Come up with a homogeneous column cross section of a fairly complex shape e.g., L shape or T shape or whatever shape you decide on that has a fair amount of complexity in terms of shape and decide on its dimensions in (mm), then calculate (Mn, Pn) in the compression controlled zone and another (Mn, P n) in the tension controlled zone , knowing that the allowable tension stress (Ft = 40 MPa), whereas the allowable compression stress (Fc = 75 MPa).

use this if necessary Fc= 28 MPa, Fy = 420 MPa