According to the different load-bearing materials, the structure can be divided into reinforced concrete structure, steel structure, wood structure, masonry structure, steel-concrete composite structure and so on. Steel structure has the characteristics of light weight, high strength, good seismic performance, convenient industrial production, energy saving and environmental protection, and recycling. Steel structure buildings mainly use H-beam, cold-formed steel and other materials as the skeleton to make stress members, special bolts and other materials are bolted (welded), and color-coated plates or other materials with heat insulation, waterproof and sound insulation functions are used as the roof, floor and wall enclosure, so the factory is modular. Steel structure buildings can be roughly divided into high-rise and heavy steel structures, long-span spatial steel structures, light steel structures, steel-concrete composite structures, residential steel structures and other structural systems.
Steel structure has basic performance requirements for steel, such as strength, plasticity, toughness and weldability. The key nodes of more important structures also require thickness performance; From the seismic point of view, it needs a certain yield ratio (≤ 0.85); In order to prolong the service life of buildings and improve the fire resistance of buildings, steel can also be required to have corrosion resistance and fire resistance.
Steel is mainly used in steel structures.
1, high-rise and heavy steel structure
Heavy plate (extra-thick), H-beam, square rectangular tube, round tube, galvanized sheet, color-coated sheet, etc.
2. Long-span spatial structure
Round tube (seamless, welded), medium plate, square tube, H-beam, thick plate, galvanized plate, color-coated plate, steel strand, high-strength steel wire, steel bar, etc.
3. Light steel structure
Plate, H-beam (small and medium), galvanized sheet, color coated sheet, cold-formed steel, round tube, square tube, etc.
4. Combined structure
Large round tube (welded), H-beam, medium plate, square tube, galvanized plate, color-coated plate, etc.
5. Steel structure residence
H-beam, round tube (welded), medium plate, square tube, galvanized plate, color-coated plate, cold-formed steel, etc.
It also includes cast steel joints, high-strength bolts, studs, various welding materials (welding wire, covered electrode) and other supporting welding materials.
First, the foreign steel structure market and technical status quo
At the beginning of 20th century, light steel structure housing was born. During World War II, due to the need of high construction speed, light steel houses developed rapidly. The portal frame structure appeared in the 1940s. In 1950s, the steel structure residence with high degree of industrialization appeared, forming a factory steel structure residence building system, which continues to this day. In the 1960s, the industrialization of residential buildings spread all over Europe, and developed to developed countries such as the United States, Canada and Japan. The lightweight enclosure system consisting of colored pressed panels and cold-formed thin-walled purlins began to be widely used. Light steel structure is the main building structure form in developed countries.
The main reasons for the rapid development of foreign steel structure industry;
First of all, the iron and steel industry provides a rich material base for construction steel.
Secondly, the steel structure has the advantages of easy installation, short construction period, good seismic performance, quick investment recovery and less environmental pollution.
Third, the strict requirements of environmental protection and the full use of resources urge owners, architects and structural engineers to choose steel structures.
Fourthly, mature supporting technologies and products have promoted the development of steel structure industry.
The advanced steel industry in developed countries makes the variety and quality of steel materials fully meet the needs of steel structures, and rich steel resources provide material guarantee. The continuous development of new steel materials has promoted the technical progress of steel structure, which has led to the popularization of steel structure industry and the development of modern construction industry. In recent years, the amount of steel used in construction abroad accounts for about 30% of the total steel used, and it is still on the rise.
Some new building steel products developed by JFE Company;
1, ultra-thick H-beam, flange thickness can reach 100 ~ 120 mm.
2, composite stainless steel plate, SS400 or SM400 substrate composite SUS304.
3. High strength steel with low yield ratio, high strength steel with 600MPa grade or even 800MPa grade, with yield ratio less than 0.8.
4.800MPa grade high strength steel is widely used as bridge material, and the preheating temperature of 800MPa grade high strength steel with low preheating can be lower than 50℃.
