120 foot tank leaning 8 feet
120 foot tank leaning 8 feet
(OP)
I'm designing a new 120 foot diameter by 60 foot high storage tank, one criteria is that it be OK if the foundation settles eight feet on one side. For this analysis, the foundation is assumed to be rigid. While 8 feet sounds like a lot (and it is!), it's only about 4 degrees over 120 feet. I'm looking for suggestions on what to zoom in on for this analysis - what portions of the tank will experience higher stresses, etc. Thanks





RE: 120 foot tank leaning 8 feet
You can calculate a net shear force parallel to the foundation and a net overturning moment on the tank and on the foundation due to the uneven loading, and the results of those will be similar to seismic loading, only as sustained loads.
Once you have that uneven loading, that may promote even more settlement.
A fixed roof might not drain right.
Manways on the down side would be inaccessible.
The tank could float when empty due to rainwater ponding around the down side.
Water ponding around the low part will lead to repad corrosion.
Leak detection tubes may be inaccessible.
Stairs or ladders could be out of plumb, or leaning backwards/outwards in hazardous ways.
Roof columns would have gravity lateral loads, I assume a minor issue, though.
You normally derive hoop tension assuming an axisymmetric loading. I don't know what happens with asymmetric loading. Could you get big buckles in the shell? You'll at least have some big shear loads that are not normally generated.
Bottom may no longer drain to the sump, and could trap several feet of product when the tank is "emptied".
A floating roof will float level, but the hole it's in will now be elliptical.
Capacity is reduced. Gauging tables are useless.
Instrumentation on the uphill side won't show depth on the downhill side and could lead to overfills.
RE: 120 foot tank leaning 8 feet
RE: 120 foot tank leaning 8 feet
Once the tank starts to bend away from a perfect circle, the forces will increase as the tank bends, meaning more bending which means more force....
That a big tank with up to 18000m3 of liquid in it. That's a lot of force even at a small angle.
How you calculate it I don't know and maybe what all it would need to "survive" is a more strengthening rings / girders than you would normally fit to keep the round tank perfectrly round.
that's not to say that the issue over foundation anchors and the tank sliding sideways needs to be ignored or the moment forces on the foundation, but again maybe just a lot more bolts and strengthening of the wall / floor plate will mean that the tank "survives"
All in all I would suggest you either remove the liquefaction potential material or pile down to something solid.
Prevention is much better than "cure"
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
RE: 120 foot tank leaning 8 feet