We're getting off topic a bit, but you will note that a new chapter in the
CBC, 7A was added to attempt a remedy.
I would assume that hurricane prone areas have similar pertinent specialized
sections added to their codes periodically as well, (at least I hope they
do).
-----Original Message-----
From: Garner, Robert [mailto:rgarner@moffattnichol.com]
Sent: Friday, May 09, 2008 9:23 AM
To: seaint@seaint.org
Subject: RE: Wind Uplift on Awning
During the recent SoCal wildfires, many residences caught fire from
burning embers entering attic vents.
Bob G.
-----Original Message-----
From: Donald Bruckman [mailto:bruckmandesign@verizon.net]
Sent: Friday, May 09, 2008 9:13 AM
To: seaint@seaint.org
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
failure,
not necessarily of the structure, but just as devastating to the
homeowner,
is the entrance of wind and water through attic vents, saturation of
insulation and drywall, collapse of the ceiling and equivalent
destruction
of the interior of the house to a structural failure.
Seemingly, one section of the code (attic ventilation) destroys what
another
(ASCE-7) seeks to preserve.
If one is going to require such a detailed wind load calc, one would
think
that the code writing committees should add a section to the code that
precludes high wind attic access.
http://woodscience.oregonstate.edu/faculty/gupta/Katrina/Hurricane.pdf
db
-----Original Message-----
From: Scott Maxwell [mailto:smaxwell@umich.edu]
Sent: Friday, May 09, 2008 6:36 AM
To: seaint@seaint.org
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
average.
The smaller the area under consideration, the more likely you will NOT
have
enough low points in that area to average out the higher points...thus,
you
end up with a higher average. In otherwords, the smaller that "item"
under
consideration, the more likely that you have have a localized area of
high
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
the
same basic reasoning, just get implemented differently to some degree.
And I agree that size is not the only thing that determines the choice,
but
it is largely the driving factor and in many ways the easiest way to
think
about it.
And that is the short winded version (pun again intended).
Regards,
Scott
Adrian, MI
-----Original Message-----
From: Conrad Harrison [mailto:sch.tectonic@bigpond.com]
Sent: Friday, May 09, 2008 3:20 AM
To: seaint@seaint.org
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
to
offer a detailed explanation...i.e. I get long winded...pun intended).
If
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
and
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
list
makes issues more immediate than journals. Plus everything posted in the
emails, also gets redirected to various other locations which are
indexed by
Google.
http://seaint.blogspot.com/ http://www.seaintarchive.org/group/seaint/
Thus information and debate is available for code writers to use to
revise
codes and commentaries and improve our understanding of intent.
Further students and graduates may be reading the list, to get a handle
on
how to put things into practice. Conflicting views to demonstrate things
are
not clear cut, and do not have exact mathematical answers is good for
them
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
from
the really long ones.
Regards
Conrad Harrison
B.Tech (mfg & mech), MIIE, gradTIEAust mailto:sch.tectonic@bigpond.com
Adelaide South Australia
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