The link you quote does a good job of explaining the situation but it
only briefly mentions an additional factor other than the weight of the
concrete itself, which is the dynamic lateral force caused by the
concrete falling from some height above the pour. That can be
considerable, and in my case caused a couple of blowouts while the
concrete was being poured in the ICF forms of my house. If you consider
the volume in the column of concrete in a typical pour falling from a
height of whatever, and then slamming into the still fluid concrete that
had already been poured, the net impact can be significant. I'm sure
there are ways of calculating that effect, but it's pretty complicated
since it depends upon the uncertain volume of the column and the
viscosity of the already poured material. As you say, the best strategy
is to overbuild.
I'd also like to point out a lesser potential issue, which is the fact
that the wood used in most concrete forms can soften when wet. Walls
that are rigid when dry bow outward if not braced really well, and
joints can separate as nails or screws pull out of the soft wood ... the
latter situation being why it is a good idea to try to put fasteners in
shear (versus tension) whenever possible.
Just some thoughts ...
73,
Dave AB7E
On 10/13/2018 5:49 AM, Mickey Baker wrote:
I studied this 30+ years ago... when I was an engineering co-op tasked with
building a rail loading platform (but EE, so I needed to figure it out.)
The strategy to build a form is to basically overbuild.
Pressure is dynamic, so you solve for peak for most pours, which occurs
just before the first bit of a pour sets. Here's a site I found that
explains the general calculations and the process. I'm interested why you
ask...
https://theconstructor.org/building/concrete-formwork-loads-pressure-calculations/14521/
Mickey Baker, N4MB
Palm Beach Gardens
*“Tell me, and I will listen. Show me, and I will understand. Involve me,
and I will learn.” *Teton Lakota, American Indian Saying.
On Sat, Oct 13, 2018 at 7:30 AM Larry Horlick <llhorlick@gmail.com> wrote:
Can anyone tell me the fluid pressure at the bottom of a concrete pour,
form size 8’ x 8’ x 6’?
Larry
VO1FOG
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