Cold-Formed-Steel-Design-Design-Standards-Part-1.pdf

Cold-Formed Steel Light- Frame Construction AISI S100 Section D4 y Roger LaBoube

1 SE University, University, February 2012

AISI Standards Development AISI Secretariat Committee on Specification for the Design of Cold-Formed Steel Structural Members

Committee on Framing Standards Standards for Cold- Formed Steel Framing General Provisions

Test Procedures Design Manual Design Guides SE University, University, February 2012

Design Methods Prescriptive Methods 2

AISI Standards Development AISI Secretariat Committee on Specification for the Design of Cold-Formed Steel Structural Members

Committee on Framing Standards Standards for Cold- Formed Steel Framing General Provisions

Test Procedures Design Manual Design Guides SE University, University, February 2012

Design Methods Prescriptive Methods 2

COFS Mission • To eli elimi mina nate te regu regula lato tory ry bar barri rier ers s and and increase the reliability and cost com co m et etit itiv iven enes ess s of co cold ld-f -for orme med d ste steel el framing in residential and light commercial building construction through improved design and installation standards. 3 SE University, University, February 2012

Member versus System Design


AISI Standards Hierarchy General Provisions

pec ca on

Requirements for engineered or prescriptive design

Design Standards

Prescriptive Methods 5 SE University, February 2012

2001 Standards 2003 Code Adoptions

6 SE University, February 2012

2007 Standards • Update Existing Standards: – – – – – –

AISI S200-07: General Provisions * AISI S211-07: Wall Stud Design * AISI S212-07: Header Design * AISI S213-07: Lateral Design * AISI S214-07: Truss Design * AISI S230-07: Prescriptive Method for One and Two Family Dwellings

• New Standards: – AISI S201-07: Product Standard * – AISI S210-07: Floor and Roof System Design * 7 SE University, February 2012

* North American Standards • Intended for adoption and use in the United States, Canada and Mexico • Integrated treatment of ASD, LRFD and LSD –

ccomp s e y nc u ng e appropr a e resistance factors (φ) for use with LRFD and LSD, and the appropriate factors of safety (Ω) for use with ASD.

• LSD is limited to Canada • LRFD and ASD are limited to Mexico and the United States 8 SE University, February 2012

AISI Framing Standards • General: – AISI S200-07: General Provisions – AISI S201-07: Product Standard – Code of Standard Practice, 2006 Edition

• Design Standards: – – – – –

AISI S210-07: Floor and Roof S stem Desi n AISI S211-07: Wall Stud Design AISI S212-07: Header Design AISI S213-07: Lateral Design AISI S214-07: Truss Design

• Prescriptive Methods: – AISI S230-07: Prescriptive Method for One and Two Family Dwellings 9 SE University, February 2012


pec ca on Design Standards


AISI S200: General Provisions A. GENERAL B. MEMBER DESIGN C. INSTALLATION D. CONNECTIONS E. MISCELLANEOUS


AISI S200: General Provisions • A. GENERAL – – – – – –

A1 Scope A2 Definitions A3 Material A4 Corrosion Protection A5 Products A6 Referenced Documents

• B. MEMBER DESIGN – B1 Members – B2 Member Condition

• C. INSTALLATION – C1 In-Line Framing – C2 Non-Structural Wall Framing – ns a a on Tolerances

• D. CONNECTIONS – D1 Screw Connections – D2 Welded Connections – D3 Other Connections

• E. MISCELLANEOUS – E1 Utilities – E2 Insulation

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Member Design • Member design is to be in accordance with AISI S100: Specification • Members shall be in good condition • Damaged members to be replaced/repaired • Not permitted without approved design: – Web holes – Cutting or notching of flanges or lips – Splicing 13 SE University, February 2012

Installation Tolerances • Foundation: – Uniform bearing surface with maximum 1/4” gap between the track and foundation

• Ground Contact: – Avoid direct contact with the ground and provide sufficient height above ground

• Framing: – Install plumb and level, spacing not to exceed span capacity of sheathing, bearing requirements 14 SE University, February 2012

Installation Tolerances • Floor joist web must not be in contact with rim joist web to prevent squeaks


Installation Tolerances • Wall stud must be seated in track with maximum gap of 1/8”


Installation Tolerance


Screw Connections • Installation: – Minimum of 3 exposed threads – No permanent separation between plies

Minimum 3 exposed threads shall protrude through steel SE University, February 2012

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Screw Connections • Stripped Screws: – Stripped screw fasteners in direct tension are considered ineffective – Stripped screw fasteners in shear may be considered effective (not more than 25% of the total number considered effective)


