steel tubing as joist
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Re: steel tubing as joist
Re: steel tubing as joist -- gnoel	Post Reply	Top of thread	Forum

Posted by: randykimball ® 05/29/2006, 18:30:06 Author Profile eMail author Edit

I realize you ask about tubing joist but I think the readers are only thinking of the single tubes as joists. We should consider welding joist out of the tubing. Let's resubmit your question for advice on how far apart the upper and lower beams should be and at what spacing you should should weld in cross braces. Tubing makes great joists. The worst suggestion of your lifetime may be the catalyst to the grandest idea of the century, never let suggestions go unsaid nor fail to listen to them. Modified by randykimball at Mon, May 29, 2006, 18:33:12

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Re: Re: steel tubing as joist
Re: Re: steel tubing as joist -- randykimball	Post Reply	Top of thread	Forum

Posted by: gnoel ® 05/31/2006, 16:45:10 Author Profile eMail author Edit

I would like to be able to look at it both ways. If I can only use the 2.5" tubes, how do I calculate things like max load, deflection, where intermediate supports need to be, etc. If I need to weld joists, how do I calculate the required parameters, such as distance between upper and lower tubes and crossbrace spacing. I was hoping to find out as much info as possible because this deck will be constructed over an as yet unpoured concrete patio and I'll need to know where the support columns should be. Thanks.

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Re: steel tubing as joist
Re: steel tubing as joist -- gnoel	Post Reply	Top of thread	Forum

Posted by: swearingen ® 05/29/2006, 14:12:30 Author Profile eMail author Edit

Those tubes, if not overstressed to failure like I suspect, would act like trampolines at a 22' span. Do you really want you deck to bounce? Quick rule of thumb for steel construction - start with a member that is 1/2 of the span in inches to keep deflections in check. In your case, I'd start looking at 10" or 12" members (22'/2 = 11), definitely not 2.5". I also would not use tubes as they are not very efficient for this type of loading. If, because of pricing, you must use the tubes, look at considerably reducing your spans (to 6' or less) and you may be able to make it work.

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Re: Re: steel tubing as joist
Re: Re: steel tubing as joist -- swearingen	Post Reply	Top of thread	Forum

Posted by: gnoel ® 06/07/2006, 15:00:01 Author Profile eMail author Edit

On one end of this deck I can place intermediate span supports every 2' if I need to (although I think 4' should be sufficient), however, the other end will extend out over a poured patio so I'll need to have as few support columns as possible. I like the idea of a welded tube joist and am capable of getting it done if I could get a little guidance on some of the design considerations as mentioned in other posts. Any help would be most appreciated.

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Re: Re: Re: steel tubing as joist
Re: Re: Re: steel tubing as joist -- gnoel	Post Reply	Top of thread	Forum

Posted by: gnoel ® 06/08/2006, 14:52:36 Author Profile eMail author Edit

I appreciate your patient assistance. My son has the fab shop and his welders are on salary so he will use this project as filler for them. I'll post back with how this turns out. Thanks again.

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Re: Re: Re: steel tubing as joist
Re: Re: Re: steel tubing as joist -- gnoel	Post Reply	Top of thread	Forum

Posted by: swearingen ® 06/07/2006, 16:02:12 Author Profile eMail author Edit

If you're dead set on using those tubes and making joists out of them, just follow the depth to span rule of thumb I mentioned before and make it look like a truss. Try and stay with 45 degree diagonals and a top and bottom chord and they'll be just fine. I must warn you that cutting, assembling, and welding them together will be a tremendous chore. You'll also probably have to build some wooden jigs to keep things straight as you weld them together. It just seems like an awful lot of work to make use of the available material. Have you thought of going to a metal shop and trading in that material for some real joists? They would be much more efficient and FAR less work.

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Re: Re: steel tubing as joist
Re: Re: steel tubing as joist -- swearingen	Post Reply	Top of thread	Forum

Posted by: gnoel ® 05/29/2006, 16:06:08 Author Profile eMail author Edit

Thanks for the quick response. You're right, a 22' span without any intermediate supports, if it held up at all, would have my brewskis bouncing off the table anytime someone walked by; just as it would in an improperly designed deck made from traditional materials. That is why I was hoping to find information that I could use to calculate what is required and minimize reliance on a guess or trial and error. Again, thanks for taking the time to respond.

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