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RE: Wood / lightframe shear walls without shear walls

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SHM & erik_g,
 
Thanks for the input, but I was expecting discussion on minimizing non-ductile mode of failure due to splitting of sill plates which, if happens, would not qualify for R=6.5 (no yielding of nails here). CUREE-Caltech tests have shown much better performance of sill plates when holdowns were present. Rocking of wood shear walls are not welcome unlike concrete or CMU shear walls.
 
Regarding dead loadstributary widths for resisting forces and seismic forces may not be necessarily same, but roof and ceiling dead loads are mostly lumped together in calculations. For example, ceiling joists and rafters spanning in different directions, or ceiling joists/rafters being supported by interior walls which are not shear walls, or due to presence of ceiling beams/ purlins/king posts etc.
 
Suresh Acharya, S.E.
 


From: ECVAl3(--nospam--at)aol.com [mailto:ECVAl3(--nospam--at)aol.com]
Sent: Tuesday, July 08, 2008 10:00 AM
To: seaint(--nospam--at)seaint.org
Subject: Re: Wood / lightframe shear walls without shear walls

Since the lateral force is derived from the dead load, if you reduce the dead load resisting moment for a more realistic dead load, you should also be able to reduce the lateral force overturning moment by the same percentage. It's a wash unless you completely negate the dead load resisting moment altogether!
SHM
 
In a message dated 7/7/2008 9:10:29 P.M. Pacific Daylight Time, erik_g(--nospam--at)cox.net writes:
". However, many times the calculated resisting moments are
unrealistically high"

If the resisting moment is obtained from the dead load, then the same can be
said for the complete vertical design. Then all beam design is conservative.


-----Original Message-----
From: Acharya, Suresh [mailto:Suresh.Acharya(--nospam--at)ci.concord.ca.us]
Sent: Monday, July 07, 2008 11:13 AM
To: 'seaint(--nospam--at)seaint.org'
Subject: Wood / lightframe shear walls without shear walls


Hi Dr Astaneh,

I got your email address from one of your postings on Seaint list server.

The reason I am writing to you is to inquire about thoughts on wood shear
walls installed without holdowns - particularly regarding preventing
splitting of sill plates and distribution of shear along the bottom of shear
walls if the wall tend to rotate. I believe all the tests in the past were
done with holdowns on both ends of shear walls. Many engineers routinely do
not specify holdowns for shear walls when calculated overturning moments due
to dead loads are shown to exceeds the overturning moments due to lateral
forces. However, many times the calculated resisting moments are
unrealistically high.


Suresh Acharya, S.E.
Building Plans Engineer

City of Concord
1950 Parkside Drive
Concord, CA 94519
(925) 671-3276
Fax (925) 680-4877


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