FWIW, and depending on what part of the country you live, you may not want to
pour directly into a "dirt" hole. We can get frost down to 24" or so here in
the Southern Tier of NY during a rough winter so I made a 4-sided tapered form
of plywood with the bottom on solid ground/gravel well below frost line and
poured concrete into that.Yes, it is necessary to provide support ribs for the
form as well as buck the whole thing against the dug hole sides. This yields a
tapered base sometimes called a "floating foot" The vector forces from freezing
are translated upwards (assuming uniform freesing). Mine (two 3.5 and one 4.5
cubic yards of concrete) have never moved/heaved in over 20 years.
73, Tom - WA2BPE
Chuck Lewis wrote:
> Hygain tower bases use welded rebar. The 1/4" thick steel tabs thru which
> the tower mounting bolts connect to the matching tabs on the tower are
> thoroughly welded to three rebar legs tied together with smaller rebar
> crossties and diagonals using tack welds. The result is an integrated
> cage/anchor system. The whole thing is suspended from the concrete form
> boards and plumbed vertical before the mix is poured. The stress analysis
> package includes drawings with proper weld callouts showing the rebar welded
> to the 1/4" plates. Makes a pretty heavy assembly; but welded it is!
>
> Chuck, N4NM
>
> From: <K7LXC@aol.com>
> To: <kbgreen@worldnet.att.net>; <barryb@i1.net>; <towertalk@contesting.com>
> Sent: Sunday, January 27, 2002 11:57 AM
> Subject: Re: [TowerTalk] Foundation too close to Tower??
>
> >
> > In a message dated 1/27/02 6:53:22 AM Pacific Standard Time,
> > kbgreen@worldnet.att.net writes:
> >
> > > Re: welding of rebar.
> > > There are two types of rebar one is suitable for welding the other is
> not.
> > > Do not have I think they are called ATSM specifications for each, any
> rebar
> > > supplier will advise on proper type to weld.
> >
> > Well, the bottom line is what does it say in your tower base specs? I
> > don't think that UST base specs or building department codes allow for
> > welding the rebar. Even those huge rebar structures used for building and
> > highway bridge footings are tied and not welded.
> >
> > While the rebar cage isn't typically structural (it's to keep the
> > concrete from shrinking and cracking), you still need to observe the LXC
> > Prime Directive to "DO what the manufacturer says".
> >
> > I've built dozens of rebar cages using tie wire and while it might be
> a
> > little slower, it works just fine. You just have to add some diagonal
> pieces
> > on the sides to give it some rigidity.
> >
> > Here's what you want to do. First, get the backhoe in to dig the hole.
> > Either have the rebar cage done or at least finished when the hole is
> done.
> > Have the backhoe pick up the cage and drop it into the hole. Then you can
> tie
> > the anchor bolt 'fixture' to the rebar cage and if none of the rebar is
> > touching the earth and any additional forms are done, then you're
> basically
> > ready to pour.
> >
> > Cheers,
> > Steve K7LXC
> > Tower Tech
> >
> > ________________________________________________________________________
> > Where do you get ICE bandpass filters & beverage matching boxes? The
> > same place that pays for the hosting of this list: The eHam Store.
> > Order online at http://store.eham.net.
> > -----------------------------------------------------------------------
> >
> > -----
> > FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> > Submissions: towertalk@contesting.com
> > Administrative requests: towertalk-REQUEST@contesting.com
> > Problems: owner-towertalk@contesting.com
> >
> >
> >
>
> ________________________________________________________________________
> Where do you get ICE bandpass filters & beverage matching boxes? The
> same place that pays for the hosting of this list: The eHam Store.
> Order online at http://store.eham.net.
> -----------------------------------------------------------------------
>
> -----
> FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> Submissions: towertalk@contesting.com
> Administrative requests: towertalk-REQUEST@contesting.com
> Problems: owner-towertalk@contesting.com
________________________________________________________________________
Where do you get ICE bandpass filters & beverage matching boxes? The
same place that pays for the hosting of this list: The eHam Store.
Order online at http://store.eham.net.
-----------------------------------------------------------------------
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|