 / )vsA T (1)

The corner period of 0.15 sec recommended by Bozorgnia and Campbell (2004) from their empirical analysis is consistent with that previously proposed by Elnashai (1997) and Elnashai and Papazoglou (1997). The ordinate of the flat potion of the spectrum ( vsA ) can be estimated according to one of the preliminary procedures for developing a vertical design spectrum defined below.

Case 1: Given the Vertical Spectral Ordinate at = 0.1VT sec

If an estimate of the vertical spectral ordinate at 0.1T = sec is available (e.g., from a seismic hazard analysis), this value can be used for the ordinate of the flat portion of the vertical design response spectrum (i.e., for 0.05 0.15VT≤ ≤ sec). Having this information is sufficient to generate the vertical design response spectrum, as shown in Figure 1.

The proposed vertical design response spectrum compared to that predicted by the vertical attenuation relationship of Campbell and Bozorgnia (2003) are presented in Figures 2 and 3. We conclude that the agreement between these spectra is reasonable over a wide range of seismological parameters.

Case 2: Given the Horizontal Spectral Ordinate at = 0.1VT sec

If only an estimate of the horizontal spectral ordinate at 0.1VT = sec is available (e.g., from a seismic hazard analysis or a national seismic hazard or design map), the ordinate of the flat portion of the vertical design response spectrum (see Figure 1) can be computed by multiplying this horizontal spectral ordinate by the corresponding ordinate of a simplified V/H spectral ratio at 0.1VT T= = sec as shown in Figure 4 (Bozorgnia and Campbell, 2004). The resulting estimate of vertical amplitude ( vsA ) can then be used to generate the vertical design response spectrum, as shown in Figure 1.

We demonstrate this method by using the 0.1-sec horizontal spectral ordinate obtained from the horizontal attenuation relation of Campbell and Bozorgnia (2004). The vertical design response spectra generated by this procedure, along with the actual vertical response spectra predicted from the same attenuation relationship, are compared in Figures 5 and 6. Considering the very limited information needed (only the horizontal spectral ordinate at 0.1T = sec) and its simplicity, this procedure would appear to be a reasonable, albeit somewhat conservative, alternative to developing a site-specific vertical design response spectrum for many practical engineering applications, including building codes.

Development of Design Procedure In order to be consistent with the shape of the design horizontal response spectrum,

the design vertical response spectrum has four vertical spectral period (Tv) regions. Based on the work of Bozorgnia and Campbell (2004), the periods that define these four

21

regions are generally independent of magnitude, distance, site conditions and other source and site parameters and can be treated as constants. In this respect, the shape of the vertical spectrum is simpler than that of the horizontal spectrum.

The definitions of the equations that are used to define the design vertical response spectrum in the four vertical spectral period regions are based on three observations made by Bozorgnia and Campbell (2004):

The short-period part of the spectrum can be uniquely defined by the amplitude of the 5% damped 0.1-sec vertical spectral ordinate;

The mid-period part of the spectrum is uniquely defined by an amplitude that decays as the inverse of the 0.75 power of period (see Equation 1), and

The amplitude of the short-period part of the V/H spectral ratio is a function of the distance from the earthquake source (for sites located within about 60 km of the fault) and site conditions.

Since the NEHRP provisions do not include seismic design maps for the 0.1-sec vertical or the 0.1-sec horizontal spectral ordinates or source-to-site distances, we modified the Case 1 procedure stated above as follows:

Use mapped 0.2-sec horizontal spectral ordinate to estimate 0.1-sec vertical spectral ordinate. In this process, we discovered that for earthquakes and distances for which the vertical spectrum might be of engineering interest (magnitudes greater than 6.5 and distances less than 60 km) the ratio of the vertical 0.1-sec and the horizontal 0.2-sec spectral ordinates have a nearly constant value of about 0.8 over all site conditions, based on the horizontal and vertical attenuation relationships developed by Campbell and Bozorgnia (2003).

Obtain the value of the 0.2-sec horizontal spectral ordinate from the NGA attenuation relationship of Campbell and Bozorgnia (2008) for magnitudes ranging between 6.5 and 8.0, distances ranging between 1 and 60 km, and NEHRP B-C site conditions. The NGA relationship for these calculations is used in order to be consistent with the use of this relationship in the 2007 update of the national seismic hazard maps. We would expect these results to be similar to those obtained using the average of all of the NGA attenuation relationships, based on comparisons that have been made with preliminary versions of these relationships. The NEHRP short-period site coefficients were used to estimate the values of the 0.2-sec horizontal spectral ordinate for other site conditions using the procedure defined in the NEHRP Provisions.

Given the estimated 0.1-sec vertical spectral ordinate, use the method given by Case 1 above to construct a simplified vertical design spectrum.

Details of the Proposed Procedure In the following sections we explain the bases for the equations in the proposed

procedure. Vertical Coefficient Cv

22

We used the dependence of the V/H spectral ratio on site conditions found by Campbell and Bozorgnia (2003) and Bozorgnia and Campbell (2004) and the dependence of the 0.2-sec horizontal spectral ordinate on distance and site conditions found by Campbell and Bozorgnia (2008) as discussed above to develop a vertical coefficient, Cv. This coefficient is used to estimate the short-period vertical spectral plateau from the horizontal spectral plateau. The dependence on horizontal amplitude is based on the mapped parameter Ss, the MCE spectral response parameter at short periods.

Note that since the 0.8 ratio between the 0.1-sec vertical spectral ordinate and the 0.2-sec horizontal spectral ordinate is applied to all of the equations that define Sav, this factor could also be included as part of the vertical coefficient, Cv, in order to simplify the equations even further. We have retained the independence of this parameter for the time being for the sake of transparency. Equation for Sav for Tv less than or equal to 0.025 sec

This equation represents that part of the design vertical response spectrum (Figure 7) that is controlled by the vertical peak ground acceleration (PGA). The 0.32 factor was calculated by dividing the 0.8 factor that represents the ratio between the 0.1-sec vertical spectral ordinate and the 0.2-sec horizontal spectral ordinate (see discussion above) by 2.5. The latter factor is the ratio between the 0.2-sec horizontal spectral ordinate and the peak horizontal ground acceleration used to develop the design horizontal response spectrum. The vertical coefficient, Cv, accounts for the distance and site dependence of the V/H spectral ratio as described above. The factors are applied to Sds, the design spectral acceleration response parameter at short periods, instead of to Ss to account for the fact that Sds has already had the site coefficient, Fa, and the two-thirds factor applied to it, which avoids an additional step in the development of the design vertical response spectrum (another simplification). Equation for Sav for Tv greater than 0.025 sec and Tv less than or equal to 0.05 sec

This equation represents that part of the design vertical response spectrum (Figure 7) that defines the linear transition from that part of the spectrum that is controlled by the vertical PGA and that part of the spectrum that is controlled by the short-period spectral plateau (see discussion below). The factor of 19.2 represents the factor required to make the transition piecewise linear between those parts of the spectrum that define the adjacent flat (period-independent) segments. Equation for Sav for Tv greater than 0.05 sec and Tv less than or equal to 0.15 sec

This equation represents that part of the design vertical response spectrum (Figure 7) that defines the short-period spectral plateau. All of the factors in this equation have already been defined above. Equation for Sav for Tv greater than 0.15 sec

This equation represents that part of the design vertical response spectrum (Figure 7) that decays with the inverse of vertical spectral period. The reason for the 0.75 power of this decay is describe above (see also Equation 1).

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Limits imposed on Sav

It is recommended that two limits be imposed on the equations used to develop the design vertical response spectrum (Figure 7): (1) that the spectrum not be used for Tv > 2 sec and (2) that the spectrum not be less than 50% of the design horizontal response spectrum. The reason for the first limit recognizes the fact that such large vertical spectral periods are rare (i.e., structures are inherently stiff in the vertical direction) and that the vertical spectrum might decay differently with vertical spectral period at longer periods. However, there is an allowance for developing a site-specific design vertical response spectrum if this limit is exceeded. The second limit recognizes the fact that a V/H spectral ratio of 0.5 is a reasonable lower bound for this ratio over the period range of interest, based on the results of Campbell and Bozorgnia (2003) and Bozorgnia and Campbell (2004), and preserves the relative conservatism that exists in the design horizontal response spectrum over this period range. REFERENCES

Amirbekian, R. V. and Bolt, B. A., 1998. Spectral comparison of vertical and horizontal seismic strong ground motions in alluvial basins, Earthquake Spectra 14, 573–595.

Bozorgnia, Y., and Campbell, K. W., 2004. The Vertical-to-Horizontal Response Spectral Ratio and Tentative Procedures for Developing Simplified V/H and Vertical Design Spectra, Journal of Earthquake Engineering, 8, 175-207.

Vertical ground motion: characteristics, relationship with horizontal component, and building-code implications, SMIP99 Seminar on

Bozorgnia, Y. and Niazi, M., 1993. Distance scaling of vertical and horizontal response spectra of the Loma Prieta earthquake, Earthquake Engineering and Structural Dynamics 22, 695–707.

Bozorgnia, Y., Niazi, M., and Campbell, K. W., 1995. Characteristics of free-field vertical ground motion during the Northridge earthquake, Earthquake Spectra 11, 515–525.

Bozorgnia, Y., Niazi, M., and Campbell, K. W., 1996. Relationship between vertical and horizontal ground motion for the Northridge earthquake, Eleventh World Conference on Earthquake Engineering, Acapulco, Mexico, Proceedings.

Bozorgnia, Y., Campbell, K. W., and Niazi, M., 1999. Vertical ground motion: characteristics, relationship with horizontal component, and building-code implications, SMIP99 Seminar on Utilization of Strong-Motion Data, San Francisco, Proceedings, California Strong Motion Instrumentation Program, Sacramento, CA, 23–33.

Campbell, K. W. and Bozorgnia, Y., 2008. NGA Ground Motion Model for the Geometric Mean Horizontal Component of PGA, PGV, PGD and 5% Damped Linear Elastic Response Spectra for Periods Ranging from 0.01 to 10 s. Earthquake Spectra 24, in press.

Campbell, K. W. and Bozorgnia, Y., 2003. Updated near-source ground motion (Attenuation) relations for the horizontal and vertical components of peak ground acceleration and acceleration response spectra, Bulletin of the Seismological Society of America 93, 314–331.

Elnashai, A.S., 1997. Seismic design with vertical earthquake motion, Seismic Design for the Next Generation of Codes (P.Fajfar and H.Krawinkler, Eds.), Balkema, Rotterdam, 91–100.

Elnashai, A.S. and Papazoglou, A.J., 1997. Procedure and spectra for analysis of RC structures subjected to strong vertical earthquake loads, Journal of Earthquake Engineering 1, 121-155.

Niazi, M. and Bozorgnia, Y., 1989. Behavior of vertical ground motion parameters in the near-field, Seismological Research Letters 60, 4.

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Niazi, M. and Bozorgnia, Y., 1990. Observed ratios of PGV/PGA and PGD/PGA for deep soil sites across SMART-1 array, Taiwan, Fourth U. S. National Conference on Earthquake Engineering, Palm Springs, CA, Proceedings 1, 367–374.

Niazi, M., and Bozorgnia, Y., 1991. Behavior of near-source peak vertical and horizontal ground motions over SMART-1 array, Taiwan, Bulletin of the Seismological Society of America 81, 715–732.

Niazi, M., and Bozorgnia, Y., 1992. Behavior of near-source vertical and horizontal response spectra at SMART-1 array, Taiwan, Earthquake Engineering and Structural Dynamics 21, 37–50.

Silva, W., 1997. Characteristics of vertical strong ground motions for applications to engineering design, FHWA/NCEER Workshop on the National Representation of Seismic Ground Motion for New and Existing Highway Facilities, Burlingame, CA, Proceedings, Technical Report NCEER-97-0010, National Center for Earthquake Engineering Research, Buffalo, New York.

Watabe, M., Tohido, M., Chiba, O., and Fukuzawa., R., 1990. Peak accelerations and response spectra of vertical strong motions from near-field records in USA, Eighth Japan Earthquake Engineering Symposium, Proceedings 1, 301–306.

