AC70-1012-R1 #12
AC70-1012-R1 #12 AC70-1012-R1 September 11, 2012 Mr. Brian Gerber Ms. Elyse Levy International Code Council Evaluation Service (ICC ES) 5360 Workman Mill Road Whittier, CA 90601 2256 RE: Agenda item 12: Acceptance Criteria AC70 Dear Mr. Gerber and Ms. Levy, I am writing concerning the proposed paragraph to be added to section 6.0 on Interior, Nonstructural Walls. The transverse pressure for this application should be 10 PSF at a minimum, and even include an exception up to 15 PSF for specific applications. The American Iron and Steel Institute (AISI) has included this 10 PSF limit in both AISI S200, and the new AISI S220 11 North American Standard for Cold Formed Steel Framing Nonstructural Members. I was involved in the discussions leading up to both limits, and provide the following points: Part of the committee concern was to exclude the exterior building envelope from the applicability of nonstructural partitions. Therefore, wording was added to AISI S220 to exclude the gravity load resisting system, lateral force resisting system, or building envelope. This is part of the definition of nonstructural member. There was a concern that allowing pressures greater than 10 PSF would permit these members and systems to be used to resist wind loads. The above exclusion prohibits that usage. Furthermore, the AISI S220 document permits an exception for pressurized air plenums, ceilings, and elevator shaft enclosures, with allowable design pressures up to 15 PSF. With respect to section 13.5.8 of ASCE 7 10, this could be referenced in this section, but should not be used to justify a 5 PSF pressure limitation. Seismic loads are definitely not pressures: seismic loads must be considered in multiple directions other than just transverse. Section 13.5.8 includes exceptions that are not stated in the proposed paragraph. A revised proposed paragraph is included as an attachment, along with referenced sections from AISI S220 and ASCE 7 10. Sincerely, DSi ENGINEERING, LLC Don Allen, P.E. Senior Engineer enclosure 5550 Triangle Parkway Suite 100 Norcross, Ga. 30092 Phone: 770-409-4487 Fax: 770-242-6305
AC70-1012-R1 Attachment 1 Proposed rewording of paragraph to be added to section 6.0 of AC70, that would appear in the design section of evaluation reports: Interior, Nonstructural Walls: For interior, nonstructural walls that are not subject to sustained tension loads, the power-driven fasteners described in Section # may be used to attach steel track to concrete or steel in all Seismic Design Categories, provided substantiating data or calculations are submitted addressing the connection capacity. Track and stud members supported by these power-driven fasteners must qualify as nonstructural members in accordance with the nonstructural member definition and scope statement in AISI S220. In addition, limitations in section 13.5.8 of ASCE 7-10 shall be considered. The design load on the fastener must not exceed the allowable load shown in Tables #, # and #, as applicable. For reference: Applicable portion of AISI S220 scope statement: This standard applies to nonstructural members that comply with the following: 1) Member is in a steel-framed system that is limited to a transverse (out-of-plane) load of not more than 10 lb/ft 2 (0.48 kpa). Exception: Pressurized air plenums, ceilings and elevator shaft enclosures are permitted to have a load of not more than 15 lb/ft 2 (0.72 kpa). 2) Member is in a steel-framed system that is limited to a superimposed axial load, exclusive of sheathing materials, of not more than 100 lb/ft (1.46 kn/m). 