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RE: Appendix B and sloping shear wall top chords

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Thor,
I agree with the way tiedown forces are calculated in your example in
Appendix B. I, however, would like to add a couple of comments:

1. Connection of the sloping top plates to the short end post will see a
force of 2500 lbs if we assume this is the only member delivering the
diaphragm force to the shear wall. In your Figure 4, there will not be a
horizontal reaction of 2165 lbs at this level. Force delivered from the
sloping plates will be transmitted to the bottom of left holdown post via a
compression strut (plywood ) while the right post acts in tension.
2. Looking at the overall elevation (Figure 1), it appears that it is
important to specify a tension member at the ceiling level to drag seismic
force generated on the left side of the roof to the shear wall(s).


Suresh Acharya, S.E.


-----Original Message-----
From: Thor Matteson, SE [mailto:matteson(--nospam--at)yosemite.net]
Sent: Wednesday, February 05, 2003 6:54 AM
To: SEAINT
Subject: Appendix B and sloping shear wall top chords


Greetings, fellow shear wall enthusiasts:

Due to great demand for "Appendix B--Engineering Principles of Shear Walls
with Sloping Top Plates,"  I have made the PDF file available at
www.shearwalls.com --the link is about half-way down the page.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
PLEASE do not e-mail me with direct requests for the Appendix.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I have also added information to the Appendix in response to a comment that
several people have made, that the force in the roof diaphragm delivers a
_purely horizontal_  force to the sloping top plate of the shear wall.
Diaphragms (by definition) only carry forces within their own plane.   A
dramatic example shows that  the bending stress produced in the diaphragm
sheathing  by an out-of-plane "diaphragm" force component would  be over
35,000 psi.

I am very interested in other well-reasoned opinions on the behavior of
sloped shear walls.  Begin with statics, and work from there;  making
assertions that can't be backed up by a free-body diagram won't get us
anywhere.

Thor Matteson



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