1. SOURCE 2
AISI SPECIFICATION

2. INTRODUCTION
Housed in the construction group of the American Iron and Steel Institute (
ANSI approved specification for the design of cold-formed steel structural members
Serves 4 primary industries:
Metal buildings (
Steel studs (
Racks (
Metal decks (

3. AISI SPECIFICATION EDITIONS
In primary use today
Basis for current LSF manual
1999 Supplement
New web crippling and shear capacity calculations for C-sections with holes
Changes to Base Test
2001 North American Edition
Combination of Canada, Mexico, and U.S.

4. 2001 NORTH AMERICAN SPECIFICATION
Broad philosophical changes
U.S., Canada &Mexico (ASD, LRFD, LSD)
Load combinations removed from the Specs.
Rational analysis clause when outside scope
Detailed changes of interest
Effective width changes
webs revised based on h/b ratio
flanges with multiple intermediate stiffeners revised (decks)
flanges with one edge stiffener cleaned up a bit
Web crippling completely revised
Fastener edge distances = 1.5d (vs. 3d before)
Fatigue provisions provided
full list at

5. 2001 NORTH AMERICAN SPECIFICATION
(from Section A1.1)

6. AISI SPECIFICATION COMPLICATION REASONS:
Typical sections are not doubly-symmetric (Torsional-flexural buckling possible)
Local buckling & post-buckling strength
Effective width
effective width = f(stress,geometry)
stress = f(effective properties: e.g., Aeff, Ieff)
iteration results
Web crippling calculations

7. AISI SPECIFICATION PRESENTATION
Basic overview
of behavior
(focusing on
C Sections)

8. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

9. A. GENERAL PROVISIONS MATERIAL DESIGN BASIS
TYPICAL APPROVED STEELS
OTHER STEEL AND DUCTILITY REQUIREMENTS
DESIGN BASIS
ASD
LRFD
LOAD FACTORS AND LOAD COMBINATIONS
STRENGTH INCREASE DUE TO COLD FORMING
Complete and detailed listing of ASTM grades that are applicable for cold-formed construction are given in the AISI Specification, Section A3.1.
Many of the grades are equally useable for cold-formed and hot-rolled construction. Differences appear in the products.
It is possible to use other steels than those listed in A3.1. However, these have to comply with the requirements of Sections A3.2 and 3.3, especially as far as ductility is concerned.
Overall, the intent is for the materials and the structural elements to display sufficient strength and ductility.
ASTM A847 and A875 have been added.

10. REQUIRED DUCTILITY (Section A2.3.1) Fu/Fy 1.08
A. GENERAL PROVISIONS
REQUIRED DUCTILITY (Section A2.3.1)
Fu/Fy
Elongation 10% (two-inch gage)
7% (eight-inch gage)
The criteria are applicable for steels used for members and connections.
Additional ductility provisions are given for low ductility steels.

11. A. GENERAL PROVISIONS MATERIAL DESIGN BASIS
TYPICAL APPROVED STEELS
OTHER STEEL AND DUCTILITY REQUIREMENTS
DESIGN BASIS
ASD
LRFD
LOAD FACTORS AND LOAD COMBINATIONS
STRENGTH INCREASE DUE TO COLD FORMING
Complete and detailed listing of ASTM grades that are applicable for cold-formed construction are given in the AISI Specification, Section A3.1.
Many of the grades are equally useable for cold-formed and hot-rolled construction. Differences appear in the products.
It is possible to use other steels than those listed in A3.1. However, these have to comply with the requirements of Sections A3.2 and 3.3, especially as far as ductility is concerned.
Overall, the intent is for the materials and the structural elements to display sufficient strength and ductility.
ASTM A847 and A875 have been added.

12. Ru Rn A. GENERAL PROVISIONS
ASD STRENGTH REQUIREMENTS (Section A4.1.1) R Rn/
LRFD STRENGTH REQUIREMENTS (Section A5.1.1)
Ru Rn
The required strength, R, is the load effect based on nominal loads using structural analysis and appropriate critical load combinations.
The nominal strength, Rn, comes from the nominal strength equations.
The Specification tabulates all factors of safety, .

