According to the CHINA country's "14th Five-Year Plan for National Economic and Social Development and Outline of Long-term Goals for 2035," it proposes to develop prefabricated buildings and steel structure residences. The Ministry of Housing and Urban-Rural Development has promoted prefabricated and upgraded steel structure residences—proportion in future housing. Prefabricated steel structure residences have the advantages of environmental protection and energy saving, green recycling, excellent wind and earthquake resistance, lightweight and high strength, and fast construction speed. They meet the country's needs to develop a green and circular economy. In economically developed countries such as the United States and Japan, prefabricated steel structure residences have been widely promoted after years of development.
Development of prefabricated steel structure housing
Although all walks of life in my country have been making continuous efforts to promote the development of prefabricated steel structure residences in recent years, due to the late start of prefabricated steel structure residences in my country, there is still a lot of room for improvement in the development of prefabricated steel structure residences. To accelerate the development of prefabricated steel structure residences in my country, the speed of residential development has essential reference value, as shown by drawing on the development of prefabricated steel structure residential buildings in developed countries.
1. Development of prefabricated steel structure housing abroad
The U.S. steel structure housing industry chain is complete, and the market is relatively total. U.S. steel structure housing mainly includes light steel structures, steel frame structures, steel and support structures, and steel frame hybrid structures. The assembly process is scientific and reasonable, the construction efficiency is high, and the steel structure accessories Have strong versatility and interchangeability. The design and construction focus on "people-oriented". The steel structure residence is comfortable and pays attention to low carbon, energy saving, and green environmental protection. As early as the late 1940s, the United States began to guide the construction of prefabricated housing. In the 1960s, it encouraged using lightweight and high-strength materials such as steel, aluminum, and wood in prefabricated housing and moved toward integration, standardization, and scale. Develop. In 2000, the United States clarified the green and sustainable development standards for prefabricated steel structure residences, guided the transformation and upgrading of prefabricated steel structure residences in a green direction, and provided preferential loans and taxes.
Japan's steel-framed houses have formed a relatively standardized building system through continuous development and improvement. The large-scale construction of steel structure housing in Japan began in the 1950s after World War II, and then developed rapidly. In 1981, Japan issued the “New Seismic Design Law”, and in 2001 and 2007, respectively, revised the “Construction Standards Law” and continuously improved the seismic standards of buildings. During the 90s Hanshin earthquake, Japan launched the “zero death” program, and better seismic lightweight materials and steel structure materials were widely used. After the Great Hanshin Earthquake in the 1990s, Japan put forward the “Zero Death” program, and lightweight materials and steel structure materials more resistant to earthquakes have been widely used. To enhance the quality of steel structure residential buildings and construction efficiency, Japan and industry organizations jointly promote the development of steel structure residential standards, the development of a series of steel structure residential fittings standardization, generalization and serialization of specifications and requirements, and inspection and certification system. Steel-framed residential buildings in Japan are mainly constructed by large-scale enterprises, which, in practice, continue to form independent intellectual property rights in terms of new construction technologies, new materials, and new techniques, providing intellectual support for the transformation and upgrading of residential buildings.
The development status of prefabricated steel structure housing of CHINA
The development history of steel structure housing in CHINA is not short, but its promotion and development are relatively slow. My country's earliest steel structure residence was the eight-story steel structure residence in Beicai, Shanghai, in 1994. In 2011, the Ministry of Housing and Urban-Rural Development organized the application for the "Double Hundred" Demonstration Science and Technology Plan for Green Buildings and Low-Energy Buildings. In 2013, the "Twelfth Five-Year Plan" was issued. "Green Building and Green Ecological Urban Development Plan," the plan clearly states, "accelerate the formation of industrialized building systems such as prefabricated concrete and steel structures" to adapt to the requirements of green economic development. In 2019, the Ministry of Housing and Urban-Rural Development proposed to promote the construction of steel-structure prefabricated housing and agreed to carry out pilot projects for steel-structure housing in Henan, Hunan, Shandong, Zhejiang, Jiangxi, and other provinces. At the same time, it identified 30 cities and 195 companies as prefabricated houses. It will serve as a model building city and industrial base as a demonstration project for pilot cities (districts).
Analysis of advantages and disadvantages of prefabricated steel structure residences
The SWOT analysis method is used to analyze the internal advantages and disadvantages of prefabricated steel structure residences and the external development opportunities and challenges they face. Through analysis, effective strategies are provided for developing prefabricated steel structure residences in my country.
