How about two steel rings with matching bolt holes?

Then you weld them together, or for two million dollars.

Building to last.

Combine simplicity with this brilliant Lego concept. A standard four port docking collar would allow for massive construction... just bolted together. Six combined with six habitat modules would create a ring (and twelve extra ports for more additions.)

Update: The ISS cost $150 billion and has a volume of 837 m3. It has two incompatible docking ports. Six BA330, each with a four port docking collar, would cost $1.25 billion to orbit providing 12 docking ports to which standard docking modules could be attached. This station would be a ring with 1980 m3 of volume 2.3 times the volume of the I.S.S. for less than 1% the cost. Almost forgot, it would have life support for 36 where the I.S.S. only has life support for six.

The hole in the center of the ring? That's the starbase's starship construction hub!