ringwall footing
ringwall footing
(OP)
I am designing a ring wall foundation for a tank which is 32 ft tall and 22 ft dia. I have designed the ring wall itself and now working on the footing part of the ring wall. I am planning to use a 4 ft wide footing. Since this footing will have both axial load and lateral moment due ti wind i will have to determine whether the resultant of the forces will fall within the kern limit. how do i find the kern limit for a circular footing whose Outer Diameter is 25' and Inner diameter is 21'.
Thank you
Thank you






RE: ringwall footing
It appears that if the footing is assumed to be rigid (a pretty big assumption), then the centroid of applied loading needs to be at a distance of 5.3 ft from the center of the circle before a the footing will experience partial uplift. Interesting little exercise. :)
RE: ringwall footing
You do not want to have different pressures, and thus different settlements between the interior part of the tank floor and the ring wall area around the perimeter as this creates stress and possible damage to the tank floor plating.
RE: ringwall footing
S = pi(d^4 - di^4)/32d
Solve for P/A - Pe/S = 0
and find e = (d^4 - di^4)/(8d*(d^2 - di^2))
d = 25; di = 21; e = 5.33
BA
RE: ringwall footing
Trying to balance the bearing under the tank and under the ringwall will generally lead to an excessively wide ringwall, rather than the other way around. Even if you do balance the two, it's only balanced at one specific depth of product, and unbalanced at any other depth.
RE: ringwall footing
http://www.eng-tips.com/viewthread.cfm?qid=219486
h
h
http://www.eng-tips.com/viewthread.cfm?qid=87532
BA
RE: ringwall footing
RE: ringwall footing
PIP has a good design guide for this, tank foundations.
I would think that with a 4 ft wide RW, you might get significant differential settlements at the interior of the RW and damage the tank floor.