P1: GIG

GRBT055-B AISC-Sample (LRFD) June 17, 2005 16:3 Char Count= 0

16 [Sect. B4.CLASSIFICATION OF SECTIONS FOR LOCAL BUCKLING

TABLE B4.1Limiting Width-Thickness Ratios for

Compression Elements

Cas

e WidthThick-nessRatio

Limiting Width-Thickness Ratios

λp λrDescription ofElement (compact) (noncompact) Example

1 Flexure in flanges ofrolled I-shapedsections andchannels

b/t 0.38�

E/Fy 1.0�

E/Fy

t

b

2 Flexure in flanges ofdoubly and singlysymmetric I-shapedbuilt-up sections

b/t 0.38�

E/Fy 0.95�

kcE/FL[a],[b]

b

t

Unju

stifi

edE

lem

ents

3 Uniformcompression inflanges of rolledI-shaped sections,plates projectingfrom rolled I-shapedsections;outstanding legs ofpairs of angles incontinuous contactand flanges ofchannels

b/t NA 0.56�

E/Fy

t

b

4 Uniformcompression inflanges of built-upI-shaped sectionsand plates or anglelegs projecting frombuilt-up I-shapedsections

b/t NA 0.64�

kcE/Fy[a]

t

b

b

t

5 Uniformcompression in legsof single angles,legs of doubleangles withseparators, and allother unstiffenedelements

b/t NA 0.45�

E/Fy

t

b

6 Flexure in legs ofsingle angles

b/t 0.54�

E/Fy 0.91�

E/Fy

t

b

Specification for Structural Steel Buildings,March 9, 2005AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC.

Un

stif

fen

ed E

lem

ents

P1: GIG

GRBT055-B AISC-Sample (LRFD) June 17, 2005 16:3 Char Count= 0

CLASSIFICATION OF SECTIONS FOR LOCAL BUCKLINGSect. B4.] 17

TABLE B4.1 (cont.)Limiting Width-Thickness Ratios for

Compression Elements

Cas

e WidthThick-nessRatio

Limiting Width-Thickness Ratios

λp λrDescription ofElement (compact) (noncompact) Example

7 Flexure in flanges oftees

b/t 0.38√

E/Fy 1.0√

E/Fy bt

8 Uniformcompression instems of tees

d/t NA 0.75√

E/Fy

td

9 Flexure in webs ofdoubly symmetricI-shaped sectionsand channels

h/tw 3.76√

E/Fy 5.70√

E/Fy

twh

10 Uniformcompression inwebs of doublysymmetric I-shapedsections

h/tw NA 1.49√

E/Fy

twh

11 Flexure in webs ofsingly-symmetricI-shaped sections

hc/tw hc

hp

√EFy

(

0.54Mp

My− 0.09

)2 ≤ λr

5.70√

E/Fy hpna

p2 2

ch

cg

wtSti

ffen

edE

lem

ents

12 Uniformcompression inflanges ofrectangular box andhollow structuralsections of uniformthickness subject tobending orcompression; flangecover plates anddiaphragm platesbetween lines offasteners or welds

b/t 1.12√

E/Fy 1.40√

E/Fyt

b

13 Flexure in webs ofrectangular HSS

h/t 2.42√

E/Fy 5.70√

E/Fyt

h

Specification for Structural Steel Buildings, March 9, 2005AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC.

P1: GIG

GRBT055-B AISC-Sample (LRFD) June 17, 2005 16:3 Char Count= 0

18 [Sect. B5.FABRICATION, ERECTION AND QUALITY CONTROL

TABLE B4.1 (cont.)Limiting Width-Thickness Ratios for

Compression Elements

Cas

e WidthThick-nessRatio

Limiting Width-Thickness Ratios

λp λrDescription ofElement (compact) (noncompact) Example

14 Uniformcompression in allother stiffenedelements

b/t NA 1.49√

E/Fy

t

b

15 Circular hollowsections

t

DIn uniformcompression

D/t NA 0.11E/Fy

In flexure D/t 0.07E/Fy 0.31E/Fy

[a] kc = 4√h/tw

, but shall not be taken less than 0.35 nor greater than 0.76 for calculation purposes. (See

Cases 2 and 4)[b] FL = 0.7Fy for minor-axis bending, major axis bending of slender-web built-up I-shaped members, andmajor axis bending of compact and noncompact web built-up I-shaped members with Sxt /Sxc ≥ 0.7; FL =Fy Sxt /Sxc ≥ 0.5Fy for major-axis bending of compact and noncompact web built-up I-shaped members withSxt /Sxc < 0.7. (See Case 2)

B5. FABRICATION, ERECTION AND QUALITY CONTROL

Shop drawings, fabrication, shop painting, erection, and quality control shallmeet the requirements stipulated in Chapter M, Fabrication, Erection, and QualityControl.

B6. EVALUATION OF EXISTING STRUCTURES

Provisions for the evaluation of existing structures are presented in Appendix 5,Evaluation of Existing Structures.

Specification for Structural Steel Buildings, March 9, 2005AMERICAN INSTITUTE OF STEEL CONSTRUCTION, INC.