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RE: RESIDENTIAL: Shearwall Line Offsets

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Bill,
I posted almost the exact question last week or maybe the week before.  I
didn't get a lot of replies, but it seems that the feeling is that yes you
compute the wind loads on the structure assuming that rectangular size, and
transfer those loads to the segment of "real wall" at the extremity of the
"inscribed rectangle".  My personal feeling is that there can be no vertical
discontinuity in the diaphragm otherwise the wind loads have no way to be
transferred to that wall.

I too have been looking at the WFCM in an attempt to find a way to help make
this residential design work.  So far, I'm not sure the WFCM is the answer,
but I haven't given up yet.

J. Grill

Joseph R. Grill, P.E. (Structural)
Shephard - Wesnitzer, Inc.
Civil Engineering and Surveying
1146 W. Hwy 89A Suite B
Sedona, AZ  86340
PHONE (928) 282-1061
FAX (928) 282-2058
jgrill(--nospam--at)swiaz.com
 


-----Original Message-----
From: Bill Polhemus [mailto:bill(--nospam--at)polhemus.cc] 
Sent: Wednesday, January 26, 2005 3:46 AM
To: seaint(--nospam--at)seaint.org; Showalter, Buddy
Subject: RESIDENTIAL: Shearwall Line Offsets

The conventional framing provisions of the Prescriptive Design as 
described in Chapter 3 of the Wood Frame Construction Manual allows a 
maximum four-foot offset for shear walls.

When the offset is greater than four feet, "the structure shall be 
considered as separate structures attached in the plane of the offset." 
(WFCM 3.1.3.3 c.)

However, the WFCM goes on to say: "FOR WIND DESIGN, the structure shall 
be permitted to be designed as a regular structure with perimeter 
dimensions which inscribe the total structure (see Figure 3.1b)."

Figure 3.1b shows an irregular structure in plan with offsets varying, 
some greater and some less than four feet. The "inscribed structure" is 
the least-size rectangle that will encompass the entire plan.

I'm not sure what this means. Does it mean that you compute the wind 
loads on the structure assuming that rectangular size, and transfer 
those loads to the segment of "real wall" at the extremity of the 
"inscribing rectangle"?

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