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Classification of Sections for Ductility per AISC 341-16 with ideCAD

How does ideCAD control width-to-thickness Ratios according to AISC 341-16?


  • IdeCAD Structural automatically controls the width-to-thickness ratios of steel elements according to Table D1.1.


Symbols

Fy = Specified minimum yield stress
Ry = Ratio of the expected yield stress to the specified minimum yield stress, Fy
Rt = Ratio of the expected tensile strength to the specified minimum tensile strength, Fu
Pa = Required axial strength using ASD load combinations, kips (N)
Pu = Required axial strength using LRFD load combinations, kips (N)
Py = Axial yield strength , kips (N)
Ca = Ratio of required strength to available axial yield strength
E= Modulus of elasticity of steel = 29,000 ksi (200 000 MPa)


Width-to-Thickness Limitations of Steel and Composite Sections

The width-to-thickness ratios of compression elements should not exceed the limiting width-to-thickness ratios from AISC 341-16 Table D1.1, for members designated as moderately ductile or highly ductile members.

Limiting Width-to-Thickness Ratios for Compression Elements for Moderately Ductile and Highly Ductile Members

Description of Element

Width-to- Thickness Ratio

Limiting Width-to-Thickness Ratio

Example

λhd
Highly Ductile Members

λmd
Moderately Ductile Members

Flanges of rolled or built-up I-shaped sections, channels and tees; legs of single angles or double-angle members with separators; outstanding legs of pairs of angles in continuous contact

b/t

Flanges of H-pile 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 I-shaped sections

b/t

Side plates of boxed I-shaped sections and walls of built-up box shapes used as diagonal braces

h/t

Flanges of built up box shapes used as link beams

b/t

Webs of rolled or built-up I shaped sections and channels used as diagonal braces

hw/t

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

  1. Walls of rectangular HSS

  2. Flanges and side plates of boxed I-shaped sections, webs and flanges of built-up box shapes

b/t

h/t

Where used in beams, columns, or links, as webs in flexure, or combined axial and flexure:

  1. Webs of rolled or built-up I shaped sections or channels [b]

  2. Side plates of boxed I-shaped sections

  3. Webs of built up box sections

h/tw

h/t

h/t

For Ca ≤ 0.114

For Ca > 0.114



where


For Ca ≤ 0.114

For Ca > 0.114

where


Webs of built-up box sections used as EBF links

h/t

Webs of H-Pile sections

h/tw

not applicable

Walls of round HSS

D/t



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