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RE: ASD Table B5.1

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The variable h is the clear depth of the web. Strictly speaking, this is 
the distance from toe of fillet at one flange to toe of fillet at the other 
flange. But h can be conservatively taken as the depth between flanges if 
you don't want to mess with the fillet radius. The variable t is the web 
thickness.

The web does affect the buckling strength of the flange for an I-shaped 
member. If the flange is to buckle, it does so in a rotational mode (when 
one flange tip goes up, the other has to go down). The web is along for the 
ride and will provide some resistance, depending upon its relative 
stiffness.

Charlie

-----Original Message-----
From:	Andrew Abbo [SMTP:AndrewA(--nospam--at)formsys.com]
Sent:	Friday, July 23, 1999 2:37 AM
To:	seaint(--nospam--at)seaint.org
Subject:	ASD Table B5.1


In table B5.1 of ASD, foot note e defines an expression compression
element restraint coefficient, kc. This expression includes the ratio
h/t.  What is the definition of h and t used in this equation? While I
think that h is well defined, the value of t is open to interpretation
as either tw (web thickness) or tf (flange thickness).

 I have been given different interpretations of both h and t by
different people, all of which have some merit. They are

(1) h is the clear distance between the flanges (height of the web) and
t is the thickness of the flange (t=tf).
(2) h is the clear distance between the flanges (height of the web) and
t is the thickness of the web (t=tw).
(3) h is the width of the compression element which, in the context
Table 5.1, is the width of the flange and t=tf.

I think that (2) is the correct interpretation and this is backed up by
the Example 12 and Page 2-220 of the green book (9th Edition). However,
it does seem unusal that the local buckling capacity of a flange is
related to the stiffness of the web. Can someone please expand this.

Andrew

--

Andrew Abbo - AndrewA(--nospam--at)formsys.com
Formation Design System - http://www.formsys.com
Maxsurf for marine design, Multiframe for structural design, Neoform for

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