25

Table 1. Database of strong-motion recordings (Bozorgnia and Campbell, 2004)

No. of Recordings Earthquake Location Year MW Faulting

Mechanism Horizontal Vertical Daly City California 1957 5.3 Reverse Oblique 1 1 Parkfield California 1966 6.1 Strike Slip 4 4 Koyna India 1967 6.3 Strike Slip 1 1 Lytle Creek California 1970 5.3 Reverse 4 4 San Fernando California 1971 6.6 Reverse 9 9 Sitka Alaska 1972 7.7 Strike Slip 1 1 Stone Canyon California 1972 4.7 Strike Slip 2 2 Managua Nicaragua 1972 6.2 Strike Slip 1 1 Point Magu California 1973 5.6 Reverse 0 0 Hollister California 1974 5.1 Strike Slip 1 1 Oroville California 1975 6.0 Normal 1 1 Kalapana Hawaii 1975 7.1 Thrust 0 0 Gazli Uzbekistan 1976 6.8 Reverse 1 1 Caldiran Turkey 1976 7.3 Strike Slip 1 1 Mesa de Andrade Mexico 1976 5.6 Strike Slip 0 0 Santa Barbara California 1978 6.0 Thrust 1 1 Tabas Iran 1978 7.4 Thrust 3 3 Bishop California 1978 5.8 Strike Slip 0 0 Malibu California 1979 5.0 Reverse 0 0 St. Elias Alaska 1979 7.6 Thrust 1 0 Coyote Lake California 1979 5.8 Strike Slip 9 9 Imperial Valley California 1979 6.5 Strike Slip 37 37 Livermore California 1980 5.8 Strike Slip 0 0 Livermore Aftershock California 1980 5.4 Strike Slip 0 0 Westmorland California 1981 6.0 Strike Slip 0 0 Coalinga California 1983 6.4 Thrust 46 46 Morgan Hill California 1984 6.2 Strike Slip 24 24 Nahanni Canada 1985 6.8 Thrust 3 2 North Palm Springs California 1986 6.1 Strike Slip 12 12 Chalfant Valley California 1986 6.3 Strike Slip 0 0 Whittier Narrows California 1987 6.0 Thrust 91 90 Whittier Narrows Aftershock California 1987 5.3 Reverse Oblique 9 9 Elmore Ranch California 1987 6.2 Strike Slip 1 1 Superstition Hills California 1987 6.6 Strike Slip 2 2 Spitak Armenia 1988 6.8 Reverse Oblique 1 0 Pasadena California 1988 5.0 Strike Slip 0 0 Loma Prieta California 1989 6.9 Reverse Oblique 29 29 Malibu California 1989 5.0 Thrust 0 0 Manjil Iran 1990 7.4 Strike Slip 3 3 Upland California 1990 5.6 Strike Slip 2 2 Sierra Madre California 1991 5.6 Reverse 4 4 Landers California 1992 7.3 Strike Slip 8 8 Big Bear California 1992 6.5 Strike Slip 1 1 Joshua Tree California 1992 6.2 Strike Slip 0 0 Petrolia California 1992 7.0 Thrust 5 5 Petrolia Aftershock California 1992 7.0 Strike Slip 0 0 Erzincan Turkey 1992 6.7 Strike Slip 1 1 Northridge California 1994 6.7 Thrust 108 108 Kobe Japan 1995 6.9 Strike Slip 15 15

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Table 2. Distribution of recordings by faulting mechanism and local site conditions

No. of Recordings

No. of Events

Minimum Magnitude

Maximum Magnitude Category

Hor. Vert. Hor. Vert. Hor. Vert. Hor. Vert.

Faulting Mechanism

Strike slip faulting 127 127 20 20 4.7 4.7 7.7 7.7

Reverse faulting 58 57 8 7 5.3 5.3 6.9 6.9

Thrust faulting 258 255 8 7 6.0 6.0 7.6 7.4

TOTAL 443 439 36 34 – – – –

Local Soil Conditions

Firm soil 241 240 30 29 4.7 4.7 7.4 7.4

Very firm soil 84 83 14 14 4.7 4.7 7.0 7.0

Soft rock 63 62 9 8 5.3 5.3 7.6 6.9

Firm rock 55 54 21 21 5.3 5.3 7.7 7.7

TOTAL 443 439 – – – – – –

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Figure 1. Vertical design response spectrum proposed by Bozorgnia and Campbell (2004)

0.01 0.1 1 10Period (sec)

Vert

ical

Spe

ctra

l Acc

eler

atio

n (g

)

Vertical Design Spectrum

Avs = Vertical PSA @ T =0.1 sec

T =

0.15

sec

Avs ( 0.15 / T )0.75

28

0.01 0.1 1 10Period (sec)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Vert

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l Acc

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n (g

) rseis= 3 kmrseis=10kmrseis=20km

Strike slip, Firm soil, M 7.5

0.01 0.1 1 10Period (sec)

0.0

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0.8

1.0

1.2

1.4

1.6

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Thrust, Firm soil, M 7.5

0.01 0.1 1 10Period (sec)

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Thrust, Firm rock, M 7.5

29

Figure 2. Preliminary vertical design response spectra proposed by Bozorgnia and Campbell (2004) for their “case 1 alternative” for a magnitude 7.5 earthquake derived from the vertical spectral ordinate at 0.1 sec (dashed lines) compared to the vertical response spectra predicted from the attenuation relationship of Campbell and Bozorgnia (2003) (solid lines).

30

0.01 0.1 1 10Period (sec)

0.0

0.2

0.4

0.6

0.8

1.0

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1.4

1.6

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Strike slip, Generic soil, M 6.5

0.01 0.1 1 10Period (sec)

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0.01 0.1 1 10Period (sec)

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0.01 0.1 1 10Period (sec)

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Thrust, Generic rock, M 6.5

31

Figure 3. Preliminary vertical design response spectra proposed by Bozorgnia and Campbell (2004) for their “case 1 alternative” for a magnitude 6.5 earthquake derived from the vertical spectral ordinate at 0.1 sec (dashed lines) compared to the vertical response spectra predicted from the vertical attenuation relationship of Campbell and Bozorgnia (2003) (solid lines).

0.01 0.1 1 10Period (sec)

0.0

0.5

1.0

1.5

2.0

V/H

Rat

io

rseis=3 km

Simplified V/H for Firm Soil

rseis=60 km

rseis=10 km

rseis=20 km

(a)

0.01 0.1 1 10Period (sec)

0.0

0.5

1.0

1.5

2.0

V/H

Rat

io

rseis ≤ 20 km

Simplified V/H for Firm Rock, Soft Rock, Very Firm Soil

rseis=60 km

(b)

32

Figure 4. Simplified V/H response spectral ratio proposed by Bozorgnia and Campbell (2004).

33

0.01 0.1 1 10Period (sec)

0.0

0.2

0.4

0.6

0.8

1.0

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Strike slip, Firm soil, M 7.5

0.01 0.1 1 10Period (sec)

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0.01 0.1 1 10Period (sec)

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34

Figure 5. Preliminary vertical design response spectra proposed by Bozorgnia and Campbell (2004) for their “case 2 alternative” for a magnitude 7.5 earthquake derived from the horizontal spectral ordinate at 0.1 sec (dashed lines) compared to the vertical response spectra predicted from the vertical attenuation relationship of Campbell and Bozorgnia (2003) (solid lines).

0.01 0.1 1 10Period (sec)

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

Vert

ical

Spe

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l Acc

eler

atio

n (g


Strike slip, Generic soil, M 6.5

0.01 0.1 1 10Period (sec)

0.0

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1.2

1.4

1.6

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Thrust, Generic soil, M 6.5

0.01 0.1 1 10Period (sec)

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Strike slip, Generic rock, M 6.5

0.01 0.1 1 10Period (sec)

0.0

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1.2

1.4

1.6

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Thrust, Generic rock, M 6.5

35

Figure 6. Preliminary vertical design response spectra proposed by Bozorgnia and Campbell (2004) for their “case 2 alternative” for a magnitude 6.5 earthquake derived from the horizontal spectral ordinate at 0.1 sec (dashed lines) compared to the vertical response spectra predicted from the vertical attenuation relationship of Campbell and Bozorgnia (2003) (solid lines).

Figure 7. Schematic of the proposed design vertical response spectrum

Sav

0.025 0.05 0.15 2.0 TV (sec)

36

Proposal 4-1 (Y=23, YR=1 , N=0, NV=2 --100%)

Manley (YR): This proposal is purely editorial in nature – I thought the PUC was going to try and avoid processing these types of proposals this cycle.

TS 4 Response: Non-Persuasive. What is editorial in nature to one person may not be so to the next. In this case the change from ACI 318-05 to ACI 318-08 has the potential for a large impact on design as well as the contents of Sec. 14.2 and is best not considered editorial in nature.

Harris (Yes): Wouldn’t it be sufficient to simply cite section 14.2 as the location where ACI 318 is referenced?

TS 4 Response: Non-Persuasive. The approach adopted in this proposal was to simply duplicate the format in currently existing in ASCE/SEI 7-05. While not obvious from the contents of the change proposal, the change from ACI 318-05 to 318-08 has permitted the elimination of nine citations to ACI 318 in the current listing in Chapter 23.

Proposal 4-2 (Y=21, YR=1 , N=1, NV=3 --96%)

Wood (No): My negative vote is purely editorial. Page 4, line 11 should refer to Section 14.2.2.7 – not Section 14.2.2.8.

TS 4 Response: Persuasive. Agreed.

Harris (YR): Even though my reservation is style, not substance, it is important enough to cast as a reservation rather than an editorial comment. We should present our differences as supplements and exceptions to ACI 318, and we should not write in the format that makes it look like the text could be cut and pasted into ACI 318. We should not be changing section numbers within ACI 318; our supplementary requirements could be identified as 1, 2, 3.. or a, b,

TS 4 explained that this proposal was just updating the text of more a current ACI document and made a motion to find the YR vote non-persuasive. Manley accepted TS 4 explanation and PUC did not require a vote and accepted the proposal as written.

TS 4 found the one No vote persuasive and agreed to make the change. Wood withdrew her negative. TS 4 found the Harris YR comments to be non-persuasive as explained and the PUC agreed by a vote (20,0,0) in agreement with TS 4.

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c…Lastly, I suggest that we consider getting rid of the “Detailed Plain Concrete Shear Walls”. If ACI doesn’t want this “system”, we should not impose it upon them and the rest of the world.

TS 4 Response (a): Non-Persuasive. This matter should be taken up by the editorial committee and not by TS-4. The current approach of a format that can be pasted into the material code is adopted for Sec. 14.2 on concrete, 14.4 on masonry and 14.5 on timber. If the format change suggested is made for concrete it should also be applied to the other materials. TS 4 Response (b). Non-Persuasive: The commentary to ACI 318 clearly documents that the provisions of Sec. 22.6 –Walls are intended to apply for basement wall construction for residential and light commercial buildings in low or non-seismic areas. Detailed plain concrete shear walls are widely used on the east coast and there is considerable opposition within TS-4 to the removal of the “system” because that removal would increase construction costs.

Proposal 4-3 (Y=23, YR=1 , N=0, NV=2 --100%)

Manley (YR): This proposal is purely editorial in nature – I thought the PUC was going to try and avoid processing these types of proposals this cycle.

TS 4 Response: Non-Persuasive. What is editorial in nature to one person may not be so to the next. In this case the change from ACI 318-05 to ACI 318-08 has the potential for a large impact on design as well as the contents of Sec. 14.2.3 and is best not considered editorial in nature.

TS 4 explained that this proposal provided additional information on piles. Manley’s YR pointed out a previous discussion at the November, 200, but it was not in regard to the technical part of the proposal. PUC understood her position but by a vote of (20,0,3) accepted the TS 4 position.

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Proposal 5-25R (Y= 17 , YR= 0 , N= 3 , NV= 5 --85%)

Hooper (No): The supporting research did not rigorously address the range of potential system designs and the associated failure mechanisms to allow the use of Ordinary AAC Masonry Shear Walls in Seismic Design Category C. I would change my vote to “Yes” if the system was limited to Seismic Design Category B only. Holmes (No): Although Appendix A of MSJC has extensive acceptability criteria for the major engineering design parameter of a structure made from AAC, I am still concerned that the appropriate assembly and configurations for these structures are inadequately documented. Every other structural system in common use is designed with fairly significant simplifications, compared to a complete model of the structure. Only selected actions on members and connections are “designed” and checked by the engineer. It is unclear to me how all the formulae and limitations in Appendix A will be applied without additional guidance. Parallel guidance for more traditional materials and systems is provided by training and mentoring in professional offices, or in well documented guideline books or text books. It is my understanding that there are essentially no limitations on the lay-up and configuration of elements to use the building blocks of AAC, other than the height limits. I think a design guide

TS 5 chair was unable to be present at the PUC meeting due to a prior commitment. A teleconference call was set up and this is permitted by BSSC 2008 PUC Goals, Structure, and Procedure rules. The TS 5 chair addressed the three No votes and made a motion to find the three No votes non-persuasive. The PUC voted (3,5,14) which means the PUC found the No votes persuasive. In an unusual step, a motion was offered to forward the proposal with the three No vote comments unresolved. This passed (15,2,5). Following the PUC meeting (Nov. 12-13, 2007), the BSSC Board met (Nov. 14, 2007) and the PUC chair briefed the Board on the progress of the PUC actions from the previous 2 days. The PUC chair highlighted to the Board the actions of the PUC that Proposal 5-25R was being forwarded with the unresolved comments. The BSSC Board found this unacceptable and voted to direct the PUC to go back and attempt to resolve the comments before this proposal is forwarded to the Member Organizations for ballot. The PUC chair informed the TS 5 chair of the Board’s decision and requested TS 5 chair to develop a plan to proceed. TS 5 chair with the concurrence of the PUC chair requested that the PUC be balloted to find the three negatives non-persuasive. The PUC was mail balloted from December 15, 2007 to January 15, 2008. The tally and comments are provided below. All three ballot items failed the mail ballot requirements and the TS 5 chair was notified. He requested time at the April 7-8, 2008 PUC meeting and presented a detailed explanation on AAC as well as a slide presentation addressing the negatives of the mail ballot. The main contention of the PUC was the use of AAC in SDC C and TS 5 provided research and several existing examples of the type of structures that are performing well. A motion was made to find the negatives non-persuasive and the PUC voted (19,5,1) approving this motion. By finding the negatives of the Dec.-Jan. mail ballot non-persuasive, this also found the three negatives on the original proposal non-persuasive. Consequently, Proposal 5-25R passed the PUC and is now forwarded to the Member Organizations for ballot.

