Tomoko Schum
New member
Here's another response from beaslbob:
Here is my extremely not to be trusted just in the ball park analysis of 8 balls' bolts.
assumptions all weight will be on 5 7/8" diameter steel bolts.
Totall force is 3500 pounds.
Further beaslbob assumption. that would be 2 rows one with 3 bolts one with two.
Further even more ridiculous assumption. each of the bolts in each row equally take that row's force.
therefore the row with 2 bolts has 3500/2=1750 pounds and the row with 2 bolts had 1750/2=850 pounds
no one ever ever bumps against the tank and stand.
Steel has various ultimate strength and bolts can be heat treated up to 170,000+ pounds per square inch.
But on reviewing the various steels I found that the compressive yield strength and shear stress remains at around 35,000 pounds per square inch. So I use that just to be save. Besides these bolts are in compression not tension.
Each bolt has 3.141596*7/8*7/8/4=.601 square inches area.
With 850 pounds per bolt we have 850/.601=1455 pounds per square inch for each bolt.
Each bolt can take 35,000 psi so each bolt is over 23 times stronger then the load.
Obviously that is no problem. Even if all the load was on one bold, the bolt would not yield ("take a set").
If the stand was "threaded" the threads would be about 7/8" in diameter for a circumference 2.75 inches through the 1/8 stand thickness. Additionally assume extremely loose fitting threads where only 1/3 of the thread are actually in contact. So instead of the 1/8" you only have .0414" in the bolt and stand leg transferring the load. 2.75*.0417 is the shear area which is .1145 square inches to shear out the 850 pound force for a stress of 7640 psi. with an allowable of 35,000 psi the stand thread hole is 3.58 times times as strong as needed.
that 3.58 makes me a little nervous for something that will remain standing for very long periods of time. Additionally this analysis assumes there is no side force on the bolts and that really makes me nervous. Welding a nut would reduce the thread stress but then the welds would have to by analyzed. but hopefully the over all effect is a much stronger structure.
I think you are correct to use shims and nuts to prevent side forces and to have more area to transfer the loads from the bolts to the stand.
also I am not a concrete person but a 1' circle on the concrete has .7854 square inches for 1114 psi. If concrete does have 3500 psi strength that means to the concrete is around 3 time stronger then it has to be. But that makes me nervous because of the long term time frame. So perhaps you could use something to spread out the are a little most or the concrete may develops a set.
whatever you do I presume you are going to make adjustments so that the bolds are a "short" as possible and before the water is added. Adjusting with the full weight would not be a good idea if you could avoid it.
but I'm just rambling right along.
All of which is worth at most .02
Bob
Here is my extremely not to be trusted just in the ball park analysis of 8 balls' bolts.
assumptions all weight will be on 5 7/8" diameter steel bolts.
Totall force is 3500 pounds.
Further beaslbob assumption. that would be 2 rows one with 3 bolts one with two.
Further even more ridiculous assumption. each of the bolts in each row equally take that row's force.
therefore the row with 2 bolts has 3500/2=1750 pounds and the row with 2 bolts had 1750/2=850 pounds
no one ever ever bumps against the tank and stand.
Steel has various ultimate strength and bolts can be heat treated up to 170,000+ pounds per square inch.
But on reviewing the various steels I found that the compressive yield strength and shear stress remains at around 35,000 pounds per square inch. So I use that just to be save. Besides these bolts are in compression not tension.
Each bolt has 3.141596*7/8*7/8/4=.601 square inches area.
With 850 pounds per bolt we have 850/.601=1455 pounds per square inch for each bolt.
Each bolt can take 35,000 psi so each bolt is over 23 times stronger then the load.
Obviously that is no problem. Even if all the load was on one bold, the bolt would not yield ("take a set").
If the stand was "threaded" the threads would be about 7/8" in diameter for a circumference 2.75 inches through the 1/8 stand thickness. Additionally assume extremely loose fitting threads where only 1/3 of the thread are actually in contact. So instead of the 1/8" you only have .0414" in the bolt and stand leg transferring the load. 2.75*.0417 is the shear area which is .1145 square inches to shear out the 850 pound force for a stress of 7640 psi. with an allowable of 35,000 psi the stand thread hole is 3.58 times times as strong as needed.
that 3.58 makes me a little nervous for something that will remain standing for very long periods of time. Additionally this analysis assumes there is no side force on the bolts and that really makes me nervous. Welding a nut would reduce the thread stress but then the welds would have to by analyzed. but hopefully the over all effect is a much stronger structure.
I think you are correct to use shims and nuts to prevent side forces and to have more area to transfer the loads from the bolts to the stand.
also I am not a concrete person but a 1' circle on the concrete has .7854 square inches for 1114 psi. If concrete does have 3500 psi strength that means to the concrete is around 3 time stronger then it has to be. But that makes me nervous because of the long term time frame. So perhaps you could use something to spread out the are a little most or the concrete may develops a set.
whatever you do I presume you are going to make adjustments so that the bolds are a "short" as possible and before the water is added. Adjusting with the full weight would not be a good idea if you could avoid it.
but I'm just rambling right along.
All of which is worth at most .02
Bob
You know we can't hold our breath so long.
