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Re: "DL" displacing LL?

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If your system is very redundant and able to handle the load.  otherwise you may be watching a budget.

On 10/20/06, Ganesh Thiagarajan < cethia(--nospam--at)> wrote:
In the scheme of things it may be best to include this as an additional DL and use the entire area for LL...It may be possible that the LL in that 5 sq.ft. area be redistributed to other areas. Definitely included in seismic mass calcs...

On 10/20/06, Bill Allen <T.W.Allen(--nospam--at)> wrote:

I've read the CBC 2001, the IBC 2003 (sorry, I don't have a copy of 2006) and ASCE 7-05 and can't come to a consensus to a quandary I have.


If I'm installing a piece of equipment to a floor (or a roof for that matter), can the uniform live load be displaced by that weight? For example, suppose I have an occupancy that dictates 50 PSF live load and I install a piece of equipment that is 5 feet square and weighs 1,250 lbs or 50 PSF. I don't have to superimpose the 50 PSF load induced by the piece of equipment onto the 50 PSF uniform live load, do I? About the only place where I see that this would not be the case would be in the case of roof loads which consider snow loads. In other words, if I install a Roof Top Unit and that load is to be combined with a snow load, then I can see where those would be additive.


The UBC definition of DL appears to be more broad than in the IBC or ASCE 7.


Of course, maybe my problem is thinking that the equipment is DL in the first place which is more in tune with the UBC definition.


Opinions are appreciated.




T. William (Bill) Allen, S.E.


Consulting Structural Engineers
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