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for each configuration approved for use, showing how the acceptability criteria of Appendix A is used, should be available before the system is approved with an R factor. Leon (No): I vote NO on 5-25R because I do not agree with the NL limit provisions for unreinforced ACC walls in SDC B. During the August 2006 Denver meeting, I had asked the sponsor of this ballot to send me more information regarding the testing of these materials. I have not received anything, and from what I have been able to determine from the literature, many of the tests have been run with substantial axial loads – in my view this improves the friction at the bottom and may give optimistic performance. I have similar misgivings about allowing 35 ft. in SDC C for reinforced ACC, but at least there the presence of reinforcement may justify its use.

TS 5 Response - Nonpersuasive

With respect to the Negative from Mr. Hooper, TS-5 notes that the testing and analysis carried out as part of the technical justification for the design provisions and seismic design coefficients did indeed incorporate a wide range of AAC shear walls, both shear-dominated and flexure-dominated, and with different levels of axial load, representing essential elements of archetypical structures. The testing did include a complete, two-story assemblage embodying all essential elements of archetypical AAC structures, including flanged shear walls, floor diaphragms, diaphragm-wall connections, and splices and anchorage of reinforcement. No research can address every possible structural detail. Nevertheless, the range of shear walls and the subassemblage itself were rigorously identified, designed, constructed and tested, and the results were rigorously combined with analysis to propose design provisions, construction requirements, and seismic design coefficients. With respect to the Negative from Mr. Holmes, TS-5 agrees that additional design guidance would be useful. That additional design documentation and guidance for AAC masonry is now available in the 5th edition of the Masonry Designers Guide, published in April 2007 by The Masonry Society. That reference includes extensive background information on the design of AAC masonry, and several complete building designs involving a range of AAC components and systems. With respect to the Negative from Prof. Leon, the Chair of TS-5 apologizes for having forgotten to send the requested information. Under separate cover, Prof. Leon is being sent pdf versions of the refereed journal papers regarding the testing, analysis, and development of seismic design coefficients, as well as the PhD dissertations on which those journal papers are based. That information was previously made available to the PUC. With respect to Prof. Leon’s concern regarding sliding, TS-5 discussions, reported to the PUC, have noted that sliding is a potential behavior mode of any lightly reinforced wall of masonry (clay, concrete or AAC) or concrete when spectral ordinates exceed 1.0 g, because 1.0 is approximately the coefficient of friction between rough concrete, masonry or AAC surfaces. We have also noted that Appendix A of the 2005 and draft 2008 MSJC provisions explicitly requires that AAC masonry shear walls be designed against sliding. Finally, we have noted that while sliding is an unacceptable response to design-level earthquakes, it may be an acceptable response to MCE. The testing that laid the technical basis for the AAC masonry design provisions in the 2005 and draft 2008

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MSJC Code, and for the AAC masonry construction provisions in the 2005 and draft 2008 MSJC Specification, used a range of axial loads that would be probable for archetypical AAC structures. Several of the specimens, including the two-story assemblage, did show some sliding. This was exhaustively documented, and its implications have been thoroughly discussed.

BALLOT RESOLUTION OF THE THREE NEGATIVE COMMENTS

Hooper’s Negative Comment(Y=9, YR= 2, N=8, NV=5 --58%) Holmes’ Negative Comment(Y=10, YR= 1, N=8, NV=5 --58%) Leon’s Negative Comment (Y=10, YR= 2, N=8, NV=4 --60%)

Holmes (No): Following is post-PUC meetings correspondence between Bill Holmes and Rich Klinger: Rich: I am shipping back the manual [the “Masonry Designers Guide”]. It is quite a tome. Thanks for the loan. The calculation examples covering AAC are extensive. However, I was looking more for a guide on how to best put the blocks together to form a building (maybe the step before the detailed calculation). I am sure that there are terrible, good, better, and best ways to do it. God knows we get stupid configurations with other materials. My concern remains that there is no history or tradition using AAC and vendors might not be the best ones to spread such training. Bill Holmes Rutherford & Chekene Kircher (No): I still find all three negative comments to be persuasive (for the reasons provided in their perspective comments). I would change my vote to Y provided the following two items are met: 1) Each of the negatives votes are resolved to the satisfaction of the respective voter (i.e., each individual effective changes their vote to Y and supports use of this new material/system.). 2) The proposed system is restricted to SDC B with a 35-foot height limit. Hooper (No): Clearly there has been a great amount of material, both research and guidelines, developed in support of the use of AAC. However, based on a brief review of some of this material and recent comments by Holmes (regarding design guidance) and Leon (research results), I remain convinced that AAC should be limited for use in SDC A and B only. I would change my vote to “Yes” if the system was restricted to SDC B as was stated in my original “No” vote. Johnson (No): I would change my negative to a positive if the proposed Table 12.2-1 additions would change from 35’ to NP for SDC “C” systems.

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Leon (No): My opinion remained unchanged because after pursuing the experimental portions of the thesis sent, I remain of the opinion that: 1. The vast majority of the specimens did not reach large interstory displacements. Most

failed, if memory serves me right, somewhere between 0.5% and 1.0% drift, with a number of them showing rapid strength and stiffness deterioration post-peak; some very-well detailed ones (if I recall the two-story specimen) did reach about 1.5% story drift but that was not the majority of them. Of course I recognize that some of the specimens were designed to fail in brittle manner to investigate failure modes, but I remain of the opinion that AAC is not a very ductile material and that great care will be needed in design to insure good performance. The typical designer using this material may not be aware of all these subtleties.

2. Most specimens were tested with fairly large axial loads and with the loading beams

braced out-of-plane so that the direction of loading was well-constrained, and the loading system, using vertical and horizontal post-tensioning, is not a good model of how load introduction will occur in practice. While I think one can detail the walls themselves to provide adequate ductility for a system with a low R, I am hesitant to approve a "system" in which out-of-plane and torsional effects on both the main members and the connections between those members and the collector/diaphragms have not been carefully tested.

3. I remain hesitant to approve this system beyond SDC B; this is perhaps because my

experience with this material dates back several years ago when the quality control for AAC was spotty at best and the properties varied greatly between nominally similar materials. I understand that QC/QA can take care of much of this problem but one's first impressions are hard to change; thus I may be biased in this issue.

Thanks for allowing me to clarify my vote; I think that the work by Richard Klingner and his students is excellent and thorough. I just happen to disagree on the final interpretation of some of those results as I do not believe that a low R factor can fully compensate for low ductilities. Sprague (No) on Leon: No comment provided. Gillengerten (No): No comments provided on all three. Cobeen (YR): I agree with the concerns raised in the comments and would like to see continued testing and design/minimum detailing development, but do not believe that these concerns should stop the proposal from being approved. Aschheim (YR): Hooper: Y/R Mr. Hooper may well be correct; if the issues can be specifically identified, language could be introduced that restricts the system designs and failure mechanisms to conform more closely to those tested. This would be preferable to a blanket prohibition on all Ordinary Reinforced AAC systems in SDC C.

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Leon: Y/R TS-5’s responses to Dr. Leon do not provide justification for the NL limits for Plain (unreinforced) AAC walls. It is not clear to me that such justification has ever been provided. Because it seems to me that the likelihood of sliding may be reduced as the height increases, and will be reduced in lower SDCs, I am voting Y/R (Nonpersuasive) rather than N (Persuasive), but the issue deserves further attention. Saunders (No):

• I agree with Hooper and Holmes that I would support the proposal if the system was NP in SDC C and above.

• I agree with Leon about NL for unreinforced AAC in SDC B.

Hawkins (No) on Hooper and Holmes: I am voting No on finding Hooper and Holmes NON Persuasive because I do not believe that the research reported to date has adequately addressed the concern of sliding shear action at the foundation and intermediate levels. In the development of ACITG5.1 on Acceptance Criteria for Special Unbonded Post-Tensioned Precast Concrete Shear Walls one of the main concerns for practicing structural engineers on the panel was the possibility of sliding which they said had to be prevented in order that the utility systems serving the structure remain unbroken. They gave examples of where sliding of concrete shear walls had occurred in past earthquakes and had lead to serious legal and post-earthquake performance issues. I have read the research cited in support of the proposal and find it lacking on specifics as to what coefficient of friction to use depending on the joint plane details. Further, for precast panel construction, the approach for evaluating sliding capacity depends on whether the wall is pre-cracked in flexure on the joint plane or not. If it is pre-cracked, then the shear capacity depends on the shear strength characteristics of the compressed toe of the wall and for AAC the effect on cyclic loading on toe shear strength and sliding shear resistance when there is reinforcement through the same toe area needs to be evaluated more rigorously than has been done to date. I would withdraw my negative if AAC construction was limited to SDC B.

Proposal 6-3 (Y=16, YR=3 , N=2, NV=3 --90%)

Wood (No): This committee does not have the authority to make changes to AISC 341-05. We can recommend that an exception be added to Chapter 14 of ASCE 7, and if accepted by ASCE 7, the committee that writes AISC 341 can adopt those changes before the next edition of ASCE 7 is published to eliminate the exception. But the PUC has no control over the second or third decision.

TS 6 addressed all comments. They found Wood, Holmes, Crouse, and Aschheim to be persuasive, editorial. Gillengerten’s first comment was due to a format issue and will be resolved. After lengthy discussion, he withdrew his second comment. The proposal was accepted to be forwarded to the Member Organizations for ballot.

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Other than this philosophical disagreement, I do not object to the specific changes, however, the table with R factors in ASCE 7-05 is Table 12.2-1, not Table 12.1-1.

TS6 Response: Persuasive. However, it seems convoluted to me to recommend the changes for Chapter 14 of ASCE7, rather than the source documents. The NEHRP Provisions have referred directly to documents such as AISC for many cycles. I realize that ASCE7 is the base document, but it still seems that it would be more confusing to do it this way. The next edition of AISC 341 will be in 2010 and will therefore be able to consider any recommended changes presented in the NEHRP Provisions.

Holmes (YR): This proposal should be formatted as a change to Chapter 14 of ASCE 7.

TS6 Response: See response to Wood above. Crouse (YR): The 0.02 minimum value for total rotation has only one significant digit (the 2), which could be interpreted to mean that total rotations computed in the range, 0.015 to 0.01999 ⋅⋅⋅, would satisfy the requirements after round off to one significant digit. If this interpretation is not the intent, then change 0.02 to 0.020.

TS6 Response: Persuasive. While this “digitization” has been used in AISC 341 for over 10 years, without being misinterpreted, it is probably good to make the change. This suggestion has also been forwarded to AISC for consideration as a global change to AISC 341.

Aschheim (YR):

1. Page 1, Line 9: Add “Part I of” to read “…15.7 of Part I of AISC…” 2. Page 1, Lines 17 and 26: add commas and spaces, and delete “and” to read “…Sections

11.2a, 11.2c, and 11.5.” 3. Page 1, Line 19: Add “Part I of” to read “…16.7 of Part I of AISC…”

TS6 Response: Persuasive.

Gillengerten (No): 1. The proposal is not in strikeout/underline format, so it is difficult to understand exactly

what is being changed. 2. I am concerned that FR ordinary moment connections are not drift-compatible with EBF

and BRBF systems. In strong ground motion, these systems experience drift levels similar to SMRF structures. I am comfortable with the general 0.02 radian requirement. I don’t believe there is evidence that FR ordinary moment connections have that level of capacity.

