The document discusses different types of structures including frame, shell, arch, mass, suspension, and mixed structures. It describes the key characteristics of each type. Frame structures are composed of joined tubes or bars and are lightweight but cannot withstand large loads. Shell structures have a thin outer layer surrounding an empty or filled space with forces spread throughout. Arches use their own weight to displace forces to the sides. Mass structures simply use clumped materials filled the entire body. Suspension structures hold elements with cables from top columns. The document also discusses structural elements, types of unions between elements, and forces on elements including tension, compression, shear, torsion, and bending.