The term 'superstructure' refers to the uppermost part of a structure, such as a building or bridge. It is typically supported by a FRAME, which is the basic underlying structure that supports the superstructure. The FRAME is usually made up of beams, columns, and other structural elements. Superstructures are often made of materials such as steel, concrete, or wood, and can be used for a variety of purposes, such as providing additional support for a building or creating a decorative feature.