In recent decades, the former Soviet Union, the United States and Japan have been the top three countries in the world in steel production, ranking first in the world in turn. Therefore, steel structures in these countries are booming. In the same period, China's development in this area is relatively slow and its level is relatively backward. In recent years, with the implementation and promotion of China's reform and opening-up policy, China's economic construction has made great progress. During this period, China's steel output jumped to the top in the world. From 65438 to 0996, the output of China steel exceeded 1 100 million tons for the first time; 1998 China's steel output has reached114.34 million tons, with an annual output increase of 3 million tons. The increase of steel output has created an excellent opportunity for the development of building steel structure construction in China. However, there are still obvious gaps between China and developed countries in many aspects. Therefore, in order to promote the further development and application of building steel structure in China, we urgently need to know the application of building steel structure abroad.

China's total construction steel accounts for about 20% ~ 25% of the total steel output, while developed countries account for more than 30%. For example, in the United States and Japan, this index has exceeded 50%. In China, steel is mainly used for building steel structures, steel bars for reinforced concrete, steel strands, steel wires, doors and windows, etc. Among them, steel for steel structure only accounts for about 65,438+00%. Of the 1 100 million tons of steel output in China, 2-3 million tons are actually used in steel structures.

According to some data on the distribution of American metal construction industry in the middle of 1998, the basic situation of the development and market of American metal construction industry is as follows: in 1950s, 1960s, 1970s, 1980s and 1990s, the annual sales in millions of dollars/annual processing capacity in tens of thousands of tons were 150/30, 300/65, respectively. 7、 10/5? 7 and 15/6.3. It can be seen that the annual sales of building metals in the United States have grown rapidly, and it is estimated that it has exceeded $2.5 billion at present, and the annual processing capacity has reached more than 2 million tons.

2, low-rise and multi-storey building steel structure and light steel structure

The main market distribution of metal buildings in the United States: industry (production workshops, warehouses and auxiliary facilities, etc. ), business (shopping malls, hotels, exhibition halls, hospitals, office buildings, etc. Community (private and public community activity centers and buildings such as schools, gymnasiums, libraries, churches, etc. ), and comprehensive aspects, accounting for 46%, 365,438+0% and 65,438 respectively.

In the United States, the use of steel structures in low-rise buildings is still very common. American Steel Structure Association and Metal Building Manufacturers Association (AISC and MBMA) have jointly compiled the design guide for low-rise buildings. The so-called low-rise buildings refer to industrial workshops, warehouses, offices and other office and community buildings with a floor height of less than 18m and no more than five floors, of which 70% are non-residential buildings with two floors or less.

In some developed countries, light steel buildings have been widely used in factories, warehouses, gymnasiums, exhibition halls and supermarkets. The so-called light steel refers to a relatively complete building system, that is, light steel structure system, which takes color steel plate as the roof and wall, thin-walled steel purlins and ring beams, welded H-shaped cross-section as the main beam, bolted or welded portal frames as the main structure on site, and then matched with parts, fasteners, doors and windows. The system is manufactured by the factory and assembled on site as required. It has the characteristics of light weight, short construction period, strong adaptability, beautiful appearance, low cost and easy maintenance. Because of its light weight, it also reduces the cost of foundation. Butler, BHP Billiton, ABC and other foreign light steel structure manufacturers have entered the China market. China enterprises should catch up and create conditions to actively develop their own light steel structure system to meet the requirements of the continuous development of building steel structure in China in the future.

3, high-rise and super high-rise steel structure

Due to the continuous improvement of human cultural life, the requirements for high-rise and long-span buildings are getting higher and higher. Steel structure itself has the unique advantages of light weight, high strength and fast construction speed, so it is very ideal to adopt steel structure for high-rise and long-span, especially for super-high-rise and super-long span. At present, the tallest and largest structures in the world are steel structures, and most of the venues in previous Olympic Games are steel structures. At present, several pure steel structures have been built in the world, which are the tallest super high-rise buildings in the world. They are:

Empire State Building in New York, USA, 102 floor, 38 1m high, built in1931(the tallest building before1969);

World Trade Center, New York, USA 1 10 Floor 4 17m high (north and south buildings);

Sears Tower in Chicago, USA, 1 10 floor, 443m high, built in1970;

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China197 Shanghai Jinmao Building, with 95 floors, has a building height of 42 1m and a structural height of 395m, ranking first in the world. If the Shanghai Pudong World Financial Center Building (95 floors, 460 meters) is completed, it will be the tallest in the world, which is really a great honor for our country. Shenzhen SEG Plaza Building is 279 meters high, with 70 floors in total. It is the tallest concrete-filled steel tubular super high-rise building in the world and another great honor of our country.

