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Cold-Formed Steel History, Innovation and Design Jon-Paul Cardin, P.E.

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Presentation on theme: "Cold-Formed Steel History, Innovation and Design Jon-Paul Cardin, P.E."— Presentation transcript:

1 Cold-Formed Steel History, Innovation and Design Jon-Paul Cardin, P.E.

2  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 Framing Design

3  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 ” for 20 gauge with tolerance of +/ ” (0.0329” – ”)  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

4 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 The History of Steel Stud Manufacturing

5  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 Benefits of Designing with Steel

6 Technical Catalogs  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

7 Composite Wall Heights Non-Composite Wall Heights Composite Vs. Non-Composite Obtained from Testing at an accredited Laboratory. Tests are performed with drywall attached both sides full height. Calculated assuming drywall attached both sides fully braced condition. The code does not allow us to take the strength of the drywall into account.

8 Composite Vs. Non-Composite MemberSpacingDeflection L/120Deflection L/ S ”22’ 10”18’ 3” 16”20’ 8”16’ 7” 24”18’ 1”14’ 6” Composite Wall Heights MemberSpacingDeflection L/120Deflection L/ S ”19’ 11”16’ 7” 16”17’ 3”15’ 0” 24”14’ 1”13’ 2” Non-Composite Wall Heights

9 Design Software  CFS RGS Software  AISIWIN - Devco Software  LGBeamer – Devco Software  Other Proprietary Software

10 AISI Standards  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

11 Design Considerations  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

12 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

13 Axial Member Bracing  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

14 Axial Member Bracing  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)

15 Web Stiffeners  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

16  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 Innovation - High Strength Steel

17 “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 362SFS162-33EQS362S Design thickness Steel yield strength57 ksi33 ksi Allowable moment6.34 in-kips5.29 in-kips

18  One and two piece pre-engineered systems available  Jamb is typically wide flange section  Clips connections from header to jamb studs

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21  Member section properties available  Typically proprietary software available  Published allowable loads for clip connection

22  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

23 Useful Links for CFS  Cold-Formed Steel Engineers Institute   American Iron and Steel Institute (AISI)   Wei-Wen Yu Center for Cold-Formed Steel Structures 

24 Cold-Formed Steel History, Innovation and Design Jon-Paul Cardin, P.E. Thank You!


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