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Wall Studs

1. Is gypsum board sufficient to brace a wall stud?

2. When evaluating the strength of a wall stud that has sheathing attached to its flange, can a composite section be considered?

3. Through the punchout bracing, does it provide adequate bracing for a wall stud?

4. Are there design guidelines for assessing the performance of a wall stud with the web punchouts?

5. How do I specify a wall stud geometry?

6. What is the definition of a plumb wall stud?

7. What are reasonable deflection limits to apply for curtain wall design?

8. How does one determine the thickness of a deflection track?

9. When designing an intermediate brace for an all steel design, what is an appropriate design load?

10.Where can I find installation guidelines for wall studs?

11. Where can one find additional information regarding wall stud design?

12. The AISI Wall Stud Standard, AISI S211, indicates that the stud should be installed in accordance with the General Provisions Standard, AISI S200. In the General Provisions Section C3.4.1 it is stated that the stud is to be installed plumb. What is "plumb"?

13. Where can I find information on the service life for exterior load-bearing steel wall studs?

Question No. 1:

Is gypsum board sufficient to brace a wall stud?

Answer No. 1:

Section D4 of the North American Specification for the Design of Cold-Formed Steel Structural Members provides design guidance for wall studs and wall stud assemblies. Section D4 enables wall stud design based on an all steel design or a sheathing braced design. The industry has preferred the use of an all steel design for commercial applications. For residential applications, either the all steel or the sheathing braced design has been used. A soon to be published Standard for Cold-Formed Steel Framing - Wall Stud Design provides a sheathing braced design methodology that can be applied to either commercial or residential applications and is based on engineering principles. When published the Standard for Cold-Formed Steel Framing - Wall Stud Design will supercede Section D4 of the North American Specification for the Design of Cold-Formed Steel Structural Members .

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Question No. 2:

When evaluating the strength of a wall stud that has sheathing attached to its flange, can a composite section be considered?

Answer No. 2:

For structural wall applications limiting wall heights based on the sheathing acting as a composite section is not used. However, based on tested performance, the composite action may be used when determining limiting wall heights for non-structural walls. Refer to the SSMA Product Technical Information

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Question No. 3:

Through the punchout bracing, does it provide adequate bracing for a wall stud?

Answer No. 3:

Bending tests using the standard detail consisting of a screw attached clip and cold-formed steel channel have shown the brace to be adequate for both the 3.625 in. and 6 in. deep sections. The standard detail was not adequate for an 8 in. deep section.

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Question No. 4:

Are there design guidelines for assessing the performance of a wall stud with the web punchouts.

Answer No. 4:

Yes. The 2001 edition of the North American Specification for the Design of Cold-Formed Steel Structural Members contains design provisions for evaluating the axial capacity and the flexural capacity of the wall stud with openings. The Specification refers to the opening as a perforation.

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Question No. 5:

How do I specify a wall stud geometry?

Answer No. 5:

The industry has adopted a standard nomenclature for specifying a cold-formed steel framing member. Section A5 of the Standard for Cold-Formed Steel Framing - General Provisions summarizes the product designator.

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Question No. 6:

What is the definition of a plumb wall stud?

Answer No. 6:

Plumb is not defined in either the AISI specification or design standards. However the AIA MasterSpec Section 05400 on Cold-Formed Steel Framing states in Section 3.3 on Installation, General subsection J on Erection Tolerances to "install cold-formed metal framing level, plumb, and true to line to a maximum allowable tolerance variation of 1.8 inch in 10 feet (1:960). It should be noted that this is a guide specification and the values are suggested, but may be edited by the specifier.

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Question No. 7:

What are reasonable deflection limits to apply for curtain wall design?

Answer No. 7:

Deflection limits for a curtain wall depend on the type of sheathing. The SSMA Product Technical Information provides minimum wall height tables for common deflection limits. The soon to be published Standard for Cold-Formed Steel Framing - Wall Stud Design addresses serviceability in Section C6. Noteworthy is the Standard for Cold-Formed Steel Framing - Wall Stud Design provision that deflection limits are to be evaluated fro 70% of the Components and Cladding wind load.

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Question No. 8:

How does one determine the thickness of a deflection track?

Answer No. 8:

Section C4.3 of the Standard for Cold-Formed Steel Framing - Wall Stud Design contains design equations for determining the thickness of a single deflection track. The equations are empirical and thus are only applicable within the range of test parameters as defined by Section C4.3.

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Question No. 9:

When designing an intermediate brace for an all steel design, what is an appropriate design load?

Answer No. 9:

Section C5 of the Standard for Cold-Formed Steel Framing - Wall Stud Design stipulates that each intermediate brace shall be designed for 2% of the compression axial load in the member.

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Question No. 10:

Where can I find installation guidelines for wall studs?

Answer No. 10:

Installation guidelines for wall studs may be found in Section C3.4 of the Standard for Cold-Formed Steel Framing - General Provisions and Section D of the Standard for Cold-Formed Steel Framing - Wall Stud Design

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Question No. 11:

Where can one find additional information regarding wall stud design?

Answer No. 11:

For addition information regarding wall stud design, additional design information can be found by contacting truss manufacturers, the Center for Cold-Formed Steel Structures, ccfss@mst.edu, or the Cold-Formed Steel Engineers Institute, www.cfsei.org.

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Plumbness is not defined in the AISI specification or standards or the building codes. However, the AIA MasterSpec Section 05400 on Cold-Formed Steel Framing states in Section 3.3 on Installation, General subsection J on Erection Tolerances to "install cold-formed metal framing level, plumb, and true to line to a maximum allowable tolerance variation of 1/8 inch in 10 feet (1:960)". It is noted that this is a guide specification and the values are suggested, but may be edited by the specifier.

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Question No. 9

Where can I find information on the service life for exterior load-bearing steel wall studs?

Answer No. 9

The service life for exterior load-bearing steel stud walls depends on the in-place condition and is a function of the building location, class of exposure, and quality of construction. More detailed information regarding the service life can be found in the AISI document Durability of Cold-Formed Steel Framing Members published in 1996. For copies of this document and other information pertaining to the serviceability of steel framing see www.steelframingalliance.com .

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