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RE: Crane Design

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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