1. Internal advantages
First, prefabricated steel structure residences have the advantages of synergistic efficiency in pollution reduction and energy conservation. In terms of pollution reduction, prefabricated steel structures and accessories can be prefabricated in the factory and installed on-site, which can significantly reduce construction waste, noise generated by construction operations, and on-site dust and other environmental pollution; in terms of energy conservation, steel structure building energy consumption It consumes less energy than concrete buildings, and the steel structure is easy to reinforce, reconstruct, Demolition can be recycled and reused, saving a lot of resources through recycling, and can also be converted into strategic reserves of steel. In terms of synergy, the high degree of industrialized production of steel structure parts and intelligent manufacturing make it possible to standardize, program-control, and automate steel structures. Speed up the construction progress, shorten the construction period, and improve production efficiency.
Second, steel frame structures have superior architectural performance. Steel structure residences have strong ductility, wind resistance, and earthquake resistance and can withstand typhoons. They are also suitable for the earthquake resistance systems of bottom-level, multi-story, and high-rise buildings. For example, the United States and Japan steel frame structures were used in the United States after the 1994 Northridge Earthquake, Southern Hyogo Prefecture, Japan, 1995. During the earthquake, it withstood the test of significant earthquakes. Because the design and installation of the steel frame and components' seismic performance are controllable, standard specifications can be used to design the steel components according to the earthquake magnitude, and professional experiments can be conducted to ensure that the seismic grade requirements are met. Thereby reducing earthquake hazards.
The third is to improve space utilization. Steel structure residences can be made into large-bay structures. Compared with reinforced concrete structures, the usable area can be increased by 6% to 8%. Under the exact location, the steel structure covers a relatively small area. The country of China has more people and less land. Resources are relatively scarce. Steel structure residences can reduce the area occupied in big, incredibly densely populated cities. The less occupied land area can be used for greening or building public leisure and entertainment venues in the community, thereby improving the living environment and building a "beautiful home.“
2. Internal disadvantages
The first is technical constraints. China's prefabricated steel structure housing started late and is technically immature. The thermal conductivity of steel structures is significant, and problems such as building thermal bridges are more prominent. Steel structures become soft when heated at high temperatures and are not fire-resistant. The high degree of assembly, excellent insulation, and fire-resistant performance of prefabricated steel structure exterior wall panels require further breakthroughs. At the same time, prefabricated steel structures in residential buildings are waterproof, energy-saving, corrosion-resistant, and fire-resistant. Penetration, sound insulation, and wall panel cracking require further study.
Secondly, the current cost is relatively high. The cost of prefabricated steel structures is slightly higher than that of concrete structures, about 200-500 yuan per square meter. It is difficult for steel structures to meet the national standard requirements for critical indicators such as exterior wall panel insulation, fire resistance, and heat insulation at a suitable price. The cost of exterior wall panels that meet national standards is too high, hindering the further promotion and use of steel structures.
Once again, there is a lack of talent. In my country's rapid development of steel structure housing, there will be an increasing demand for senior talents. Senior management talents with international vision are needed, and compound professionals and R&D talents with intelligent construction and construction expertise are also required. The cultivation of these high-level talents takes time. In addition to the lack of high-level talents, there is a relative shortage of construction personnel. Fewer and fewer people of the younger generation are willing to engage in the construction industry. The primary construction workers of the older generation are migrant workers and lack the professionalism required for steel structure housing.
3. External opportunities
First, there is strong support for national policies. At the policy level, the country strongly supports the development of prefabricated steel structures and buildings. The "14th Five-Year Plan" clearly proposes to "develop intelligent construction, promote prefabricated buildings and steel structure residences," and deploy pilot steel structure prefabricated residence construction. Sort out the steel structure construction technology system and increase the promotion and application publicity, organize and carry out the selection of prefabricated building demonstration projects, establish and improve a new model for quality and safety supervision of prefabricated construction projects, and help promote the promotion and application of steel structure buildings. Under the guidance of national policies, steel structure housing will usher in better development opportunities.
Second, using steel structures in residential buildings has broad application prospects. In developed countries, steel structure buildings account for more than 40% of the total construction volume. In CHINA, steel structure buildings account for only 5%-7%, and steel structure residences only account for about 1%. There is still huge market development space for steel structure buildings. The broad application prospects of steel structure residences have attracted the attention of upstream and downstream enterprises such as steel companies, steel structure companies, and real estate companies to the steel structure construction market. In 2011, Baosteel Group took the lead in establishing a technological innovation strategic alliance for the prefabricated civil steel structure construction industry, covering the entire industry chain of technology, research and development, construction, prefabricated parts production, and real estate development. Building the whole industry chain of steel structure housing has broken through the prefabricated. The standard and critical technical bottlenecks in the steel structure civil construction industry should accelerate the development and application of steel and steel structure products in the construction field.
