I wonder if a large X made out of proper sized steel beams with screw anchors
at the ends could be an alternative to a concrete plate/base. The anchor I have
for my guy wires are rated 14,400# in dry sand. A beam, 10' long would give you
a torque of 144,000 foot-pound. How much do you need and can that be approved
by a PE?.
As I don't know the prices for concrete or steel beams I don't know what comes
out ahead but I have been wondering for some time if it is a feasible
alternative. The installation would be rather easy. No digging, no concrete
truck.
Any thoughts?
Hans - N2JFS
-----Original Message-----
From: Gene Smar <ersmar@verizon.net>
To: lists <lists@subich.com>; towertalk <towertalk@contesting.com>
Sent: Tue, Aug 26, 2014 11:09 am
Subject: Re: [TowerTalk] Pier-pad foundation, under a house?
Bryan:
I concur with Joe. Move the pier-and-pad (P-A-P) away from the house.
The
way this design works is the vertical pier transfers the overturning forces
from
the tower/wind to the pad. The pad then pushes up against the dirt above it
and
at an angle away from it. If you were to dig underneath your house's
foundation
to install the P-A-P, these wind forces would be applied to the footer and
walls
of the foundation. I'm positive these house systems weren't designed for that
kind of stress.
A civil engineer friend of mine once suggested to me that my tower's
similar P-A-P ought to be constructed away from my home's footer foundation by
a
distance equal to the depth of the bottom of the hole. In my case the hole was
5 feet deep so that meant I needed to place the tower foundation hole at least
5
feet away from my home. As it turned out, I built the tower much farther away
than that.
One more thing: If you do go the P-A-P route, make sure you compact the
dirt when you backfill the excavation. Rent a powered tamper and use it on
every foot of backfill depth around the P-A-P as you are backfilling the dirt.
The denser the backfill, the more weight there will be to resist overturning
from the wind. If the P-A-P were to be made heavy enough, you could just pour
it on top of level ground. But its been engineered to use the weight of
(cheap)
dirt instead of (less cheap) concrete to resist the wind forces.
Good luck with the project.
73 de
Gene Smar AD3F
On 08/26/14, Joe Subich, W4TV
wrote:
Don't even think of undermining the house. If you need to stick with
the 15' pad.move the appropriate distance away from your foundation.
The typical Florida home is slab on grade. Your area has enough issues
with sink holes, etc. I would not risk creating one artificially.
73,
... Joe, W4TV
On 2014-08-26 8:48 AM, Brian Amos wrote:
> You are going to need to get a structural engineer and a geotechnical
> engineer involved. Its very possible to do this, it won't be cheap, but
> done incorrectly you could cause some severe damage to your home. You will
> want to find good local engineers who work for smaller companies, a large
> company probably won't even take on a small job such as this. It also might
> be possible that they can redesign your foundation so you don't have to
> mess with the pad. Its very likely that they will save you money in the
> long run.
>
> Brian
> KF7OVD
> On Aug 25, 2014 8:49 PM, "Bryan Fields" Bryan@bryanfields.net> wrote:
>
>> I'm considering building a AN wireless tower at my property in St Pete
>> Beach,
>> and it must be rated for 120 MPH wind which means it's large foundation.
>> Good
>> news is the city says I'm good up to a 70' tower without a zoning
>> variance. I
>> only need stamped drawings for it.
>>
>> II want to keep it centered on my lot behind my house which is an L shape.
>> Looking at the foundation "K" which is required, I need a 7' pier and a 15'
>> pad under it. I'd like to have the 7' pier flush in the corner of the L
>> of my
>> house with the pad extending under the house.
>>
>> Has anyone ever done something like this before? I'm assuming I'll need to
>> support the foundation of the house with some steel beams and then dig out
>> under it.
>>
>> Thoughts?
>>
>> --
>> Bryan Fields
>>
>> 727-409-1194 - Voice
>> 727-214-2508 - Fax
>> http://bryanfields.net
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|