3) Member is limited to a superimposed axial load of not more than 200 lbs (0.89 kn). AISI S220 definition of nonstructural member: Nonstructural Member. A member in a steel framed system that is not a part of the gravity load resisting system, lateral force resisting system or building envelope. ASCE 7 10 section 13.5.8, with exception: 13.5.8 Partitions 13.5.8.1 General Partitions that are tied to the ceiling and all partitions greater than 6 ft (1.8 m) in height shall be laterally braced to the building structure. Such bracing shall be independent of any ceiling lateral force bracing. Bracing shall be spaced to limit horizontal deflection at the partition head to be compatible with ceiling deflection requirements as determined in Section 13.5.6 for suspended ceilings and elsewhere in this section for other systems. EXCEPTION: Partitions that meet all of the following conditions: 1. The partition height does not exceed 9 ft (2,740 mm). 2. The linear weight of the partition does not exceed the product of 10 lb (0.479 kn) times the height (ft or m) of the partition. 3. The partition horizontal seismic load does not exceed 5 psf (0.24 kn/m 2 ). 13.5.8.2 Glass Glass in glazed partitions shall be designed and installed in accordance with Section 13.5.9. 5550 Triangle Parkway Suite 100 Norcross, Ga. 30092 Phone: 770-409-4487 Fax: 770-242-6305
AC70-1012-R1 #12 Subject: Comments on Proposed Revisions to ICC-ES AC70 September 11, 2012 Dear Mr. Gerber, Hilti is offering the following public comments on your letter dated August 21 st, 2012 regarding proposed revisions to ICC-ES AC70 Acceptance Criteria for Power-Driven Fasteners in Concrete, Steel and Masonry Elements. In reference to Item 8 in your letter, Hilti does not believe that a 5 psf limitation should be placed on the transverse load of the partition wall. We believe that this is an incorrect and overly conservative interpretation of the code. Instead, AC70 and the ESRs should simply point the Design Professionals and Building Officials to the relevant code sections for the particular application. We feel that since engineering calculations are required to be submitted to the Building Official, the Design Professional should use their judgment as to what type of fastening system to use and justify that use through calculations that are submitted to the Building Official for the project. Our proposed alternative language is as follows: Interior Walls and Partitions: For interior walls and partitions that are not subject to sustained tension loads, the power driven fasteners described in Section 3.1 may be used to attach steel track to concrete or steel in all Seismic Design Categories, where the design is done in accordance with IBC Section 1607.14 and ASCE 7-10 Section 13.5.8, provided substantiating calculations are submitted addressing the fastener-tobase material capacity and the fastener-to-attached material capacity. Interior walls and partitions are limited to locations where bearing walls, shear walls or braced walls are not required by the approved plans. The design load on the fastener must not exceed the allowable load shown in Tables 2, 3, 4 and 5, as applicable. In particular, IBC 2012 Section 1607.14 states Interior walls and partitions that exceed 6 feet (1829 mm) in height, including their finish materials, shall have adequate strength to resist the loads to which they are subjected but not less than a horizontal load of 5 psf (0.240 kn/m 2 ). This contradicts the language proposed by ICC-ES. Imposing a 5 psf transverse load limitation on this very common application would essentially render it undoable with power-driven fasteners, which have been used safely and successfully for cold-formed steel track attachments for many decades in seismic and non-seismic regions. The ICC-ES proposed load limitation of 5 psf is not reasonable and will damage both the cold-formed steel industry and the fastener industry. If the AC hearing discussion additional and arbitrary load limitations are imposed, then Hilti Hilti, Inc. 5400 South 122 nd East Avenue Tulsa, OK 74146 1-800-879-8000 www.hilti.com