I will change my negative to a yes if the proposal is formatted properly to identify changes, and either:

1. Evidence that FR ordinary moment connections can accommodate 0.02 radians of rotation is provided for the PUC, or

2. The proposal is changed to require intermediate moment frame connections.

TS6 Response: Partially Persuasive. Regarding item #1, the original proposal was submitted in strikeout/underline mode for the portion relating to Section 15.7 of AISC 341. Please see below:

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15.7. Beam-to-Column Connections

Beam-to-Column Connections away from the link shall be designed as either moment resisting connections or as connections that can accommodate at least a total rotation of 0.02 radians.

IfWhere the EBF system factors in the applicable building code require moment resisting connections are provided away from the link, then the beam-to-column connections away from the link shall meet the requirements for FR Ordinary Moment Connections beam-to-column connections for OMFas specified in Sections11.2 2a and 11.2c and11.5.

If the EBF system factors in the applicable building code do not require moment resisting connections away from the link, then the beam-to-column connections away from the link are permitted to be designed as pinned in the plane of the web.

1) Add Section 16.7 to AISC 341-05 as follows:

16.7 Beam-to-Column Connections

Beam-to-Column Connections shall be designed as either moment resisting connections or as connections that can accommodate at least a total rotation of 0.02 radians.

Where moment resisting connections are provided, then the beam-to-column connections shall meet the requirements for FR Ordinary Moment Connections as specified in Sections 11.2a and 11.2c and 11.5.

Regarding item #2, the proposal is intended to be a consolidation of the EBF and BRBF system definitions. In AISC 341-05, the EBF system had language on the beam-column connections (citing the OMF provisions of Section 11.2 and 11.5), but BRBF did not. This makes the two more consistent. Note that in most configurations, the beam-column connections in both EBF and BRBF bays are modified by the introduction of a brace and associated connection plates. As a result, it does not act like a true moment connection, and the force distribution through the connection will be significantly different. The specification for Sections 11.2a, 11.2c and 11.5 is primarily to provide a redundant load path through the connection that will minimize the demands on the welded joints. Some commonly used design details have used traditional shear tab style connections for these beam-column connections (no welds between the beam flanges and the column), which fails to account for the major force transfers from the brace that need to be accommodated by the connection. While it is recognized that a specific interstory drift angle is specified for OMF connections, it is felt by TS6 that the provisions in Section 11.2 and 11.5 will meet the intended connection performance.

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Proposal 7-1R (Y=21, YR=3 , N=1, NV=1 --96%)

Hamburger (YR): I am concerned about the explicit designation of wood frame, as opposed to residential buildings, with regards to reference to the IRC. This would require light steel frame structures that conform to the IRC to also conform to the NEHRP Provisions, which seems inappropriate.

TS 7 Response: Non-persuasive. TS6 was specifically asked to determine whether a parallel reference was needed for CFS light-frame construction; they concluded that it was not necessary. Addressing prescriptive construction beyond wood light-frame is beyond the expertise and jurisdiction of TS7, and needs to be handled by the TS for the material. This was discussed at the last PUC meeting.

Bachman (No): The term “light frame construction” is currently used interchangeably for both metal and wood stud construction. This proposal removes exemptions metal stud construction but retains them for wood. I believe TS-6 and TS-7 should come with a joint proposal that covers both materials. I would change my vote to yes if the modified exception of Section 11.1.2 provided in the proposal applied to both metal and wood stud construction.

TS 7 Response: Non-persuasive. See response to Hamburger. Klingner (YR): I am voting YR on this proposal because I would like to hear a discussion from TS7 on the extent to which the wood-frame provisions of the IRC and IBC “substantially meet the intent of the conventional construction provisions included in the NEHRP Provisions through the 2003 Edition.” I agree with the general intent of the proposal.

TS 7 Response: Non-persuasive. The core requirements of the 2003 NEHRP provisions are listed below with references given to parallel treatment in the IRC. The IRC provisions are further developed, resulting in some differences; however all of the major 2003 NEHRP concepts and provisions are addressed within the IRC provisions. As a result, we are no longer providing any benefit by maintaining separate NEHRP provisions.

1. Sec. 12.4.1.1 masonry and concrete wall limits. IRC Sec. R301.2.2.2.2, Item 7.

TS 7 addressed the Hamburger YR and the Bachman No much the same way. The concern was this proposal was only for wood yet there should be something compatible for steel. This had been discussed at the November, 2007 PUC meeting and TS 7 proceeded with this proposal and if TS 6 thought there was need for a steel equivalent proposal they could do so. They have not. Bachman withdrew his negative. The Klingner YR was addressed and the response to the comment described the comparable sections of the IRC so TS 7 was finding Klingner non-persuasive. The Harris comment specifically addressed very large residences in seismic areas. TS 7 pointed out that square footage was not addressed as a method to limit, but by length of unsupported vertical walls and by weight. Harris agreed that this should be discussed in more detail but had no objection to this proposal moving forward. A motion was made to accept this proposal as written and the PUC voted (22,0,0) in favor.

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2. Sec. 12.4.1.1 weight of construction limits. IRC Sec. R301.2.2.2.1. 3. Sec. 12.4.1.1 number of story limits. IRC Table R602.10.1. 4. Sec. 12.4.1.1 height of story limits. IRC Sec. R301.3. 5. Sec. 12.4.1.1 braced wall line on-center spacing limits. IRC Sec. R602.10.1.1 and Sec.

R602.10.11.1. 6. Sec. 12.4.1.1 masonry veneer limits. IRC Sec. R702.1 and R703. 7. Sec. 12.4.1.2 irregularity limits. IRC Sec. R301.2.2.2.2. 8. Sec. 12.4.2.2 braced wall line sheathing requirements. IRC Sec. R602.10. 9. Table 12.4-2 length of braced wall line sheathing. IRC Table R602.10.1. 10. Sec. 12.4.3 detailing requirements. IRC Sec. R602.10.8, R602.11.1, & R602.11.2. 11. Sec. 12.4.3.5 foundations supporting braced wall lines. IRC Sec. R602.10.9 12. Sec. 12.4.3.6 stepped foundation requirements. IRC Sec. R602.11.3. 13. Sec. 12.4.3.7 diaphragm opening. IRC – detail not picked up, but opening size limited per

IRC Sec. R301.2.2.2.2, Item 4. Harris (YR): The IRC does not place limits on the physical size of dwellings. So far as seismic resistance is concerned, size does matter. Some of these very large residences have very large mass, large rooms, very large expanses of glass, and I don’t think we have empirical experience that indicates they will perform well without an engineered design. I propose that we limit the floor area for exception 2 so some arbitrary value, such as three or four thousand square feet.

TS 7 Response: Non-persuasive. The IRC does place limits on vertical dimensions through limits on the height and number of stories. Further IRC limits the weight of construction in high seismic hazard areas. In lieu of specifically limiting building horizontal dimensions, the IRC requires that braced wall lines be provided at intervals through the floor plan. This limit is 25 feet in high seismic hazard areas and 35 feet in low seismic hazard areas. This IRC approach to limiting seismic demand is consistent with previous NEHRP provisions and previous UBC provisions.

Proposal 8-1 (Y=10, YR=7, N=3, NV=3 -- 85 %

Bachman (YR): I would change my vote to yes if the identified changes can be shown to have occurred in the final adopted version of NFPA 13 which I believe it has.

TS-8 Response – Persuasive. Final copies of the full text of the new NFPA 13 will be provided to both TS-8 and the PUC when the document is available (estimated date of availability is first week of September 2006) along with a short narrative describing how the changes to the document meet the requirements of the Provisions. At that time,

The PUC directed TS 8 to resolve the negative comments and find them nonpersuasive. It was the general sense of the PUC that NFPA 13 is to be published within two weeks after the PUC meeting. Review of the final drafts support the TS 8 position and the PUC felt that this proposal should be accepted by a vote of (18-0-6).

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Proposal 8-1 will be re-balloted by TS-8. If passed by TS-8, Proposal 8-1 will be resubmitted to the PUC for consideration.

Kircher (No): I concur with the concerns of TS-8 members (regarding the premature nature of these proposals) and would change my vote to yes, after each of those TS-8 members change their vote to yes (i.e., after they review and concur with the subject documents).

TS-8 Response – Persuasive. See response to Bachman. Wood (YR): I agree with the subcommittee members and do not believe that this change can be approved until the final version of NFPA 13 has been approved and reviewed by the subcommittee.

TS-8 Response – Persuasive. See response to Bachman Manley (YR): Once it is finalized at the end of July, confirm that the 2007 edition of NFPA 13 contains the appropriate changes.

TS-8 Response – Persuasive. See response to Bachman Klingner (YR): My vote will be changed to “Yes” when the identified changes are made to NFPA 13.

TS-8 Response – Persuasive. See response to Bachman Aschheim (YR): The “yes” is contingent on the identified changes being made to the final version of NFPA 13.

TS-8 Response – Persuasive. See response to Bachman Cobeen (YR): Per TS YR votes, suggest that this not be finalized until TS has chance to review the 2007 NFPA 13.

TS-8 Response – Persuasive. See response to Bachman Leyendecker (No): My ballot will change to Yes on final approval of NFPA 13 with the stated changes.

TS-8 Response – Persuasive. See response to Bachman Hooper (YR): While the change appears appropriate, my “Yes with Reservation” is based on not having the revised NFPA 13 to review. I may change my vote to “Yes” if the identified changes are made in the final version of NFPA 13.

TS-8 Response – Persuasive. See response to Bachman

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Gillengerten (No): Ballot Items 8-1 and 8-2. While I support these proposals in principal, they propose adoption of draft standards that have not been finalized. I would change my negative to a positive once the standards in final form have been considered by TS8.

TS-8 Response – Persuasive. See response to Bachman

Proposal 8-2R (Y=20 , YR= 1 , N= 0 , NV=1 --100%)

Wood (YR): Line 10, page 1 – consider revising as “Alternatively, steel storage racks shall be designed in accordance with the requirements of Sections 15.5.1 and 15.5.3.1 through 15.5.3.4.”

Proposal 8-4 (Y= 24, YR=0, N= 0, NV= 1 -- 100%)

(Unanimous – Move to MO Ballot)

Proposal 8-10R (Y=18, YR=3 , N=2, NV=3 --91%)

\

Hamburger (No): My negative vote is because I believe that TS8 is an inappropriate group to originate this proposal. This should have come through TS3. I will withdraw my negative if evidence is presented that TS-3 is substantially in support of this proposal.

TS-8 Response: Partially Persuasive. The commentary included in this proposal was written by C. B. Crouse of TS-3 and is included in the TS-3 Proposal 3-122 with slight changes. The commentary was unanimously passed by the TS-3 membership (12 yes and 1 person did not vote). Because the commentary section is duplicated in TS-3 Proposal 3-122 (not the case at the time 8-10R was created), the commentary section in 8-10R will be dropped. The intent of the proposal is to lower the floor value used to compute the sloshing wave height when a site specific study indicates a lower value for the convective acceleration, which is appropriate for TS-8 to consider. TS-3 asked that TS-8 sponsor this proposal.

TS 8 addressed the two No votes and each withdrew their comment. Bachman’s comment was found non-persuasive since it is believed TS 3 will cover in commentary. The Crouse comment was persuasive and changes will be made. This also satisfied the Manley comment. A motion was made to accept proposal 8-10R as amended and the PUC voted (22,0,0) approving this proposal.

TS 8 reviewed the Wood comment and found no appreciable difference than what is written. A motion was offered to find Wood’s comment nonpersuasive and the PUC voted (12,0,3) to approve this motion. The proposal proceeds to Member Organization ballot.

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Crouse (YR): Line 11, p. 2 of 4: Replace “at too large a scale” with “are too small.” Line 13, p. 2 of 4: Replace “are new in this edition” with “were introduced in ASCE 7-05.” Line 24, p. 2 of 4: Replace “[ref. here]” with “[Next Generation Attenuation, Power et al., 2006, 2008].” Also, include edits Mike Valley made to same commentary in Proposal 3-122.

TS-8 Response: Persuasive. The proposed commentary section in 8-10R will be deleted since it has been proposed in TS-3 Proposal 3-122.

Hooper (No): It’s not clear whether this proposal was formally balloted by TS-3. Given the nature of the proposal, their concurrence is important. Also, even though this is only a tank issue, it also can the site specific process could also be used for tall buildings in certain instances. As such, I suggest this “exception” be placed in Chapter 21 (again, if there is concurrence with TS-3). I would change “No” to “Yes” if the above corroboration occurred and the location of the provision was changed.

