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RE: wind lines and jurisdictions

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Comparing the seismic and wind maps is like comparing
apples and oranges.

The seismic maps use lines representing constant
values of acceleration.  The wind maps use areas or
regions of constant values of wind speed, not lines.  

The seismic acceleration won't change much if you're a
hair on one side or the other of an isoline.  The
design wind pressure changes by a factor of 20 percent
or so on one side or the other of the dividing line
between regions.

d a v e e v a n s

> My thought was directed at the structural engineer
trying to be too
> precise
> in picking a wind zone to determine application of
environmental loads.

Well, are we being "too precise" in picking seismic
factors, then?

It's the same methodology: You have a map over which
is superimposed a set
of contours. You can sort of "pick out" on the map the
location of
interest, and interpolate the wind speed there from
the contours.

It's quite simple, really.

In the end, just like the seismic factors, it comes
down to probabilities.

I find it interesting that we just had a discussion
about coming up with
seismic factors using latitude and longitude, when the
profiles are about the same as for wind load.

If anything, I wonder why we're "straining at gnats"
trying to figure out
lines of demarcation. Pull out the map, look where you
are, pull off the
wind speed.

Very, very simple.

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