13. A. GENERAL PROVISIONS MATERIAL DESIGN BASIS
TYPICAL APPROVED STEELS
OTHER STEEL AND DUCTILITY REQUIREMENTS
DESIGN BASIS
ASD
LRFD
LOAD FACTORS AND LOAD COMBINATIONS
(More on this later)
STRENGTH INCREASE DUE TO COLD FORMING
Complete and detailed listing of ASTM grades that are applicable for cold-formed construction are given in the AISI Specification, Section A3.1.
Many of the grades are equally useable for cold-formed and hot-rolled construction. Differences appear in the products.
It is possible to use other steels than those listed in A3.1. However, these have to comply with the requirements of Sections A3.2 and 3.3, especially as far as ductility is concerned.
Overall, the intent is for the materials and the structural elements to display sufficient strength and ductility.
ASTM A847 and A875 have been added.

14. A. GENERAL PROVISIONS MATERIAL DESIGN BASIS
TYPICAL APPROVED STEELS
OTHER STEEL AND DUCTILITY REQUIREMENTS
DESIGN BASIS
ASD
LRFD
LOAD FACTORS AND LOAD COMBINATIONS
STRENGTH INCREASE DUE TO COLD FORMING
Complete and detailed listing of ASTM grades that are applicable for cold-formed construction are given in the AISI Specification, Section A3.1.
Many of the grades are equally useable for cold-formed and hot-rolled construction. Differences appear in the products.
It is possible to use other steels than those listed in A3.1. However, these have to comply with the requirements of Sections A3.2 and 3.3, especially as far as ductility is concerned.
Overall, the intent is for the materials and the structural elements to display sufficient strength and ductility.
ASTM A847 and A875 have been added.

15. A. GENERAL PROVISIONS
Increase in yield and ultimate strength due to cold-work

16. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

17. LOCAL BUCKLING
PLATE BUCKLING
BUCKLING OF COMPONENT PLATE ELEMENTS

18. POST LOCAL BUCKLING STRENGTH
Photo shows post buckling behavior and interaction of local and overall buckling
P= 0.07 k k k k k k Pult= 7.9 k

19. EFFECTIVE WIDTH CONCEPT
The effective width, b, shall be determined from the following equations:
where
w = Flat width
is a slenderness factor determined as follows:

20. EFFECTIVE SECTION FOR COLUMNS
Actual Stresses

21. EFFECTIVE SECTION FOR BEAMS
Actual Stresses
Effective Section

22. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

23. AXIALLY LOADED COLUMNS
MODES OF BUCKLING
AXIALLY LOADED COLUMNS
Flexural Buckling
Torsional-flexural buckling
Column just bends during buckling
Column twists and bends during buckling

24. BEAMS
LOCAL
DISTORTIONAL
LATERAL

25. INTERACTION OF LOCAL AND OVERALL BUCKLING
Find long column elastic buckling stress Fe based on full section, Fe = min (flexural and flexural-torsional)
Find nominal column buckling stress Fn using Fe
Find effective column area Ae at stress Fn
Column strength considering local buckling is AeFn

26. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

27. STRUCTURAL ASSEMBLIES

28. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

29. Bolted connections Welded connections Screw connections
CONNECTIONS AND JOINTS
Bolted connections
Welded connections
Screw connections
(more on these topics during the numeric examples)

30. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

31. TESTS FOR SPECIAL CASES
- Tests for Determining Structural Performance
LRFD (Calculation of resistance factors)
ASD (Calculation of factors of safety)
- Tests for Confirming Structural Performance
- Tests for Determining Mechanical Properties

32. DESIGN OF COLD-FORMED STEEL STRUCTURES USING THE 2001 AISI SPECIFICATION
A. GENERAL PROVISIONS
B. ELEMENTS
C. MEMBERS
D. STRUCTURAL ASSEMBLIES
E. CONNECTIONS AND JOINTS
F. TESTS FOR SPECIAL CASES
G. CYCLIC LOADING (FATIGUE)

