square piping

Does anyone know a simple way to create steel tubing along a polyline that has kinks?  I'm looking for something similar to the pipe command, but with a square cross-section. 

Essentially, I have a large tube that I would like to wrap with structural steel tubing to create a trussing system with points that can be altered along the edge curves.  I have achieved the wrapping of the tube with an editable polyline, but am now looking for a way to give it thickness in three dimensions.  I have tried sweeping a cross-section along the polyline, but that creates problems at the kinks.  I've also tried offsetting the polyline and lofting the curves, which works as I offset along the larger tube, but I could not figure out how to offset towards a center point and could not isolate the individual sections of the polyline to offset that way.

Thanks for your help.  I'm still fairly new to this program and any advice is appreciated.

I can upload an image to help illustrate what I'm trying to do if necessary.