From ROI Wiki

A Spaceframe is the core structural framework of any starship, and is the foundation on which a starship is built. Without a good, solid, reinforced spaceframe, a ship would become weak and easily break apart easily, or be unable to handle the riggers of FTL or sublight travel, especially when high speed maneuvering is taking place. It's like the metal skeleton of a skyscraper, only for a starship, and is heavily reinforced across its length so that it will not twist or bend or flex in any way, allowing the extreme rigidity of the frame to maintain the structural integrity of the ship through all forms of use and abuse. It's also the framework on which all internal and external structures of the ship are built and/or attached. The term "Spaceframe" is primarily an Earth term, used extensively by those in Earthfleet, however the concept and practice stretches to all sectors of the galaxy, including The Nine Ancient Races.