would prefer to not include this language in ICC-ES AC70 or the ESRs at all, as it has not been done historically in this context. Doing so would significantly impact our business in a negative way. Furthermore, it should also be noted that power-driven fasteners are specifically approved for use in partition wall track fastening applications by OSHPD in California. If power-driven fasteners are acceptable for OSHPD, then they should be acceptable to ICC-ES. Regards, William G. Gould, P.E. Director, Codes & Approvals Hilti, Inc. Hilti, Inc. 5400 South 122 nd East Avenue Tulsa, OK 74146 1-800-879-8000 www.hilti.com
AC70-1012-R1 #12
AC70-1012-R1 #12
1 of 4 Design Example 1 - Full Height Partition Wall 9/4/2012 CFS Interior Nonstructural Walls - Using Power Driven Fasteners Outline This example will illustrate the following parts of the design process A. Transverse (out-of-plane) loads on interior nonstructural walls B. Design of CFS stud size and spacing C. Distribution of transverse (out-of-plane) loads to the CFS anchorage D. Allowable service load for fasteners driven into steel and concrete Given Information Interior Nonstructural Wall (Full Height Partition Wall): Partition Wall Height = 14'-0" 1/2" Gypsum Wallboard each side Dead Load of Interior Nonstructural Wall (Table C3-1, ASCE 7-10) = 8 psf Ceiling : Separation joint between Partition Wall and Ceiling meeting Ceiling horizontal deflections requirements of ASCE 7-10 z/h = 1.0 (Value 1.0 allows for installation at any floor or roof level of the building) CFS stud and runner (track)material strength: F y = 33 ksi ; F u = 45 ksi Power Driven Fasteners fastening to: Case 1, Structural Steel Support, 3/16" thick steel, ASTM A36 Case 2, 4" thick, normal-weight Concrete, f'c = 2500 psi Code Level Seismic Design Lateral Load Criteria: I p (Component Importance factor per Section 13.1.3, ASCE 7-10) = 1.5 S DS (Spectral acceleration, short period) = 1.95 A - Transverse (out-of-plane) Loads on Interior Nonstructural Walls 1. Interior walls and partitions that exceed 6'-0" in height,--- shall have adequate strength to resist the loads to which they are subjected to but not less than a horizontal load of 5 psf, per Section 1607.14 of 2012 IBC. 2. For all Seimic Design Categories (A, B, C, D, E and F) Seismic Design Force shall be calculated per Section 13.3.1 of ASCE 7-10. 3. Partitions that are tied to the ceiling and all partitions greater than 6 ft in height shall be laterally braced---. Bracing shall be spaced to limit horizontal deflection---. EXCEPTION: 1.-----. 2. ------, 3. The partitition horizontal seismic load does not exceed 5 psf, per Section 13.5.8.1 of ASCE 7-10. 4. Maximum transverse (out-of-plane) load is limited to 10 psf for Non-Structural member, per Section A2, Definitions of AISI S200. Generally ASD seismic transverse loads (0.7E) calculated per A 2 above are less than 5psf, thus minimum transverse load of 5 psf specified per A 1 above governs. Note that 10psf limit specified in A4 above is not a minimum transverse load for the design of non-structural member.
