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Re: OT - broncos rule - really a wind load question

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Okay, I'll bite, if for no other reason than to
prevent a fourth posting of this question.

Sounds like you are on to the same subject we
discussed a few weeks ago about l/720 and l/600
deflection for brick veneer backup walls.  I don't
know the answer, but perhaps the 0.7 is the same as
the reduction from a 50-year to a 10-year wind, as was

The few times that I have compared ASCE to IBC wind
loads, I have come up with the same numbers.  IBC just
incorporates some of the ASCE factors for you when
preparing the tables.  Double check all of the factors
such as category and exposure and they should be the
same, shouldn't they?

And perhaps ASCE felt it was beyond their jurisdiction
to prescribe a 30% reduction for lateral deflection
due to C&C loads.

I have no thought at the moment about comparing the
0.7 to the 0.85 provided in ASCE.  I'm still not awake
enough to pull it off the shelf, but I don't believe
they should be used in the context that you have
proposed.  Is there an IBC commentary on the notes to
Table 1604.3?

Sorry, that's the closest thing to an answer that I
can come up.


--- David Adie <DavidA(--nospam--at)> wrote:

> i hated to do that but you made me.
> does anyone have input on this?
> footnote f for ibc 2003 table 1604.3 allows reducing
> the wind by 30% when
> considering deflections.  it seems implied that in
> order to use this
> reduction, one needs to be using the design
> procedure presented in the ibc
> (the simplified one).  *** i know the ibc references
> asce ***
> is it wrong to use this reduction in combination
> with the detailed procedure
> presented in asce 7-02?  it seems like it would be
> since i think the
> simplified procedures gives higher values than the
> detailed procedure.
> maybe the footnote should say "0.7 * W when using
> the simplified procedure
> and 0.85 * W when using the detailed procedure".
> tia
> da

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