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Re: Pf - Snow Load on Flat Roofs Subjected to Solar PV Array

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The O'Rourke recommendation that RTUs be raised to deal with snow drifts is good advice.

In the late 1970s I was involved in a project on the sea shore of the Arctic Ocean . We planned to raise all of the gas plant buildings on piles for two reasons: to allow winter air to circulate under the buildings to re-freeze the permafrost (that may have thawed during the summer) around the piles ; and to keep snow drifts away from the buildings (the snow drifts would have blocked the air flow, hence, allowing the permafrost to thaw with potentially catastrophic results). We had an engineering company in Guelph, Ontario, conduct a hydraulic model study on the snowdrift problem.

This study produced some expected and some unexpected results. In the high Arctic for our site (an island in the delta of the Mackenzie River) there is only about a foot or so of snow but very high winds that cause major drifts (Drifts 15' to 20' high and more are now unheard of.). When buildings were set flat on the ground the drifts were tight against the buildings much like you probably saw on the TV news for the major snow storm in Buffalo, New York, yesterday. When the buildings were raised 5' to 7' (our buildings were planned to be about 80' square by 50' high) the snow drifts were about 1.5 to 2 time as far away from the buildings as the hight the buildings were raised above the grade. The snow drifts around circular tanks on grade were always a few feet away from the tank and never right up against the tank.

Setting the support framework for the RTUs 2' above the expected snow level is reasonable based on my experience.



On 19/11/2014 4:59 AM, Matthew Stuart wrote:
This message was also sent by MStuart(--nospam--at) to: Harold.Sprague(--nospam--at)
Thanks for the input

D. Matthew Stuart, P.E., S.E., F.ASCE, F.SEI, SECB, MgtEng
Structural Division Manager
Pennoni Associates Inc.
Office 215-222-3000 x7895
Mobile 908-309-8657 | mstuart(--nospam--at)

-----Original Message-----
From: Sprague, Harold [mailto:Harold.Sprague(--nospam--at)]
Sent: Tuesday, November 18, 2014 6:27 PM
To: seaint-seaosc(--nospam--at)
Cc: Matthew Stuart
Subject: RE: [SEAINT-SEAOSC] Pf - Snow Load on Flat Roofs Subjected to Solar PV Array


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