Editing in 3D - Autodesk AutoCAD 2013 Practical 3D Drafting and Design - page 178

5. Now, apply to all objects the 3DARRAY command, a rectangle, ten rows,
one column, and one level; the distance between rows is 2.9 .
Note
As we just want a multiple copy in one direction, instead of applying
this command, we could get the same result with Version 2012 or
later, the COPY command, the Array option, and the ARRAY , -ARRAY ,
or ARRAYCLASSIC commands. With versions prior to 2012, the
ARRAY command would be easier.
6. Finally, delete the last set of circular beams.
7. Save the drawing with the name A3D_06_02FINAL.DWG .