16.1–16 MEMBER PROPERTIES [Sect. B4.

Specification for Structural Steel Buildings, June 22, 2010AMERICAN INSTITUTE OF STEEL CONSTRUCTION

TABLE B4.1aWidth-to-Thickness Ratios: Compression Elements

Members Subject to Axial Compression

Examples

LimitingWidth-to-Thickness

Ratio �r

(nonslender/slender)

Width-to-Thickness

RatioDescription of

Element

Cas

e

Flanges of rolled I-shaped sections,plates projectingfrom rolled I-shapedsections; outstandinglegs of pairs ofangles connectedwith continuous contact, flanges ofchannels, andflanges of tees

Flanges of built-up I-shaped sectionsand plates or anglelegs projecting frombuilt-up I-shapedsections

Legs of singleangles, legs of double angles withseparators, and allother unstiffenedelements

Stems of tees

Webs of doubly-symmetric I-shapedsections and channels

Walls of rectangularHSS and boxes ofuniform thickness

Flange cover platesand diaphragmplates between linesof fasteners or welds

All other stiffenedelements

Round HSS

b/t

b/t

b/t

d/t

h/tw

b/t

b/t

b/t

D/t

Sti

ffen

ed E

lem

ents

Un

stif

fen

ed E

lem

ents

0 75.EFy

0 56.EFy

0 64.k EFc

y

0 45.EFy

1 49.EFy

1 40.EFy

1 40.EFy

1 49.EFy

0 11.EFy

1

2

3

4

5

6

7

8

9

[a]

Sect. B4.] MEMBER PROPERTIES 16.1–17

Specification for Structural Steel Buildings, June 22, 2010AMERICAN INSTITUTE OF STEEL CONSTRUCTION

TABLE B4.1bWidth-to-Thickness Ratios: Compression Elements

Members Subject to Flexure

Examples

LimitingWidth-to-Thickness Ratio

�p �r

(compact/ (noncompact/noncompact) slender)

Width-to-Thickness

RatioDescription of

Element

Cas

e

Flanges of rolled I-shaped sections,channels, and tees

Flanges of doublyand singly symmet-ric I-shaped built-upsections

Legs of singleangles

Flanges of all I-shaped sectionsand channels in flexure about theweak axis

Stems of tees

Webs of doubly-symmetric I-shapedsections and channels

Webs of singly-symmetric I-shapedsections

Flanges of rectangular HSSand boxes of uniform thickness

Flange cover platesand diaphragmplates betweenlines of fasteners or welds

Webs of rectangularHSS and boxes

Round HSS

b/t

b/t

b/t

b/t

d/t

h/tw

hc/tw

b/t

b/t

h/t

D/t

Sti

ffen

ed E

lem

ents

Un

stif

fen

ed E

lem

ents

3 76.EFy

0 38.EFy

0 54.EFy

0 84.EFy

hh

EF

M

M

c

p y

p

y

r

0 54 0 092

. .−⎛

⎝⎜⎞

⎠⎟

≤ λ

1 12.EFy

1 12.EFy

2 42.EFy

0 07.EFy

10

11

12

13

14

15

16

17

18

19

20

[a] [b]

0 38.EFy

0 38.EFy

1 0.EFy

0 95.k EFc

L

0 91.EFy

1 0.EFy

5 70.EFy

1 03.EFy

1 40.EFy

5 70.EFy

1 40.EFy

5 70.EFy

0 31.EFy

[c]

[a] kc = 4� but shall not be taken less than 0.35 nor greater than 0.76 for calculation purposes. [b] FL = 0.7Fy for major axis bending of compact and noncompact web built-up I-shaped members with Sxt /Sxc ≥ 0.7;

FL = FySxt /Sxc ≥ 0.5Fy for major-axis bending of compact and noncompact web built-up I-shaped members with Sxt /Sxc < 0.7.[c] My is the moment at yielding of the extreme fiber. Mp = plastic bending moment, kip-in. (N-mm)E = modulus of elasticity of steel = 29,000 ksi (200 000 MPa)Fy = specified minimum yield stress, ksi (MPa)

h tw/