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RE: Beam Bearing Stiffeners

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Ricky,

 

This is one of the areas that was revised in the LRFD.  Keep in mind that there has been little or no research or effort to update ASD in over 10 years.  I would suggest that you look at the parallel sections in the 3rd Ed of the LRFD.  Notably you will see that the sections on web yielding, web buckling, and web sidesway buckling have been revised with the aid of more research.  I would also suggest that you look at the commentary to these sections.  The commentary is much better than the 9th Ed ASD.

 

If you had a problem with local web yielding in the ASD, you will have the same problem in web local yielding in the 3rd Ed. LRFD.

Regards,
Harold O. Sprague

-----Original Message-----
From: Ricky Leblanc [mailto:Rick.Leblanc(--nospam--at)halliburton.com]
Sent:
Wednesday, October 29, 2003 10:14 AM
To:
seaint(--nospam--at)seaint.org
Subject: Beam Bearing Stiffeners

 

Reference the AISC ASD, 9th edition:

Section K1.4 (web crippling) states that if stiffeners are provided and extend at least 1/2 web depth then Eqns K1-4 & K1-5 need not be checked.

 

In section K1.8 there is a sequence of statements saying "If required by Sect's K1.2, K1.3 or eqn K1-9, stiffeners need not extend more than 1/2 the depth of the web, except as follows:"

 

"If stiffeners are required by Sects. K1.4 or K1.6, the stiffeners shall be designed as axially compressed columns in accordance with sect E2 with an effective length = 0.75h, ...."

 

My question is this, if sections K1.3 indicates stiffener is need than is ½ depth fine and will it satisfy section K1.4.  Or do I need also to check K1.4 and if eqn K1-4 or K1-5 indicated a stiffener is needed, do the comments in section K1.8 imply the need for a full depth stiffener to meet web crippling requirements?

 

For my case, stiffeners are required only for K1.3 or K1.4.  The other sub-sections in Chapter K are either not applicable or indicate no stiffener required. 

 

 

Ricky LeBlanc

KBR Offshore

713-243-4047