A questions for any structural engineers

[howdy20012002]

just wondering if anyone knows what size and thickness of metal tubing I would need to hold 2 x 4 foot 130 gallon tanks above another tanks. I want to make a stand that holds 2 x 4 tanks above a 7 foot tank.
any info would be greatly appreciated
thanks
Neal

[sphelps]

Assuming you're talking about two 120 gallon tanks over another tank meaning you'll be running two 8 foot beams over the lower tank to support the two tanks above (1400 lbs each) you'll need 3"x3"x.313 HSS tubing (grade 50W or better).

[howdy20012002]

that big eh?
lol
was hopping for a big smaller. Could I go 2 inch but thicker?
that is exactly what I am looking to do btw
thanks again
Neal

[sphelps]

You could use 4"x2"x.313" (2" height) and get the same strength.

You could use a smaller size if you add a center support column. The weakest point in going to be at the ends where the weld is in place, if you reinforce that area with truss support or something similar you could get away with 2"x2"x.25" but it really depends on how the stand is designed and fabricated.

[no_bs]

The smaller the tubing the more gussets and vertical supports you will need.

[hillegom]

[QUOTE=sphelps;468908]You could use 4"x2"x.313" (2" height) and get the same strength.

Sphelps: Did you mean the 4" as vertical? I would have thought that deeper would hold more weight.

[sphelps]

Sphelps: Did you mean the 4" as vertical? I would have thought that deeper would hold more weight.
Deeper would hold more weight in terms of beam strength however the guy asked for a lower profile than 3" so I suggested a 2" x 4" instead of a 3" x 3". Has enough beam strength if laid out 2" tall and the 4" width provides more support at the ends which is the critical spot anyway.

[golf nut]

If you have space behind the tanks you could run a cantilever.

[Fishward]

What kind of defelection are you going to get with an 8ft beam like that? i imagine standard design tolerance is greater than that for a big glass fish tank. it may hold it up but if the beam bends you won't be level and you'll get uneven loading in the tank (and on the beam).

Unless you're on the basement floor (or Concrete Slab) i would also suggest having someone look into your flooring situation. 2 four foot tanks and a 7 foot tank over the same joists is a boatload of weight... a quick guess is over 4000lbs.. not including any rock. or you standing over them to feed/clean/gawk...

[sphelps]

What kind of defelection are you going to get with an 8ft beam like that?
About 40 thou on the sizing I suggested which is about 1mm.

[golf nut]

What kind of defelection are you going to get with an 8ft beam like that? i imagine standard design tolerance is greater than that for a big glass fish tank. it may hold it up but if the beam bends you won't be level and you'll get uneven loading in the tank (and on the beam).

Unless you're on the basement floor (or Concrete Slab) i would also suggest having someone look into your flooring situation. 2 four foot tanks and a 7 foot tank over the same joists is a boatload of weight... a quick guess is over 4000lbs.. not including any rock. or you standing over them to feed/clean/gawk...


What does Gawking typically weigh?

[Fishward]

What does Gawking typically weigh?

Haha.. think Howdy would have to answer that... typically between 150-300 lbs. unless of course he gawks as a family, which could push it a fair bit higher..

i imagine you could draw quite the crowd with about 400 Gal. of tank space in those 3 tanks. (which without rock/glass is already ~2 metric tonnes) add 400 lbs of LR/sand... 500lbs of glass... big numbers...

[howdy20012002]

i am actually going to go with 3 x 3 by .375 inch because they dont have the .313. so I am going to go bigger vice smaller.

underneath there is 2 x 10's at a 12 foot span every 12 inches running in the same direction as the tanks.
there is also a 2 foot retaining wall at the 6 foot mark running perpendicular to the joists with 2 x 12 foot pilings under that. One of the pilings is directly under where the tanks will be sitting.
there is also 3/4 tongue and grove OSB flooring.

