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James Lane wrote:

Have an existing 20'x20'x16'height box with the top open. The box sets on
the top of a roof.

Question: Does the second (leeward wall) pick up full wind pressure as the
first wall? Any good references for how much the second wall will pick up.

In the past I have always been conservative and used full pressures on both.
What if the bax were smaller the first wall would shield the second wall and
you would think pressures would be less.

Any comments

***********************

Sounds like you have a partially enclosed structure.  The near wall must be
designed for both internal pressures pulling in and windward pressures pushing
in.  The far wall must be designed for both internal pressures pushing out and
leeward pressures pulling out.  In both cases, the effects are additive.  Of
course, for the structure as a whole, the interior pressures are equal and
opposite.  Depending on which code you are designing for, see either 1997 UBC
Table 16-H, Item 2, Wall elements or ASCE 7-95, Tables 6-1 and 6-4.4

Rick Drake, SE
Fluor Daniel, Aliso Viejo, CA


                                                                
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