5. New color-coated plates, such as: high corrosion resistance (used for outdoor equipment), high processability (good formability, used for building roofing materials), and "skeleton color" color plates for interior decoration (color sense, corrosion resistance, chemical corrosion resistance and lubricity have been greatly improved).
Second, the domestic steel structure market and technical status quo
High-rise steel structures: From the early 1980s to March 2003, 59 high-rise steel structures have been built and under construction in China, and the steel structures of high-rise buildings have entered the international ranks and achieved great success. Representative works include: Shanghai Jinmao Tower with a height of 420.5 meters, Shenzhen Seg Tower with a height of 29 1 meter, which has reached the international leading level, and Dalian World Trade Center with a height of 200 meters, which is made of domestic steel and designed, manufactured and constructed in China. At first, the main steel products of steel structure high-rise buildings in China were imported profiles or plates such as A572 and SM490B. In recent years, due to the increasing variety of steel products, satisfactory performance and low price, steel products are widely used in China, but Q420 and Q460 plates are still used for the import of key projects with high requirements.
Heavy industry workshop: in recent years, the construction has increased rapidly and the steel structure is large. Mainly distributed in steel, thermal power, shipbuilding, electronics, automobiles, machinery manufacturing and water conservancy construction industries. A typical example is the large-scale steelmaking and rolling workshop built by various iron and steel enterprises in recent years. In 2004, the completion area of heavy industry workshops such as metallurgical workshops was about 8 million ㎡, and the steel consumption reached 800,000 tons. Its steel technical requirements are the same as those of high-rise steel structures.
Spatial structure: In recent years, spatial structures represented by grids and reticulated shells have been applied not only to civil buildings, but also to industrial workshops such as tobacco industrial workshops and automobile assembly workshops, hangars, terminal buildings, gymnasiums, exhibition centers, theaters and museums. In recent years, long-span spatial structures such as terminal building, conference center, stadium, grand theatre and concert hall have been built one after another. Circular steel pipes and rectangular steel pipes are used to make space trusses, arches and cable-stayed grid structures, and corrugated roofs have become novel and modern landmark buildings everywhere. At present, the amount of suspension cable and membrane structure is not large, and it is still in the development stage. However, ETFE and PTFE membrane materials have been selected as the roof and wall venues for the 2008 Olympic Games, such as the National Stadium (Bird's Nest) and the National Aquatics Center (Water Cube).
Light steel structure: the steel consumption of light steel structure is generally about 40㎏/㎡ (excluding the amount of steel bars), and the structural types include portal frame and arched corrugated steel roof structure. In recent years, it has been rapidly developed and widely used in China. Mainly used in light industry workshops, grain and cotton warehouses, docks and bonded warehouses, agricultural products, building materials, furniture and other trading markets, stadiums, exhibition halls, mobile homes, storey-adding buildings and so on.
Steel-concrete composite structure: fully and reasonably combines the advantages of steel and concrete, has excellent static and dynamic working performance, saves a lot of steel, reduces project cost and speeds up construction progress. In different situations, it can replace reinforced concrete structures and steel structures, with little environmental pollution. This is a relatively novel structure, which conforms to the development direction of China building structure and can be widely popularized. Since 1980s, it has been widely used in metallurgy, shipbuilding, electric power, transportation and other departments. And enter the bridge engineering and high-rise and super-high-rise buildings.
Steel structure residence: construction industrialization, steel structure residence is in the primary stage of development in China. A large number of low-rise, multi-storey and high-rise steel structure residential pilot demonstration projects have been built in various places, which reflects the good momentum of steel structure residential development. In recent years, the pilot project of steel structure residence has been completed nearly 3 million square meters, and the steel consumption is about 6.5438+0.5 million tons.
Statistics of steel quantity for various steel structures in China (2004);
Special structural steel structure 6.1%; Hydropower construction 2.3%; Boiler steel structure 4.6%; Tower mast structure11.4%; Offshore platform1.5%; Railway and highway bridges 3.8%; Formwork and scaffolding19.8%; Heavy industry workshop 6.1%; Grid and reticulated shell 0.8%; Grid 0.5%; 3.4% for portal frame and light factory building; Arch corrugated steel and roof structure 0.3%; Residential steel structure1.1%; Urban construction steel is 38. 1%.
