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Dead Load or Live Load?

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Good question Jeff!

The basic definition of Live Load that I use is that a Live Load is a load 
that is moving or movable.  I would doubt that the solar panels are either.

Now, there is the question of roof live load.

Are the panels flat on the deck or sloped to take maximum advantage of the 
sun, particularly in the winter months?  If they are sloped, what maintenance 
is performed on the panels over the years?  What equipment is required for 
maintenance of any kind on the panels?  Can the roof be reroofed without 
removing the panels or do the panels have to be removed for reroofing?  If 
the panels are sloped, what is the likelihood of material being stored under 
the panels?  Maintenance personnel don't like to haul 5-gallon buckets of 
plastic cement to the roof every time to patch a leak and tend to store this 
material on the roof.

Depending on how you can answer these questions determines how good an 
argument you can make to use a reduced live load for the roof.

No answers, but lotsa questions!

A. Roger Turk, P.E.(Structural)
Tucson, Arizona

Jeff Smith wrote:

. > I have a 40'x50' flat roof with 10 4x6 skylights. The client wants to 
. > pretty much fill up all areas except the skylights with solar panels. 
. > Overall the panels weigh about 4psf. They are permanent, but after 
. > installed there is really no room left for live loads other than wind and
. > rain. My understanding is that a 20 psf roof live load is for
. > construction/maintenance loads. Are the panels a dead load or live load?
. > Normally I would just add the panel weight to the DL and use 20psf LL. The
. > only reason I ask is that I am on the cusp of it figuring.

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