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Cantilevered Wood Diaphragm

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I recently designed a wood framed, two story, apartment building for
lateral loads.  In the longitudinal direction, there are no exterior
shear walls, however, there are longitudinal shear walls along a 6' wide
corridor along the center of the building.  The floor and roof
diaphragms are cantilevered out about 25' on each side of the corridor
walls (building is about 56' wide x 184' long).  There are transverse
shear walls at about 46' oc between living units.  The shear wall plan
looks something like this;

   46'      46'      46'     46'
|          |          |          |          |  25'
|          |          |          |          |
____________________    6'
|          |          |          |          |
|          |          |          |          |  25'

Shear walls on the first and second floors stack, seismic governs (Zone
4), diaphragms are assumed flexible.  I am analyzing the diaphragm as a
continuous 184' deep horizontal beam symmetrically cantilevered out 25'
on each side of the building.  I maintain that because the seismic
loading and the ("H shaped") geometry are symmetrical, there is no
rotation that would distribute forces to the transverse shearwalls.

The municipal plan checker, who is a licensed engineer, has stated that
the shear walls must be designed for diaphragm rotation, with each of
the living units (bounded by it's three shear walls) acting as a "three
sided box".  The plan checker's written comment on this issue is as

           "Engineers assertion that the diaphragm will not rotate
because the center of mass is at the
           geometric center is not correct.  Flexible diaphragms
distribute forces to shear walls based on location and
           not the rigidity of the elements.  Only rigid diaphragms act
in that way.  Also, the shear walls break the
           diaphragms into smaller pieces, and these pieces are not H
shaped as assumed.  Each small diaphragm
           acts in rotation, although the forces on the center elements
may be canceling each other out- that is
           subject to analysis.   Please check all three-sided elements,
and provide design for the diaphragm, the chord forces, the nail
           slip, and the added shear and overturning of the back walls
as a result of rotation forces.  Show all
           elements on the plans."

If this was a simple "three sided box" structure, I would certainly
agree with the plan checker about designing for rotation.  However, I do
not believe the condition is comparable.  I have been unable to locate
any literature that addresses the design of a symmetrically cantilevered
flexible diaphragm, although I know it is not that unusual in apartment
buildings.  Any opinions or information, pro or con, would be greatly

Monty Hart
Associated Design Consultants, Inc.
Anchorage, Alaska