Proportion of steel consumed by domestic steel structures:
High frequency welding H-beam 0.3%; Hot rolled H-beam16.6%; Extra thick plate 2.2%; Color steel plate11.8%; Galvanized steel plate1.5%; Seamless and straight seam steel pipe 3.7%; Cold-formed steel 6.3%; Others (steel, etc. ) 13.3%; Medium plate 44.3%.
In 2004, the steel for steel structure in China was about13.5 million tons, accounting for 4.6% of the total steel output of 292.66 million tons. Domestic steel can basically meet the needs of steel structure processing, but there is still a gap compared with foreign countries in specific varieties, specifications and properties, such as high-strength large-size ultra-thick H-beam and high-strength ultra-thick plate, and the gap between high-grade products is still large.
Third, the current situation of domestic steel structure enterprises
China's steel structure industry has developed rapidly in recent years, and a number of large-scale steel structure processing enterprises have emerged. The total number of steel structure enterprises has grown to thousands. Among them, there are more than 10 with an annual production capacity of 5000 ~150 thousand tons; There are more than 10 enterprises whose equipment level, production technology and management ability are close to the international level. The design, drawing and lofting of these enterprises are basically completed by computers equipped with various special software, which can undertake the steel structure manufacturing of national projects in China. Such as long-span bridges, giant dams, high-rise and long-span building structures, etc. Under the market mechanism, a large number of small and medium-sized processing enterprises came into being. Although the annual production capacity is less than 1000 tons, these enterprises have their own advantages and specialties, which can make up for the shortcomings of large enterprises. In addition, with the entry of foreign capital and technical equipment into China, many Sino-foreign joint ventures, wholly-owned enterprises, private enterprises and joint-stock enterprises have emerged, and the development of steel structure industry in China is diversified in system, scale and processing direction. In 2005, the output of steel structure in China has reached150,000 tons, and the output value is about 120 billion yuan. However, at present, the steel structure industry is facing the following chaotic situation: the steel structure production capacity is far greater than the actual output, and many enterprises have insufficient tasks, which leads to a large gap between supply and demand, leading to vicious competition and mutual price suppression.
Important domestic steel structure enterprises (2004):
Zhong Tieshan Bridge Group; China No.22 Metallurgical Company; Shanghai Baoye Construction Co., Ltd.; COSCO Kawasaki Heavy Industry Steel Structure Co., Ltd.; Shanghai Guandaer Steel Structure Co., Ltd.; Jiangsu Huning Steel Machinery Co., Ltd.; Zhejiang Southeast Power Grid Group; China Railway Baoqiao Company Limited; Changjiang Seiko Steel Structure (Group) Co., Ltd.; Shandong Laigang Construction Co., Ltd.; Hangzhou dida net rack manufacturing co., ltd
The gap between China's steel structure industry and foreign countries: first, the concept is backward, and the understanding that the steel structure industry conforms to sustainable development needs to be improved; Second, the design concept is backward and cannot meet the market demand; Third, steel prices change too fast, prices rise and fall too much, market competition is disorderly, and corporate profits fluctuate greatly; Fourth, the investment in scientific research is insufficient, and the revision period of steel structure standards and codes is long; Fifth, steel structure processing, construction and installation equipment are relatively backward, and management and labor productivity need to be further improved.
Fourth, the analysis of the operation mode of domestic steel structure enterprises
Foreign-funded steel structure companies: Wholly foreign-funded steel structure companies have the characteristics of high reputation, abundant funds, advanced technology, well-known brands, excellent quality and high fees. These enterprises (such as Shanghai Meijian Steel Structure Company and Shanghai Butler Steel Structure Company) have accumulated more steel structure technologies, have greater comprehensive advantages, and have unique business and design software support systems. The market covers the whole country.
Business model: integration of design, processing and construction, in which Chongqing Iron and Steel Co., Ltd. mainly focuses on design and general contracting.
