|Busy, busy, busy.|
This is the unoriginally named "Gateway Station", a commercial hub like those mentioned in our Space Infrastructure series. It services "Liberty Bell"-type spacecraft and holds cargo moving to and fro from orbit to the La Grange points. This is just a section; the complete station would have at least two such spines, with a spin hab and power core in the center. The truss is modular; new sections can be added as needed.
The truss segments hold docking ports for the cargo 'Bells, radiators, and pressure modules that connect the docking ports of the the segments together. People can move between the segments and to the central core, and the modules contain bathrooms, vending machines, duty-free shops and all the other things you'd see in an airport. The crews of the Liberty Bells can mingle together in free-fall, but probably won't tarry very long, as time is money and their cargo (hopefully) won't take long to load.
Anyway, I hope you enjoy, and I'll keep you updated on the upcoming P-SM as the project nears completion.