Table B4.1b: Width-to-Thickness Ratios: Compression Elements Members Subjected to Flexure

	Case	Description of Element	Width-to- Thickness Ratio	Limiting Width-to-Thickness Ratio		Examples
	Case	Description of Element	Width-to- Thickness Ratio	λ_p (compact/ noncom- pact)	λ_r (non- compact/ slender)	Examples
Unstiffened Elements	10	(1) Flanges of rolled I-shaped sections (2) Flanges of channels (3) Flanges of tees	b/t	0.38 √(E/F_y)	1.0 √(E/F_y)	[Diagram]
	11	Flanges of doubly and singly symmetric I-shaped built-up sections	b/t	0.38 √(E/F_y)	[a] [b] 0.95 √(k_cE/F_L)	[Diagram]
	12	Legs of single angles	b/t	0.54 √(E/F_y)	0.91 √(E/F_y)	[Diagram]
	13	Flanges of all I-shaped sections and channels in flexure about the minor axis	b/t	0.38 √(E/F_y)	1.0 √(E/F_y)	[Diagram]
	14	Stems of tees	d/t	0.84 √(E/F_y)	1.52 √(E/F_y)	[Diagram]

(d) For flanges of rectangular hollow structural sections (HSS), the width, $b$ , is the clear distance between webs less the inside corner radius on each side. For webs of rectangular HSS, $h$ is the clear distance between the flanges less the inside corner radius on each side. If the corner radius is not known, $b$ and $h$ shall be taken as the corresponding outside dimension minus three times the thickness. The thickness, $t$ , shall be taken as the design wall thickness, per Section B4.2.
(e) For flanges or webs of box sections and other stiffened elements, the width, $b$ , is the clear distance between the elements providing stiffening.
(f) For perforated cover plates, $b$ is the transverse distance between the nearest line of fasteners, and the net area of the plate is taken at the widest hole.
(g) For round hollow structural sections (HSS), the width shall be taken as the outside diameter, D, and the thickness, t, shall be taken as the design wall thickness, as defined in Section B4.2.

B4.1b (continued)

Width-to-Thickness Ratios: Compression Elements Members Subjected to Flexure

	Case	Description of Element	Width-to- Thickness Ratio	Limiting Width-to-Thickness Ratio		Examples
	Case	Description of Element	Width-to- Thickness Ratio	λ_p (compact/noncompact)	λ_r (non- compact/ slender)	Examples
Stiffened Elements	15	Webs of doubly symmetric I-shaped sections and channels	h/t_w	3.76 √E/F_y	5.70 √E/F_y	[Diagram: I-beam and Channel cross-sections]
	16	Webs of singly symmetric I-shaped sections	h_c/t_w	[c] h_c √E/F_y h_p (0.54 M_p/M_y - 0.09)² ≤ λ_r	5.70 √E/F_y	[Diagram: I-beam cross-section with h_c, h_p, PNA, ENA]
	17	Flanges of rectangular HSS	b/t	1.12 √E/F_y	1.40 √E/F_y	[Diagram: Rectangular HSS cross-section]
	18	Flange cover plates between lines of fasteners or welds	b/t	1.12 √E/F_y	1.40 √E/F_y	[Diagram: I-beam with flange cover plates]
	19	Webs of rectangular HSS and box sections	h/t	2.42 √E/F_y	5.70 √E/F_y	[Diagram: Rectangular HSS and Box section]
	20	Round HSS	D/t	0.07 √E/F_y	0.31 √E/F_y	[Diagram: Round HSS cross-section]
	21	Flanges of box sections	b/t	1.12 √E/F_y	1.49 √E/F_y	[Diagram: Box section with flange]

[a]k_c = 4/√(h/t_w) but shall not be taken as less than 0.35 nor greater than 0.76 for calculation purposes.

[b] $F_{L}=0.7 F_{y}$ for slender web I-shaped members and major-axis bending of compact and noncompact web built-up I-shaped members with $S_{x t} / S_{x c} \geq 0.7$ ; and $F_{L}=F_{y} S_{x t} / S_{x c} \geq 0.5 F_{y}$ for major-axis bending of compact and noncompact web built-up I-shaped members with $S_{x t} / S_{x c}<0.7$ , where $S_{x c}, S_{x t}=$ elastic section modulus referred to compression and tension flanges, respectively, in ${ }^{3}\left(\mathrm{~mm}^{3}\right)$

$\left[\mathrm{c}^{l}\right] M_{y}$ is the moment at yielding of the extreme fiber, kip-in. (N-mm); $M_{p}=F_{y} Z_{x}$ , plastic moment, kip-in.

(N-mm), where $Z_{x}=$ plastic section modulus taken about the x-axis, in. ${ }^{3}\left(\mathrm{~mm}^{3}\right)$

ENA = elastic neutral axis

PNA = plastic neutral axis

User Note: Refer to Table B4.1 for the graphic representation of stiffened element dimensions.

For tapered flanges of rolled sections, the thickness is the nominal value halfway between the free edge and the corresponding face of the web.

Table B4.1b: Width-to-Thickness Ratios: Compression Elements Members Subjected to Flexure

B4.1b (continued)

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