DXF layers of ground plans cannot be used directly in FEA programs because only the outer contours of the elements (walls, ceilings, and so on) are available in the drawing. The FEM programs require system axes, but only the outer contours of the elements (walls, ceilings, and so on) are available in the DXF drawing.
In SHAPE-THIN, you can import cross-section geometries that are available as contour or centroid layouts in DXF format and use them as a basis for modeling.