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Re: WOOD MOMENT FRAMES, Rw = 3

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In Chapter 16 of the 1997 UBC (also in the 1996 Supplement), a line has been
added to Table 16-N, requiring Rw=3 for "Cantilevered Column Systems".  We now
follow this guideline if we are designing cantilvered columns with either a
grade beam or pole foundation, such as at a garage door.  I think this was
invoked to help prevent Northridge Meadows type soft-story collapses.  It
creates rather large columns, especially because you still have to satisfy the
0.005H drift requirement.

The real question we have in the office, is whether or not the Rw=3 now
applies to the entire building since you are using it for one shear line in
one direction.

As to "wood moment frames", I think this optimistic to say the least.  Either
use the cantilivered steel columns, or add a steel beam and make a steel-to-
steel moment connection.

Bruce Resnick, SE
Parker Resnick Str. Eng.