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RE: 10/lw term in calculation of rho

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Here's a tidbit that should help your rho calculations.  I got this from the
SEAOC email list, which has some pretty interesting things now & then.  Like
I said, they added the 10/lw factor to account for the many panels in
tiltups and sort of didn't think about what it did to residential shear
walls.  You can sign up by reading the stuff at bottom, though you'll get
about 30 emails a day.

-----Original Message-----
From: Dan Morrow [mailto:dmorrow(--nospam--at)]
Sent: Wednesday, October 27, 1999 10:18 AM
To: 'seaint(--nospam--at)'
Subject: 10/lw term in calculation of rho

In a 10/25/99 post by Robert Shaffer, he commented that if you have less 
than a 10 ft shearwall you are penalized by the 10/lw term when calculating 
ri.  I attended an SEAOC/ICBO seminar here in Seattle a couple of weeks ago 
on the Seismic Design Manual, Vol 1.  One thing that the moderator brought 
to light is that the term 10/lw was never meant to exceed 1.0.  Apparently 
this fact is not documented in the 1997 UBC or commentary.
So if your structure has shearwalls less than 10 ft long there is no 
The little things they (the code folks) forget to mention!

Dan Morrow, EIT