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IBC & ASCE 7-98 Wind

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I'm working on a single family residence (tract home, multiple use).  The
original design was for UBC 97, 110 mph wind Exposure B, Seismic Zone 3.
I'm revising the plans for the IBC.  I called the building official, and
wind speed is still 110 mph.  (I know, 3 sec gust vs fastest mile, but he's
the building official.)

I'm using ASCE 7-98 for wind.  One thing that really puzzles me is that for
a 5:12 pitch roof, the forces on the windward side pretty much offset the
forces on the leeward side.  This results in the roof area not affecting the
wind force very much.  Is this correct?

I'm calculating wind forces that are 45% of the 1997 UBC forces.  Combine
this with the 40% increase in allowable wood shear wall stresses in the IBC,
and I'm really getting nervous.

I would expect some decrease in force due to the 3 sec gust vs fastest mile,
but cutting the force in half and increasing the allowable stresses 40%
seems like a bit much.  Is anybody else getting results like these, or
should I start looking for something that I've fouled up?

Conrad Guymon, P.E.




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