33. FATIGUE DESIGN Resistance to be evaluated for:
Cold-formed corners and sheared edges of sections
Longitudinal and transverse fillet welds
Spot welds
Bolt and screw connections
Evaluation of fatigue resistance is not required for wind and seismic loads

34. An excellent reference for hand calculations.
(Available from the AISI)
Similar document is in preparation for Europe using Eurocode

35. COLD-FORMED STEEL PROVIDES OPTIMUM SOLUTIONS
COLD-ROLLED
(efficient and elegant solutions)
HOT-ROLLED
(heavy)
(comparison for European sections)

36. AISI SPECIFICATION EXAMPLE
“Simple” axially loaded column

37. Problem Geometry: 800S163-54, 50ksi h = 8 in. b = 1.625 in.
d = in.
t = in.
r = in. r d h t

38. Lx = 96 in. (8 ft.) Ly = 48 in. Lt = 48 in. Kx = Ky = Kt = 1
Column & support conditions:
Lx = 96 in. (8 ft.)
Ly = 48 in.
Lt = 48 in.
Kx = Ky = Kt = 1 A A AA

39. AISI Procedure Find gross properties
Find long column elastic buckling stress (Fe)
Fe = min (flexural and flexural-torsional)
Find nominal column buckling stress (Fn)
launder Fe through AISC column curve →Fn
Find effective column area Ae at stress Fn
effective width of web, heff
effective width of flange, beff
effective width of lip, deff
Ae=t(heff+2beff+2deff)
Column strength is AeFn

40. Centerline approximation:
A centerline approximation of the geometry, ignoring corners, is allowed (centerline approximations tend to overestimate flexural and flexural-torsional buckling but are conservative on local buckling (Ae))
800S163-54, 50ksi
hCL= h - t = in.
bCL = b - t = in.
dCL = d - t/2 = /2 in.
t = in.

41. example completed in Mathcad®

42. Gross Properties

44. Long Column Buckling

46. Nominal Buckling Stress
AISC column curve

47. Effective Area at Fn:
Effective width of each element of the cross-section must be determined. The steps are
find appropriate plate buckling coefficient, k
determine local plate buckling slenderness, l
calculate effectiveness ratio r
effective width = r x full width
To find k, we must know what kind of element we have (and what kind of loading – in this case pure compression)
web = stiffened element
flange = edge stiffened element
lip = unstiffened element

48. Elements
edge stiffened element, supported on one edge fully, other edge by a stiffener, 0.43 < k < 4, depending on stiffener size and slenderness of flange itself
unstiffened element, supported on only one edge, k =0.43, assumes element is simply supported on 3 sides for local buckling consideration
stiffened element, supported on both edges, k = 4 used, assumes element is simply supported on all 4 sides for local buckling consideration

49. Effective Width
Web:

50. Edge Stiffened Elements (fun):

51. as low as it goes (unstiffened)
adequate stiffener size
sensitivity to stiffener ratio
stiffener adequacy ratio
lip/flange interaction reduction
final reduction to get k

53. Flange:

55. Lip:

56. Ae=t(heff+2beff+2deff) Ae=0.409 in2 Ag=0.684 in2
Effective Area:
Determined at Fn
heff = in.
beff = in.
deff = in.
Ae=t(heff+2beff+2deff)
Ae=0.409 in2
Ag=0.684 in2 Fn

57. Capacity Pn = AeFn = (0.409)(29.35) = 12 kips ASD
Pallowable = Pn/W = (12)/(1.8) = 6.7 kips
compare vs. unfactored load combinations
LRFD
Pnominal = fPn = (0.85)(12) = 10.2 kips
compare vs. factored load combinations

58. How is a beam different Mn=SeffFn
Fn = nominal lateral-torsional buckling stress
Seff = effective section modulus
Seff determination (iteration)
Seff = Ieff / ycg-eff
web heff = function of stress gradient
stress gradient = function of ycg-eff
Even symmetric sections become unsymmetric when effective width of compression flange is less than full width… iteration…
Calculations become quite tiresome