Due to the above characteristics of steel and steel structures, steel structures are often used in various engineering structures. The reasonable application range of steel structure is generally as follows:

　　①Large span structure. As the span of the structure increases, the proportion of the self-weight of the structure in the total load is also larger, and the reduction of the self-weight can obtain obvious economic benefits. For large-span structures, the advantages of light-weight steel structures are particularly prominent. The gymnasium in Shanghai, my country, which can accommodate 80,000 people, is an elliptical building with a spatial steel roof structure composed of radial cantilever lattices and circumferential trusses. The long axis is 288.4m, the short axis is 274.4m, and the maximum cantilever span of the roof is 73.5m. The Runyang Yangtze River Bridge was completed and opened to traffic in 2005. The main bridge in Nanhan is a single-hole double-hinged steel box girder suspension bridge with a main span of 1490m, which is currently the first in China and the third in the world.

　　②High-rise buildings. High-rise buildings have become a symbol of modern cities. The characteristics of high strength of steel and light weight of steel structure are of great significance to high-rise buildings. If the strength is high, the section size of the component is small, which can increase the effective usable area; the light weight can greatly reduce the load on the component, foundation and foundation, and reduce the cost of foundation engineering. Among the 50 tallest buildings in the world today, steel structures and steel-concrete hybrid structures account for more than 80%. Completed in 1974, the Sears Tower in New York has a total of 110 floors and a total height of 443m. It is an all-steel structure building. In recent years, steel structures of high-rise buildings in my country have sprung up like mushrooms after a rain. It has 98 floors and a total height of 460m. This shows that it is possible to build super high-rise steel structures entirely by ourselves.

　　③Industrial buildings. When the span and column spacing of industrial buildings are large, or large-tonnage cranes are installed, and the structure needs to bear large dynamic loads, steel structures are often used partially or completely. In order to shorten the construction period and exert the investment benefits as soon as possible, in recent years, a large number of steel structures have also been used in ordinary industrial buildings in my country.

　　④Light structure. A structure with a small load or a small span is called a light structure. Self-weight is the main load of this type of structure, and light steel structures made of cold-formed thin-walled steel or small steel are often used.

　　⑤Tall structure. Such as towers and masts, their height is large, the cross-sectional size of the components is small, wind loads and earthquakes often play a major role, and the self-weight has a greater impact on the structure, so steel structures are often used.

　　⑥ Active structure. Such as hydraulic steel gates, ship lifts, etc., can give full play to the characteristics of light weight of steel structure, reduce the cost of opening and closing equipment and the power consumed by operation.

　　⑦ Detachable or movable structure. Such as construction and steel trestle bridges, mobile exhibition halls, mobile platforms, etc., can play the advantages of light weight, easy transportation and installation of steel structures.

　　⑧ Vessels and large diameter pipes. Such as liquid (gas) tanks, transportation (oil, gas, raw material) pipelines, hydraulic pressure pipelines, etc. The inner diameter of the penstock used for the generator set in the Three Gorges Water Control Project is 12.4m.

　　⑨Structures with high seismic requirements in earthquake zones.

　　⑩ Projects that are in urgent need of early delivery. This type of project can take advantage of the short construction period of the steel structure, light weight and easy transportation.

　　In summary, steel structure is an important structural form widely used in various projects. With the development of my country's economic construction and the improvement of steel production, steel structures will play an increasingly important role.