The plane shape of flat grating is flexible and can be designed into various shapes. According to the different settings of web members, it can be divided into cross truss system, four-corner pyramid system, triangular pyramid system and other systems. When the chord of the grid is perpendicular to the boundary, it is called vertical grid, and when the grid is inclined to the boundary, it is called oblique grid. Many countries in the world have successfully built many grid structures on large and medium-sized roofs, such as the World Expo in Canada and Japan, the Capitol in Chicago, and the hangar in London, England. All of them are large in plane size and the total steel consumption is economical. The former Soviet Union also adopted prestress in grid structure. In a word, grid structure has become one of the new structures widely used in the world today. China began to study and adopt it in 1960s. In recent years, due to the rapid development of electronic computing technology, the calculation problem of high-order statically indeterminate structure of grid structure has been solved, which has promoted the rapid development of grid structure in types and practical engineering applications. At present, it is mainly used in large and medium-span public buildings, such as gymnasiums, hangars, clubs, exhibition halls and waiting rooms. And small and medium-sized industrial workshops have also begun to be widely used. The greater the span, the more obvious the superiority and economic effect of adopting this structure. Grid structure is a spatial structure in which multiple members are connected by nodes according to certain regular geometric figures, which is called grid structure. Two-layer or multi-layer plane grid structure is called grid structure or grid structure. It is usually made of steel pipe or section steel.