bar joist with diagonal on one side of chord only

[structSU10]

I have someone looking to understand if joist are reusable. I only have photographs, and havent seen these in person yet - based on the photo it doesn't look like a great idea to reuse, but I want to get some opinions. The web members are only on one side of a double angle chord - See attached photo - any thoughts on what this would do to capacity? Does it put undue stress on the weld due to eccentricities?

The proposed use is an agricultural storage building. I think to assign a capacity may be tough, as they seem to be a custom bar joist, and welds may be suspect, but maybe I am being too critical?

 

[CANPRO]

Looks symmetrical to me. The verticals are single angles on each side of the chord, and the diagonals are sandwiched between the back to back angles forming the chords.

I don't think you're being too critical, just cautious. They aren't perfect joist, but I'd take an honest look at the section and connection capacity and see what you come up with. You might be surprised at what you get.

 

[structSU10]

I misinterpreted the diagonals from the photo and brief description I received - upon further review the diagonal are flat plates, set between the chord members, so it is concentric. Are there any manufacturers that made joists with flat plate diagonals? I have never come across that before, and these have no tag or building to reference.

 

[DaveAtkins]

I know of no manufacturers of joists like this, but there were a lot of joist manufacturers in the first half of the 20th century who made odd joists.

I think this joist could work, but the flat web members won't be able to take much compression, so uplift due to wind may present a challenge.

DaveAtkins

 

[T_Bat]

If you have a rough idea of the date these were used you can send measurements over to the Steel Joist Institute and they can usually track down some literature or point you towards an old manuf.

Link

They look similar to some joists made by Bethlehem Steel in the 1950s (see attachment)...

 

[BUGGAR]

If I remember, bar joists could be qualified and accepted by testing. So you see configurations that "don't figure", but they work (just barely).
Look at their welds! They don't necessarily follow AWS.

 

[CANPRO]

The analysis is fairly straight forward once you have the measurements, connection details, and material grade. Agree with DaveAtkins that web compression could be an issue, especially for an agricultural building where I'm picturing a lot of uplift.

If they're serious about re-using the joists, I'd suggest the following course of action:

- Write them a proposal to evaluate the joists. With the understanding that they have to pay whether they like the results of the analysis or not. They may end up paying you just to determine that they're garbage.
- If they agree to that, you obviously need to see the joists first hand for detailed measurements. At that time, I'd pick one joist that was badly damaged (the one in the picture looks like a decent candidate) and cut coupons out of the webs/chords for material testing.
- Provide them with an "as-is" capacity, and if that isn't enough, maybe you give them a detail to stiffen the slender webs for compression.

Sounds like a fun project to me, I like the challenge of trying to re-use old crap for new projects.

 

[structSU10]

It is similar to the bethlehem joists - the chord sizes used are not quite the same, but the web member match, so I think thats it. It at least give me a good ballpark for initial design values. Thanks for the insight everyone!