Market positioning: special buildings such as large factory buildings, multi-storey projects and large exhibition halls.
Large private steel structure company: well-funded, well-known brand, strong design and construction strength, good quality, market coverage throughout the country. Generally, branches are set up in various places and regions, and most of them have specific advantages in steel structure system (for example, Hangzhou, Zhejiang, Seiko of high-rise steel structure, and southeast grid structure).
Business model: integration of design, processing and construction.
Market positioning: all kinds of workshops, multi-storey projects, exhibition halls and other special buildings.
Small and medium-sized private steel structure companies: enterprises are flexible in operation, weak in overall strength and average in quality. The market scope is concentrated in their specific areas, and they rely on certain business relationships established with owners in the surrounding areas of enterprises to intervene in the market, with low production and operation costs. There are three types of business models:
One of the business models: mainly providing materials and processing. Market positioning: parts processing.
The second business model: integration of design, processing and construction. Market positioning: factory buildings and multi-storey projects.
The third business model: general contracting and design. Market positioning: various workshops, multi-storey projects, etc.
State-owned steel structure companies: generally large and medium-sized steel structure enterprises with wide market coverage (such as Baoye and China Construction System).
Business model: mainly providing materials, processing and engineering construction, with a large proportion of internal engineering.
Market positioning: heavy steel is the main industry, and there are many kinds of workshops and building structures.
Five, the elements of the development of domestic iron and steel enterprises:
First, it must be market-oriented and efficient. In the field of steel structure, a good brand and a certain network of owners and design institutes are the sources of obtaining projects. At the same time, enterprises must have strong ability of rapid response design, quotation and accurate cost and profit estimation (familiar with component processing, material supply, construction and installation, and able to grasp the cost and time limit).
Second, technology and product quality should have advantages. Excellent talents and excellent software and hardware equipment are the core technical advantages of steel structure enterprises, and relying on technical advantages to ensure the quality of scheme design, component production, construction and installation is the main magic weapon for the survival and development of steel structure enterprises (taking Hangxiao, Zhejiang Province as an example, the R&D Center Building was specially established to solve the housing problem of foreign talents, with advanced special processing equipment for heavy steel; Foreign steel structure companies have unique business software support systems).
Third, we should pay attention to the control of capital flow. At present, the advance payment of steel structure enterprises in China is serious, and the final withdrawal of project funds is a difficult problem, which is prone to problems in actual operation and capital flow. State-owned steel structure enterprises have both institutional and procedural problems in advance payment.
Fourth, we should establish a good company operating mechanism. Most state-owned steel structure enterprises have inflexible management mechanism, single property right structure, extensive management and a large number of employees, which greatly restricts the survival and development of enterprises. Only by implementing the market-oriented operation system can the rigid and slow-developing state-owned enterprises get out of the predicament.
The development of steel structure industry is related to the level and speed of economic development in China. The continuous emergence of new technologies and materials in the steel industry has laid a material and technical foundation for the rapid development of the steel structure industry. The national policy orientation has changed from saving and rational use of steel to encouraging the use of steel, which has provided a strong guarantee for the development of steel structure industry. Steel structure industry has gradually become an important industry in the national economy. In 2005, the total steel structure in China was150,000 tons. From now until 2020, the steel structure in China will grow at an annual rate of 6-7%. The steel structure industry is in the stage of development and growth, which belongs to the growing sunrise industry and has a good development prospect.
It is a common practice for large foreign companies to deeply process steel products, extend the industrial chain and increase the added value of products. For example, Thyssen uses its own raw materials to develop the auto parts industry; The new company has set up a building system department to produce parts for metal houses. Posco is mainly made of steel, and also involves civil construction, electronics, communication, semiconductor chip manufacturing, factory automation, energy and environmental protection. Nippon Steel covers electronics, engineering manufacturing, information and other fields. , has been widely recognized in the world. Therefore, it is necessary for large domestic steel mills to take advantage of their own building materials products to develop steel structure industry.