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Re: Are Roof Top Units considered Dead or Live Loads?

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On Jan 4, 2005, at 12:13 PM, Rich Lewis wrote:

That being said, and considering LRFD load factors, I am inclined to
consider them as live loads.
You might also want to consider vibration, imbalance and start-up loading as part of your service environemnt. A/C units vibrate as do stacks. Piping expands and contracts. And you've always got people stomping around up there working on A/C units seasonally.

The weight issue is always a problem, even for us ME's. It's the same problem in reverse when I try to get weights of building structures. When I do a finite element model of a crane or a weldment, I always put in an extra 20% on the model weight, to account for all the extra stuff hung on, like machinery and parasitic weight. The additional 20% usually jibes with weights measured for shipping purposes. I haven't run into many manufacturers who really know what their equipment weighs in service.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)    | this distance" (last words of Gen.
...................................| John Sedgwick, Spotsylvania 1864)

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