Screw Connections • Spacing: – Provides for an allowance if the spacing is less than 3 times screw diameter, as specified by AISI S100: Specification – If spacing is greater than 2 times screw diameter, screws can be considered 80% effective


Screw Connections • Pattern: - Distinct pattern vs. shotgun blast


Corrosion Protection • “Additional corrosion protection is not required on edges of metallic-coated steel framing members, shop or field cut, punched .” • Recognizes zinc's ability to galvanically protect steel, and • Exposure of the underlying steel at a cut edge will not result in corrosion of the steel away from the cut edge 22 SE University, February 2012

In-Line Framing • No restriction existed that specifically a resses e case where the bearing stiffener is attached to the back side of the floor joist


In-Line Framing


AISI S201: Product Data A. GENERAL B. MATERIALS C. PRODUCTS D. QUALITY ASSURANCE


AISI S201: Product Data • Scope: – Materials, Coatings and Thickness – Shapes and Dimensions – Designators and Marking – Tolerances and Quality Assurance

• Purpose: – Simplify process for specifiers – Simplify process for inspectors – Enable development of load-span tables 26 SE University, February 2012

Materials • Referenced Standard: – ASTM A1003: Standard Specification for Steel Sheet, Carbon, Metallic- and Nonmetallic-Coated -

• Requirements: – Type H (high ductility), Structural Grade 33 or 50 – Type L (low ductility), Structural Grade 33 or 50 – Type NS, Nonstructural Grade 33


Thickness


Coatings • Referenced Standard: – ASTM A1003: Standard Specification for Steel Sheet, Carbon, Metallic- and Nonmetallic-Coated for Cold-Formed Framing Members

• Requirements: – Structural: G60 or equivalent – Non-structural: G40 or equivalent 29 SE University, February 2012

Shapes


Shapes S T U F L

= C-shaped stud or joist = Tr k = Cold rolled channel = Furring (hat) channel = Angle or L-header 31


Product Designator

600 S 162 - 54 2 or 3 digit numeral indicating base metal thickness in 1/1000 inch (mils) (0.054”) 3 digit numeral indicating flange width in 1/100 inches (1-5/8”), followed by a dash Letter indicating the type of product (C-shape section) 3 or 4 digit numeral indicating web depth in 1/100 inches (6”) 32 SE University, February 2012

Dimensions


Dimensions


Punchouts


Punchouts


Product Marking • Stru Structu ctura rall mem membe bers rs sha shallll be ma marke rked d leg legib ibly ly to indicate conformance with the following minimum characteristics: – manufacturer (name, logo or initials) initials) – steel designation designation thickness exclusive exclusive of coatings – minimum coating designation designation if other than G60 G60 – minimum yield strength strength if other than Grade 33

• Co Colo lorr co codi ding ng of me memb mber ers s or or bun bundl dles es 37 SE University, University, February 2012

Manufacturing Tolerances • Reference ced d Sta tan ndards: – Structural: ASTM ASTM C955 – Non-Structural: ASTM ASTM C645 C645

• – – – – –

Length Web Depth Flare and Over-bend Over-bend Hole Center Width and and Length Crown, Camber, Bow Bow and Twist 38

SE University, University, February 2012

Quality Assurance • Do Docu cume ment nted ed qu qual alit ity y cont contro roll prog progra ram m • Fi Fililing ng me meth thod ods s tha thatt doc docum umen entt the the procedures


Code of Standard Practice A. B. C. D. E. F. G. H.

GENERAL CLASSIFICATION OF MATERIALS CONTRACT INSTALLATION DRAWINGS MATERIALS INSTALLATION QUALITY CONTROL CONTRACTUAL RELATIONS


Scope • Defines and sets forth accepted norms of good practice for fabrication and installation of cold-formed steel s ruc ura ram ng • Supplement to legal building regulation • Would be used unless differing instructions in the contract documents • Voluntary document 41 SE University, February 2012

Model Documents • AISC - Code of Standard Practice for Steel Buildings and Bridges •

– Steel Joists and Joist Girders


Other Related Documents • CASE (Council of American Structural Engineers) – National Practice Guidelines for Specialty Structural Engineers – National Practice Guidelines for the Structural Engineer of Record – A Guideline Addressing Coordination and Completeness of Structural Construction Documents

• STCA Standard Practices and Recommended Guidelines on Responsibilities for Construction Using Cold-Formed Steel Trusses and Components 43 SE University, February 2012

Example 2 • Responsibilities for field modifications and repairs must be c ear y e ne an communicated


