[TowerTalk] Tower on top of a building?

[Jim Lux]

At 02:32 PM 3/3/2006, tom scott wrote:
>I am working with a small school that has won an FCC LPFM100 (low power 
>FM, 100 watt) broadcasting license (actually the FCC construction permit). 
>The FCC has approved us going up 36 meters above HAAT. The antenna load in 
>this case is a simple circularly polarized VHF (96.3 MHz) that is very 
>little wind load or weight.
>
>For a variety of reasons, I was thinking I would like to put a tower on 
>top of the athletic building.
>
>Our gymnasium building was originally a commercial industrial concrete 
>tilt-up structure with some stick-built office facade on the front. I was 
>thinking we might put a tower on top of the middle of the front wall of 
>the tilt-up, between the tilt-up and the stick built offices, almost in 
>the middle of the building, and then run two guys to the back corners of 
>the tilt-up, and one across the parking area to the planter strip next to 
>the road in front.



>I haven't yet tried to get this engineered, but wondered if anyone has any 
>experience doing this sort of thing. I have questions about guy anchors to 
>the concrete building, and building codes. Should I find an engineer with 
>real tower experience, or can any good structural engineer do the job?

Any licensed engineer is capable of doing the job.  An engineer used to 
towers or things like theatrical lighting trusses might be faster at it, 
and therefore cheaper.  There are almost certainly peculiarities like the 
compression loads the tilt up wall can be expected to take and the design 
of the anchors that will be unique.


>I guess I just want to have an idea what we should be able to do before we 
>spend money on an engineer.
>
>The building is around thirty or forty feet tall, so the tower would only 
>have to go up another sixty or seventy feet more.

What about a 100ft tower anchored to the side of the building, and 
unguyed?  You've got that 30 ft slab of concrete to anchor to, after all.



>Thanks!
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