The question needs a bit more detail, is the connection to resist moment, is the column pre-cast or in situ, is the cold formed steel section a beam, etc. Sketch would be helpful

 Dear sir,

i want to design the connection design of concrete column and cold formed steel section column as shown in figure.

Dear Mr. Chandani, is the concrete column pre-cast (constructed already) and you want to connect the cold formed steel (CFS) section column to it? or you want to construct both of it together?

- If the the concrete column is Pre-cast, then you can use the roll bolts, and the number of bolts you can follow the ASTM code.

- If you want to construct both of it at the same time, then you have two options:

1- you can design small hols at the bottom end of the CFS columns  to increase the interaction between both of columns. (don't forget the overlap 500 mm minimum)

2- You can add bolts at the bottom end of the CFS columns and try to chose bolts with 30 mm long to increase the interaction as well.

hope my answer will be helpful a bit .

Regards

https://www.dlsweb.rmit.edu.au/toolbox/buildright/content/bcgbc4010a/10_floor_systems/03_concrete_slab_reinforcement/page_006.htm

http://www.tatasteelconstruction.com/en/reference/teaching-resources/architectural-teaching-resource/elements/connections/connections-between-steel-and-concrete

http://www.strongtie.com/products/strongwall/steel-strongwall/cfs-1st-story.asp?source=swnav

http://www.strongtie.com/literature/c-cfs.html

You can refer to the concepts used in the following post:

http://www.sepakistan.com/topic/2141-steel-beam-to-concrete-column-connection/