TS-8 Response: Partially Persuasive. See response to Hamburger concerning the corroboration issue. TS-8 sees this proposal as only applying to tanks, It actually will only significantly impact tanks with convective periods greater than 8 seconds. If it is felt that tall buildings with periods on the order of 8 seconds need the reduced floor value, it is suggested that TS-2 prepare a proposal.

Bachman (YR): The number of large magnitude near field earthquake records with reliable recordings beyond 4 seconds is quite limited and the records we do have are quite variable at long periods. I would change my vote to yes if the following sentence was added to the end of Long-Period Transition Maps part of the proposal “Because of the sparseness and large uncertainty associated with these records, it is recommended that a one-standard deviation probabilistic level be used to establish site specific design values”.

TS-8 Response: Non-Persuasive. See response to Crouse. Since the commentary portion of this proposal has been picked up by TS-3, TS-8 will forward your comment to TS-3.

Manley (YR): How will the user know that the commentary on the exception in Section 15.7.6.1 can be found in the Chapter 22 commentary? Consider adding a pointer in the Chapter 15 commentary, if it is not there already.

TS-8 Response: Non-Persuasive. See response to Crouse.

Proposal 8-43 (Y=15, YR=4 , N=2, NV=5 --90%)

TS 8 went through each comment and negatives were either persuasive or withdrawn. The YR comments were addressed and several accepted as persuasive. A motion was made to accept this proposal as amended and the PUC agreed by a vote (22,2,1).

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Hooper (YR): The wording in item b is a bit cumbersome. It states that the reduced cross-section may be designed for R = 2 subject to some additional requirements, which is the value that the entire concrete chimney needs to be designed for. It seems it would be more straightforward to simply require opening size subject to the follow-on requirements. I would change my vote to “yes” if this change was made.

TS-8 Response: Persuasive. The reference to R=2 does not add value and will be eliminated as you suggest.

Hawkins (YR): The references in ACI 318 should be more specific than those proposed.

Revise l. 19- 25 as follows: “ Appropriate reinforcement development lengths should be provided beyond the required region of overstrength. The jamb regions around each opening shall be detailed using the column tie requirements in Section 7.10.5 of ACI 318. …….The percentage of longitudinal reinforcement in jamb regions shall meet the requirements of Section 10.9 of ACI 318 for compression members.”

Revise l.4 of page 2 as follows: “using the requirements in Section 21.3.5 of ACI 318.”

TS-8 Response: Persuasive. The changes you recommend will be made.

Wood (No): I support this change, but believe that two issues must be addressed:

• Table 15.4-2 gives R=2 for a concrete chimney. Design option (b) seems to be implying that the R factor can be increased, if the level of detailing is increased. However, “R=2” appears in line 27 (p. 1). Should this be “R=3?”

• The detailing provisions for columns in intermediate frames include closely-spaced hoops near the joints (within ol ) and more relaxed requirements near the middle of the member. The intent of option (b) item ii seems to be that the hoops in the jamb regions would satisfy the requirements near the joints, but this is not stated explicitly. The transverse reinforcement in the jamb regions should also extend above and below the opening, but this is not addressed.

• In addition, the 2003 reference in the ACI Structural Journal is Kilic and Sozen – not Sozen et al.

TS-8 Response: Persuasive. For the first bullet item, see the response to Hooper. For the second bullet item, we will make the changes requested. For the third bullet item, we will correct the reference.

Ghosh (No): I did not realize that ACI technical committees were in the business of setting R-values. ACI 318 has so far deliberately avoided that. I think TS8 should make up its own mind on this issue, rather than defer to ACI Committee 307. I do not know how much seismic expertise that committee has. Item b is not making sense to me. If the whole thing is to be designed for an R of 2, why are we talking about an R of 2 for the reduced cross-section?

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TS-8 Response: Partially Persuasive. The proposal reduces the R value to 2.0 from the current value of 3.0 and requires specific detailing requirements for a known problem area. It is the judgment of TS-8 that the R value of 2 proposed in ACI 301 is “more correct” than the current value of 3 in ASCE 7. We are also proposing detailing requirements not found in ACI 301 to address a known problem. Regarding item b, see response to Hooper.

Manley (YR): I wonder if the ‘average’ user will know how to interpret the sentence “Appropriate development length shall be provided beyond the required region of overstrength.”? Is there commentary on this section?

TS-8 Response: Persuasive. See response to Hawkins. Klingner (YR): This proposal may be technically sound. I am not as concerned about this as I am about some of the other proposals involving seismic design factors, because the proposed R factor is quite low. My YR can be satisfied by evidence that the proposed seismic design factors are justified by something like the procedure currently under development by ATC-63. I believe that this proposal should be discussed at a PUC meeting.

TS-8 Response: Non-Persuasive. The proposal reduces the R value to 2.0 from the current value of 3.0 and requires specific detailing requirements for a known problem area. ATC 63 is not complete, it is not published, and currently does not address nonbuilding structures not similar to buildings. It is the judgment of both TS-8 and the ACI 301 committee that the R factor for this structure needs to be reduced and it needs to be done now.

PUC-2 (ASCE 7 Seismic Proposal TC2-CH12-18 JCC 12)

Proposal 2-8 (Y=16, YR=3 , N=4, NV=3 --83%)

This proposal is one of 15 received by ASCE Seismic Committee in May, 2007. The Joint Correlating Committee (JCC), made up of select members of both BSSC/PUC and ASCE 7 Seismic, reviewed all 15 and 9 were determined to be first reviewed by BSSC/PUC for consideration. The ASCE 7 number for this proposal is TC2-CH12-18 JCC 12 and is one of the 9. During the PUC meeting of April 7-8, 2008, the PUC determined that this proposal has merit and should be included in Part 1 of the 2009 NEHRP Provisions and voted Yes = 20, No = 0, and Not Voting = 4 to have it balloted by the BSSC Member Organizations. The proposal has been reformatted to match other PUC proposals and assigned the proposal number PUC-2 (2009).

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PART 2

Proposal 2-117 (Y= 15 , YR=6 , N=0 , NV=1 --100%)

Crouse (YR): p. 6 – line 19: The word “matching” implies time history is to be spectrally matched, which is

not allowed. Revise by deleting phrase “requires matching” and rework sentence. p. 7 – line 5: State the three procedures before proceeding with the rest of paragraph. line 9: Why would base isolation be used for “especially flexible buildings”? Hamburger (YR): My reservations are as follows: Page 6, line 16 – correct “site-specific in order to account for in the analysis for near-fault effects” to “site-specific in order to account for near fault effects in the analysis” Page 7, line 6- correct “fixed b base” to “fixed base” Section C17.4 seems to be largely a restatement of the requirements, rather than an explanation. This should be improved.

Bachman (YR): I have the following comments:

1. Figure C17.8-1 is missing and needs to be provided 2. It would be good if the commentary discussed non-linear time history analysis if the

average of 7 option is used. In particular, it would be good if the commentary discussed the situation if one of the 7 ground motions considered results in a very large

The PUC reviewed each comment during the PUC meeting held November 12-13, 2007: Crouse’s comments were found to be editorial and TS 2 will make the changes. The last comment (line 9, page7) was found nonpersuasive. (PUC vote: 20,0,1) The first Hamburger comment was found persuasive, the second editorial, and the third was found nonpersuasive. The changes will be made. (PUC vote: 19,0,2) Bachman’s first comment was editorial, the second persuasive and TS 2 will attempt to resolve in Chapter 16 ( yet to be reviewed by PUC). The third comment was found nonpersuasive. (PUC vote: (20,0,0)) Wood’s first comment was found nonpersuasive, the second persuasive/editorial and the third was found editorial. Klingner’s comment was found nonresponsive (format issue). Aschheim’s comments were editorial. TS 2 will make the changes and submit to BSSC for future Member Organization ballot.

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displacement that would exceed the proposed gap even though the average of the 7 calculated displacements would not, and how the impact of the isolated structure with the non-isolated moat wall is to be considered (or ignored).

3. In Section C 17.4, discussion is provided on the reduction factors used for design with base isolated structures. However, it’s more a statement of fact rather than justification or explanation of how the reduced reduction was determined. It would be good if the commentary provided more of justification for the reduced reduction. Also no discussion is provided about height limits for isolated structures. It would seem that since reduction factors are much reduced increased height limits should be permitted for at least some structural systems. In the UBC the height limits for isolated structures are separately identified. It should be explained why they are not separately identified in the NEHRP provisions.

Wood (YR): Page 5, line 19 – Is it appropriate to refer to specific load combinations to assist the engineer in defining the bounding values? Page 6, line 7 – replace “rigid structures” with “structural elements.” Page 7, line 6 – typographical error “fixed-b base.” Page 9, Figure C17.5-1 – test associated with “total maximum displacement” has been clipped. Klingner (YR): I believe that this proposal is technically reasonable and deserves to proceed forward. I am voting Yes with Reservations because its pedigree is not clear. Did it come from TS-2 or TS-3? What was the relevant discussion in TS-2? If it was approved by TS-3 as stated, what was the result of the TS-3 vote?

Aschheim (YR): My reservation is simply to draw attention to some editorial issues: 1. Figure C17.5-1: one label in the figure has text that is partially cut-off. 2. Figure C17.8-1 is missing. 3. The reference to Constantinou has “xxxx” on line 17 of Page 14.

Proposal 2-118 (Y=19 , YR= 2 , N= 0 , NV=1 --100%)

Hamburger (YR): General comment – should references to the “standard” be to “this standard” or “these provisions”? PUC should discuss. Page 3, line 10 – remove the parenthetical “[moved from below]” On page 3, line 7 – I believe the sentence: “The seismic force resisting system must comply with the requirements of this standard, except that the damping system may be used to meet drift

The PUC reviewed each comment at the PUC meeting held November 12-13, 2007: Hamburger’s first comment was found editorial, the second and third were found persuasive, and the fourth (page 4, line 4) was found nonpersuasive.( PUC vote: (21,0,0). Klingner’s comment was found nonresponsive.(format issue) TS 2 will make the changes and this proposal will be forwarded for Member Organization ballot.

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limits.”is both incorrect and misleading. I believe what is implied here is that the SFRS must comply with all “detailing and similar” criteria. Strength criteria need only comply with 75% of the other requirements. Recommend rewrite of this section as: “C18.2.2 System Requirements Structures with a damping system must have a seismic-force-resisting system that provides a complete load path. The SFRS must comply with the requirements of this standard except that the damping system may be used to meet drift limits. all of the height, Seismic Design Category, redundancy limitations and detailing requirements specified in this standard for the particular type of SFRS. The SFRS without the damping system must be designed to have at least 75% of the base shear resistance strength required in this standard for undamped structures having that type of SFRS (and not less than 100% if the structure is highly irregular.) The damping systems may however, be used to meet the drift requirements of this standard. This approach provides ….note some rearrangement On page 4, line 4 - The damping system must be designed for the actual (unreduced) earthquake forces (such as peak force occurring in damping devices) and deflections. Klingner (YR): I believe that this proposal is technically reasonable and deserves to proceed forward. I am voting Yes with Reservations because its pedigree is not clear. Did it come from TS-2 or TS-3? What was the relevant discussion in TS-2? If it was approved by TS-3 as stated, what was the result of the TS-3 vote?

Proposal 3-119 (Y=20, YR=2, N=0, NV=4 --100%)

Hamburger (YR): Overall, this commentary is very good. Section C19.1 introduces the three principal types of SSI and indicates that only inertial effects are considered by Chapter 19. Since the other effects have been introduced in this section, the Commentary should discuss whether it is permissible to account for these other effects (wave incoherence, embedment). With the publication of FEMA 440, engineers are more familiar with these phenomena and more comfortable with their use. I believe we should attempt to deal with this issue in the Commentary at this time.

Malley (YR): This is a well written and helpful commentary section. I would like the last sentence of the discussion of Section 19.1 (line 26 on page 3 of the proposal) to give some more quantitative guidance as to what is meant by “short-period” structures.

Proposal 3-120 (Y=21, YR=1 , N=0, NV=4 --100%)

The two comments were found to be persuasive and a motion was made to accept the proposal as modified. It passed the PUC (22,0,2).

The one comment was found to be partially persuasive and a motion was made to accept the proposal as modified. It passed the PUC (22,0,2).

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Bachman (YR): This commentary needs to discuss the situation where bedrock is encountered before you reach 100 feet. This is a very normal occurrence. Wording was added to end of Section 20.4.2 of ASCE 7-05 that provided procedures for treating this situation. Commentary should also discuss this situation. Also, it should be clearly stated in the commentary that site coefficient for structures supported on deep foundations should be based on based coefficients determined at the ground’s surface and not on the coefficient determined at depth. I would change my vote to yes if commentary was added as described.

