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# Re: RESIDENTIAL: Shearwall Line Offsets

• To: seaint(--nospam--at)seaint.org, "Showalter, Buddy" <Buddy_Showalter(--nospam--at)afandpa.org>
• Subject: Re: RESIDENTIAL: Shearwall Line Offsets
• From: Bill Polhemus <bill(--nospam--at)polhemus.cc>
• Date: Wed, 26 Jan 2005 04:57:13 -0600

```Bill Polhemus wrote:

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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)."
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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.
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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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Follow-up questions:

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Suppose I have two walls at the extremity of the "inscribing rectangle" that are offset less than the four feet. May I use the entire length of those two walls?
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Also, what is the rule concerning "C-shape" shear wall configurations for wind design? That is, I have one exterior wall that really HAS to be a shear wall under normal circumstances but has little or no capacity for providing shear resistance (because it is almost entirely made up of window and door openings, for instance). Is it possible (or even advisable) to use rigid diaphragm analysis for such a case? Would that still fall under the prescriptive design provisions of the WFCM? (Yes, that's really stretching it, I know).
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If only one "system" (i.e. only the shearwall design) falls outside the prescriptive design provisions, may the designer use prescriptive provisions for other "uncoupled" elements of design? (e.g. the floor/ceiling joists, etc.)
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