Reinforcement of Cold Formed Chord Joists

[jjeng2]

Does anyone know of a method or have any experience reinforcing Bethlehem Steel H or J Series Cold Formed Chords Joists. I also am looking for a way to attach struts/angle frames to the joists. The chords are shaped like a U with wings. The total chord is about 5” wide. The top chord faces up like a regular U and the bottom chord is an inverted U. Is it possible to weld something to the wings on the chords?

 

[strguy11]

If the chord members are steel (not light gauge) you could weld a round bar or plate to the exist chors to increase the area for compression. Also, check the welds from the webs to the chords. These may need to be reinforced as well.

 

[jjeng2]

If they were hot rolled double angle chord joists, I have done what you suggest many times and have the typical details, etc. I dont know if I can do that here. SJI sent me a cut from Beth Steel and they identify them as "cold formed".

 

[youngstructural]

"Cold Formed" means that they have been bent without heat from steel sheet stock. This would form strain-hardened areas about the corners of the bends which have significantly higher Fy than the base steel. That, however, does not automatically mean to say that the design capacity of the joists depends on these cold worked areas.

Cold forming can be done with plates to significant thicknesses; If I remember correctly off the top of my head AS/NZS 4600 says up to 25mm thick.

If you have a plate thickness of 3mm or more, I would say welding is possible. That doesn't mean to say you can definately weld. You probably need to consider the application and see if the base steel strength without cold working could span with the applied loads in your application.

Cheers,

YS

B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...