36LH10 Joist Information

[mackerel]

I am working on adding some roof top units to an existing structure that was built in 1963. I know the existing joists are 36LH10 60'-0" long. Due to timing and other issues, I am not able to uncover these guys until after the design is done. So I am assuming that top and bottom chords are angles.

I am not sure about the web members. I would like to think that the web members are at a minimum a single angle possible crimped. I guess there is also the possibility of rod (not likely in my opinion given the size an span), there is also the chance that there could be (2) back to back angles for web members.

Anyone have any thoughts, or run into a similar situation?

Thanks,

 

[UcfSE]

In my experience for joists that deep, and given it's an LH series, the webs will be angles, single crimped or double overlapped with the chords. I would plan details for both conditions. A manufactuer should be able to give you a reasonable idea as to what size angle to expect so you can plan reinforcement detailing. I've found them to be helpful in the past with that.

 

[JedClampett]

And my experience is just the opposite. If you can find the manufacturer and if they're still in business and if they haven't lost all their documentation, they're going to say, "A 36LH10 is good for the loads specified. We made them out of whatever crap we had on hand that day. It could be angles, rods or paper clips wound into a wire rope."

 

[msquared48]

Could also be a hat channel.

Mike McCann
MMC Engineering

 

[dhengr]

Mackerel:
You can gather your load info. now and do a prelim design, but you won’t be able to finalize your design, details or the DL’s for that matter until you can open things up, and get a look-see. You’ll want your new loads from above coming onto the jsts. at top chord panel points so that may mean moving your curbs or the legs on your support frame a foot or so, to these actual locations. And, these may vary a bit from one jst. manufacturer to another. But here’s some jst. info. from one of my old ARMCO catalogs, see attached. You should be able to get a handle on whether the existing jsts. will carry the new load, or how many jsts. you have to distribute that load to.