add panels on roof, does it add wind load to roof structure members?
add panels on roof, does it add wind load to roof structure members?
(OP)
MWFRS wind load for flat/monoslope roof is only uplift load, no downward load. so we don't add wind load for joist/girder design.
But when we add tilted panels on half of the roof, panels will take uplift and downward wind load, most time downward wind load is over 20psf and uplift is only 15psf. do we need to add panel downward wind load to roof stuctural members, when we check the roof joist/girders?
Or we don't need to, since joists/girders are not roof c/c.
Thanks
But when we add tilted panels on half of the roof, panels will take uplift and downward wind load, most time downward wind load is over 20psf and uplift is only 15psf. do we need to add panel downward wind load to roof stuctural members, when we check the roof joist/girders?
Or we don't need to, since joists/girders are not roof c/c.
Thanks






RE: add panels on roof, does it add wind load to roof structure members?
Mike McCann
MMC Engineering
RE: add panels on roof, does it add wind load to roof structure members?
Dead+0.75Wind+0.75Live+0.75Snow both snow and wind count
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
Do we need to use the load combination and include wind load on panels? Or we should ignore since joist/girders are main force resisting over areas bigger than 700 square feet?
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
Just wondering I can get away with it since building members won't design like roof components and cladding.
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
there are so many roof are adding panels, nobody even think they would add downward wind due to panels.
RE: add panels on roof, does it add wind load to roof structure members?
I don't think it is proper to ignore the vertical components of the wind load for solar panels.
RE: add panels on roof, does it add wind load to roof structure members?
Just want to confirm that for any enclosed building roof (flat/monoslope/gable) framing, net wind load is uplift, so regular design we only have D (say 20psf)+L/S (30psf). For roof c/c, it may have smaller downward load, but uplift is bigger. Joist/girder cover bigger than 700psf area are not designed as component/cladding.
When we add panels on half of the roof, panels are at 10 degrees, having about 14psf uplift and 19psf downward load. we need add weights to hold the uplift and horizontal load, that's about 17psf dead load added on roof. Usually we only consider the added roof dead load, and existing roof framing may still figure since 17psf is only added to half of the roof area. Very strange in my area, all roof panels never get any roof framing reinforcement from all projects.
But if I need to consider the wind downward load, I believe no existing roof can hold it:
without considering wind downward load: Dead+0.75Live/0.75Snow= 20psf+17psf/2+0.75*25psf=47.25psf <50psf design
consider wind downward load: Dead+0.75Wind+0.75Live/0.75Snow= 20psf+17psf/2+0.75*19psf/2+0.75*25psf=54.375psf >50psf design
So I am thinking the panels may be only treated as component/cladding for all connections, but for roof joist/girder, the panel induced wind load won't apply. Am I right?
RE: add panels on roof, does it add wind load to roof structure members?
On the other hand, live loads do need to consider that ALL loading (and maintenance and solar panel installation weights (stacks of panels and frames and motors and people and tools) are going to be concentrated in the walkways between the rows of solar panels. Assuming "live loads" are nicely spread out all over a "generic roof" is no longer correct.
RE: add panels on roof, does it add wind load to roof structure members?
"Whom the gods would destroy, they first make mad "
RE: add panels on roof, does it add wind load to roof structure members?
I might suggest that with a roof design the joist/girder designs do indeed include C&C wind. The perspective I take is that MWFRS wind pressures and C&C wind pressures aren't mutually exclusive for a member design. The wind itself doesn't "know" that it is MWFRS or C&C - it's just wind. The fact that girders and joists may have large areas (>700 s.f.) doesn't mean you can ignore C&C wind (which might include downward pressure). It only means that the larger area allows a reduction in the C&C wind pressures to a level more closely matched to the MWFRS wind.
The ASCE 7, which we use, may have language that specifically says - If > 700 s.f. then USE MWFRS vs. reducing C&C (I'll have to check). But the premise that you simply ignore a downward pressure may not be right.
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
JAE: Can I have a silly question? for regular building roof design, do you have min. 10psf downward wind applied to joist/girder beside the dead and live/snow load? Thank you!
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?
RE: add panels on roof, does it add wind load to roof structure members?