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Re[2]: Crane Design

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Harold:

I would consider an overhead bridge cranes supported by a building structure as 
an example of manufacturing and process machinery, covered by Chapter 6 
(Nonstructural components) of the 1997 NEHRP Provisions, and therefore the 2000 
IBC.  Grade-mounted (gantry) cranes should be covered by Chapter 14 (Nonbuilding
Structures) of the 1997 NEHRP Provisions.

Rick Drake, SE
Fluor Daniel, Inc.

*********************************************

Drew,
     
Your post reminded me of the frustrations that I have encountered with many 
industrial structures.  Architects in particular look to the building code 
for prudent design practices (standard of care) as opposed to minimum life 
safety (which is the charge of the code).
     
The issue is greatly exacerbated when the topic turns to nonbuilding 
structures and nonstructural components.  Whenever a code change that 
requires more calculation is submitted, one of the voices invariably asks, 
"Where are the bodies?".
     
The current remedies lie within the court.  When the owner's business is 
shut down due to an earthquake (whatever the magnitude) knocking a crane off 
the rails, the owner will sue and the engineer will loose unless he is very 
clear in the performance expectations.
     
I would suggest that you read Chapter 14 of the 1997 NEHRP Provisions and 
Commentary.  Cranes are not specifically covered, but there is the "other" 
listing that may be of help.  We do need to put something in the NEHRP for 
cranes.
     
Suggestions are welcome.
     
Regards,
Harold Sprague
The Neenan Company
     
     
-----Original Message-----
From: Drew A. Norman, S.E. [mailto:DNormanSE(--nospam--at)email.msn.com] 
Sent: Tuesday, March 16, 1999 9:08 PM
To: SEAINT List Service
Subject: Crane Design
     
     
To all who responded to or followed the recent thread on crane design:
     
I forwarded all of the items from the list to my architect client.  From 
this and whatever research he has done independently he says he has 
concluded that (1) the bridge cranes in commercial buildings standard (as 
opposed to essential) occupancy are NEVER designed for seismic loads and 
that (2) such bridge cranes are usually designed by mechanical (as opposed 
to civil or structural) engineers.  He is on this basis taking issue with 
our having specified a design submission including seismic analysis under 
the signature of a structural engineer.  I have suggested that proper design 
of the thirty ton and sixty foot span crane in our building (apx 71 kips 
dead load including rails) requires not only a seismic analysis but a 
DYNAMIC analysis.  My client thinks that I am being overly conservative, 
asking for something that is never done and will cost a lot of money, and 
generally being outrageous.
     
Needless to say, my client and I are not seeing eye to eye here.  I have NOT 
drawn the same conclusions from the discussion on the list.  Either he or I 
appear to be misunderstanding the meaning of the posts.  If anyone would 
care to offer a final comment on the subject that might help us to move 
closer together by getting a better grasp on the issues, we would both 
appreciate your efforts.
     
Thank you
     
Drew Norman, S.E.
Drew A. Norman and Associates