Richard Thorne - WB5M wrote:
>
> Are there any engineers out there?
>
> Heres what I plan to do:
>
> - Mount my 60' rohn 25g on top of my 15' high office building
> - The roof top is concrete with asphalt. I'm assuming its 4" thick.
> - The base plate and guy points all fall on 2' square concrete pillars
> that support the roof. The guy points are going to be located to meet
> rohn specs as far as distance from the tower and 120d spacing.
>
> Now for my question to the engineers listening.
>
> My guy plates will be 4" to 6" square and will be mounted to the concrete
> with expansion bolts. The specs on the bolts say a 3/8" diameter bolt
> embedded in 4000 psi concrete and 1 1/2" has a pullout of 3219lbs. If
> I use 4 of these per plate thats a total of +-12,800 lbs. If that
> calculation is correct my 2 sets of guys will fail first since they
> are rated at 4000lbs each or a total of 8000lbs.
>
> Now thats my approach to it. Am I missing something here or am I on
> the right track? By the way the name brand of the bolts are Hilti. I
> know that they also offer an epoxy method but really don't want
> to mess with them.
>
> I'm going to use the same method on my 2' square baseplate. The shear
> rating on the above bolt is 4000 lbs and using 4 of them is a total of
> 16000lbs. So I don't think I'll have a problem here.
>
> Any advice will be greatly appreciated.
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