Jon-Paul Cardin, P.E.
JPCardin@SCAFCO.com

 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

 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

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.
 Currently, the SSMA, Steel Framing Industry Alliance (SFIA) and
Certified Steel Stud Association (CSSA) are the three manufacturers associations

Benefits of Designing with Steel
 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

 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 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 Wall Heights
Member
362S125-30
Spacing
12”
16”
24”
Non-Composite Wall Heights
Member
362S125-30
Spacing
12”
16”
24”
Deflection L/120 Deflection L/240
22’ 10” 18’ 3”
20’ 8”
18’ 1”
16’ 7”
14’ 6”
Deflection L/120 Deflection L/240
19’ 11” 16’ 7”
17’ 3”
14’ 1”
15’ 0”
13’ 2”

 CFS 8.0 - RGS Software
 AISIWIN - Devco Software
 LGBeamer – Devco Software
 Other Proprietary Software

 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

 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 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

 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

 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 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

 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

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
Steel yield strength
Allowable moment
0.0295
57 ksi
6.34 in-kips
0.0346
33 ksi
5.29 in-kips

Engineered Header and Jamb Systems
 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

 Cold-Formed Steel Engineers Institute
 www.cfsei.org
 American Iron and Steel Institute (AISI)
 www.steel.org
 Wei-Wen Yu Center for Cold-Formed Steel Structures
 www.ccfss.org

Jon-Paul Cardin, P.E.
JPCardin@SCAFCO.com