[TowerTalk] Substitute thicker Phillystran?

[Michael Rauh]

Hello All,

My tower plans call for 11,200 lb Phillystran for the top guys.  I've been 
offered 27,000 lb Philly.  Questions:

1. Do I need to pretension the 27,000 lb breaking strength Phillystran to 
2,700 lbs (10%)?

2. This will add 3X 0.707 X 1600 = 3400 lbs of base reaction to my system, 
right?  (Top guy is at 45 degrees).

3. The tower is 120 feet of Rohn 55G.  There are tree tiers of guys. I 
calculate the base reaction to be about 7500 lbs.  So if I increase to 
10,900 lbs what happens?  The 55G is undoubtedly good for the extra load at 
the base, but do I need to beef up the lower guys to hold the tower in 
column with the extra load? Or to put it another way, how does one decide 
how many tiers of guy are needed and what the loads on the lower guys will 
be?

Can anyone out there help me understand how this works?

Mike Rauh, NV7X
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