Proposal 3-121 (Y=21, YR=2 , N=0, NV=3 --100%)

Bachman (YR): Section 21.1.2 of ASCE 7-05 requires that uncertainties in soil properties be included in site response modeling but not specific requirements are provided in the section on how uncertainties are to be included. I believe recommended guidance should be proposed in the commentary. I would change my vote to yes if the following sentence was added to the end of the commentary to Section C.21.1.2 “It is recommended that the shear moduli be varied by multiplying and dividing by a factor of 1.5 and the results of the site response analyses be enveloped to establish site specific design motions”. This was the factor that was recommended by Seed and Lysmer for determining design ground motions with programs such as SHAKE and FLUSH were used for such determinations. Wood (YR): The commentary will need to be revised if the risk coefficients are included in the MCE – see reservation related to Proposal SDPRG-1R2.

Proposal 3-122 (Y=20, YR=2 , N=0, NV=4 --100%)

Crouse (YR): Line 26, p. 2 of 4: Replace “at too large a scale” with “are too small.” Line 30, p. 2 of 4: Replace “are new in this edition” with “were introduced in ASCE 7-05.”

Ghosh (YR): p. 2, Line 24 – Suggest you delete: “This site can also be used to obtain values from the 2002 edition of the standard.” This is basically irrelevant information. p. 2, Line 26 – Too large a scale or too small a scale? Manley (Yes on Ballot; YR on comment): Clarification needs to be added to the Reason for Proposal indicating that the proposed modifications to the Chapter 22 Commentary

The Bachman comment was found to be persuasive and the Wood comment non-persuasive. A motion was made to accept the proposal as modified. It passed the PUC (21,0,2).

The YR comments were found to be persuasive and a motion was made to accept the proposal as modified. It passed the PUC (21,0,0).

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are based upon the language proposed in Proposal 8-10R. I imagine that approval of this proposal is contingent upon acceptance of Proposal 8-10R.

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PART 3

Proposal 2- 6 (Y=13, YR= 7, N=1 , NV=2 --95%)

Crouse (YR): 1) Eqn 17 is incorrect. The 90 should be deleted. 2) Symbols should be defined directly below the equation where they are first used. Some are and some aren’t. 3) Glossary of symbols at beginning or end of paper would be beneficial.

Kircher (YR): I think the proposal should be included in Part III (white paper), but am voting YR to ask the proposes/authors to verify that all symbols and nomenclature used in the white paper be checked for consistency (and made as consistent, as possible) with existing symbols and nomenclature of the NEHRP Provisions (ASCE 7-05).

Saunders (YR): Agree with Kircher (TS 2 member) that symbols and notations should be checked for consistency with NEHRP Provisions.

Leon (YR): At least two of the references (Goel et al.) have not apparently appeared in print yet. They will probably be available soon, but I am uncomfortable voting on something for which I cannot read the background material and for which not even the name of the journal to which they were submitted appears in the references.

Manley (YR): I agree with C. Kircher’s comment – the authors should check the white paper for consistency and based their symbols, nomenclature and references on ASCE 7-05, which is the basis of this edition of the NEHRP Guidelines.

Wood (No): p. 2, line 5 – why are floor accelerations mentioned in this sentence, if they are not addressed in the design approach? p. 2, line 29 – Recommend deleting this last sentence. The reference to pencil and paper seems to be inconsistent with the examples provided. Complete nonlinear analyses were used to justify that the preliminary designs were appropriate.

The PUC reviewed each comment and found several persuasive. Editorial comments were all accepted. Wood’s comments were reviewed and several were found persuasive. TS 2 will revise the proposal by deleting floor accelerations, modifying the reference to regular structures because this proposal has limited applicability (Gillengerten comment too), and to correct the SI units in several of the figures. Klingner’s comment was found nonpersuasive since this proposal is to included in Part 3 where introductory provisions are presented. The motion the PUC considered was to accept these comments and rely on TS 2 to make the corrections. The PUC voted on this motion (18,0,0)

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General comments: A complete list of notation and definitions is required. The procedures seem to have been developed for highly idealized, regular structures. It is not clear that these simple procedures would be appropriate for actual structures. In addition, the number of structural systems that can be considered with this approach is quite limited. It seems very odd that some of the calculations must be done using SI units and most are done in in.-lb units. Surely key graphs can be converted to assist the engineer. I am not convinced that this approach is appropriate for codification. It may be a useful design tool for some simple structures, but not all design tools are included in the NEHRP provisions.

Klingner (YR): I believe that this is a very ambitious effort, and will ultimately give us more rational designs for structures whose behavior can be idealized as elasto-plastic. It is similar in many ways to a displacement-based design approach that TS-5 has been working on for masonry shear walls with openings, and that I plan on introducing within the MSJC seismic subcommittee in the 2011 cycle. This is potentially one of the most useful things that BSSC could introduce. I do not believe that it is ready yet to be presented as an alternative to the equivalent lateral force procedure or to our current period-based procedure. I encourage the technical subcommittee and PUC to continue to address the following technical issues:

• How can the method be applied to structures whose post-elastic response is degrading (as is likely to be the case with low-rise, wall-type structures? Would that be addressed by an effective drift limit? Would pushover analysis detect the possibility of brittle failure in a particular element?

• How can the method address irregularities in strength or stiffness?

• How can the method be made more reliable with respect to the relationship between

available ductility (or drift ratio) and different levels of detailing?

Gillengerten (YR): There should be some expansion of the discussion of how this approach is used to account for structural irregularities. Since this approach is offered as an alternative to the Equivalent Lateral Force procedures, to be of practical use it should cover the same ground.

Proposal 4-5 (Y=17, YR=3 , N=0, NV=6 --100%)

Line (YR): Page 7 of 34, line 7: change “smearing” to “distributing” or “spreading”.

TS 4 found the Klingner comment non-persuasive, however, he appreciated the response. Wood’s comments were mostly persuasive, but the first was found non-persuasive. She accepted TS 4’s explanation in the response and withdrew that section. Line’s comment was found persuasive. A motion was made to approve as modified and it passed (20,0,0) .

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Page 10 of 34, line 28: change “attack” to “application” or delete words “of attack”. Page 10 of 34, line 50: change “funnel” to “distribute”. Page 22 of 34, line 31: change “smeared” to “distributed”

TS 4 Response: Persuasive. Changes will be made.

Wood (YR): I do not think that the discussion of Figures 1 through 3 is sufficient to illustrate the design approach. In addition, many key issues are “currently under consideration.” It seems premature to include this information in the 2009 Provisions.

TS 4 Response: Non-Persuasive. Ballot Item PUC-1, as approved by the Member Organizations stated: “Part 3 will focus on new technologies, procedures and systems. In this part, new materials, not currently addressed in referenced standards may be introduced for consideration by the design community, researchers, the standards development organizations, and building codes. Generally, it is intended that information introduced in this part would be available for use by design professionals on a provisional basis…” Inclusion of the information in this white paper in the 2009 Provisions is consistent with the BSSC’s concept for Part 3 and the content of the white paper on anchorage. While the ongoing studies and testing of the PCI project are deriving specific values for the diaphragm force amplification factor, diaphragm shear over strength factor, …etc., it is highly unlikely that the overall methodology for diaphragm design, as proposed in the white paper, will be altered unless there is a completely unexpected result for the UCSD shaking table test specimen for which ambient testing was begun April 4 and for which the test to failure is scheduled for May 9, 2008

• Please note that ACI 318-08 does not require the chord reinforcement to resist the in-plane bending moment in the diaphragm (page 10, line 20.)

TS 4 Response: Persuasive. The wording reflects practice for designs according to ACI 318-05 and earlier editions of that document. A fourth bullet is added after l.36 on p.10. • “In ACI 318-08 the assumption that the chord reinforcement alone resisted the assumed design moments is replaced by an approach permitting all the longitudinal reinforcement in the diaphragm to be assumed to contribute to its flexural strength.”

• Proposal 4-6 recommends deleting Appendix A to Chapter 9 of the Provisions. Therefore, a

complete reference must be provided for the discussion on page 12.

TS 4 Response: Persuasive. Amend l. 26 p.12 as follows: “The NEHRP ( BSSC 2000) Appendix A…”

• The year of the reference is missing on line 39, page 33 – should be 2000.

TS 4 Response: Persuasive. Amend as follows: “Wood, S. L., Stanton, J. F., and Hawkins, N. M., 2000, “New ….”

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Klingner (YR): The background information behind this proposal in well written and technically impressive. My YR is motivated solely by a wish to have it presented to and discussed by PUC. I believe that the way in which the authors have tried to relate element performance to system performance for structures with complex force paths is relevant to other types of structures in addition to the ones addressed by the proposal.

TS 4 Response: Non-Persuasive. This proposal was discussed at the prior UC meeting. The proposal is relevant to other types of diaphragms that use panelized construction and both the wood and timber representatives that were present at the last PUC meeting agreed to forward the proposal for review to individuals in their material areas interested in panelized diaphragm construction.

Proposal 4-6 (Y=20, YR=1 , N=0, NV=5 --100%)

Klingner (YR): I am voting YR on Proposal 4-6 because it is linked to Proposal 4-5, on which I also voted YR.

TS 4 Response: Non-Persuasive. See reason described in response to comments on Proposal 4-5.

Proposal 7-2R & 6-2R (Y=17, YR=1 , N=0, NV=8 --100%)

Klingner (YR): I believe that the “white paper” is a valuable contribution to designers’ understanding of the intended response of different shear wall systems, and of the relationship between that response and expected test results. My “YR” is motivated by uneasiness over the classification of systems by their R values. While I understand that this classification is useful (common types of required details, for example), I believe that it could be misinterpreted as implying that a certain level of detailing will result in a certain predictable level of system ductility. I am not suggesting that the proponents run ATC-63 type studies on all their systems. I am suggesting that it would be more useful to describe the systems using the words in the R tables, rather than the R values themselves.

This proposal is a follow on to 4-5 that if passed deletes Appendix to Chapter 9 in Part 3. Since the Klingner comment was based on approval of 4-5, it was considered non-responsive and the PUC was not required to take an additional vote. This proposal passes and moves on to Member Organization ballot.

TS 7 addressed the Klingner comment and he accepted their response. This comment was withdrawn and the proposal was accepted as written. There was no need for the PUC to vote and this proposal moves to member organization ballot based on the approval of the mail ballot vote.

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TS 7 Response: Non-persuasive. The white paper merely reflects the fact that the NEHRP/ASCE7/IBC provisions have lumped these light-frame shear wall systems into two groups by R-factor, making this the most direct way to address the systems. Klinger’s comment would be appropriate to consider in future updates to the white paper.

Proposal 7-3 (Y=8 , YR= 4 , N= 4 , NV=6 --75%)

Soules (No): My negative has to do with Table 1 – Seismic Design Coefficients for Glulam Arches. First, there is very little difference in the R-values for the two entries. So little difference in fact it is difficult to believe that the Special Glulam Arch provides any benefit. The value of Ω for “Glulam arch not specifically detailed for seismic resistance” appears too high. The note limiting “Glulam arch not specifically detailed for seismic resistance” to SDC’s A, B, and C is too subtle. To remove my negative, I recommend increasing R for “Special glulam arch” to 3, reducing Ω for “Glulam arch not specifically detailed for seismic resistance” to 2, and reformatting Table 1 to include SDC limitations (similar to Table 12.2-1) in the table instead of as a footnote.

TS7 Response: Non-persuasive. A suggested increase in R for the “Special” system to separate it from “not specifically detailed” as well as reduction in Ω for the “not specifically detailed” system was not accepted in prior TS7 balloting (see response to Skaggs and Mahaney). For the “Special” system, required special detailing ensures greater strength of wood member in the vicinity of the connection to promote fastener yielding and wood crushing; however, the level of inelastic response of the structure could not be precisely quantified and as a result R =Ω is proposed. For the “not specifically detailed” system, Ω=2.5 is considered to be reasonable given minimum requirements of NDS for connection design. We agree that it is better to show SDC limitations in the Table instead of a footnote -considered editorial (see Response to Hooper).

Borcherdt (YR): Concerns expressed by TS 6 and TS 7 memebrs with “YR” and “No” votes may need to be addressed more thoroughly.

TS 7 provided a revised proposal incorporating all the editorial comments and several of the technical comments. There was an extensive discussion on introducing a seismic-force-resisting –system without adequate testing similar to being developed like the ATC 53 project. On the other hand, the PUC realized that this system has been utilized for several decades and significant numbers have been constructed. The TS moved to have the PUC vote on the revised proposal which basically found several no votes as nonpersuasive. The PUC voted (11, 4, 4). This proposal passed (> 73%) and will be forwarded for member organization ballot .

