Trusses can be classified according to different characteristics. According to the shape of truss, it can be divided into: parallel chord truss (easy to arrange double-layer structure; Conducive to standardized production, but the distribution of rod force is not uniform enough); Broken chord truss (such as parabolic truss beam, whose shape is the same as the bending moment diagram of simply supported beam under uniform load, the force distribution of members is uniform, the material use is economical and the structure is complex); Triangular truss (the stress distribution of members is uneven, and the structural layout is difficult, but the inclined plane meets the needs of roof drainage). According to the geometric composition of truss, it is divided into: simple truss (composed of a basic hinged triangle and binary body in turn); Composite truss (composed of several simple trusses according to the simple combination rules of geometrically invariant systems); Complex truss (different from the other two statically indeterminate trusses).