Wind Load Calc 4 Wood Power Poles

[2banee]

I have a table that our power co uses for wind load calcs for wood poles of different types and classes. I'm wondering if anyone can tell me how these were calculated. Per the CPUC GO 95 (State of CA) we are required to use a safety factor of 4 for class "A", SF of 3 for class "B", and SF of 2 for class "C" construction. Using these values I should be able to work backwards to find the ultimate value of the modulus of rupture for each type and height of pole, but it doesn't work out. Can anyone please enlighten me as to the proper calculation process?

 

[jghrist]

See Rural Utility Service (RUS) Mechanical Design Manual for Overhead Distribution Lines at

http://www.usda.gov/rus/regs/bulls/160-2.pdf