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TS7 Response: Persuasive. Due to ballot timing, responses to TS7 ballot comments were not prepared prior to the PUC ballot. Proposed responses to TS7 voter comments are now available.

Hooper (No):

Technical Issues: An R of 2.0 for an arch not specifically detailed for seismic is too high. A value of 1.5 would be more appropriate. The corresponding omega value should be reduced to 1.5 as well. The Seismic Design Category (SDC) should not be in a footnote. Either the table should be expanded or a paragraph should be added outlining the applicable SDCs. In addition, the arch not specifically detailed for seismic design should be limited to SDC A and B. Editorial Issues: In section 1.0 Scope, the last sentence specifies that Sections 1.1 through 1.7 are for special glulam arch systems. The remaining sections should consistently include, or exclude, the “special glulam arch” systems in the title. Commentary section C1.5 refers to ASCE 7 Section 12.14. Is the system intended only for use utilizing the simplified design requirements? If not, the section references need to be changed. I will change my vote to “Y” if the above items are implemented/corrected.

TS7 Response: Non-persuasive. The suggested limit of SDC A and B and R=1.5 for the “not specifically detailed” system was raised in TS7 balloting and not accepted. These suggested limits are not in line with other seismic design coefficient assignments for wood systems (see following Table). For example, cantilever column systems and adhesive systems without potential for favorable response in connections are assigned R = 1.5. Light frame walls with shear panels of all other materials, which exhibit limited connection yielding, have assigned R = 2 and are permitted in SDC A-C (gypsum shear walls permitted in SDC D). The proposed limitation of SDC A-C and R=2 for the specific wood frame system covered, and having limited yielding at connections, is considered to be more appropriate by comparison.

Structural System Limitations and Building Height (ft) Limit

Seismic Design Category

Seismic force resisting system Response Modification Coefficient, R

System Overstrength

Factor

Deflection Amplification

Factor

B C D E F A. Bearing Wall Systems 13. Light-framed walls sheathed with wood structural panels rated for shear resistance or steel sheets

6.5 3 4 NL NL 65 65 65

14. Light-framed walls with shear panels of all other materials 2 2.5 2 NL NL 35 NP NP

* Light-frame walls with adhesive attachment of sheathing 1.5 2.5 1.5 NL NL NP NP NP

B. Building Frame Systems

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23. Light-framed walls sheathed with wood structural panels rated for shear resistance or steel sheets

7 2.5 4.5 NL NL 65 65 65

24. Light-framed walls with shear panels of all other materials 2.5 2.5 2.5 NL NL 35 NP NP

G. Cantilevered Column Systems Detailed To Conform To The Requirements For: 7. Timber frames 1.5 1.5 1.5 35 35 35 NP NP

*in accordance with AF&PA Special Design Provisions for Wind and Seismic.

Note that “not specifically detailed” systems addressed by this proposal must comply with all applicable connection and member detailing provisions of the NDS which include prescriptive fastener placement provisions, maximum dowel size of 1 inch diameter for lateral design, revised wood shear strength checks at connections (revised in 2001 NDS) and new design provisions for checking stresses in members at connections (introduced in 2001 NDS).

Editorial issues:

Agree that it is better to show SDC limitations in the Table instead of a footnote. Propose editorial revision as follows:

“Table 1. Seismic Design Coefficients for Glulam Arches.

Seismic Force Resisting System R Ω Cd 1. Special glulam arch 2.5 2.5 2.5 2. Glulam arch not specifically detailed for seismic resistance a - limited to seismic design categories A, B and C

2.0

2.5

2.0 a Seismic coefficients are limited to seismic design categories A, B and C.

Glulam arch systems not specifically detailed for seismic resistance shall comply with recommended detailing in AITC 104-2003 Typical Construction Details, requirements of the 2005 National Design Specification® for Wood Construction (NDS®) including Appendix E, ASCE 7-05 Minimum Design Loads for Buildings and Other Structures, and the applicable building code.”

Agree to strike “special glulam arch” from section titles for consistency. Agree that it is not intended to limit use of provisions to the simplified design requirements. Section references will be expanded in Commentary section C1.5 to include ASCE 12.11.

Malley (YR): In the spirit of the “White paper”, I think this is an acceptable document. However, I have serious doubts about whether such a system will ever make it into a standard. Certainly not in its present form. The lack of justification for the basis of the proposal would be unacceptable to me. I also have doubts as to the need for such a system definition.

TS7 Response: Non-persuasive. We agree that any future standards work will come with it’s own set of new questions and need for refinement. The basis of the proposal is largely from a) calibration with 1997 UBC such that design seismic base shear in accordance with the proposal generally exceeds base shear per the 1997 UBC, and b)

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our understanding of overstrength present in standard dowel connections used in these structure types based on cyclic tests. The specific system definitions were largely influenced by American Institute of Timber Construction (AITC) glulam arch designers who have faced wildly different recommendations for seismic design of the common three-hinge arch since the roll-out of IBC 2000 as well as IBC users seeking guidance for the specific structure type.

Holmes (No): Although this material is proposed for Part 3, it apparently represents a future proposal to create a new system for Table 12.2-1. However, nothing is included to indicate equivalency to an existing system (as required in section 12.2.1) or the necessary analysis do rationalize response coefficients per ATC 63. Very low R factors have been recommended, but a rationale is still required. Much of the commentary relates to very specific detailing that would better be contained in an industry design guide.

TS7 Response: Non-persuasive. An expectation is that proposed seismic detailing for the common three-hinge arch will eventually lead to inclusion of seismic design coefficients in Table 12.2-1 of ASCE. Calibration with 1997 UBC practice is viewed as providing equivalence to the broad class of timber frame structures permitted by the 1997 UBC. Wood connection provisions have also improved since the 1997 UBC (1991 NDS referenced) and include revised provisions for shear at connections (revised in 2001 NDS) and new tear-out provisions in NDS Appendix E (introduced in 2001 NDS). New seismic detailing in this proposal will be incorporated into industry guidelines which currently address design for gravity and wind.

Klingner (No): I am voting Negative on this proposal because my reading of the ballot comments received from Mahaney and others on TS-7 indicates that a significant number of technical issues have not yet been resolved within the subcommittee. I respectfully request that the subcommittee be requested to continue working.

TS7 Response: Non-persuasive. Note that the (YR) from Jim Mahaney utilized Word’s comment feature and comments shown were mostly a repeat of Commentary from the proposal. TS7 comments and responses to TS7 ballot comments are now available. The proposal was broadly supported with only one No vote, three YR votes which were supportive of the proposal, and nine YES votes.

Aschheim (YR): I did not see any indication that arch systems should/must comply with story drift limits. If such compliance is required in the referenced standards, then text in the Commentary should indicate that the referenced standard drift limits are applicable. If no such limits are applicable, I would like to know the basis for the exemption. I am concerned that an R-factor is being suggested without demonstrating system adequacy. Details of the connection are critical to system performance. The current language doesn’t seem to constrain connection deformation capacity, and does not relate connection deformation capacity to system characteristics. It seems to me that identifying a “not-specifically detailed” system as a class of Seismic Force Resisting System opens up too many possibilities. Can the minimum detailing requirements

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(perhaps representing current practice) be stated? If not, it seems better not to identify a system that can’t be adequately defined. I prefer reserving the term “Special” for higher R systems, and suggest “Detailed glulam arch” as a preferred alternative to the current phrasing.

TS7 Response: Non-persuasive. Reference to ASCE 7 intended to address requirements for drift. Seismic coefficients were based on calibration with 1997 UBC such that design seismic base shear in accordance with the proposal is in line with base shear per the 1997 UBC, and our understanding of overstrength present in standard dowel connections used in these structure types based on cyclic tests. Effect of connection deformations is addressed by detailing guidance and design. Minimum detailing for the “not specifically detailed” system are limited to the 3-hinge arch structure type and based on requirements of the 2005 NDS which includes improved provisions for connection design relative to 1991 NDS referenced in the 1997 UBC. “Special” is considered more suitable than “Detailed” because the detailing requirements for the “Special” system are unique to seismic and in addition to standard detailing.

Line (YR): The need for this proposal stems from numerous designer requests to develop guidance for this common wood structure. AITC has assisted in development of this proposal and has provided comments to me following a recent conference call of glulam arch designers and manufacturers. I am voting YR to share AITC comments I feel will improve the proposal. A) Revise 1.3.2 as follows (based on AITC recommendations):

1.3.2 End grain bearing: At the arch base and moment splice regions, end grain bearing shall be on a metal plate with sufficient strength and stiffness to distribute the applied load. At moment splices, end grain bearing shall be on a metal plate when fc > (0.75)(Fc

*) as required in accordance with NDS 3.10.1.3.

Reason: Revised proposal requires design for overstrength at moment splices. Based on this change, the required use of a metal bearing plate should be per NDS provisions rather than always required by prescription. A related editoral change can be made to 1.7 on Moment Splices as follows:

1.7 Arch Moment Splice Arch moment splices shall utilize a metal bearing plate (when required), metal side plates, shear plates, bolts, steel dowels, timber rivets or combination thereof in accordance with AITC 104 Typical Construction Details. …

TS7 Response: Persuasive. Modification of 1.7 to address revised provision for bearing plate is editorial.

B) Revise 1.6 as follows (based on AITC recommendations):

1.6 End fixity

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In accordance with assumed pinned behavior of a 3-hing arch, determination of reaction and arch member forces is based on assumed idealized pin behavior at the arch peak and base. Actual detailing may introduces partial moment fixity at reactions, and consideration shall be given to the effect of such fixity on member and connection response.

Reason: Editorial. True pin figure inserted in 2nd TS7 ballot leading to addition of “may”.

TS7 Response: Editorial.

C) Expand commentary C1.1.1 to address concerns over “daily loading” due to shrinkage (based on AITC recommendations):

C1.1.1 The connection at the arch base utilizes a metal shoe (see Figure C1.1.1a and b) and typically employs a thru-bolt loaded in double shear. Placement of the bolt(s) is an important consideration. In-service drying of the member causes shrinkage which must be accounted for in the detailing of the connection to prevent splitting due to the development of tension perpendicular to grain stresses.

It is recommended that the bolt(s) be placed within 6 inches of the back of the arch if standard size holes are used. Where bolt(s) are placed farther than this from the back of the arch to resist the required loads, the designer should provide detailing to allow the wood to shrink without pulling away from the bearing seat. This may be accomplished through the use of slotted holes or oversized holes in the arch member. It is recognized that some movement of the arch at the base will occur before the bolt is engaged. This practice is used to prevent wood splitting due to occurrence of dimensional change under gravity loads. In some situations a bearing seat is also used at the inside face of the arch. In such a case, the bolt(s) is generally placed at the geometric center of the section with the hole(s) detailed to accommodate shrinkage.

Timber rivets as well as lag screws installed at each side of the arch base are expected to produce comparable performance provided that the controlling yield mechanism is based on dowel yielding or rivet capacity.

Under outward loads, the bending yield capacity of the plate at the back of the metal shoe will typically determine the size of the bearing area (i.e. the plate will yield before the wood reaches its design compression perpendicular to grain stress).

TS7 Response: Persuasive. Expansion of commentary to address effects of dimensional change is a reminder that detailing for both seismic and dimensional change should be addressed in design.

D) Replace Figure C1.1.1a with C1.3.2 (based on AITC recommendations) because timber rivets are not commonly used in the US. AITC considers the bolted connection at the shoe is the appropriate default connection type.

TS7 Response: Persuasive. Guidance on design using timber rivets remains but the figure is replaced with the more common detail.

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E) Revise C1.1.2 as follows (based on AITC recommendations) to avoid implication that bevel cuts are always required:

C1.1.2 The connection at the peak (see Figure C1.1.2) typically employs use of a shear plate or plates with thru-bolt(s) and is typically pre-fabricated in a manufacturing facility to establish proper fit and alignment. For arches with slopes of 3:12 and greater, typical connections employ shear plates and bolts or a combination of shear plates and bolts and dowels to transfer both horizontal and vertical forces. For low pitch (low slope) arches, steel side plates on each face are used in combination with shear plates. Figure C1.1.2 shows one example of a peak connection.

The bevel cuts shown at the top of the arch peak connection are used to minimize wood crushing and permit rotation due to downward deflection of the peak connection of deep members. They are not required for all designs but should be considered by the designer where significant rotation is expected. Bevel cuts are generally not used on the bottom side of the connection.

TS7 Response: Persuasive. Proposed commentary clarifies purpose of bevel cuts at the peak and also clarifies that figures are for illustration of common details versus requirements.

