Tensile strength of Poly reinforced Concrete Tanks

[fat_tony]

I posted this on another forum also Hopefully somebody can help because the so called experts around here are no help.
I am currently disabled (kids listen to your parents Crotch rockets are not safe!!) so I have been dreaming up a rediculous aggressive tank. I was actually inspired by "BlackTip's" 1700 gallon tank. I would like to create an 11'x6'x6'(outside dimensions) tank of concrete with two 4'x4' Polycarb viewing panels. Giving approximately 1875 gal of water. Is the pressure on the concrete similar to lateral earth pressure calculations used for retaining walls, or is there a formula that I can use to determine if 6" of concrete is thick enough for the walls? Assuming I use 1.5% poly mixed concrete with tensile strength of 500 PSI.
Thanks in advance for any help!
Matt

 

[dreeves]

Go to www.mr4000.com see what he has to say...and check his tank out.

 

[fat_tony]

That link doesn't seem to go anywhere. If you have any Idea what it changed to that would be great, because I am imagining a 4000 gal tank!! LOL I can't imagine the elecrtic bill to keep that tank warm in the winters up here in MI.
Thanks for the reply
Matt

 

[slofish]

Originally posted by Fat_Tony
I posted this on another forum also Hopefully somebody can help because the so called experts around here are no help.
Matt
First of all, dont rip on the people your asking for help from. Thats just not right. If you dont want our "so called expert help", dont ask for any help.
But anyhow, using some mechanics equations, the pressure at the very bottom of the tank is about 400 pounds/sq ft. You may want to have someone else double check this just incase. So your 6 inch walls sound quite safe. Personally, id add some rebar within the concrete walls too.

 

[fat_tony]

OMG I am so Sorry I meant locally!!!! NO Offence please!
Ahhhh My first post on here and already making people angry.

 

[dreeves]

Dont worry about it...some people just are too quick to point and jump...
Sorry about the link not working...yes it is a 4000 gallon tank...he built it into his basement...had 2, 100 gallon (i think 100) sumps, tons of halide's...it was pretty nice...he had a couple of pictures of him scuba diving in it...really neat.

 

[slofish]

Originally posted by Fat_Tony
OMG I am so Sorry I meant locally!!!! NO Offence please!

NO worries, no offense was taken.

 

[tony detroit]

go to the agressive forum and post a thread NOVICE 150, he is the big tank expert.
Also I know if you are building a concrete sided tank the rebar will corrode and enter the water slowly and mess up your sharks. I think I heard you have to cover the walls with marine grade epoxy so that no water reaches contact with the concrete/metal.
And most importantly.....post pictures

 

[bridge man]

Don't worry about the tensile strength of concrete, it is basically worthless. In design, we don't even consider the tensile strength of the concrete in basic design. The design parameter used is the compressive strength. I'll use 3000 psi and 6" walls for the numbers to come later. The thing you have to worry about is the bending. At six foot deep, the water will exert a pressure of about 400 pounds per square foot or 2.8 pounds per square inch. This causes a bending moment (vertical wall bent like a cantilever) on the walls of 2400 lb-ft. This requires an area of vertical steel of 0.15 in^2. You can use #3 rebar @ 8" or #4 rebar @ 12" to take care of that. For horizontal steel in all the long sides (moment at base of tank walls and bottom requires 0.4 in^2), use #4 rebars @ 6". Horizontal steel in short sides (requires 0.11 in^2), use #3 rebars @ 12". Be sure to bend the rebar around the corners to strengthen them. Holy moly that was a lot of mumbo jumbo, hopefully someone out there will understand it.

 

[fat_tony]

Hey I think I understand
Can I weld the rebar at the corners and basically make a cage inside the forms ? Or should I bend the rebar and weld after the bend? Or not weld at all?
I plan on creating a "bathtub" inside the tank using fiberglass and then coat the whole thing with epoxy, to keep away seepage from the concrete and corrosion of the rebar.
I will definately keep pics of every step as soon as I get it started. No sooner than 1 month from now... Stupid broken legs...
Thanks again
Matt

 

[tony detroit]

what kind of bike were you on?

 

[fat_tony]

Brand new CBR 600rr all Black, owned it less than 2 months.

 

[skierguy]

Nicely explained Bridge Man. Fat Tony you don’t want to weld the rebar. It weakens the steel. You should bend each side around the corner lapping them each about 18''-24''. The reinforcement gets its strength from its contact with the concrete not the tie wire it’s held together with so welding the steel will do more harm than good.

 

[fat_tony]

Thank you, that makes sense.
One more quick question, can I insulate the entire project using Styrofoam or similar insulation to prevent some heat loss to the ground and to the air. I know it probably wont lose too much heat to the air, except for evap, but I am trying to have a somewhat efficient tank.

 

[dreeves]

Do a search for Lagoonal reef...Bang Guy built a huge lagoon in his basement..anyways...he insulated it with styrofoam insulation...he has a pic of it too.

 

[bridge man]

I would agree that bending the rebar around the corner is the best option. Welding would work if done right, but with the low cost of rebar per pound, it would save time and probably some money to just bend them. There are rebar fabricators that will bend the steel for you to the required dimensions. Plus, bending the rebar around the corners strengthens the corners which is helpfull since they take vertically bending and also anchor the walls from the lateral water pressure load.