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RE: Tale 6-1 of ASCE 7-05

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It is a by product of my "mis-spent youth" (if you call last week my youth
<grin>) time reading some of the meeting minutes from ASCE 7's meeting in
April (that I was never told about...but I do appear to be back on the
notification list now).  I was potentially going to come to the Wind
Subcommittee meetings this week, but finances are such that it turned out to
be not viable.  I still want to read through the proposed changes before the
end of the week and maybe submit some comments, but not sure if I will have
time.  I would REALLY like to see the wind provisions simplified...in
particular for things like signs.

I figured you (or someone else) might be able to put better phrasing and
words to it...I kind of "jiggered" the explanation.  <grin>

Regards,

Scott
Adrian, MI

-----Original Message-----
From: Ehrlich, Gary [mailto:gehrlich(--nospam--at)nahb.com] 
Sent: Tuesday, June 03, 2008 9:31 AM
To: seaint(--nospam--at)seaint.org
Subject: RE: Tale 6-1 of ASCE 7-05


Scott,

Beat me to it. Section C6.5.5 of the commentary talks about the importance
factor and notes the difference in return periods between the non-hurricane
zones (50-year MRI) and hurricane zones (500-year MRI factored down to 50,
and incorporating the old coastal multipliers). So the lower importance
factors in the hurricane region bridge that "jiggering" and give about the
same reliability for both the hurricane and non-hurricane regions.

Gary

Gary J. Ehrlich, PE 
Program Manager, Structural Codes & Standards 
National Association of Home Builders (NAHB) 
1201 15th Street, NW, Washington, DC 20005 
ph: 202-266-8545  or 800-368-5242 x8545 
fax: 202-266-8369 
gehrlich(--nospam--at)nahb.com 

-----Original Message-----
From: Scott Maxwell [mailto:smaxwell(--nospam--at)umich.edu] 
Sent: Friday, May 30, 2008 5:46 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: Tale 6-1 of ASCE 7-05

That and the wind speed maps are kind of "wonky" and "jiggered" to work with
the importance factor and the combination of hurricane zones and
non-hurricane zones.  I am offering this based upon the fact that there are
discussions about going to three different wind speed maps for different
importance factors/levels/occupancy types.

Regards,

Scott
Adrian, MI

-----Original Message-----
From: chris.slater(--nospam--at)gmail.com [mailto:chris.slater(--nospam--at)gmail.com] On Behalf Of
Chris Slater
Sent: Friday, May 30, 2008 2:42 PM
To: seaint(--nospam--at)seaint.org
Subject: Re: Tale 6-1 of ASCE 7-05


This is a guess, but hopefully a logical one.

Since wind loads are a function of V squared, and since Category I buildings
are just storage and Ag buildings, it seems likely that they're giving a
break in the Importance factor for those buildings in the higher wind areas
to reduce the overall outcome of the calculation.

The calculated loads will still be higher in the V > 100 mph areas, since
they will be a function of V squared.

Hope that makes sense...

Chris

On Fri, May 30, 2008 at 11:22 AM, Casey K. Hemmatyar <khemmatyar(--nospam--at)gmail.com>
wrote:
>
> Is anyone familiar with the logic behind the coefficients 0.87 and
> 0.77 in Tale 6-1 (page 77) of ASCE 7-05? The Importance Factor "I" for 
> Hurricane Prone Regions with V>100 mph is 0.77.
> While for Non-Hurricane Prone Regions & Hurricane Prone Regions with V<100
> mph, it is 0.87.
>
> Regards
>
> Casey (Khashayar) Hemmatyar, SE
>

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