Proposal IT3-1 (Y=14, YR= 7, N=1 , NV=2 --95%)

Hamburger (YR): Line 19- "or" should be "of"

IT 3 Response: Editorial It is not clear what the table on the top of page 11 is supposed to be. Please clarify.

IT 3 Response: Editorial. The table format was revised to improve appearance, and the Title of the table has been enhanced to better clarify the purpose.

Bachman (YR): This is a very well written document but I have a couple of comments. While I understand the chain analogy as presented, I do not this it is a good analogy for the foundation-structure system. Earthquake loads are not static loads and the structure is typically

IT-3 chair accepted all the editorial comments. The remaining comments were discussed and several revisions were proposed. Since most comments were from Yes with Reservation votes, the IT chair agreed to revise the white paper proposal to satisfy those comments. The Klingner comments were from a NO vote. However, several of them matched other voters. A motion was made for IT 3 to revise the proposal edits, YR comments, and to find the Klingner comments nonpersuasive. The PUC voted (18,0,0) to accept this motion and the revised proposal will be forwarded to the member organizations for ballot.

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not fixed to the earth. If, for example, the structure just rested unanchored to a foundation and it were allowed to uplift and slide (i.e. no link in the chain) it might perform just fine even for MCE level motions.

IT 3 Response: Nonpersuasive - as long as we use a force-based analogy to design structures for seismic (as opposed to multiple nonlinear response histories) then the load path concept is an essential tool for design.

Also, there is a problem with nonstructural component anchorage forces when an Rp = 1.5 is used. The margin between component design forces and anchorage forces is inconsistent between components located at the top of the structure and those located at the base of the structure. It is recommended that instead of using an Rp = 1.5, a factor of 2 be used in the design of anchorage, except where ductile anchorage provides the primary behavior in which case a minimum stretched length of the anchorage should be provided.

IT 3 Response: Nonpersuasive. Rp is related to capacity not demand. Also, the “base” generally does not include a foundation, therefore there is no correspondence with cantilever R values although it should probably be less.

Wood (YR): The following comments are primarily editorial.

• p. 7, “SPSW” is not defined – first row of Table 1. IT 3 Response: Editorial. Add “Steel Plate Shear Wall” definition as a footnote. • p. 8, line 5, add “the” before “soil” and before “foundations.” IT 3 Response: Editorial, even though it does not seem much different. • p. 9, line 18, “structure actions” should probably be “structural actions.” IT 3 Response: Editorial. • p. 12, line 1, it is unfortunate that this observation was not submitted to ACI during

the public comment period for ACI 318-08, as it probably could have been resolved. This concern should be shared with ACI for resolution in 318-11.

IT 3 Response: So noted. • p. 13, line 18, P’ should be defined in the text (the fact that it is defined in the

appendix is not sufficient) IT 3 Response: Editorial. • p. 13, line 23, “if Figure 6” should be “in Figure 6.” IT 3 Response: Editorial. Looks like it has been corrected… • p. 13, line 30, “.i.e.” should be “ i.e.” IT 3 Response: Editorial. • p. 13, line 33, Rd and Ro should be defined in this paper. IT 3 Response: Editorial. Does anyone have a suitable definition we can use? Other than the 1997 Blue Book? • p. 13, paragraph beginning on line 34, please provide a better explanation of why

foundation rocking/sliding is or is not acceptable for different types of structures. IT 3 Response: Persuasive. Suggested wording follows: “While this might be an acceptable or desired characteristic for structures using high-R systems or for essential facilities, it is probably an undesirable characteristic for ordinary-use structures using moderate- or low-R systems.

Because modest levels of foundation nonlinearity is generally considered to be acceptable for ordinary structures using moderate or lower R systems, the use of

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special load combinations would prevent such action and would result in an increase in their construction cost.

• p. 14, line 2, “a” is missing after “same manner as.” IT 3 Response: Editorial. • p. 14, line 20, the reference to the “assumption made” is rather vague. Please modify

to remove the ambiguity. IT 3 Response: Editorial. Suggested wording: …foundation capacity that is used. • p. 14, line 23, “precise” should be “accurate.” IT 3 Response: Editorial. http://en.wikipedia.org/wiki/Accuracy • p. 15, line 7, please revise sentence such that “assumed” is not used two times in the

first ten words. IT 3 Response: Editorial. Suggested wording follows:

It is likely that this scaling would be apply to the full value of E = Eh + Ev used in design, with no other reduction permitted, although it is recognized that the full effects of design including redundancy factors, importance factors and the vertical seismic component has not been studied in depth and might warrant some further improvements in the future.

• p. 15, line 11, the justification for the recommendation is rather general. How were the distinctions made between 5R ≥ , 3 5R≤ < , and 3R < ? Additional discussion of the recommendations is appropriate.

IT 3 Response: Nonpersuasive. However, the following edit might help with this point:

of 1.5 E might be more appropriate. However, until a more rational means of determining R values is determined this relatively simple table was judged to be effective in resulting in the preferred inelastic behavior distribution.

Crouse (YR):

p. 2 – line 6:allowable stress design (ASD) format toward an ultimate strength design (USD) IT 3 Response: Editorial.

p. 6 – line 4: Replace “behavior” with “response”. IT 3Response: Editorial

p. 9 – table: Fix headers so that words on one line don’t spill over into next line. IT 3 Response: Editorial.

p. 11 – table: same word spillover. Supply Section number. Provide references for values in table.

IT 3 Response: Editorial line 7: Should NEHRP 450-1 be FEMA 450-1?

IT 3 Response: Editorial The 2003 NEHRP Recommended Provisions

For New Buildings And Other Structures Part 1: Provisions (FEMA 450)

p. 12 – line 21: soil pressures, Qa, ⋅⋅⋅ soil strength, Qu, ⋅⋅⋅ IT 3 Response: Editorial. Assume that the suggestion is to add definitions? Perhaps a “frequent words” and “nomenclature list” could be added?

p. 13 – lines 18 & 19:Define P′. IT 3 Response: Editorial. line 23: Replace “if” with “of”.

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IT 3 Response: Editorial. line 33: Define Ro . IT 3 Response: Editorial. p. 14 – line 2: same manner as a IT 3 Response: Editorial. line 21: Replace “stain” with “strain” IT 3 Response: Editorial. line 39: Explain “increased strength.” It’s increased relative to what? IT 3 Response: Editorial. See following suggested wording:

It might therefore justify an increase of deep foundation strength relative for structures having occupancies and sites in higher seismic design categories. Thosestructures are expected to experience more than one damaging earthquake during the foundation service life, because the potential loss-of-use and cost for repairs is less acceptable.

p. 15 – tables: Reference citation for ASCE 41 should be provided at end of document. Also, suggest citations be provided for all codes, documents, and standards mentioned in paper. IT 3 Response: Editorial. p. 17 – Eqn (1): P′′ should be P′ IT 3 Response: Editorial. p. 23 – figures: Scales need to be labeled and units provided. Put number “2” in top figure and “4” in bottom figure in correct locations.

IT 3 Response: Editorial.

Johnson (NV): I am too close to this proposal and therefore abstain.

Line (YR): What AC is used to establish E/1.4 for uplift devices? It seems that E is the correct value for hold-downs per AC 155.

IT 3 Response: Abstain. We don’t understand question.

Aschheim (YR):

1. Page 2, Line 5: I wondered if perhaps “existing load combinations” was intended to refer to just ASD combinations; if so, rephrasing is needed since both ASD and USD/LRFD formats are in existence.

IT 3 Response: Nonpersuasive. The way it is written is encompassing: both the ASD and USD (Strength design) load combinations are in question.

2. Page 4, Line 20: structures do not show preferences (but people do) so some rephrasing is needed.


Designer’s of some types of non-building structures have shown a preference for using foundation anchor bolts as a yield mechanism to provide structural ductility. For example, ASCE 7-05 Section 15.7.5 and API standards require that vertical vessel

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structures typically found in oil refineries, which do not have significant ductility, be intentionally designed to create a plastic mechanism of tensile yielding in the anchor bolts used to attach the vessel to its foundation. The anchor bolts are specified to use ductile material and installed in a manner to facilitate tensile yielding over a significant length of the bolt. The anchorage used to attach the anchor bolts to the vessel as well as the vessel itself is then designed to mobilize the full strength of the anchor bolts.

Nonstructural components such as fan motors, piping systems and building facades often have cast-in or post-installed anchors with limited or no ductility for support. In some instances, the anchorage or bracket used to attach the component to the anchor is the element most capable of providing some degree of ductility in the attachment. In many cases imposed displacements may be the controlling factor in the anchorage design.

3. Page 5, Lines 16 and 17: periods are needed at the ends of these lines.

IT 3 Response: Editorial. 4. Page 11, Line 2: “Section xxx Load Conditions’ –seems like a change of some type is

needed. IT 3 Response: Editorial.

5. Figure 6, Page 13, and possibly elsewhere: would “curves” be preferable to “lines” ? IT 3 Response: Editorial, reject.

6. Page 13, Line 23: change the last word from “if” to “of” IT 3 Response: Editorial.

7. Page 16, Lines 16-19: the references should be completed. IT 3 Response: Editorial.

Manley (YR): Minor comment – on page 12 of 23, first paragraph, I recommend using the full designation ACI 318 when citing a specific section.


Cobeen (YR): I support the discussion that the white paper is initiating. I would like to have the following considered now or in future development of this white paper: 1) Regarding summary and recommendations on page 5: Figure 3 and Item 3 on page 6 (work performed in a small anchorage may not provide adequate hysteresis) make the argument that yield of the anchorage may not always be necessary and/or desirable. This fundamental issue does not appear to be taken up in the white paper discussion. As a designer I would like to see discussion of yielding/controlling behavior in the superstructure elements, the anchorage to foundations (bolt, plate, etc.), the foundation, or the soils, addressing in simple terms a) when it is permitted, b) with what design requirements for other parts of the system and c) with what goal for system behavior.

IT 3 Response: Nonpersuasive. However the points are well taken and should be addressed when this paper is developed further.

2) Page 15, Line 3 – I believe that this should be referring to the Basic Combinations for Strength Design per ASCE 7 Sec. 12.4.3.2.

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3) Page 15. I believe the discussion has focused on isolated shallow foundations. Consideration should be given in the future to continuous shallow foundations.

IT 3 Response: Nonpersuasive. However the point is well taken and should be addressed when this paper is developed further.

4) I am concerned that the recommendations in the page 15 tables are going to significantly effect the dead load that needs to be mobilized to resist overturning, as well as the quantities of concrete and rebar that are put into foundations; where as the problem that is being attacked has more to do with adequate bearing area to avoid soil failure or significant deformation under bearing loads. I would like to see further explanation of what the proposed changes in the tables will accomplish in terms of improved performance.

IT 3 Response: Persuasive. We should consider ramifications, benefit from increasing foundation cost. However, if this whitepaper is only the springing board to open discussion, we see no harm in leaving this question unresolved.

Klingner (No): I am not sure what we are voting on here. My understanding is that this “white paper” is intended to provide the background for future provisions and commentary. While I think that it’s appropriate for us to vote on those future provisions and commentary, I’m not sure what a “yes” vote on this item means. I believe that this “white paper” is on the right track, but it’s not done yet.

IT 3 Response: Nonpersuasive. The intent and findings of the whitepaper may lead a direction, one that we all should be comfortable in pursuing.

• The material on performance requirements for base plates and anchorages provisions

is generally good, but not nearly specific enough, and does not address the considerable work that has been done in this area by ACI Committee 355 and the joint BSSC task group. While the authors of the white paper have correctly distinguished between possible requirements for deformation capacity and for ductility, they will need to develop precise requirements in terms of ASTM test procedures and design provisions. For example, we cannot require that the specified strength of one part of an anchorage exceed the actual strength of another part of the anchorage, because we don’t know that actual strength. If we want to estimate a probable strength, we must either have a basis for doing so, or we must assume a probable system overstrength. For another example, if we require testing, we must specify the testing protocol (ASTM or ICC ES).

IT 3 Response: Nonpersuasive. The excellent points and the need for collaboration with ACI Committee 355 et. al. do need to occur, but that should be at a later date; this white paper was intended to provide a roadmap for development of future code provisions, not the actual provisions themselves. • The material on performance requirements for foundations is good but limited. It

needs to be extended to quantifiable requirements. I believe that the entire question of appropriate ASD factors deserves much more study than has been presented here.

IT 3 Response: Nonpersuasive. As above.

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• The section on performance requirements for anchorages could be much better

integrated with the section on performance requirements for foundations, because many of the fundamental objectives are quite similar. The designer is trying to encourage certain types of behavior and discourage others. The trick is to figure out appropriate margins of encouragement versus discouragement.

IT 3 Response: Nonpersuasive.