2 of 4 B - Design of CFS stud size and spacing 9/4/2012 1. Seismic Design Force: F p = 0.4 a p S DS W p (1 + 2 (z/h)) (R p /I p ) (13.3-1) F p 1.6S DS I p W p (13.3-2) = 1.6x1.95x1.5W p = 4.68W p F p 0.3S DS I p W p (13.3-3) = 0.3x1.95x1.5W p = 0.88Wp a p = 1.00 R p = 2.50 Table 13.5-1, ASCE 7-10 At any level of floor or roof level of the building (F p ) = 0.4x1.0x1.95x(1+2(1.0) (2.5/1.5) = 1.40W p Use Fp = 1.40 Wp 0.88 W p 4.68 W p Transverse load on wall (F p )ASD = 1.40 x 8 psf /1.4 = 8.0 psf Use 8 psf 5 psf (see A1, page 1) Seismic Load (ASD) Governs 10 psf (see A4, page 1) For Serviceability, Gypsum Wallboard finish is classified as flexible finish, per Section 1604.3 (Table 1604.3) of 2012 IBC, deflection limit = L/120. Using Interior Non-Structural Non-Composite, Wall Height Tables, Steel Stud Manufacturers Association, ICBO ER-4943P*, Product Technical Information, following is stud size and spacing: * Note that this Product Technical Information does not comply with 2012 IBC. 362S 125-27 @ 16" o.c.: Limiting Wall Height = 15'-11" (for 7.5 psf) Limiting Wall Height = 13'-10" (for 10 psf) For Partition Wall Height = 14'-0" and 8 psf; USE 362S 125-27 (F y = 33 ksi; F u = 45 ksi) @ 16" o.c. C - Tranverse (out-of-plane) Loads to the CFS Anchorage Calculation of shear load to CFS anchorage Shear load (ASD) to CFS anchorage at top or bottom of wall = (1.40/1.4) x 8 lbs/ft x 14.0'/2 = 56 lbs / ft
3 of 4 D - Allowable Service Load for Fasteners Driven into Steel and Concrete 9/4/2012 1. Allowable Service Loads for fastener driven into steel: 3/16" thick steel (support thickness), ASTM A36 Using Hilti Universal Knurled Shank fastener X-U, Shank Diameter d = 0.157" Allowable Shear Load = 720 lbs (Table 2, ICC-ES, ESR-2269) 2. Allowable Service Loads for fastener driven into concrete: 4" thick (support thickness) normal-weight concrete, f'c = 2500 psi Using Hilti Universal Knurled Shank fastener X-U, Shank Diameter d = 0.157" For minimum embedment = 1" < 4"/3 = 1.33" (Max. Embed) Allowable Shear Load = 190 lbs (Table 3, ICC-ES, ESR-2269) 3. Allowable Service Loads for fastener "Limited by Tilting and Bearing", Section E4.3.1, AISI S100: CFS runner (track) 27 mils (design thickness = 0.0283") F y = 33 ksi ; F u = 45 ksi Using Hilti Universal Knurled Shank fastener X-U, Shank Diameter d = 0.157" Allowable Shear Load = (2.7 x t 1 x d x F u1 )/Ω ; Ω = 3.0 (Eq. E4.3.1-4) (t 2 /t 1 2.5) = (2.7 x 0.0283 x 0.157" x 45000 psi )/3.0 Allowable Shear Load = 180 lbs Case 1, Structural Steel Support, 3/16" thick steel, ASTM A36 Allowable Shear Load = 180 lbs, item 3 above governs Anchorage at top and bottom of wall: Fastener spacing = (180 lb/ft / 56 lb/ft)x12 = 38.6" Use Hilti Universal Shank Fastener X-U at 36" o.c. (ICC-ES ESR-2269) Case 2, 4" thick, normal-weight Concrete, f'c = 2500 psi Allowable Shear Load = 180 lbs, item 3 above governs Anchorage at top and bottom of wall: Fastener spacing = (180 lb/ft / 56 lb/ft)x12 = 38.6" * Spacing of power driven fasteners (Fastening of runner to concrete slabs) not to exceed 24" o.c. per Section 5.2.2 of ASTM C754. Use Hilti Universal Shank Fastener X-U (Min. Embed = 1") at 24" o.c.* (ICC-ES ESR-2269)
4 of 4 Codes and Reference Standards: 9/4/2012 1. 2012 International Building Code (IBC), International Code Council. 2. ASCE/SEI 7-10, Minimum Design Loads for Buildings and Other Structures, American Society of Civil Engineers. 3. AISI S100, North American Specification for Design of Cold-Formed Steel Structural Members, 2007. 4. AISI S200, North American Standard for Cold-Formed Steel Framing - General Provisions, 2007. 5. Standard Specification for Installation of Steel Framing Members to Receive Screw-Attached Gypsum Panel Products (ASTM C754).
