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Re: Crane Design; SE v. ME

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Drew ---

In general, cranes are cranes, not building structures.  The manufacturer
certifies complience with Crane Manufacturers Association of America
(CMAA), ANSI, and OSHA requirements, including installation (if within
contract scope).  None of these codes and standards address earthquake
loads and seismic design.  CMAA even states that the owner must look
elsewhere for seismic design of cranes.  AISC attempts to elucidate
somewhat, but is too simplified, and is not invoked by the crane codes
and standards.  Bottom line is that the crane manufacturer needs NO
ENGINEERING LICENCES to build and sell a crane.  The California
certifier, licensed by CalASHO, needs to have a licensed ME or CE on
staff in order to certify the final installation.  This requirement
varies by state, and is different for federal installations.

In general, most building cranes will withstand zone 4 seismic loads, but
the attachments to the building will not, if designed per crane standards
(not even close).  Also suspect might be the runway beams.  The crane
codes and the building codes are truely disconnected, as are the
practices of engineering of cranes vs. engineering their installations. 
The loads you have been supplied by the crane engineer do not include
seismic, as you have suspected.  That disconnect was directly responsible
for industrial bridge cranes failing and falling to the floors below
during the 1994 Northridge Earthquake.

I will repeat my offer from a few months ago.  I wrote and published a
paper on this subject , delivered at the 1996 ASCE Natural Disaster
Reduction Conference.  I will send the paper and other enlightening
material to anyone is interested and  who send me thier name and mailing

Russ Nester, SE, GE

On Tue, 9 Mar 1999 19:28:30 -0500 "Drew A. Norman, S.E."
<DNormanSE(--nospam--at)> writes:
>An appeal to the voice of my colleagues' experience.  Is there anyone 
>there with crane design experience, or anyone from BORPELS and/or 
>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 
>operations).  Lateral loads along the axis of the bridge are 
>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 
>our design of the supporting structure) under the seal and signature 
>of a
>licensed SE.  We were recently advised that the crane supplier asserts 
>the crane is a machine, not a structure, and that an SE signature is 
>required (they have an ME who proposes to sign the documents).
>We have been asked to assist our client in responding to this 
>Because the cost of proper engineering is not insignificant, the issue 
>not immaterial, and there is some pressure to accept an ME signature.
>Does anyone know if the Professional Engineers Act or the BORPELS 
>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 
>pass on to my client?
>Drew Norman, S.E.
>Drew A. Norman and Associates

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