I should be fine with the weight I think.
I actually built it specifically for tanks to go there.
however, they were going to go in the same direction as the retaining wall, but decided to put them all against the outside wall instead.
it is alot of weight, but I think the saving grace is the 2 foot retaining wall at the halfway mark. I don't see how the 2 x 10's could really go anywhere with that there.
opinions would be greatly appreciated.

btw, as for gawking.....no comment on the weight issue...I am trying to lose a few lbs ok...lol
thanks again
Neal

[Fishward]

My worry is that you will have the footings of this steel frame, holding up 3000lbs and hiting the floor at almost exact midspan of the 2x10s. (provided im understanding your geometry correctly). At a 12'' spacing of those joists you can, at best, hope to split that load over 2-3 of them. On top of the 2 tanks you have there already, i personally wouldn't trust it. Sphelps may be able to comment better on the numbers side (don't have any refence books on hand) but my gut says dont do it.
If you can, I would say make sure there is a support (concrete ideally, or cinderblock) directly under where your stand footing hits the floor, and join the 2x10s together to prevent any torsion. (12'' pieces placed between them)

[sphelps]

I should note at this point that my advice is only relative to the steel structure holding the two tanks. I can't comment too much on the floor holding that much weight as there are way too many variables to consider. I assumed this was on a solid floor, you'll definitely need something above normal floor conditions to support the weight on a raised floor.

[Fishward]

I should note at this point that my advice is only relative to the steel structure holding the two tanks. I can't comment too much on the floor holding that much weight as there are way too many variables to consider. I assumed this was on a solid floor, you'll definitely need something above normal floor conditions to support the weight on a raised floor.

Im going to go ahead and qualify all this advice as well as i've not seen your actual flooring. I really dont need to get sued after the floor collapses and causes 20K in damage. My recommendation stands though that you seriously consider the strength of your floor before you put that kind of load on it.

Something to consider: general design parameter for living space is 40lbs/sqf. the are under this tank will be facing loading about 10 times that.

[howdy20012002]

Hello all
first of all - No one worry about getting sued..i don't think I would have much of a chance of sueing someone for some free advice I got from an online forum. and even if I could, I wouldn't. So no worries there.
i do appreciate your inputs.
just to clarify about the structure of the house.
the room is 12 feet across.
beneath this is a crawl space.
the 2 x 10's are actually resting on the perpendicular 2 foot retaining wall at the 6 foot mark or halfway mark, which has the 2 - 12 inch by 12 feet deep pilings.
I am not sure if this was clear.
I don't really see how, being that it is actually resting on the retaining wall in the middle of the room, that there could be any movement at all really.
or am I right out of it?
the concrete wall is 10 inch thick reinforced by lots of rebar.
let me know what u think

[new but handy]

You should be fine with the joists but I would worry about where the feet of the stand are. (ie. between the joists.)

[Norseman]

aluminium doesn't rust. come in aircraft grades and is light weight easy to weld and looks nice and takes powdercoat well. just a thought.

[Fishward]

[/QUOTE]
I don't really see how, being that it is actually resting on the retaining wall in the middle of the room, that there could be any movement at all really.
[/QUOTE]

I trust the retaining wall, what i dont trust is 2 2x10s at a 6 ft span holding up 3000lbs.

http://www.awc.org/calculators/span/calc/timbercalcstyle.asp

at 100 psf (pounds per square foor) this calc says your max span is 10ft. you've got 4 times that....

[new but handy]

doesn't that chart say 100 at 11'6? so double that because of the 6' span. and consider that according to the BCBC (British Columbia Building Code) 12kPa or 250lbs/foot is the required strength for loaded bus or all truck parking over living spaces. You should be ok

[Fishward]

doesn't that chart say 100 at 11'6? so double that because of the 6' span. and consider that according to the BCBC (British Columbia Building Code) 12kPa or 250lbs/foot is the required strength for loaded bus or all truck parking over living spaces. You should be ok

You should switch the chart to only allow for deflection of L/720. rigidity is important for loaded glass boxes... that will give you a different span

"250lbs/foot is the required strength for loaded bus or all truck parking over living spaces" - my point exactly.. he's got loading of over 400lbs/ft. would you park a fully loaded bus or truck on 2 2x10s?

[howdy20012002]

but the 2 x 10 have no where to go....they are completely supported by the retaining wall below them...they would basically have to be crushed for them to go anywhere or the retaining wall would have to be pushed down.
as well the the retaining wall will be dead centre of where the tank is going to be above it. so the tank will be stradling the wall.
as for the stand ends, I woudl be running a 3 x 3 beam along the bottom of the stand along the floor. that way the weight will be dispersed along the entire length.

[new but handy]

how wide are the stands? if they are 2' then you are only supporting 250lbs/ft
with the added support you will be fine

[Fishward]

but the 2 x 10 have no where to go....they are completely supported by the retaining wall below them...they would basically have to be crushed for them to go anywhere or the retaining wall would have to be pushed down.
as well the the retaining wall will be dead centre of where the tank is going to be above it. so the tank will be stradling the wall.
as for the stand ends, I woudl be running a 3 x 3 beam along the bottom of the stand along the floor. that way the weight will be dispersed along the entire length.

