What is the correct procedure for using the "Import Autocad DXF" command in Midas GSD?

Actually, this is a limitation in GSD.  One shape can have only 1 material property.  Also, the material shapes can't overlap.  Now, kindly refer to the image below.

First is outer shaper, i.e., 0.3m x 0.3m square.  Now, since material properties (and hence, shapes) can't overlap, we have to create a circular hollow region, which would be shape 2.  Then, shape 3 would be the steel pipe.  And to generate the section as required, there would have to be an inner circular shape with concrete material, which isn't possible.  This limitation can also be understood very quickly by simply trying to import the element from civil to GSD.  The section taken into GSD would be as below.