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Re: Wind Uplift on Awning [OT: Embers in attic, etc.]

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Yes, fire effects are a bit OT, but I'd like to comment that following the "Great Oakland-Berkeley Firestorm of 1994" that burned more than 3,000 homes to the ground, they instigated fire requirements that prohibited attic vents, non-fire protected decks, etc., in an attempt to minimize the disastrous effects of such features in "urban wildfire" environments.

Ralph Hueston Kratz, S.E.
Richmond CA USA

In a message dated 5/9/08 9:24:27 AM, rgarner(--nospam--at) writes:
During the recent SoCal wildfires, many residences caught fire from
burning embers entering attic vents.

Bob G.

-----Original Message-----
From: Donald Bruckman [mailto:bruckmandesign(--nospam--at)]
Sent: Friday, May 09, 2008 9:13 AM
To: seaint(--nospam--at)
Subject: RE: Wind Uplift on Awning

...and so, with all this talk about MWFRS,or C&C and the like, I come
upon a
site which informs me, among other things, that a common mode of
not necessarily of the structure, but just as devastating to the
is the entrance of wind and water through attic vents, saturation of
insulation and drywall, collapse of the ceiling and equivalent
of the interior of the house to a structural failure. 

Seemingly, one section of the code (attic ventilation) destroys what
(ASCE-7) seeks to preserve.

If one is going to require such a detailed wind load calc, one would
that the code writing committees should add a section to the code that
precludes high wind attic access.

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)]
Sent: Friday, May 09, 2008 6:36 AM
To: seaint(--nospam--at)
Subject: RE: Wind Uplift on Awning

You kind of did it for me.  The basic reasoning is that you do have
localized "peaks" or "spikes" of pressure.  When looking at a large item
(say the whole building for MWFRS), you have a lot more low points to
average out the high points and thus end up with a lower overall
The smaller the area under consideration, the more likely you will NOT
enough low points in that area to average out the higher points...thus,
end up with a higher average.  In otherwords, the smaller that "item"
consideration, the more likely that you have have a localized area of
wind pressure acting on that area that does not get "cancelled" out.  It
seems from your explanation of the Australian code that it is following
same basic reasoning, just get implemented differently to some degree.

And I agree that size is not the only thing that determines the choice,
it is largely the driving factor and in many ways the easiest way to
about it.

And that is the short winded version (pun again intended).


Adrian, MI

-----Original Message-----
From: Conrad Harrison [mailto:sch.tectonic(--nospam--at)]
Sent: Friday, May 09, 2008 3:20 AM
To: seaint(--nospam--at)
Subject: RE: Wind Uplift on Awning

Scott Maxwell wrote:

Note, I did not go into why C&C pressures tend to be larger because I am
assuming that you know why already and did not want to appear to be
"insulting your intelligence" (which is never my intent, but I have been
told that I sometimes come across that way when I am merely just trying
offer a detailed explanation...i.e. I get long winded...pun intended).
my assumption is wrong and you want that explanation (at least at I
understand it), then I would be more than glad to engage the long winded
mode and elaborate.

<end quote>

Please elaborate. If everyone on the listserver was fully knowledgeable
experienced in all areas, then there wouldn't be anything to discuss:
and no
need for the list. Also not everyone questions what they do, and this
makes issues more immediate than journals. Plus everything posted in the
emails, also gets redirected to various other locations which are
indexed by

Thus information and debate is available for code writers to use to
codes and commentaries and improve our understanding of intent.

Further students and graduates may be reading the list, to get a handle
how to put things into practice. Conflicting views to demonstrate things
not clear cut, and do not have exact mathematical answers is good for
to learn.

Then again: some of my posts are so long winded, the listserver seems to
reject. So for those who think what I post is long, you have been saved
the really long ones.

Conrad Harrison
B.Tech (mfg & mech), MIIE, gradTIEAust mailto:sch.tectonic(--nospam--at)
Adelaide South Australia

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