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RE: ASCE 7-02 Enclosure Classifications

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So if the conclusion is that "ALL" non-impact rated windows are openings
then most office buildings with evenly spaced windows (i.e. typical
office building) would be classified as Enclosed (GCPi = +/- 0.18).

Now if it is just ONE wall that is assumed with openings at any given
time then our same office building would be considered as Partially
Enclosed (GCPi = +/- 0.55).

Which scenario does your insight and experience indicate that the code
requires / intended to require?

-----Original Message-----
From: Harold Sprague [mailto:spraguehope(--nospam--at)hotmail.com] 
Sent: Thursday, February 03, 2005 1:53 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: ASCE 7-02 Enclosure Classifications

I have had this conversation with Jon Paterka of CPP.  He is on the ASCE
7 
wind committee.  Jon told me that it was the intent of the code to 
characterize the high probability that the windows would be broken out
in 
ANY or all walls during a hurricane.  This would likely significantly 
increase the loads on the walls.  Basically, if the windows are not
impact 
resistant and you have not provided for some sort of storm covering, all
of 
the windows without impact resistant glazing should be treated as
openings.

This was watered down considerably from what was intended from the
original 
authors of the provisions in the Standard Building Code.  This provision
was 
a result of some typhoon studies in Australia and Hurricane Andrew meets

Dade County.  The provision for the plywood covering was not what the
code 
developers wanted.  But the developers did not want to provide the very 
robust glazing required for wind borne debris impact resistance.

Regards,
Harold Sprague




>From: "Rob Still" <robs(--nospam--at)adcengineering.com>
>Reply-To: <seaint(--nospam--at)seaint.org>
>To: <seaint(--nospam--at)seaint.org>
>Subject: ASCE 7-02 Enclosure Classifications
>Date: Thu, 3 Feb 2005 09:25:59 -0500
>
>To all,
>
>I'm hoping to solicit opinions from fellow engineers and possibly any
>ASCE Committee members that the list may be distributed to regarding
>ASCE 7-02 and the Enclosure Classifications as it relates to Partially
>Enclosed and Enclosed.  We are currently having a lengthy debate in our
>office (Charleston, SC) regarding both the letter and the intent of the
>code specifically section 6.5.9 and its subsections.  The heart of the
>debate lies in the use of impact resistant glass in hurricane regions.
>Section 6.5.9.3 requires that all glazing in hurricane regions shall be
>impact resistant or protection (operable shutters or plywood panels) be
>provided.  The Exception below, however, allows non-impact rated
glazing
>to be used if the "unprotected glazing that receives positive external
>pressure is considered an opening."
>
>So herein is our crossroads.  If "Positive External Pressure" is
related
>to each specific load case generally there is one wall which receives
>positive external pressure.  This would mean that if non-impact glazing
>is provided and only one wall has glazing considered as openings (the
>other 3 walls with non-impact rated glazing are not receiving pos ext
>pressure so not an opening) then the building would nearly always be
>considered Partially Enclosed.
>
>The other side of the coin is if the "Positive External Pressure"
>statement is really intended to mean at any point during loading then
>one would assume that each perimeter wall would have openings.
Assuming
>the openings are symmetrical and evenly dispersed the building would be
>classified as Enclosed.
>
>I have several other questions in this area, particularly the
>commentaries description of operable windows and doors as openings that
>seem to muddy the waters even more, but if I could at least get some
>opinions regarding the overall question first I would be much
>appreciative.
>
>Thanks in advance,
>
>Rob Still, P.E.
>ADC Engineering, Inc.
>

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