The net frame plane shape is flexible, may design each kind of shape. According to the different setting of the web bar, it can be divided into the cross truss system, the pyramid system, the pyramid system and some other systems. When the chord of the grid frame is perpendicular to the boundary, it is called the positive grid frame, and when it is oblique to the boundary, it is called the oblique grid frame. Countries in the world have successfully built a lot of grid structure in the large and medium-sized roof, such as the expo in Canada and Japan, the United States Chicago congress hall and the United Kingdom London hangar, plane size is very large, the total amount of steel is also relatively economic, the former Soviet union also used prestress in the grid structure. In short, the grid structure has become one of the new structures widely used in the modern world. China began to research and adopt in the 1960s. In recent years, the rapid development of electronic computing technology has solved the calculation problem of the high-order statically indeterminate structure of the grid structure, and promoted the rapid development of the grid structure both in terms of type and practical engineering application. At present, it is mainly used in large and medium-span public buildings, such as gymnasiums, hangars, clubs, exhibition halls and waiting halls, etc., and small and medium-sized industrial plants are also being promoted and applied. The greater the span, the more obvious the advantages and economic effects of this kind of structure will be.
