What are the characteristics of trusses?

Truss: A structure in which members are hinged at both ends. Truss is a plane or spatial structure of triangular elements composed of straight bars. Truss members mainly bear axial tension or pressure, so that when the span is large, the strength of materials can be fully utilized, materials can be saved, self-weight can be reduced, and stiffness can be increased. The word "truss" is pronounced "héng". Because the word "truss" is rarely used, it is mispronounced as "háng" (line). Therefore, "Hangjia" got its name. Definition of truss: The supporting beam structure composed of members connected by welding, riveting or bolts is called "truss". The advantage of truss is that the members mainly bear tension or pressure, which can give full play to the role of materials, save materials and reduce the weight of the structure. Commonly used are steel truss, reinforced concrete truss, prestressed concrete truss, wood truss, steel-wood composite truss and steel-concrete composite truss. Truss requirements: sufficient strength-no fracture or plastic deformation; Sufficient rigidity-no excessive elastic deformation; Sufficient stability-it will not collapse due to sudden changes in the form of balance; Good dynamic characteristics-earthquake resistance and wind resistance. Design requirements of truss: there must be components that meet the requirements; There should be good connectors, including rivets, pins and welds. These involve the types of trusses, the sizes and materials of members, but the first is static analysis. Form selection: from the mechanical analysis, when the truss shape is similar to the bending moment diagram of simply supported beam, the upper and lower chord axial forces are evenly distributed, and the web axial force is small, which saves the most materials; From the aspects of materials and manufacturing, it is suggested that wood truss adopt triangle, steel truss adopt trapezoid or parallel chord, and reinforced concrete and prestressed concrete truss adopt polygon or trapezoid.

The height-span ratio of trusses is usually1/6 ~112, which is stipulated in design manuals and specifications. Trusses are widely used. When choosing the truss form, the purpose, material, support mode and construction conditions of the truss should be considered comprehensively. The principle of choosing the best form is to minimize the materials and labor used in manufacturing and installation on the premise of meeting the use requirements.