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Re: ASCE 7-05

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Freeman Tang wrote:
I have a question regarding the standard practice especially in
California of considering the uplift and horizontal loads simultaneously
for wood-framed construction. First of all in the previous UBC codes
(say from UBC 1982 to UBC 1977/CBC 2001) considering the uplift and
horizontal wind loads acting simultaneously on a building was not
explicitly addressed and not mandatory required. Even though text books
and references have been indicating that these loads are acting
simultaneously but it seems to me that in our practice we just consider
them separately.  We use the horizontal wind load to design our lateral
force resisting systems and the uplift wind load is basically a
detailing issue by anchoring roof framing to the top level of the
building.  We never have any uplift problems for the buildings that we
designed and also we never have any questions from any building
departments.  In the ASCE 7-05 both the Simplified Method and Analytical
Method require, explicitly with diaphragms, that these two loads are to
be considered simultaneously.  Will there still be a difference between
standard practice and code requirements for wood-framed construction?
Anyone can give me some insight and comments on this issue?

It seems that current practice is to uncouple the vertical and horizontal forces. Years ago it was explained to me that the load combination 0.6DL+/- Wind took into account the uplift forces acting concurrently with the horizontal forces by using 60% of the dead load. Yet using ASCE 7 of any vintage, the uplift suction should zero out the dead load.

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