Short column of rectangular cross section 160mm by 60mm carrying point load of 40 KN at max eccentricity position along the longer axis so that no tensile stress is applied.

I worked out max eccentricity as 26.66 mm from RH and LH, and compressive stress as 4.167 MPa.

The column is to be replaced by an I beam having at least same section modulus (Z) as the rectangular column.

Not sure how to work out Z ??