AISC Cruciform Column Design?

[Ganesh Persaud]

Hello everyone,

I’m a graduate junior structural engineer in Practice. Currently I’m designing a cruciform column according to aisc standards, as seen in pic, it’s not a doubly symmetric member. I would like to know how I should approach this design and any information on this cruciform column, would be appreciated.

Thank you.

 

[BAretired]

This subject is addressed in: "Theory of Elastic Stability" by Timoshenko and Gere.

It is also addressed in:

https://www.google.com/url?sa=t&rct...boefeAhVLhlQKHajvDW8QFjAAegQICBAC&url=http://

http://www.newsteelconstruction.com...l06_Tech.pdf&usg=AOvVaw0s9cn69PQf_Umms3zBexcR

I do not believe it is specifically addressed in AISC documents.

BA

 

[Ganesh Persaud]

There isn’t anything in the aisc documents as it pertains to cruciform columns. I will definitely have a read with the links you sent. Thank you

 

[robyengIT]

some samples :

 

[dhengr]

Ganesh Persaud:
How did you arrive at those two particular WF shapes for your column? Are the moments on the column that unsymmetrical, or are the loads more symmetrical, so the cross section can be too? Usually, you would be better off on column designs, with stockier webs and flanges because of their improved resistance to buckling. You probably/generally don’t need CJP welds btwn. the two members or btwn. webs and flanges. If you go with two WF shapes, you will leave one intact and split the other into a WT and then weld it back onto the web of the intact shape, so your weld detail needs some change. Talk to a few fabricators in your area, you might be better off making a col. shape like that completely out of plates for webs and flgs. which you can optimize in thickness and width, and then welding the whole thing up, into a final shape.

 

[271828]

Use Chapter E of the Specification just like for any other compression member. Torsional buckling in Section E4 is likely to control.

 

[Ganesh Persaud]

@dhengr, i modeled the structure in Etabs, using first principles, that’s how I got those w shapes. I agree that one would be split and welded onto the other. The moments in both directions were not much of a difference and I’m aware I could use another w14, however I didn’t because i needed to make sure there was enough space from the flanges for welders to carry out their job. Cjp might be over doing it with the weld, I’ve seen some built up shapes where fillet weld was applicable. The reason for the cjp, I wanted the the cruciform section to be somewhat homogeneous.