Help Identify this unusual steel joist

[frogit22]

See attached photo.


constructed in 1962 in Norwich, CT
2.5" seat
spans about 20'-8"
joists spaced at 48"
12" depth
top and bottom chord are 5.25" wide, 1.25" tall, and 1/8" thick

somehow I doubt this is from an SJI member.

see attached photo.

thanks for any insight.

 

[frogit22]

one more picture.

 

[msquared48]

No visible joist tag?

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[Brad805]

No calipers? Seriously, that is an easy joist to analyze considering the web style.

Brad

 

[mmillerpe]

I have seen similar joists in Southern NY with a similar age of construction. The use of the hat channel chords was used in that era. I believe that they were a standard SJI joist. I would suggest sending the measurements and photos to SJI (they have an online submittal form for identifying steel joist.) The thing you need to watch out for with these is that the top chord will retain water from any roof leak and rot from the inside out. See link attached.

 

[pcronin]

See attached. It looks like what you need.

You can get it from SJI as well. I use their forms when verifying existing joists and they are always helpful.

 

[racookpe1978]

So - If the top "hat" - the one that has caught water from roof leaks in the past - were catching water now, could you test for that by drilling small (1/4 - 3/8 inch) holes into the top hat steel and seeing what came out? If there were no water dribbling out, and if the drilled steel were "dry" and bright, then that would be more indication that topside problems did not happen.

 

[BAretired]

I think there are still fabricators who use cold formed "hat" sections as chords. I have never considered the possibility of them filling with water. That is scary! Drilling small drainage holes seems like a good idea but it is a heck of a lot of work.

BA

 

[hokie66]

It looks like there is ample room between the deck ribs to get your fingers in there to feel for corrosion. Maybe even something like a borescope would be useful to examine the chords without having to do a lot of drilling. I hadn't heard of that problem...maybe the case posted by mmillerpe just indicated a lack of roofing maintenance.

 

[mmillerpe]

I don't know all the in's and out's of what happened at that particular location, but if I recall correctly NYS had mandated that all schools with that type of bar joists be inspected.
I have not heard of any recent issues with the joists fabricated with hat channels, but whenever I see a roof with similar construction that story always tends to creep into the back of my mind.

Personally, I have not come across too many structures with the SJ type of joists, and the ones I have seen did not express any significant deterioration.

The company I used to work for in NY used to use an ultrasonic thickness gauge to test for deterioration in these types of members.