1 of 4 Design Example 2 - Partial Height Partition Wall 9/4/2012 CFS Interior Nonstructural Walls - Using Power Driven Fasteners Outline This example will illustrate the following parts of the design process A. Transverse (out-of-plane) loads on interior nonstructural walls B. Design of CFS stud size and spacing C. Distribution of transverse (out-of-plane) loads to the CFS anchorage at bottom of wall only D. Allowable service load for fasteners driven into steel and concrete Given Information Five story Building, each story height = 15'-0" Average roof height of structure (h)= 75'-0" Interior Nonstructural Wall (Partial Height Partition Wall): Partition Wall above 4th floor, Height = 12'-0" 1/2" Gypsum Wallboard each side Dead Load of Interior Nonstructural Wall (Table C3-1, ASCE 7-10) = 8 psf Ceiling: Partition that are tied to the ceiling shall be laterally braced to the building structure per Section 13.5.8.1 of ASCE 7-10. This example assumes ceiling lateral load is transferred by the brace above to the building structure CFS stud and runner (track)material strength: F y = 33 ksi ; F u = 45 ksi Power Driven Fasteners fastening to: Case 1, Structural Steel Support, 3/16" thick steel, ASTM A36 Case 2, 4" thick, normal-weight Concrete, f'c = 2500 psi Code Level Seismic Design Lateral Load Criteria: I p (Component Importance factor per Section 13.1.3, ASCE 7-10) = 1.0 S DS (Spectral acceleration, short period) = 1.25 A - Transverse (out-of-plane) Loads on Interior Nonstructural Walls 1. Interior walls and partitions that exceed 6'-0" in height,--- shall have adequate strength to resist the loads to which they are subjected to but not less than a horizontal load of 5 psf, per Section 1607.14 of 2012 IBC. 2. For all Seimic Design Categories (A, B, C, D, E and F) Seismic Design Force shall be calculated per Section 13.3.1 of ASCE 7-10. 3. Partitions that are tied to the ceiling and all partitions greater than 6 ft in height shall be laterally braced---. Bracing shall be spaced to limit horizontal deflection---. EXCEPTION: 1.-----. 2. ------, 3. The partitition horizontal seismic load does not exceed 5 psf, per Section 13.5.8.1 of ASCE 7-10. 4. Maximum transverse (out-of-plane) load is limited to 10 psf for Non-Structural member, per Section A2, Definitions of AISI S200. Generally ASD seismic transverse loads (0.7E) calculated per A2 above are less than 5psf, thus minimum transverse load of 5 psf specified per A1 above governs. Note that 10 psf limit specified in A4 above is not a minimum transverse load for the design of non-structural member.
2 of 4 B - Design of CFS stud size and spacing 9/4/2012 1. Seismic Design Force: F p = 0.4 a p S DS W p (1 + 2 (z/h)) (R p /I p ) (13.3-1) F p 1.6S DS I p W p (13.3-2) = 1.6x1.25x1.0W p = 2.00W p F p 0.3S DS I p W p (13.3-3) = 0.3x1.25x1.0W p = 0.38Wp a p = 1.00 R p = 2.50 Table 13.5-1, ASCE 7-10 At fourth floor base, z = 60.0' (F p ) = 0.4x1.0x1.25x(1+2(60.0/75.0) (2.5/1.0) = 0.52W p Use Fp = 0.52 Wp At top of partition wall, z = 72.0' (F p ) = 0.4x1.0x1.25x(1+2(72.0/75.0) (2.5/1.0) = 0.58W p Use Fp = 0.58 Wp Transverse load on wall (F p )ASD = 0.5(0.52 + 0.58)8 psf /1.4 = 3.1 