Classification of Sections for Ductility per AISC 34116 with ideCAD
How does ideCAD control widthtothickness Ratios according to AISC 34116?
IdeCAD Structural automatically controls the widthtothickness ratios of steel elements according to Table D1.1.
Symbols
F_{y} = Specified minimum yield stress
R_{y} = Ratio of the expected yield stress to the specified minimum yield stress, Fy
R_{t} = Ratio of the expected tensile strength to the specified minimum tensile strength, Fu
Pa = Required axial strength using ASD load combinations, kips (N)
P_{u} = Required axial strength using LRFD load combinations, kips (N)
P_{y} = Axial yield strength , kips (N)
C_{a} = Ratio of required strength to available axial yield strength
E= Modulus of elasticity of steel = 29,000 ksi (200 000 MPa)
WidthtoThickness Limitations of Steel and Composite Sections
The widthtothickness ratios of compression elements should not exceed the limiting widthtothickness ratios from AISC 34116 Table D1.1, for members designated as moderately ductile or highly ductile members.
Limiting WidthtoThickness Ratios for Compression Elements for Moderately Ductile and Highly Ductile Members  

Description of Element  Widthto Thickness Ratio  Limiting WidthtoThickness Ratio  Example  
λ_{hd}  λ_{md}  
Flanges of rolled or builtup Ishaped sections, channels and tees; legs of single angles or doubleangle members with separators; outstanding legs of pairs of angles in continuous contact  b/t 

 
Flanges of Hpile sections per Section D4  b/t  not applicable 
 
Stems of tees  d/t 

 
Walls of rectangular HSS used as diagonal braces  b/t 

 
Flanges of boxed Ishaped sections  b/t 

 
Side plates of boxed Ishaped sections and walls of builtup box shapes used as diagonal braces  h/t 

 
Flanges of built up box shapes used as link beams  b/t 

 
Webs of rolled or builtup I shaped sections and channels used as diagonal braces  h_{w}/t 

 
Where used in beams or columns as flanges in uniform compression due to axial, flexure, or combined axial and flexure:
 b/t h/t 

 
Where used in beams, columns, or links, as webs in flexure, or combined axial and flexure:
 h/t_{w} h/t h/t  For C_{a} ≤ 0.114 For C_{a} > 0.114  For C_{a} ≤ 0.114 For C_{a} > 0.114 where  
Webs of builtup box sections used as EBF links  h/t 

 
Webs of HPile sections  h/t_{w}  not applicable 
 
Walls of round HSS  D/t 