Summary • Addresses “Who is responsible for what?”



pec ca on Design Standards


AISI S210: Floor and Roof System Design • Load Combinations • Member Design: – – Continuously Braced Design

• Connection Design: – Bearing Stiffeners

• Bracing Design 47 SE University, February 2012

Member Design • Discretely braced design: – Neglect attached sheathings – Discrete braces provided along member len th

• Continuously braced design: – Sheathing or deck attached to compression side – Continuous or discrete bracing attached to tension side 48 SE University, February 2012

Connection Design


Bracing Design • Provides a “prescriptive” approach for compression side bracing: – 3/8 inch wood structural sheathing or 9/16” x . c ness s ee ec – attached with No. 8 screws at 12 inches o.c.

• Adapts requirements for tension side bracing from AISI S100 (Specification) requirements for members where neither flange is attached to sheathing 50 SE University, February 2012

MEMBER BRACING (AISI S100 Section D3.2.1)

Neither Flange Restrained and the load acts through the plane of the web: •

Design brace force, PL:

•

Uniform load, PL = 1.5 K'W

•

Concentrated load, PL = 1.0 K'P + 1.4K'P(1- l/a)


51

MEMBER BRACING


52

C-SECTION BRACING FORCES P F

For a uniform load per unit length, P: PL = 1.5K’aP SE University, February 2012

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MEMBER BRACING P F F

F=

Pm d

P

F


= PK’

F

54

AISI S211: Wall Stud Design • Load Combinations • Sheathing Braced Design - • Deflection Track Connection


Load Combinations • Combined Bending and Axial Strength: – MWFRS wind loads

• – C&C wind loads

• Deflection Limits: – 70% of C&C wind loads with no axial loads


Wall Stud Design • All-steel design: – Neglect attached sheathings

• Sheathin braced desi n: – Identical sheathing attached to both sides – Unbraced length (strong axis) taken as distance between member ends – Unbraced length (weak axis and torsion) taken as twice the distance between sheathing connectors 57 SE University, February 2012

Wall Stud Design


Wall Stud Design • Special load combination for evaluation of the stud without sheathing in the event the sheathin has been removed or has accidentally become ineffective 1.2D + (0.5L or 0.2S) + 0.2W


Stud-to-Track Connection

Pnst

 R  N  h        1 + C N 1 − Ch = Ct Fy 1 − C R     t  t  t   2


D110-07: Example 1 – Curtain Wall • Height = 13 ft • Spacing = 16 in. o.c. •

= w = 28(16/12) = 37.33 lbs/ft

• Deflection Limit = L/360

•

Check 600S162-43, Fy = 33 ksi (based on two rows of bridging). 61



Check 600S162-43 (Fy = 33 ksi) (Per AISI Specification) Applied Moment = wL2/8 = 37.33(13)2/8 = 789 ft-lbs = 9.46 in.-kips section modulus, Sxe; Ma = 15.2 in.-kips (without punch-out) = 15.1 in.-kips (with 1.5 in. punch-out) OK for bending check! 63 SE University, February 2012

Sxe and Post-Buckling Stress Distribution

AISC E7 64 SE University, February 2012

Check 600S162-43 (Fy = 33 ksi) Deflection,

δ

= 5wL4/(384EIx) = 0.351 in.

Ix = full moment of inertia = 2.316 in. 4 w = 37.33 lbs/ft . 70% of Components & Cladding wind load) δ δ =

0.246 in.

L = 13x12 = 156 in. ; E = 29500 ksi Permissible Deflection = 156/360 = 0.433 in. OK for serviceability check! SE University, February 2012

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Check Shear (Per AISI Specification) Applied End Shear: V = 0.5wL = 0.5(37.33)(13) = 243 lbs = 0.243 kips Using Section C3.2 and CFS software: Va = 1.42 kips (without punch-out) = 1.24 kips (with 1.5 in. punch-out) OK for shear! 66 SE University, February 2012

Check Web Crippling Applied End Reaction: P = 0.5wL = 0.5(37.33)(13) = 243 lbs = 0.243 kips


Web Crippling (Per AISI Specification) Using Section C3.4: Check web crippling at bottom track  R  N  h        Pn = Ct Fy sin θ 1 − CR 1 + CN 1 − Ch     t t t    2

E .C3.4.1-1

C = 4, CR = 0.14, CN = 0.35, Ch = 0.02, Ω = 1.75 Note: the above value is for a web without a web opening near the support. See AISI Section C3.4.2 if a web opening is near the support. 68 SE University, February 2012

Web Crippling (Per AISI Specification) Assume a 600T125-43 track Section A2.4 stipulates the requirement of .95tdesign = .

