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Re: tapered steel beams

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The fire damaged building belongs to a third generation family business, structural steel fabricator. The grandfather fabricated the original tapered girders, present owners (son and grandson) nostalgically want to fabricate and put back in tapered girders. I tried my best to convince them to use Vulcraft girders instead but, no luck.
 
Regards,
 
Mark
 
----- Original Message -----
Sent: Thursday, September 12, 2002 1:28 PM
Subject: RE: tapered steel beams

Mark,
 
I would echo Charlie on this one...  Part of the answer may depend on where the building is located...  The city of Chicago has in the past required that Appendix F be used.  I can't think of any others off the top of my head though...  So for the most part, PEMB suppliers don't use Appendix F due to its conservative results and the extra difficulty in applying that section.
 
Most of the analysis I have seen are as Charlie mentions, broken up into multiple prismatic sections and checked.  Some even involve specialized matrices to determine the stiffness of the tapered member (vs several small prismatic sections).  Remeber to check at the bracing locations and between because either could control, and don't forget weld designs (VQ/I) and the other small details..  Make sure you design the beam such that your fabricator can manufacture it also... taper ratios, flange widths, beam depths, thickness changes, weld requirements, etc.
 
Hope this helps,
Greg Effland, P.E.
KC, MO USA
-----Original Message-----
From: Carter, Charlie [mailto:carter(--nospam--at)aisc.org]
Sent: Thursday, September 12, 2002 1:47 PM
To: 'seaint(--nospam--at)seaint.org'
Subject: RE: tapered steel beams

>I am going to be designing a tapered steel beam to replace those damaged
>in a fire. I have been looking over Appendix F of AISC manual and this appears
>to be the necessary information along with Chapter F. I need some assurance
>from someone with experience in the design of tapered steel beams that I am
>looking at the correct source.
 
The Appendix F provisions can be used. Most tapered members are found in metal buildings and I know metal building companies rarely use those provisions as they can be conservative. Instead, I have seen modeling that breaks the beam into an appropriate number of prismatic segments and more traditional FE approaches as well. They also typically do product testing to ensure that they are doing things that work.
 
>Charlie Carter.....are you out there today???
 
Some would say waaaayyyyy out there. (-:
 
Charlie