[Towertalk] Windload "partway up"

[Joe Subich, K4IK]

> 
> > If I place 4 square feet at the mid point of the tower do I 
> > need to change what the top of the tower could hold?
> 
> I have been dying to ask Steve this same question, since I think 
> he said in Dayton that "you just add it all up."  My basic 
> understanding makes me think that 10 square feet halfway up a 
> 100' tower is not the same as the same load at the top of the tower.

The handling of side mounted loads depends on the nature of the 
TOWER SYSTEM.  

If one is dealing with a free standing tower, the failure modes are 
either due to side loads (wind) or crushing (total weight).  For 
wind, one could easily use a sum of surface area times height (i.e. 
twice as much surface at half the height) for an estimate.  If a 
tower is maxed out at the top it is maxed out completely. 

For guyed towers, there are other failure modes (e.g., guy failure) 
and one needs to analyze possible failure modes.  For a better 
understanding of some of these issues see K7NV's informative site 
at: http://yagistress.freeyellow.com/  (look at the "guyed tower 
study" link).

73, 

   ... Joe, K4IK