Steel structures are divided into building steel structures, bridge steel structures, etc. Compared with the reinforced concrete structures commonly used in the current construction field, steel structures have the advantages of high strength, low engineering cost, light weight, short construction period and factory production. Such advantages have been widely valued and developed rapidly. From the use of steel structures in major projects and landmark buildings to the widespread use of steel structures, it has presented an unprecedented prosperity.
1. Current status of steel structure application
1. High-rise heavy steel structure
High-rise steel structure buildings are often regarded as a landmark building in a city. Since the 1980s, more than 100 high-rise steel structures have been built and are under construction, with a total area of about 8 million square meters and more than 800,000 tons of steel.
There are more than ten high-rise steel structures under construction and newly built in Beijing and Shanghai. Such as: Shanghai Tower (under construction, 632 meters), Shanghai World Financial Center (101 floors, 492 meters high, 65,000 tons of steel); Beijing Television Center (building area of 183,000 square meters, height of 41 floors, 227.05 meters, steel consumption of 38,000 tons); China World Trade Center Phase III (building area of 540,000 square meters, height of 330 meters); CCTV new building (building area of 50,000 square meters, height of 234 meters, steel consumption of 128,000 tons). Every year, there are 2-3 million square meters of high-rise steel structure construction in the country, with a steel consumption of about 450,000 tons.
2. Large span, space steel structure
In recent years, space structures represented by grids and grid shells have continued to develop in large quantities, not only for civil buildings, but also for industrial plants, hangars, terminals, gymnasiums, exhibition centers, theaters, museums, etc. Industrial plants with large steel structure consumption include Caofeidian Iron and Steel Base, Shanghai Jiangnan Shipbuilding Base, etc. Representative venues include the National Stadium (Pavilion) of the 2008 Beijing Olympic Games, the 2010 Shanghai World Expo (steel structure consumption reached more than 300,000 tons), the 2010 Asian Games (Guangzhou), Jinan National Games, Shenzhen Universiade and Nanyang National Farmers Games and other urban sports venues. According to statistics from the Space Structure Branch of the China Steel Structure Association: the production of grids and grid shells has been stable in recent years, with 1,500 units per year, about 2.5 million square meters, and about 70,000 tons of steel. The steel used in steel structures is characterized by a variety of varieties, miscellaneous specifications, large consumption and high strength. The main varieties are: Q235C, Q345C, 390D (for underground pre-buried piles), Q345GJ, Q420, Q460, etc.
With the in-depth research and development of cable and membrane tension structures and the promotion of engineering applications. Prestressed space structures have begun to be used. A large number of new steel structure buildings and structures are emerging, such as Hangzhou Leifeng Pagoda, Hainan Millennium Pagoda, Guangzhou New TV Tower (610 meters high, 40,000 tons of steel) and Kunming World Expo Park Art Square membrane structure. Cable and membrane structures are currently in the development stage, and the usage is not large. There are many membrane structure engineering companies in China, which undertake the design and construction of many stadiums, airports, parks and street landscapes. At present, high and medium retaining membrane materials still need to be imported (such as PTFE, ETFE).
3. Light steel structure
Light steel structure is relative to heavy steel structure. Its types include portal frame, arched corrugated steel roof structure, etc. It is mainly used for light industrial plants, cotton and grain warehouses, docks and bonded warehouses, agricultural products, building materials, furniture and other trading markets, stadiums, exhibition halls and mobile houses, multi-storey buildings, etc. The steel usage is generally about 30-40kg/㎡ (excluding steel bars). Every year, 8 million square meters of light steel houses are newly built in the country, and about 200,000 tons of steel are used.
4. Steel-concrete composite structure
Steel-concrete composite structure is a reasonable combination that gives full play to the advantages of both steel and concrete. It not only has excellent static and dynamic working performance, but also can save a lot of steel, reduce project costs and speed up construction progress. It has less environmental pollution and is in line with the development direction of my country's building structure. It has developed very rapidly in my country and has been widely used in buildings in metallurgy, shipbuilding, electricity, transportation and other departments, and has entered bridge engineering and high-rise and super high-rise buildings with a rapid momentum. In terms of high-rise buildings, a super high-rise building with a composite structure has been built-Shenzhen SEG Plaza Building, which is 291.6m high and is the world's tallest steel-concrete composite structure. There are more than 40 high-rise buildings with composite structures built in the country. More than 300 composite arch bridges have been built.
