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Re: CMU Wall Supported by Plywood Sheathed Roof Diaphragm and Shearwalls

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I think your best bet is to make the masonry a non-structural wall (i.e., free standing or tied into the roof diaphragm for out of plane restraint only. ) Use post framing (if you can cantilever the diaphragm , i.e. have an interior wood shearwall near the masonry wall, perhaps for a corridor)  or steel moment frame with the masonry acting as sort of a facade between columns. The foundation will be your biggest problem since it will probably be eccentrically loaded.

As far as deflection limit for a masonry wall, there is a slender wall design procedure in the code that account for P-delta effects when the wall is supported out of plane at the roof (UBC 2108.2.4). If not, design it as a cantilever wall with the lateral force being the seismic mass of the wall and allow for movement at the top in your detailing so it imposes no load to the diaphragm.


Gerard Madden, P.E.
Civil Engineer

Middlebrook + Louie, Structural Engineers
71 Stevenson Street, Suite 2100
San Francisco, CA 94105
Tel: 415.546.4900
Fax: 415.974.3680
Email: gmadden(--nospam--at)