Mega-steel structure is a brand-new high-rise or super-high-rise building system to meet special functions or comprehensive functions. It has good architectural adaptability and potential high-efficiency structural performance, and is a very developed structure. For example, the 43-story NEC building in Chiba Prefecture, Japan, with a height of 180m and a large bay, has a large space courtyard inside, and its giant structure is a giant space truss system consisting of four giant structural columns and four giant space truss beams. Through analysis, the system has strong anti-push stiffness. Another example is the new commercial bank building built in Frankfurt 1997, Germany, with 63 floors and a height of 298.74m, which is also the tallest super high-rise building in Europe. The building plane is an equilateral triangle with a side length of 60m, and its structural system is a giant tube system. The three independent frame tubes at the apex of the triangle are "giant columns", which are connected by eight layers of steel frames to form a "giant beam". The overall effect and anti-push stiffness are excellent, and the "beam" has a huge "spiral hoop" effect. The third example is the proposed electric power intelligent building (DIB-200) in Japan, with a height of 800m, 200 floors above ground and 7 floors underground, with a total construction area of 65,438+500,000 m2, and consisting of 12 mega units. Each unit is a frame-tube column with a diameter of 50m and a height of 50 stories (200m), with 4 stories in 1 ~ 100, 3 stories in10/~150, and15/kloc-. The structure is equipped with an active control system, which further weakens the seismic response. HSBC also belongs to a huge steel structure building, which is Norman. Fuerte designed it.

4. Long-span steel structure

Most long spans or large spans are steel structures, and of course there are "membranes". However, due to some shortcomings, inflatable membranes are rarely used in recent years, and tension membranes also need the support of steel cables and steel rods.

