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RE: Crane Girder Fatigue

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Since it's 20 years old, there's a good chance there are fatigue problems
associated with the structural detail practices back then.  Get a copy of
AISC Engineering Journal for an excellent article titled "Tips for Avoiding
Crane Runway Problems"; Fourth Quarter, 1992; Volume 19, No. 2.

Last time I was called in on that vintage crane, the top flange of the
runway girder was deflecting laterally 3/4" when the unloaded crane passed
over.  Scared the **** out of me when they demonstrated.  Turned out to be a
13" long through wall crack, not a rust stain.  Crack occurred on 50% of the
connections (all on one side).

Paul F. Blomberg
Jacobs Engineering Group
Phoenix, AZ
 ----------
From: Fountain Conner
To: seaint(--nospam--at)seaint.org
Subject: Crane Girder Fatigue
Date: Saturday, January 22, 2000 9:19AM


I'm looking at a 20 year old foundry bridge crane runway -- 'Not a huge
capacity -- 10T main, 5T auxiliary, but fairly severe service.  I make it
what used to be called "Class D, HEAVY DUTY SERVICE", from an old Whiting
Crane Handbook.

I've visited the site.  The owner has replaced many of the structural
bolts, because they'd "worked loose".  The steel (crane girder & columns)
does not show any immediately obvious distress -- cracked welds;  cracking
in the top flange cap channel...  The crane itself is being replaced,
because rehab will cost nearly as much as replacement.

I'll be analyzing the crane girder, the attachments, the supports and the
overall stability of the structure.

Using Appendix K, AISC, ASD, 9th Edition, TAbel A-K4.1, I place this crane
in Loading Condition 4.

Seismic is not likely a factor, since it's Zone 1.

Are there any traps I should look out for?

Thanks,

Fountain E. Conner, P.E.
Gulf Breeze, Fl. 32561