Radial cracks from 10 ft dia storage tamls in containment

[baw1]

I am evaluating a storage tank concrete foundation and cannot determine a plausible cause for the cracking pattern. I was wondering if anyone had seen a simular pattern?
I evaluated the foundation using a fea analysis and found it adequate as long as the subgrade modulus is about 90 lb/ft^3.
Facts
Bearing cap per 1994 report 2000 psf
10 ft dia tanks 15 ft appart 10,000 gal cap ea
12 in slab no 4 at 12 in top n bot
Radial crack pattern 10 ea tank even aroun perimeter
2 ft high containment wall 1 ft thick. No cracks in wall except for two.
40 ft by 36ft. Tanks ae 15 ft fr9m one side.

 

[BAretired]

#4 @ 12 is pretty light reinforcement for a 12" thick slab. Maybe the cracks you are seeing are shrinkage cracks.

Are the tank walls steel or concrete? How much gravity load is transferred from wall to slab?

BA

 

[paddingtongreen]

Is the tank significantly warmer than the low ambient temperature?

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin