The History of Steel Stud Manufacturing

Report
Cold-Formed Steel
History, Innovation and Design
Jon-Paul Cardin, P.E.
[email protected]
The History of Steel Framing Design
 Use of cold-formed steel members started in both the United States
and England in 1850’s
 Although, use of steel framing limited up to the 1930 due to lack of
design standards
 1939 American Iron and Steel Institute (AISI) sponsored a research
project at Cornell University to develop specification for CFS
 In 1946 the first Design Specification was published by AISI
 The Specification has been updated and revised incrementally over
the years
 In 2001 the first NASPEC was published in coordination with Canada
and Mexico
The History of Steel Stud Manufacturing
 In the 1980’s every steel stud manufacturer had products with
different dimensional profiles, steel thicknesses, and design
specification catalog
 Standard steel thickness was a Nominal thickness 0.0359” for 20
gauge with tolerance of +/- 0.0030” (0.0329” – 0.0389”)
 The tolerance was put in place because the steel mills could not
guarantee minimum thicknesses during this time
 By the end of the 1980’s the mill equipment was improved and the
tolerances became tighter
The History of Steel Stud Manufacturing
1990’s - Present

In the 1990’s manufacturers decided to standardize the steel framing
industry by developing two manufacturing associations – one for the
east coast and one for the west coast

In 1998, these two groups merge into the Steel Stud Manufacturing
Association (SSMA) and standardizing the rest of the USA.
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Currently, the SSMA, Steel Framing Industry Alliance (SFIA) and
Certified Steel Stud Association (CSSA) are the three manufacturers
associations
Benefits of Designing with Steel
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Consistent material quality
Noncombustible
Dimensionally stable
 No Rot
 No Freeze/Thaw Effects
 No Warp due to Moisture
Insect resistant
Flexibility in design
Lightweight
High strength-to-weight ratio
Most recycled material
Technical Catalogs
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Member Section Properties
Allowable Span Tables
 Interior Wall Heights
 Composite
 Non-Composite
Curtain Wall Heights
Combined Axial and Lateral
Floor Joist Spans
Ceiling Spans
Connection Capacity Tables
Composite Vs. Non-Composite
Composite Wall Heights
•Obtained from Testing at an accredited
Laboratory. Tests are performed with
drywall attached both sides full height.
Non-Composite Wall Heights
•Calculated assuming drywall attached
both sides fully braced condition. The
code does not allow us to take the
strength of the drywall into account.
Composite Vs. Non-Composite
Composite Wall Heights
Member
Spacing
Deflection L/120
Deflection L/240
362S125-30
12”
22’ 10”
18’ 3”
16”
20’ 8”
16’ 7”
24”
18’ 1”
14’ 6”
Non-Composite Wall Heights
Member
Spacing
Deflection L/120
Deflection L/240
362S125-30
12”
19’ 11”
16’ 7”
16”
17’ 3”
15’ 0”
24”
14’ 1”
13’ 2”
Design Software
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CFS 8.0 - RGS Software
AISIWIN - Devco Software
LGBeamer – Devco Software
Other Proprietary Software
AISI Standards
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North American Specification – NASPEC (S100)
 Main Specification
 Members, Assemblies, Systems, Connections
General Provisions (S200)
Floor and Roof System Design (S210)
Wall Stud Design (S211)
Header Design (S212)
Lateral Design (S213)
Truss Design (S214)
Prescriptive Method for One and Two Family
Dwellings (S230)
CFS Design Manual (D-100)
 Section Property Calculation Examples
 Member Design Examples
CFS Design Guide (D-110)
 Full System Design Examples
Design Considerations
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Most failure modes of structural steel apply
In addition, CFS deals with thin/slender elements
 Web Crippling
 Local Buckling
 Distortional Buckling
 Flexural-Torsional Buckling
Utilize effective section properties
Web and Flange to Thickness Ratio Limitations for AISI Code
Equations
Flexural Member Bracing

Flexural Members require bracing to resist torsion due to
non-symmetric profile
 Sheathing Both Sides
 CRC Clipped to Stud
 Flat Strap and Blocking
 Sheathing One Flange with Rigid Bracing on Opposite
Flange
Axial Member Bracing
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Sheathing is not adequate for axial bracing
Bracing to resist both torsion and lateral displacement
Brace forces accumulate along stud wall at 2% of axial load,
so the forces must be terminated to the structure or floor
system
Axial Member Bracing
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Brace forces must be terminated to the structure or floor
system
 Flat strap cross bracing (Figure 5)
 Stud orientated in plane of the wall (Figure 6)
Web Stiffeners
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Web stiffeners may be required at bearing locations due to
web crippling
Web stiffeners required for h/t ratio between 200 and 260
 h = flat portion of web
 Ratio tables available in catalogs
Catalogs and software specify when required due to loading
Back to back member typically adequate web stiffener
Clips at member ends (head of wall or base connections) or
bypass locations considered web stiffeners
Innovation - High Strength Steel
 In 2005, Dietrich puts UltraSteel on the market with the following
characteristics:
 Excessive knurling of the entire stud (dimpled)
 Added a V-grove in the flanges
 Increased steel yield strength from 33 ksi to 40 ksi
 UltraSteel ended up NOT being a success, but it did open the door for the
concept of engineered studs
 The three characteristics that affect the strength of the stud:
 Thickness
 Profile
 Grade/strength of steel
“EQ” Framing
Why is it called EQ?
 EQ is an abbreviation for “equivalent”
 The strength of steel studs used to be related to the thickness of
the steel, but with the engineered studs, that is no longer the case
 EQ means that the stud is manufactured with thinner material, but
produces equivalent strength as the mentioned traditional stud
 Example:
33EQS
vs.
33mil
362SFS162-33EQS
362S162-33
Design thickness
0.0295
0.0346
Steel yield strength
57 ksi
33 ksi
Allowable moment
6.34 in-kips
5.29 in-kips
Engineered Header and Jamb Systems
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One and two piece pre-engineered systems available
Jamb is typically wide flange section
Clips connections from header to jamb studs
Consistent Installation and Connections
Consistent Installation and Connections
Member and Connection Capacities
 Member section properties available
 Typically proprietary software available
 Published allowable loads for clip connection
Published Capacities Based on Testing
 Test Ultimate Load and Serviceability Load (1/8”)
 Reduction factor based on material tested
 Safety factor based on test data reliability
 Publish lower of serviceability and reduced ultimate load
Useful Links for CFS

Cold-Formed Steel Engineers Institute
 www.cfsei.org
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American Iron and Steel Institute (AISI)
 www.steel.org
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Wei-Wen Yu Center for Cold-Formed Steel Structures
 www.ccfss.org
Thank You!
Cold-Formed Steel
History, Innovation and Design
Jon-Paul Cardin, P.E.
[email protected]

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