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AISC 2005 Table B4.1 Case 1

AISC 2005 Table B4.1 Case 1

AISC 2005 Table B4.1 Case 1

(OP)
Table B4.1, Case 1 description says “Flexure in flanges of rolled I-shaped sections and channels.” For bending about the major axis, the stress distribution on the top flange (for a simply supported beam subject to gravity loads) is uniform compression.

Therefore, Case 3 should be used for the flange. This isn't the case according to AISC design examples and any steel design book.

What it should say based on its use is "Flanges of rolled I-shaped sections and channels in flexure".

Is this clarified in AISC 2010? Has anyone else noticed this poor wording?

Also, if flanges are in uniform compression for both case 1 and 3, why is the buckling criteria different? Does axial compression effect the flange differently than bending compression?

Thanks!

RE: AISC 2005 Table B4.1 Case 1

(OP)
Found LRFD AISC 1995 manual at the office. The description used to be "Flanges of I-shaped rolled beams and channels in flexure". Why would they change it?

RE: AISC 2005 Table B4.1 Case 1

9th edition ASD (Green Book)also has "Flanges of I-shaped rolled beams and channels in flexure".
I read it as Case 1 being the member is in flexure and Case 3 both flanges are in compression.

RE: AISC 2005 Table B4.1 Case 1

Bagman2524 is correct. Case 1 is for strong-axis bending (flexure) and Case 3 is for axial compression. For the 2010 AISC Specification (AISC 360-10), Table B4.1 has been divided into two parts: Table B4.1a for members subject to Axial Compression and Table B4.1b for members subject to Flexure. Using two tables also eliminated the "NA" (not applicable) entry for the compact/non-compact limit for members subject to axial compression (that width-thickness limit only applies to flexure).

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