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Dual System

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I am designing a one story church structure with an upper mezzanine area.  I
would like to use a dual system for the lateral load.  The building will be
wood framed.  The mezzanine requires some steel framing to support the floor
and roof area.  Below is a sketch of the building cross section.  Use a mono
spaced font like courier to see it.

           /    \
         /        \
        |          |
        |          |
       /|          |\
     /  |          |  \
   /    |----------|    \
 /------|          |------\ 
|                          |
|                          |
|                          |

for longitudinal lateral forces (perpendicular to the section shown) I was
thinking of using a dual system of steel moment frames in the center core and
plywood shear walls on the outer walls.  97 UBC Section 1629.6.5 states

1.A dual system an essentially complete space frame that provides support for
gravity loads.....
2. Resistance to lateral load is provided by shear walls or braced frame and
moment resisting frames.....
3. The two systems shall be designed to resist.....

97 UBC Section 1627 definition of space frame is "a three dimensional
structural system, without bearing walls, composed of members....."

My question has to do with item #1.  It requires a space frame to support
gravity loads.  Does this mean I can not use the exterior stud walls, which
will be the shear walls, as bearing walls?  What is the reason for this?

Thanks for your help.

Rich Lewis


Richard Lewis, P.E.
Missionary TECH Team

The service mission like-minded Christian organizations
may turn to for technical assistance and know-how.