Long-span steel structures are mostly used in multi-functional gymnasiums, exhibition centers, exhibition halls, waiting rooms and hangars. The earliest plane grid structure with the largest span was 9 1m× 122m (quadrangular pyramid) in the gymnasium of UCLA in 1960s. The largest double-layer reticulated shells are the Houston Cosmic Dome (diameter 196m) and the New Orleans Super Dome (diameter 207m), which were also built by the United States in 1970s. In 1990s, Nagoya, Japan built the world's largest single-layer reticulated shell with a building diameter of 229.6m and a structure diameter of 187.2m, and the joints are rigid joints that can bear axial force and bending moment. The largest indoor gymnasium in the world is the main gymnasium (quasi-elliptical plane, 186m×235m) of the United States 1996 Olympic Games. It adopts a tensegrity roof, which is mainly composed of cables, rods and membranes. This is a new type of space structure with great development prospect. 1993 Fukuoka Gymnasium, with a diameter of 222m, is the largest retractable steel roof at present, while 1989 Skydo me (with a diameter of 203m) built in Toronto, Canada has been reduced to the second retractable structure in the world. Roof structures above 300m are all made of steel plates and sections, which is not the optimal scheme. In recent years, hybrid structure, that is, the use of rods, cables and membranes together, has been successfully studied. The most typical example is the Millennium Dome at the turn of the century, which was built in June 1997. It took only one year to construct, and a capping ceremony was held in June. 1998. It is located in Greenwich on the south bank of the Thames in London, England, and it is the largest roof in the world today. The dome is as cool as a flying saucer. The dome with a diameter of 320 meters is suspended by 12 mast towers with a height of 100 meters, including the support of 100 meters (the tower itself is 90 meters) passing through steel cables with a total length of 70 kilometers, and the mast towers are arranged on a circle with a diameter of 200 meters ... The dome grid consists of 72 pairs of radial cables and 7 circumferential cables. The dome is 50m high, with a cable truss in the center and a ring with a diameter of 70m in the middle. It is covered with 144 huge white glass fiber cloth coated with Teflon. The total area of the project is 80,000 square meters and the total budget is 758 million pounds. An exhibition with the theme of "novel times" will be held in the museum to welcome the arrival of 2 1 century. There are 12 exhibition areas such as "Exploring the Human Body", "Time Classroom", "Window of Finance", "Miracle of the Earth" and "Looking into the Future" in the museum. Of course, in theory, it is also possible to realize a structure with a larger span. To this end, Japanese and American scholars and research units are conducting research. For example, in 1959, Fuller proposed to build a short-range reticulated shell with a diameter of 3.22km, covering the 23rd-59th block of new york, and the reticulated shell weighed 80,000 t. The Japanese Batu Iron Works once proposed a blueprint for reticulated shells with spans of 200m, 500m and 1000m, of which 500m was an all-weather multifunctional sports and entertainment hall,1000 m. Although whether this idea can be realized in reality needs further study, in terms of bridges, the span of about 1000m has been realized. The largest cable-stayed bridge in the world is Japan's Totoro Bridge, with a total length of 890 m; The largest suspension bridge is Shi Ming Bridge (199 1m) in Japan, and the longest span highway-rail bridge is Tsing Ma Bridge (suspension bridge 1377m) in Hong Kong. The earliest hyperbolic paraboloid cable-stayed roof in the world is the famous Raleigh Arena in America. In addition, all previous Olympic Games and World Expo can show the development level of steel structure. Such as 1972 Munich, Germany (cable-net complex covering 74800 m2 stadium), 1976 Montreal, Canada, 1980 Moscow, 1984 Los Angeles, 1988 Seoul, South Korea (120m diameter gymnasium 1992 St. George Stadium in Barcelona, Spain (128m), 1996 Georgia Dome in Atlanta, USA (186m×235m cable dome). In 2000, the main stadium in Sydney, Australia (1 10000 people, two hyperbolic parabolic reticulated shells of 220m×70m). Airports and hangars belong to long-span structures, and steel structures are basically used in engineering. For example, the Heathrow hangar in London, England (Phase I and Phase II) should be a relatively large-scale project. However, the Capital Hangar (2- 153m×90m) built in China in recent years adopts a three-story inclined quadrangular pyramid grid structure and a welded ball joint flat grid structure, which is one of the best in the world and is another great honor of China's steel structure. The steel roof of the airport is more colorful because of its high architectural requirements. Both Hong Kong Airport and Malaysia Airport use large-area single-layer reticulated shells. At present, a three-dimensional truss system with wavy surface, tree-like support and direct intersection of nodes is popular in the world and China. It looks magnificent and beautiful. China's Shenzhen Airport, Capital Airport and Shanghai Pudong Airport are typical examples.

5. Prospects and gaps of building steel structures in China.

From the experience of the United States, Japan and some developed countries in Europe, the construction industry will soon become the main market for steel applications. At present, there is still a gap in China. Therefore, China's high-rise building steel has been imported from abroad, especially the thick steel plate larger than 50mm, and the Z-direction performance of domestic products can not meet the requirements. In foreign countries, steel plates are not only thick, but also can meet various performance requirements. For example, Japan can produce 100mm thick steel plates as follows:

① There are 590N/mm2 (HT590) high-strength and low-preheating thick steel plates (preheated at 75℃ before, but now preheated at 50℃);

② Seismic thick steel plates mainly include high-strength steel with low yield ratio (HT 590 ~ HT 780 grade) and low yield point steel plates, which are mainly produced in Japan and used in secondary structures. When an earthquake occurs, this material first yields to ensure that the main structure can reduce earthquake losses;

③ Fireproof thick steel plate. There are 400N/mm2 and 490N/mm2, and the yield strength at 600℃ can reach 2/3 of that at room temperature.

④ Austenitic stainless steel plate and ferritic stainless steel plate for decoration (coastal use is better than the former).

At present, almost all domestic high-rise steel structures are imported from abroad, and the general project contracting is undertaken by foreign countries, while the manufacturing and installation are contracted by domestic cheap labor. This situation should be reversed as soon as possible, because it is not commensurate with China's status as a domestic steel power. Long-span steel structures are not as prominent as high-rise steel structures, but design schemes (including buildings and structures) often win the bid abroad. This situation is far from the call of the central government to establish our own scientific and technological innovation system, which should attract the attention of China's construction industry. Whether it is low level or other reasons deserves our deep consideration.