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Fwd: Re: Dead Load On Shear Walls

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With regard to my earlier post concerning the impact of a cross wall =
framing into a shear wall for estimating dead load on the shear wall =
resisting overturning:

Statics alone does not seem adequate to model the situation...I believe =
there is an issue of strain compatibility here.  Won't the holdown at =
the chord in tension have to fail or strain excessively before the cross =
wall begins to pick up load?=20

The dead load of the cross wall under ordinary loading goes straight =
down to its own foundation through the studs.  Until the shear wall has =
the chance to "pick up" the cross wall a bit during lateral loading, =
won't the cross wall's deadload still simply follow it's own studs down =
to the foundation, not delivering *any* of it's DL to the shear wall?  =
With the cross wall located half the distance from the compression =
chord, for every unit vertical displacement in the tension chord of the =
shear wall, the cross wall would see only 1/2 the displacement even it =
was fully anchored to the shear wall.  My concern is that by the time =
the shear wall has moved far enough (through elongation at the tension =
chord connetion) to "pick up" a substantial part of the cross wall, the =
chord connection would probably have already failed.....so the question =
remains, how much of the cross wall DL can one reasonably count on?

----------
From: 	Dennis S. Wish PE[SMTP:wish(--nospam--at)cyberg8t.com]
Sent: 	Tuesday, April 01, 1997 8:42 PM
To: 	'seaoc(--nospam--at)seaoc.org'
Subject: 	RE: Dead Load On Shear Walls

Bill, there is one flaw that I see with your reasoning. Forgeting the =
concrete foundation for one moment, the governing factor will be the =
capacity of the holddown at the connection to the shearwall. If there is =
no positive connection from the perpendicular crosswall "within" the =
shearwall by transfer, AND if the resistance to uplift is considered =
from the crosswall, then the holddown connection may not be designed =
adequately. Without the possitive connection of the crosswall above the =
foundation to the shearwall, the shearwall will uplift and the =
connection at the holddown will probably fail in the post (ie, if the =
holddown required without consideration for the crosswall is an HD7 but =
becomes an HD2 with the wall, the HD2 may fail without positive =
conneciton of the crosswall above the slab).
Unless I missed something from your post, I think you missed this one.

Dennis

-----Original Message-----
From:	Bill Allen, S.E. [SMTP:ballense(--nospam--at)concentric.net]
Sent:	Tuesday, April 01, 1997 7:30 PM
To:	seaoc(--nospam--at)seaoc.org
Subject:	Re: Dead Load On Shear Walls

Aren't the walls connected at the footing? As the shear wall tries to
uplift, it is resisted by some trib. length of the perpendicular wall,
footing, etc. The transfer mechanism would be through shear in the
perpendicular footing at the intersection of the shear wall and the
perpendicular wall. Even if using a working stress shear capacity of
1.1*sqrt(f'c)*1.33=3D65 psi or about 9,400 lbs for a single story =
residential
footing. Now you KNOW I'm an old geezer when I reference WSD for
concrete!!! The point is, I don't believe you need any special =
connection
at the wood framed section of the wall to consider the perpendicular =
wall
contributory to the resistance of overturning. This should also apply at
corners.

Regards,
Bill Allen

> You would have to connect the perp. wall to the V-wall adaquately to
transfer
> the load.  Also connection of the perp. wall to foundations is =
critical.
>  Tough to do with wood.....
>=20
>=20
> Bill Thorpe, SE






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To: "'seaoc(--nospam--at)seaoc.org'" <seaoc(--nospam--at)seaoc.org>
Subject: RE: Dead Load On Shear Walls
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