Column Effective Length

[SunshineTown]

This might be a discussed question in this forum but I really have problem understanding the effective length so please forgive me for asking

I am confused by how to define translation restraint for columns. Does this restraint need to be directly on column ends or can I rely beams that connects to column to bring translation restraint from far ends.
I have uploaded a pic together with a screenshot of standard regarding effective length. My question is how much the effective length in X direction is gonna be for the column in red? As I have bracing at void ends, can I reply beams B1 to bring the translation restraint in X direction from bracing for column in red so the effective length of column will be 3 meter or do I need to take a full length which is 9*2.2(sway) meters as the effective length in X direction?

What if I introduce a transfer beam to terminate the column as shown in section A-A option 2? How much is the effective length is gonna be for that red column in X direction then? Thank you.

 

[KootK]

- it appears that each beam passing continuously through your column will constitute its brace points and define its effective length(s).

- the lateral stiffness of each beam used as column bracing ought to be assessed.

- at a minimum, you'll probably want your uppermost beam to be continuous and serve as a brace point.

 

[SunshineTown]

@KootK, Thanks for your help. So if I choose the uppermost beam to be continuous over red column, what effective length will it be for the red column in X direction then? ( I can't make the beams to be continuous on 1st and 2nd floor because otherwise it will be option 2). For a simplified method without running buckling analysis, how much lateral stiffness of the beam should be if treated as translation restraint for column in X direction?

 

[KootK]

You're most welcome.

kL=9m. AISC manual has an appendix dealing with brace stiffness. I recommend using that procedure. Also consider P-delta effects if your column axial loads are significant.