Existing steel bar joist splice

[Ccook75]

I am working on a school rehabilitation project that has roughly 50 steel bar joist ends that are severely rusted and must be repaired. The joists are 8" deep, spaced at 2'-6" o.c. and consist of a double angle top chord made from 2x2x3/16 angles, a 1/2" diameter bent rod for the web, and two 1/2" diameter rods for the bottom chord. There is significant loss of section at the exterior end of the top chord due to corrosion, delamination, and rust jacking. Does anyone have any suggestions on how to repair the damaged end? I'm thinking about removing a 3' section of roof to expose the joist ends, temporarily shore the joists, remove the corroded end section of the top chord and web diagonal, and weld new, similar material to the joist ends. This seems difficult, but perhaps it is cheaper than completely replacing the joists or installing new joists between the existing ones. Any suggestions or advice will be greatly appreciated.

 

[jike]

If these are only 8" joists, the chord and web material will be pretty small which is going to make it difficult to repair. The 8" joists cannot be spanning very far.

Would it be possible to add steel beams between the joists for less cost than repairing the existing joists? You might want to discuss this with a local steel erector. There is a potential problem of supporting the deck where it splices over a joist.

 

[hokie66]

If the joists are in that condition, what is the condition of the roof deck? Sounds as if there has been long term leaking. Are the 50 joists all along the same area or scattered all over the place? If all together, probably better to remove the entire roof section and replace.

I would not consider trying to repair the end of these joists in kind, although you could talk to a joist manufacturer about the possibility. Bar joists are a commodity, not really something you work on in the field.

Can you install new joists between the old ones? May have to get them fabricated with slightly less deep ends to get them in, but then if the old ends are badly corroded, the expansion has probably created a bit of extra space on the bad end at least.

 

[DarthSoilsGuy]

Ccook, you didn't make reference to the type of joist so forgive me if my advice is obvious or already done. you should also look at the SJI 60-yr history manual to determine what joists you're dealing with and to see the historic load charts since codes change. if you have too repair, i'd look into not removing existing materials, but bulking them up. absolutely get an erectors take on it because the overall weldability and potential for contaminated welds is going to be there and big-time too.