Peer-to-Peer Standards Exchange

I am trying to understand when to use note 4 factor. I recently went through an old forum that had a good example posted for RISA and explained it very well. They didn't, however touch on note 4.

Is there a diagram that illustrates this part of the note "when the wind is directed along a tower diagonal". I take this to mean coming at a corner. 

Second, In the examples below they don't use it even though it is a square cross-section example. Does applying the winds per Figure 27.4-8 exceed that factor and create the worse cases? 

Risa Example:Wind Loading on Non-Building Structures in RISA

Old Forum: Discussion: View Thread

Thank you,

Brian Frey, PE

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Brian Frey Aff.M.ASCE
Senior Structural Engineer
LJB Inc.
Houston TX
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I will not comment on the RISA example, but rather the intent of the footnote to the figure, which remains in ASCE 7-22.  

The maximum forces (base shear and overturning moment) on the overall structure and the maximum forces on individual components of the tower depend on the shape of the tower.  A general rule would be to check the tower separately for wind loads applied in three directions – loads applied across the flats of the tower and loads applied across the diagonal of the tower.  The diagonal for a square tower would be at an angle of 45 degrees.  If the tower is a triangle, rectangle, or a polygon, the force would be applied at a different angle than 45 degrees.

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Ronald Hamburger, SE
Consulting Principal
Simpson Gumpertz & Heger
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