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RE: 3-D modeling - ASCE 7-05 12.7.3 needs an exception for light-frame timber

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Bill,

Unfortunately, it's too late for the ASCE 7-10 update cycle. Technical
changes to the seismic requirements had to be submitted by last
February. This was requested so the Provisions Update Committee for the
NEHRP provisions could vet the technical proposals prior to ASCE 7's
seismic committee considering them.

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, William N [mailto:William.N.Scott(--nospam--at)conocophillips.com] 
Sent: Friday, January 18, 2008 12:16 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: 3-D modeling - ASCE 7-05 12.7.3 needs an exception for
light-frame timber

Scott,

You have a valid point. Use the following link and submit your
suggestion directly to ASCE.

 http://content.seinstitute.org/committees/codes.html

Bill Scott

-----Original Message-----
From: Haan, Scott M POA [mailto:Scott.M.Haan(--nospam--at)usace.army.mil] 
Sent: Thursday, January 17, 2008 5:41 PM
To: seaint(--nospam--at)seaint.org
Subject: RE: 3-D modeling - ASCE 7-05 12.7.3 needs an exception for
light-frame timber

ASCE 7-05 12.7.3 should have an exception for light frame construction
that
says the model for light frame construction can use approximate methods
for
wood panel shear walls on cantilevers, non-parallel systems and soft
stories.

12.5.4 says that you can do a 2-D analysis for flexible diaphragms
except
where required by 12.7.3. 

The more you read ASCE 7-05 12.7.3 the more you realize it has not
considered
light frame structures or that the steel/concrete building eggheads were
the
only ones in attendance to vote.  Light frame shear walls are set on
cantilevered floor joists all the time.  This is an out-of-plane offset.
The
code already has special requirements for framing supporting at the
cantilevers.  You already get tagged with a redunancy factor for walls
full
of windows or garage door openings. As for non-parallel systems in wood
buildings - add an exception to the code to say the architect should be
water
boarded.

The code writers should consider that 99.99999% of structural engineers
are
not going to do a finite element model for light frame wood panel shear
wall
structure. I worked at a busy building department for 8 years and only
saw a
couple of designs with Woodworks which I don't know meets 12.7.3.  There
were
a couple of residential designers that used Maxquake which I don't know
meets
12.7.3. A vast majority of light timber designers did it by hand.



-----Original Message-----
From: Matthew Shear [mailto:MShear(--nospam--at)RMByrd.com] 
Sent: Tuesday, January 15, 2008 1:31 PM
To: seaint(--nospam--at)seaint.org
Subject: 3-D modeling

Based on ASCE Section 12.7.3, a 3-D model is required if a structure has
an
irregularity type 1, 4, or 5.  Would this be required for a light framed
shear wall structure?  Or even on a structure with a flexible diaphragm?

 
Thanks
 
Matthew
 
 

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