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RE: Dead Load or Live Load?

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Jeff,

Based on these questions and others that are similar, like... When the
panels become broken or obsolete will they be permanently removed from the
roof in some areas, help point into another conservative direction.

The solar panels could be considered a "collateral load" (i.e. dead load
that does not provide uplift resistance or count as part of the 20 psf or
other live/snow loads). This assumption takes the worst case for gravity
loads (panels included), seismic loads (panels included), and wind loads
(panels not included typically).

Other considerations not already mentioned might include:
1) if panels are sloped, do they increase wind loads (lateral or vertical)
2) if in a snow load area do they increase the potential for snow drifting.
3) if in a seismic area do the solar panel connections to the roof/support
structure meet the code requirements for cladding supports (if applicable in
the code)
4) make sure panels don't cause localized ponding problems

Hope this helps,
Greg Effland, P.E.
KC, MO USA

-----Original Message-----
From: Roger Turk [mailto:73527.1356(--nospam--at)compuserve.com]
Sent: Wednesday, November 21, 2001 2:31 PM
To: seaint(--nospam--at)seaint.org
Subject: Dead Load or Live Load?


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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