The beam at the bottom helps a bunch. I was under the impression this would be point loaded at the feet of the stand. If you can truss the bottom beam into the uprights, that will help keep the load spread out. I would also still suggest putting braces in between the joists immediately below the tanks, to prevent them from buckling sideways.. especially near the retaining wall.

would love to see some pics of the setup when its all together.. sounds like quite the operation.

[howdy20012002]

the stands will be 2 foot wide.
I will also be putting cross members from one truss to the other along the 2 8 foot spans(probably at 2 foot intervals) and along the sides.
that way it can't go anywhere.
unfortunately, I no longer have access to the crawl space.
but I think we did put braces anyways.
I will definitely be posting pics of it when it is up and running and probably as it gets to that point as well.
this will be one of 5 systems I am going to have in my house.

[new but handy]

You should switch the chart to only allow for deflection of L/720. rigidity is important for loaded glass boxes... that will give you a different span

"250lbs/foot is the required strength for loaded bus or all truck parking over living spaces" - my point exactly.. he's got loading of over 400lbs/ft. would you park a fully loaded bus or truck on 2 2x10s?
Not a bus but I would have no problems driving my 6000# truck across 2 6' 2x10's. I put 2 2500# lifts of lumber on 10' spans all the time.

[new but handy]

sorry for the arguing. I could have just said that I have 3000# sitting on the second floor of my house (6'x2' stand = 250#/ft)I doubled up 1 12' 2x10 in my floor, because the gf was a little scared. to help the 3 joists it sits on. There is 0 movement when I jump next to my tank. (I'm not that small:lol:). Stick to your plan you will be fine.
I wouldn't be surprised if a bus was only sitting on 12 sq/ft

[howdy20012002]

thanks again for the input guys..
now for the next one....lol
i have a 230 gallon 7 foot tank that I want to put in another part of my house.
it will be running perpendicular to the 2 x 8 floor joists and pretty much right above the support beam downstairs in the basement (the wall behind the tank is right above the support wall below it)the support beam is 3 - 2 x 8 together.
as well, the support beam has a 2 x 6 wall beneath it from the floor up to the support beam.
i have already had a 180 there with no real problems..and I don't think the extra 50 lbs will make much of a difference
what do u think?
Neal

[Fishward]

sorry for the arguing. I could have just said that I have 3000# sitting on the second floor of my house (6'x2' stand = 250#/ft)I doubled up 1 12' 2x10 in my floor, because the gf was a little scared. to help the 3 joists it sits on. There is 0 movement when I jump next to my tank. (I'm not that small:lol:). Stick to your plan you will be fine.
I wouldn't be surprised if a bus was only sitting on 12 sq/ft

not arguing, its a good discussion to have.. i guess this is the difference between what an engineer will tell you (they always tend to be conservative because if you're EVER wrong its your career) and what a handyman will tell you (which will work for most situations). im not at all worried that his tank is gonna collapse through the floor or anything, its deflection and creep over time that will cause the floor to fail.

[Fishward]

thanks again for the input guys..
now for the next one....lol
i have a 230 gallon 7 foot tank that I want to put in another part of my house.
it will be running perpendicular to the 2 x 8 floor joists and pretty much right above the support beam downstairs in the basement (the wall behind the tank is right above the support wall below it)the support beam is 3 - 2 x 8 together.
as well, the support beam has a 2 x 6 wall beneath it from the floor up to the support beam.
i have already had a 180 there with no real problems..and I don't think the extra 50 lbs will make much of a difference
what do u think?
Neal

first off ....50 gallons of water is alot more than 50 lbs. 50 gal = ~250L = ~275KG = ~600lbs :-)

the 2x6 wall below the beam is pretty much worthless. If you are interested in beefing up the beam, i would suggest getting an expandable steel column support form RONA or somewhere and putting it inside the wall thats under the beam.

[howdy20012002]

sorry I mean 50 gallons.
the 2 x 6 wall is actually a built wall between the furnace room and the bedroom.
there is also one of the original support beams that would fall under where the tanks is as well.
i could look at putting one under the other side as well, if necessary

[Fishward]

Ya, you're in a much better situation on this one. lots of joists (tank perpendicular to them) a proper structural beam very close and a vertical support column to the foundation if im reading you right. not too much to worry about.

[howdy20012002]

glad to hear.
I thought it would be ok.
now for the 3 other systems, those I am going to need to put more support under those..lol
thanks again for taking the time to help me out
Neal