Atlas - Cutaway Ring
The basic structure for the ring is 16 "3" technic connecters. The struts are 1x1 round barrels with a 1x1 hollow round plate on the bottom, reinforced by a 1x4 bar. The bar slots into the "T" piece which is connected to the 1x2 technic liftarms, which are in turn connected to the "3" connector. Repeat until circular, but be warned, they're not as strong as you'd like them to be.