.

= .

.

R/t = 0.0712/0.0451 = 1.58 h/t = 5.767/0.0451 = 128 Assume N = 1 in. with a ¼ in. gap N/t = 1/0.0451 = 22.2 69 SE University, February 2012

Web Crippling (Per Wall Stud Standard) If a 600T125-43 is specified and N = 1 in., the stud to track gap is 0.25 in. Note: track thickness does not have to match stud c ness. Section C1 of the Wall Stud Standard stipulates that for curtain walls the ends of the wall studs shall be seated squarely in the track with no more than 1/4 in. gap between the end of the stud and the track. 70 SE University, February 2012

Web Crippling (Per AISI Specification)

.

. .

Pa = Pn/Ω = 0.453 kips/1.75 = 0.259 kips, which is greater than 0.243 kips - OK Note: the above value is for a web without a web opening near the support. See AISI Section C3.4.2 if a web opening is near the support. 71 SE University, February 2012

Web Crippling (Per AISI Specification) Section C3.4.2 for a web opening near the support. [EOF], assume x = 9 in.: Rc = 1.01 – 0.325(do/h) + 0.083(x/h) ≤ 1.0 q.

. . -

= 1.01 – 0.325(2.5/5.767) + 0.083(9/5.767) = 0.999 ~ 1.0 No reduction is required for a punch-out located 10 in. from the end of the member to the near edge of the web punch-out (per industry standard). 72


Web Crippling (Per Wall Stud Standard)

Eq.C4.2-1

. ,

R

.

,

N

.

,

h

.

,

Ω = 1.70 Why the increase? Consider the load path! Note: the above value is for a web without a web opening near the support. See AISI Section C3.4.2 if a web opening is near the support. SE University, February 2012

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Web Crippling (Per Wall Stud Standard)

Eq.C4.2-1

Pa = Pnst/Ω = 0.666 kips/1.70 = 0.392 kips Note: Using the Wall Stud Standard results in a 51% increase in web crippling design strength. 74 SE University, February 2012

Single Deflection Track


Deflection Track Connection wdt

Track

θ

e

θ

D

Stud

bstud

Figure C4.3-1 Deflection Track Connection


Deflection Track Design (Per Wall Stud Standard) Assume single deflection track: Gap, e = 1.5 in.; D = 1.0 in. - tdesign = 0.097/0.95 = 0.102 in.

Studs must have a line of bridging 12 in. from the end. 77 SE University, February 2012

Deflection Track Design (Per Wall Stud Standard)


Deflection Track Design (Per Wall Stud Standard)

wdt wdt SE University, February 2012

= effective track width = 0.11(e0.5/t1.5) + 5.5 ≤ S = 9.64 in. ≤ 16 in., Use 9.64 in.

79

Deflection Track Design (Per Wall Stud Standard) Pnst(e) = ZFy ; Z = wdt t2/4 Pnst

= wdt t2Fy/(4e) = 9.64(0.102)2(50)/(4x1.5) = 0.836 kips

Pa = Pnst/Ω = 0.836/2.8 = 0.298 kips End reaction from before = 0.243 kips Since 0.298 kips > 0.243 kips 600T250-97 OK! SE University, February 2012

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Deflection Track Design (Per AISI Specification) • Web crippling of stud at the top track location must still be checked. N = D = 1 in. • Use unfastened coefficients for EOF Loading in Table C3.4.1-2 of the AISI Specification. • Pa = 0.255 kips, which is greater than 0.243 kips OK SE University, February 2012

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AISI Framing Standards •

General: – AISI S200-07: General Provisions – AISI S201-07: Product Standard – Code of Standard Practice, 2006 Edition

•

Design Standards: – – – – –

•

AISI S211-07: Wall Stud Design AISI S212-07: Header Design AISI S213-07: Lateral Design AISI S214-07: Truss Design

Prescriptive Methods: – AISI S230-07: Prescriptive Method for One and Two Family Dwellings 82


Cold-Formed Steel Design, 4th Edition

The book has been thoroughly updated and expanded to reflect: 2007 North American Specification 2007 North American Framing Standards and other newly published standards and documents.

Ordering information:

www.ccfssonline.org Price: $110 plus shipping 83 SE University, February 2012

Wei-Wen Yu Center for Cold-Formed Steel Structure [email protected], 573-341-4481


Cold-Formed-Steel-Design-Design-Standards-Part-1.pdf

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