[Greenbuilding] Fence posts--gravel or concrete

Lawrence Lile LLile at projsolco.com
Thu May 12 13:11:06 PDT 2011


Hmmm.   We were involved in testing some trailer anchors that looked a lot like these.  The trailer anchors had two 48" steel pins that were driven through a steel clip that was supposed to hold everything together.  Although they weren't meant to be foundations, just anchors, the experience may be relevant. 

When we pull tested them, they were not able to hold more than a few hundred pounds of uplift force, let alone the 4000 lbs that was specified by the trailer regulations.  It is hard to tell from the little video how long these pins are, but if they are just 48" or so, then they'll pull out of the ground quite easily under heavy uplift forces like high winds.   Also, typically these anchor components (in the trailer industry anyway) are made with the poorest quality steel, and despite being 1/2" thick would bend readily under quite small forces.  I do believe I could probably bend one over my knee if I really tried hard. 

Even when drilled into solid rock (limestone, which is not too strong) this type of anchor was unable to withstand a 4000 lb uplift force, bending and then failing.  The rock would chip away, then the anchor would bend, and then the whole thing falls apart.  

I'm pretty suspicious.  


--Lawrence Lile, 


> -----Original Message-----
> From: greenbuilding-bounces at lists.bioenergylists.org [mailto:greenbuilding-
> bounces at lists.bioenergylists.org] On Behalf Of JOHN SALMEN
> Sent: Tuesday, May 10, 2011 8:45 PM
> To: 'Green Building'; Greenbuilding at bioenergylists.org
> Subject: Re: [Greenbuilding] Fence posts--gravel or concrete
> 
> I hadn't thought of precasting but I like that they are using tubes (much
> more surface area). Would be hard to get the pad placement accurate I would
> think on hard soils as the pounding loves to shift things. Looks like a
> great product - ducks unlimited must love them for boardwalks.
> 
> The timber trellis structure at providence (including the rock bases) is
> supported on pounded tripods (disturbed clay base) and I expected some
> settlement over time but nothing over 6-7 years. I had hoped parks might get
> interested in the approach but they seem to like heli lifting concrete.
> 
> -----Original Message-----
> From: greenbuilding-bounces at lists.bioenergylists.org
> [mailto:greenbuilding-bounces at lists.bioenergylists.org] On Behalf Of Chris
> Koehn
> Sent: May-10-11 6:25 PM
> To: Greenbuilding at bioenergylists.org
> Subject: Re: [Greenbuilding] Fence posts--gravel or concrete
> 
> John's post reminded me of a company offering a pre-engineered post solution
> for decks and elevated walk-ways: <http://www.pinfoundations.com/>
> Anyone use these? Minimal site disturbance is a good thing..
> 
> Chris
> TimberGuides
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