columns braced or not against sidesway

[ramihabchi]

Hi I need some explanation for how to check if a column is slender or not according to ACI.so I have these 3 questions.
1)if columns are not designed to resist lateral load..in other word considering the column connection with slab as hinged so that there is no moment transfer,could I consider the columns braced against sidesway regardless of the stiffness of columns in relation to stiffness of bracing elements?
2)if yes, is the term M1/M2 then cosidered in equation klu/r<=34-12M1/M2 as equal to zero?
3)in determining the stiffness ratio(psi) should I take a portion of the slab with calculation of beam stiffness?if yes how much?is it the T beam width?.and what if a column is not connected to columns,directly supporting the slab,how should I calculate the stiffness ratio?(i mean how wide the portion of the slab should be taken in stiffness ratio calculation.

 

[DaveAtkins]

My responses:
1) If you want to consider the top of the column braced, the diaphragm must be braced somewhere else, by a shear wall or a moment frame, for example.
2) Yes. I think of it this way--M1 is zero, and M2 is a tiny number greater than zero.
3) I am not sure this has anything to do with determining klu/r.

DaveAtkins

 

[ramihabchi]

hi thank you for the answer.
In my third question I mean that in case a column is not connected to beams how do I find psi that enable me to know the value of k.I mean the stiffness of the flexural member is not clear in such case because there are no beams so how wide do i take the slab in moment of inertia's calculation

 

[DaveAtkins]

The most conservative approach would be to assume it is pinned at the top.

DaveAtkins