[TowerTalk] Recommendations for structural, civil, or architectural firms with roof tower experience?

[kr7x at comcast.net]

Chris:

First off do you need a building permit? If so, and it appears that you are in Michigan, you will need a licensed PE (in Michigan)  to design and/or review any design you submit.

10 kips of load from 40 mph with 1" radial ice is a bit much. Off hand I would think the load would be in the 3 to 5 kip range or less. The max load would be for full wind velocity at 30 degrees off a guy direction in plan. The max force in a guy would occur at 60 degrees.

As far as the W16x26's go they are fairly light and not knowing the span I couldn't say what their capacity would be for additional load. A concept could be to connect several together with a tie beams at 90 degrees to their span, either at their under side or on top of the roof deck, to get several working for you at once not just a single beam. In addition the position of the tower base relative to the ends of the beams is critical, most likely in this case this occurs at mid-span (worst place).

I see from your E-mail that you are at U of Michigan. Are there any engineering professors that could take on this problem?

Maybe we could discuss this more off the reflector, if you wish, to reduce QRM.

Regards
Lonberg Design Group, Ltd.

H.S. Lonberg, P.E.,S.E. / KR7X
President

-------------- Original message -------------- 
From: "Christopher J Galbraith" <cgalbrai at umich.edu> 

> Hi Gang, 
> 
> We are looking for a civil/structural engineering firm that has expertise in 
> roof-top tower installations. Does anyone have any recommendations, or 
> suggestions where to look (maybe an industry organization in broadcasting or 
> commercial wireless?) 
> 
> We are currently working with two engineering firms that are giving us 
> widely varying opinions on our proposed roof-top installations. In 
> particular, one is telling us that a 40 ft guyed tower (base at 60 ft) will 
> generate 10+ kips of axial load (40 MPH, 1 in radial ice) and that our 
> W16x26 I-beam based roof structure will only support 2 kips of axial load. 
> These firms admittedly do not have any experience with our particular type 
> of installation. Also, we have received many skeptical comments about these 
> results, so we are seeking a second opinion. 
> 
> Thanks for any pointers. 
> 
> 73, Chris KA8WFC 
> 
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