psf Use 5.0 psf 5 psf (see A1, page 1) For Serviceability, Gypsum Wallboard finish is classified as flexible finish, per Section 1604.3 (Table 1604.3) of 2012 IBC, deflection limit = L/120. Using Interior Non-Structural Non-Composite, Wall Height Tables, Steel Stud Manufacturers Association, ICBO ER-4943P*, Product Technical Information, following is stud size and spacing: * Note that this Product Technical Information does not comply with 2012 IBC. 250S 125-18 @ 16" o.c.: Limiting Wall Height = 12'-0" (for 5.0 psf) USE 250S 125-18 (F y = 33 ksi; F u = 45 ksi) @ 16" o.c. C - Tranverse (out-of-plane) Loads to the CFS Anchorage Calculation of shear load to CFS anchorage Shear load (ASD) to CFS anchorage at bottom of wall = (0.52/1.4) x 8 lbs/ft x 12.0'/2 = 18 lbs / ft Shear load (ASD) to CFS anchorage at bottom of wall = 5 psf x 12.0'/2 = 30 lbs / ft Governs
3 of 4 D - Allowable Service Load for Fasteners Driven into Steel and Concrete 9/4/2012 1. Allowable Service Loads for fastener driven into steel: 3/16" thick steel (support thickness), ASTM A36 Using Hilti Universal Knurled Shank fastener X-U, Shank Diameter d = 0.157" Allowable Shear Load = 720 lbs (Table 2, ICC-ES, ESR-2269) 2. Allowable Service Loads for fastener driven into concrete: 4" thick (support thickness) normal-weight concrete, f'c = 2500 psi Using Hilti Universal Knurled Shank fastener X-U, Shank Diameter d = 0.157" For minimum embedment = 1" < 4"/3 = 1.33" (Max. Embed) Allowable Shear Load = 190 lbs (Table 3, ICC-ES, ESR-2269) 3. Allowable Service Loads for fastener "Limited by Tilting and Bearing", Section E4.3.1, AISI S100: CFS runner (track) 18 mils (design thickness = 0.0188") F y = 33 ksi ; F u = 45 ksi Using Hilti Universal Knurled Shank fastener X-U, Shank Diameter d = 0.157" Allowable Shear Load = (2.7 x t 1 x d x F u1 )/Ω ; Ω = 3.0 (Eq. E4.3.1-4) (t 2 /t 1 2.5) = (2.7 x 0.0188 x 0.157" x 45000 psi )/3.0 Allowable Shear Load = 120 lbs Case 1, Structural Steel Support, 3/16" thick steel, ASTM A36 Allowable Shear Load = 120 lbs, item 3 above governs Anchorage at bottom of wall: Fastener spacing = (120 lb/ft / 30 lb/ft)x12 = 48.0" Use Hilti Universal Shank Fastener X-U at 48" o.c. (ICC-ES ESR-2269) Case 2, 4" thick, normal-weight Concrete, f'c = 2500 psi Allowable Shear Load = 120 lbs, item 3 above governs Anchorage at bottom of wall: Fastener spacing = (120 lb/ft / 30 lb/ft)x12 = 48.0" * Spacing of power driven fasteners (Fastening of runner to concrete slabs) not to exceed 24" o.c. per Section 5.2.2 of ASTM C754. Use Hilti Universal Shank Fastener X-U (Min. Embed = 1") at 24" o.c.* (ICC-ES ESR-2269)
4 of 4 Codes and Reference Standards: 9/4/2012 1. 2012 International Building Code (IBC), International Code Council. 2. ASCE/SEI 7-10, Minimum Design Loads for Buildings and Other Structures, American Society of Civil Engineers. 3. AISI S100, North American Specification for Design of Cold-Formed Steel Structural Members, 2007. 4. AISI S200, North American Standard for Cold-Formed Steel Framing - General Provisions, 2007. 5. Standard Specification for Installation of Steel Framing Members to Receive Screw-Attached Gypsum Panel Products (ASTM C754).
