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Re: Crane Design; SE v. ME

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> 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?
Interesting distinction in this case. I do a fair amount of crane work on 
the mechanical side, but not buildings. Design practice for a crane is a 
good deal different than buildings, primarily because of the large 
proportion of live loading and also because control of the crane load is 
an issue which doesn't have a parallel in building design. First, you 
don't design cranes against ultimate loading since service loads govern. 
Also fatigue and dynamic loading is a major concern. CMAA-70 is usually 
the standard for design, and it in turn is based on AISC WSD design, with 
some added provisions for the machinery and for determining design loads. 

Second, seismic loading isn't covered specifically. Some sites specify 
simple static acceleration be applied, according to the static 
coefficient approach. Nuke plants require site specific response spectrum 
analysis. Because the dynamics are a lot different than buildings, I 
think response spectrum analysis is the only approach that makes much 
sense. 

It's also possible that the crane itself be required to remain functional 
during an earthquake, to maintain control of a load or maybe help clean 
up afterward, say in a hazardous materials site or a nuke plant. 
Refineries probably require something of the sort to help contain damage 
and the possibility of fire. 

I think the distinction between SE and ME in this case is nowhere near as 
relevant as experience with crane systems and the sorts of loads which 
are supposed to be carried and criteria for supporting the loads. This 
kind of interfacing should be set forth at the very beginning and not 
just trotted out the day before the plans get approved. If the owner 
needs to have his crane stay operational during an earthquake, it's no 
good if the building designer sizes things so they just hang together 
long enough for everyone to get outside.

>Does anyone know if the Professional Engineers Act or the BORPELS Rules
>address the issue of when a machine becomes a structure?
All machines are structures; they just aren't the kinds of structures 
covered on the CE or SE test. This is an area where specific competencies 
are required, not just the right two initials.

Christopher Wright P.E.    |"They couldn't hit an elephant from
chrisw(--nospam--at)skypoint.com        | this distance"   (last words of Gen.
___________________________| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw