[TowerTalk] Concrete base - tower

[Jim Thomson]

Date: Thu, 12 Oct 2017 14:29:59 -0230
From: Larry Horlick <llhorlick at gmail.com>
To: towertalk at contesting.com
Subject: [TowerTalk] Concrete base - tower

<I am preparing to install a 70' Trylon SuperTitan S500. Nothing is done at
<this stage...I'm thinking about pouring the base first. Hi.

<The manufacturer has supplied a drawing of the required concrete base. It
<is a pad and pier design. Doing a pad and pier is significantly more work
<(i.e. creating the form) than, say, just a rectangular block that I could
<simply pour in the hole with very little form work.

<My question is...Can do that? Can I change the pad/pier to a block, by
<altering the dimensions, amount of rebar, etc. to arrive at an "equivalent"
<to the pad/pier??

<I welcome any relevant comments/questions/suggestions.


<Larry
<VO1FOG

##  pad + pier is a pita.   The dirt you put back in there..around the pier, that
sits on the concrete base is...free weight.  You can easily dispense with the
form..but then  you will use a helluva lot more concrete..which is OK per Trylon.
But the re-bar setup is different. 

##  If ground is clay, or solid enough, so the sides of the hole   dont cave in, 
you dont require the megabuck, pita  wooden form.   Flip side is.... the wooden form
is very expensive to build.  It comes out a wash,  or close to it.    Cost of wooden form
vs cost of extra concrete. 

##  If a wooden form is used, it has to be carefully constructed.  Concrete weighs aprx
4000 lbs  per cubic yard....=  150 lbs per cubic foot.   There is a huge stress on the wooden form as is.
There is also a huge stress on the portion of the wooden form that encompasses the pad.  Thats from the
sheer vertical compression weight of the  concrete in the pier.   Get it wrong...and  form starts to come apart
when you have poured 80% of the concrete into the form.... u are in for a rude awakening. 

##  Even if it all goes ok, the  wooden form has to be removed.   Which means the hole has to be big enough
to work in.  IE  u gotta be able to get down into the hole and squeeze between the dirt side walls and the 
wooden form, to dismantle the wooden form.   Here in BC, if the hole is 6 ft deep, or deeper, the dirt sides have to be shored up,
which involves yet a ton more wood.    WCB here in BC  will severely fine any contractor violating shoring regs. 
Ok, now you toss the wood into the scrap heap, never to be used again. 
It would be a different story  IF you are a contractor, and are installing 4-10  identical towers,  and the expensive 
wooden form can be re-used. 

##  BTW,   AN wireless, who makes a similar product,  depicts BOTH methods on their website.   The owner tells me
nobody uses the wooden form and  pad and pier method.   Sure, you save some $$ on concrete, then you lose it all 
on the wooden form, and elaborate re-bar bending....  PLUS a ton more effort and time involved with  the form + pier + pad. 
Contact Trylons eng dept....  and they will provide you the... normal base diagram..which is not on their website.  Local tower
contractor has installed the newer  Trylon Super titans  for commercial use...and none of em used a pad + pier.  Besides the cost
of the form...+ shoring, there is a ton of expensive labour involved, both building the form + shoring, and removing it.  
A lot quicker to just dump more concrete  in.     BTW, dont use anything less than 30 MPA  concrete.    30 mpa is 50% stronger than
20 mpa, and you wont end  up with any hair line cracks....esp in winter, with sub freezing temps.   If I remember  correctly, the pad
+ pier method also involved installing styrofoam  sheeting on top of the exposed pad, after the form removed. 
That depended on how deep the frost line is.   It was typ 1-2 inches thick. More pita.  You dont require any of this with a giant
block of concrete.    I was going to install a 90 or 100 ft of super titan, with the 6 ft wide base...at my daughters place, since 
she was on 5 acres.   She ended up selling it...and moving to denman island...now on 11 acres.  I gave up on that project.  The logistics
of driving 150 miles each way, was too much. On the island, its then a 10 min ferry trip each way, on top of the drive.   And concrete
on that island shes now on is  stupid expensive.  

Later.... Jim   VE7RF