Vintage Windmill and Wind Generator Forum

I got a Bundle of 2x8x11ga tubing, I am wanting to use it for floor joists to span a 16 ft room. I am going to set them on concrete and build a block wall up with the tubes going all but through the outside wall. I am going to weld my rebar to the tubes both coming from concrete below and also going up into the block so when I grout it will all be solid. I am going to box in between the tubes like you would with wood joists and weld it all together nice and solid. I can not find much for engineering on tubes for joists, this is a non code project so I can do as I want but I don't want to regret it either. Anyone know about deflection on that type of tubing for 16 ft? I assume if nothing else I will block a chunk up on edge over 16 ft and start putting 100 lb weights in the middle and measure with a lase for bending? Any help would be appreciated. Aaron

Oh boy , i cant wait for the answer to that one .........

Aaron , what will the roof pitch be ?
snow load ?

Snow really isn't a problem here, I got a lot of nearly flat roofs, we almost always have 45 mph wind if it snows! The roof is 6-12 and will be all steel truss with Z purlins and tin screwed to it. Its going to be a heavy building, putting in 38x12 caged footers. I have talked to an engineering student since I posted this and it sounds like I should be well within the margin of safety. If you are wondering why I want to go steel, well, its cheap, I am doing this myself and might take a while so rain isn't an issue and I have always liked the old brick buildings that ran the floor joists into the masonry pockets. I wouldn't want to do that with modern wood but the steel should make a nice way to hold all my block walls together where I will fasten the joists to vertical bar before grouting. I am going to go overboard with the beam block and reinforcement so I don't have to worry about this thing. What are your thoughts?

Aaron
L+360 is pretty much standard for floor deflection. L is your span in inches. Individual components have deflection but ratings are given for a "floor system". Deflection of L+360 is for the floor system. The other components besides I joists 16" OC is 3/4" T&G OSB perpendicular glued and screwed. It is easier to find deflection on manu I joists than dimension lumber. Compare what manufactured I joists are to your steel rectangular tube. People with initials PE after their surname will get you there too.

If you are building the Taj Mahal, marble floors require L/720. My limited knowledge on floor systems came about 30 years ago when floor systems needed to have the L+360 deflection min for tile floors. Tile was just getting popular and needed min deflection rating of a floor system.

Snow load on typical construction doesnt come in to play on floor deflection. Snow load is carried by engineered trusses via "roof system" to the exterior footing wall. Interior walls on single story trussed construction are non load bearing even tho tied to the bottom chord of the truss.

Ron Stauffer
Montrose CO

and this is why i leave these situations to the professionals !
my simple mind is not capable of these types of mathamatics .......