1 of 2 Design Example 3 9/4/2012 Based on OSHPD Preapproved Details (OPD) - 2010 CBC Standard Partition Wall Details CFS Interior Nonstructural Walls - Using Power Driven Fasteners Outline This example will illustrate the following: A. Transverse (out-of-plane) loads on interior nonstructural walls Given Information* * From Reference 1 Partition Wall Height = 9'-0" to 16'-0" Interior Nonstructural Wall (Full Height Partition Wall): Two layers of Gyp Board on one side or one layer of Gyp Board on both sides Dead Load of Interior Nonstructural Wall = 7.5 psf (See General Notes 7C, sheet ST0.01) Seismic Coefficients (See General Notes 7D, sheet ST0.02): a p = 1.0 R p = 2.5 I p (Component Importance factor) = 1.5 S DS (Spectral acceleration 0.25 to 1.95, use 1.95) = 1.95 z/h = 1.0 (Value 1.0 allows for installation at any floor or roof level of the building) A - Transverse (out-of-plane) Loads on Interior Nonstructural Walls 1. Interior walls and partitions that exceed 6'-0" in height,--- shall have adequate strength to resist the loads to which they are subjected to but not less than a horizontal load of 5 psf, per Section 1607A.13 of 2010 CBC. 2. For all Seimic Design Categories (A, B, C, D, E and F) Seismic Design Force shall be calculated per Section 13.3.1 of ASCE 7-05. 3. Maximum transverse (out-of-plane) load is limited to 10 psf for Non-Structural member, per Section A2, Definitions of AISI S200. Seismic Design Force: F p = 0.4 a p S DS W p (1 + 2 (z/h)) (R p /I p ) (13.3-1) F p 1.6S DS I p W p (13.3-2) = 1.6x1.95x1.5W p = 4.68W p F p 0.3S DS I p W p (13.3-3) = 0.3x1.95x1.5W p = 0.88Wp (F p ) = 0.4x1.0x1.95x(1+2(1.0) (2.5/1.5) = 1.40W p Use Fp = 1.40 Wp 0.88 W p 4.68 W p Transverse load on wall (F p )ASD = 1.40 x 7.5 psf /1.4 = 7.5 psf 5 psf (see A1, page 1) Seismic Load (ASD) Governs 10 psf (see A4, page 1)
Codes and Reference Standards: 2 of 2 9/4/2012 1. 2010 California Building Code (Based on 2009 International Building Code). 2. ASCE/SEI 7-05, Minimum Design Loads for Buildings and Other Structures, American Society of Civil Engineers. References: 1. OSHPD Preapproved Details (OPD) - 2010 CBC Standard Partition Wall Details.
AC70-1012-R1 #12
AC70-1012-R1 #12 September 11, 2012 Mr. Brian Gerber, S.E. Principal Structural Engineer ICC Evaluation Services, LLC. 5360 Workman Mill Road Whittier, CA 90601 RE: Proposed Revisions to the Acceptance Criteria for Fasteners Power-driven into Concrete, Steel, and Masonry Elements, Subject AC70-1012-R1 Dear Mr. Gerber, We have reviewed the changes to AC70 that have been suggested and provide the following comments. Item #3 Please clarify whether the 1/8 inch minimum thickness limitation proposed is also applicable to Section 3.4.3.1 where the minimum thickness is listed as 3/16 inch. Item #4 While we understand the changes proposed to reflect Section 13.4.5 of ASCE 7, we recommend language be added to clarify that the use of fastener in steel material to resist seismic load of up to 250 pounds is for connection of a nonstructural component. The language may be suggested as follows: In steel base materials when used for non-structural applications where the service load on any individual fasteners does not exceed the lesser of 250 pounds (1112 N) or the published allowable load. Item #5 Please clarify whether the minimum thickness limitation for steel listed in Section 1.2 is applicable to metals other than steel. While we do not object to adding metals other than steel to AC70, it may be appropriate to discuss the issue of galvanic corrosion of dis-similar metals. Thank you for consideration of these comments. Should you have any questions, please do not hesitate to contact me. Sincerely, Ken Cho, P.E. Engineer kcho@strongtie.com Simpson Strong-Tie Company Inc. 5956 W. Las Positas Boulevard Pleasanton, CA 94588 Phone: 925.560.9000 Fax: 925.847.3871 www.strongtie.com
AC70-1012-R1 #12
AC70-1012-R1 #12