5. Steel structure housing
The weight of a residential building built with steel structure is about 1/2 of that of a reinforced concrete residential building, which can meet the needs of large residential bays and increase the usable area by about 4% compared with reinforced concrete residential buildings. Steel can be recycled, and it causes less environmental pollution during construction and demolition, which is in line with the national policy of promoting the industrialization of housing and developing energy-saving and land-saving housing. my country is currently the largest construction market, with an average annual housing construction of about 2 billion square meters (the housing construction area reached 3.2 billion square meters in 2009), of which steel structures account for about 2-3%, the vast majority of which are reinforced concrete structures and brick concrete structures, and there are also a all number of wooden structures, masonry structures and adobe houses. The same is true for nearly 800 million square meters of urban residential housing per year. The proportion of steel structure buildings in my country's entire construction industry is less than 5%, while in developed countries it has reached more than 50%, and the potential development space for residential steel structures is very large. At present, pilot demonstration projects of low-rise, multi-story and high-rise steel structure residential buildings have been built in Beijing, Shanghai, Tianjin, Hebei, Wuhan, Qingdao and other places, with more than 5 million square meters of construction and about 200,000 tons of steel. Baosteel has invested a lot of money and researchers in the industrialization of steel structure housing, and has designed and built many steel structure demonstration housing projects in Wuhan, Shenyang and other places. In 2007, a steel structure demonstration housing project - Cyber Park Affordable Housing Community was built in Hanyang District, Wuhan, meeting the technical requirements of the World Steel Association's "International Civil Construction Steel Project". In addition, Baosteel has completed a pilot project on the use of board house materials for more than 600,000 mobile board houses provided to the Sichuan earthquake-stricken areas as transitional resettlement housing.
6. Bridge steel structure
Major cities regard the construction of transportation infrastructure such as bridges as an important foundation for economic development. Cable-stayed bridges use more steel structures, mainly in steel boxes, cables, bridge towers and other parts. All large bridges over 600 meters are steel structure bridges? In the first three years of the "Eleventh Five-Year Plan", an average of 30,000 new bridges were built per year, with an average annual steel consumption of 13 million tons. According to statistics, 3,480 concrete bridges on highways currently under construction can be converted to steel structure bridges, and the net increase in steel consumption after the conversion to steel structure is 5.46 million tons. As of the end of 2008, less than 1% of the 590,000 bridges in China were steel structures. This is a big gap compared to the 33% of the 600,000 bridges in the United States and the 41% of the 130,000 bridges in Japan. The first bridge in China with all-steel towers is the Nanjing Third Bridge, and the steel used in the tower alone is 14,400 tons. The Hong Kong Stonecutters Bridge (1,018 meters long) and the Sutong Yangtze River Bridge (1,088 meters long) are the world's largest cable-stayed bridges. By 2015, China will build five cross-strait bridges with a total steel consumption of 6.25 million tons.
2. The gap and future trend of the steel structure industry
At present, the steel used in my country's steel structure industry accounts for only about 4% of the total steel in the country, which is a big gap compared with the proportion of about 10% in developed countries. Domestic steel can basically meet the needs of steel structure processing, but there is still a gap with foreign countries in terms of specific varieties, specifications and performance, such as high-strength large-size ultra-thick H-shaped steel, high-strength ultra-thick plates, etc. At present, Japan is promoting the use of high-strength Q690 steel in buildings and bridges, and has maturely adopted Q960 mechanical steel.
The development of steel structure is constantly promoting the development of high-performance steel. The national standard "Steel Structure Design Code" currently under revision is planned to include Q390, Q420, and Q460 in the code, changing the situation where Q235 and Q345 are the main structural steels for a long time.
my country's steel structure output is about 23 million tons, with an output value of more than 300 billion yuan. The total amount of steel structure will maintain an annual growth rate of 9%-10%. By 2015, it will double to 50-65 million tons, accounting for 10% of the total crude steel output in the country, and steel structure housing construction will account for about 15-20% of the total housing construction in the country.
In the future, the variety, quality and specifications of domestic steel products must not only meet the needs of domestic and foreign steel structure development, but also be internationally leading in the application and development of high-performance steel in related fields; steel structure products, accessories and supporting technical products must reach international advanced levels. The focus is on the potential market and independent innovation technology development of steel structure housing, steel structure bridges and non-standard, complete equipment manufacturing (including new energy wind power, nuclear power, art grid, three-in-one, marine engineering steel structure network, etc.) which have large quantity and wide range and prominent output value proportion in the industry, promote the overall improvement of the quality of steel structure building construction, increase the service life and actual life of buildings to be more advanced, promote the improvement of related supporting products and components, and gradually make the steel structure industry a strategic emerging industry in my country, and initially achieve the goal of becoming a strong country in steel and steel structure.