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Re: Crane Design; SE v. ME

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Some things you may want to pass onto your client:          

Having formerly worked at a nuclear facility where we asked for the crane's 
structural calculations on a regular basis I can tell you that your request is 
not abnormal.  In fact, if you look at the relevant bridge crane design standard
(CMAA document) it specifically describes the "structural" design of the crane 
members (although not getting into seismic effects).  As many others on the list
have already mentioned, there is usually a disconnect between the design of the 
crane (normal operating loads) and the building structural design. The response 
of the building can have a dominant impact on the structural design of the crane
members and their connections (i.e., accelerated response spectrum at the crane 
level).  Any major bridge crane supplier who has any experience in the nuclear 
arena should be very familiar with this type of situation and request for 
structural calculations.

I can also tell you, based on conversations I have had with many individuals, 
the % of bridge cranes which fall during earthquakes (observed by 
post-inspection teams) is low.  I'm sure that some folks at EQE could share some
other insight into this issue.  They have been involved with the Dept. of Energy
in looking at the analysis of existing bridge cranes at DOE sites around the 
United States.  Any EQE folks on the list who have something to add ?  

Hope this helps.

Robert C. Rogers
______________________________ Reply Separator _________________________________
Subject: Crane Design; SE v. ME
Author:  seaint(--nospam--at) at Internet
Date:    3/9/99 8:13 PM

An appeal to the voice of my colleagues' experience.  Is there anyone out
there with crane design experience, or anyone from BORPELS and/or CAL-OSHA,
who could shed some light on the following situation?

My office has designed a building to support a thirty ton bridge crane.  The
hoist runs along a bridge spanning 54' between trolleys which in turn run on
rails spanning 27' between supports points where they are hung from our roof
structure.  Reactions at these suspension points were provided to us by the
crane supplier.  The installation will be in California, in seismic zone 4.
Laterally, the two bridge beams are (we think) interconnected as a truss to
resist horizontal inertial forces created by acceleration or deceleration of
the mass of hoist, bridge and load (whether due to earthquake or normal
operations).  Lateral loads along the axis of the bridge are presumably
transferred to the rails, which must span horizontally between lateral
bracing we provide at the supported points.

We have asserted that the bridge crane and its rails, which are to be
designed by their supplier, are a substantial structure.  Our documents call
for the design to be submitted to us (for verification of consistency with
our design of the supporting structure) under the seal and signature of a
licensed SE.  We were recently advised that the crane supplier asserts that
the crane is a machine, not a structure, and that an SE signature is not
required (they have an ME who proposes to sign the documents).

We have been asked to assist our client in responding to this situation.
Because the cost of proper engineering is not insignificant, the issue is
not immaterial, and there is some pressure to accept an ME signature.

Does anyone know if the Professional Engineers Act or the BORPELS Rules
address the issue of when a machine becomes a structure?

Does anyone know if CAL-OSHA or any regulatory agency has policy on when a
crane requires structural (v. mechanical) design?

Does anyone have any useful suggestions or relevant information that I could
pass on to my client?

Drew Norman, S.E.
Drew A. Norman and Associates