Third, CHINA has the industrial foundation to develop steel structure housing vigorously. CHINA is the largest in steel production, with crude steel production in 2021 reaching 1.033 billion tons, accounting for more than 50% of world steel production. The rapid development of the steel industry, the industrialization technology of steel companies, and the well-trained workforce of steel companies have laid a solid foundation for the development of the steel structure industry. At the beginning of 2022, the Ministry of Industry and Information Technology, the National Development and Reform Commission, and the Ministry of Ecology and Environment jointly issued the "Guiding Opinions on Promoting the High-Quality Development of the Steel Industry," which will "promote green and low-carbon buildings, carry out pilot projects for the construction of steel structure residential and rural houses, and optimize steel structure building standards." The system, establish and improve the steel green design product evaluation system, guide the upgrading of steel used in downstream industries" as one of the important tasks, and promote the application of steel structures in residential buildings.
Fourthly, the scale of China's steel structure market and technology level have reached the international leading level. Statistics from the China Steel Structure Association show that during the “13th Five-Year Plan” period, the output of steel structures increased from 51 million tons to 89 million tons. It is predicted that the national steel structure processing volume will be around 97 million tons in 2021, with a year-on-year growth of about 8.9%, accounting for about 9.4% of the proportion of crude steel output. According to the China Steel Structure Association, it is expected that by the end of 2025, the national steel structure usage is targeted to reach about 140 million tons, accounting for more than 15% of the national crude steel production ratio; by 2035, China's steel structure output will get more than 200 million tons per year, accounting for more than 25% of the crude steel production ratio. Steel structure companies are located in all provinces and municipalities directly under the central government, and the scale of the industry ranks at the forefront in the world. During the epidemic in Wuhan, the construction of two designated hospitals, “Vulcan Mountain and Thunder Mountain”, which were constructed with assembled steel structure box-type houses, was completed in just more than 10 days, which shows that the technological level of China's steel structure has already entered into the advanced ranks in the world.
4. External threats
First, the market's acceptance of steel structure residences and residents' awareness of steel structure residences need to be improved. On the one hand, my country's steel structure housing is still in the pilot demonstration stage, and there is still some distance before large-scale market application and promotion. The market's acceptance of steel structures has yet to be tested. On the other hand, residents' acceptance of steel structure housing is low. , my country's residential structures are currently dominated by reinforced concrete, and residents have an insufficient understanding of steel structure residences. The survey results of rural residents in Henan show that rural residents have cognitive barriers to the quality and safety of prefabricated steel structure housing, and farmers are not very accepting of steel structure housing.
Second, young people in the "Z era" have high requirements for housing. Young people in the "Z era" are the new generation born after 1995. This group is the leading group of people buying houses. Unlike the older generation, the younger generation has different requirements for housing performance, quality, environmental protection, living environment, and location advantages. They and their neighbors in the community have higher standards, and those born in the 1970s and 1980s who have homes want to replace them with more comfortable, environmentally friendly, and beautiful homes. Therefore, steel structure residences must meet quality requirements such as beauty, durability, comfort, safety, green health, etc., to gain favor from the market.
Third, insufficient coordination exists across the entire upstream and downstream industrial chain. Iron and steel companies, real estate companies, steel structure companies, and raw material companies lack coordination and cooperation, making it difficult to form a highly consistent relationship in terms of design, research and development, manufacturing, processing, and assembly construction in the short term. Although driven by solid advocacy for the construction of steel structure residences, a large number of steel structure construction companies have emerged that design and build prefabricated steel structure residences, such as Yuanda Group, China Construction Group, etc., overall the scale of these companies is still relatively small. Small, the market has not yet formed a leading steel structure enterprise that can integrate the upstream and downstream industrial chains, and the large-scale market system needs to be further improved.
Development trend of prefabricated steel structure housing
1. The promotion and application of prefabricated steel structure residences will become a future trend
Under the dual-carbon background of "carbon peaking and carbon neutrality," traditional concrete residences with high energy consumption and pollution will be replaced by green, environmentally friendly, and energy-saving steel structure residences. The requirements for sustainable development of the ecological environment will make the "green buildings," known as "Prefabricated steel structure residences, have developed rapidly. The importance of prefabricated steel structure residences will become increasingly prominent, and the market share will also steadily increase. The industrial production of prefabricated steel structure residences, total life cycle carbon emissions, and the circular economy of steel structure residences Research will become an essential trend in future development.
2. Special steel research and technological research will become a trend
Applying fire-resistant and corrosion-resistant special steel in steel-structured residences can significantly improve residences' fire-proof and anti-corrosion capabilities and their ability to withstand high temperatures in extreme environments. However, special steel is expensive and cannot be promoted and applied. Therefore, it is necessary to strengthen research and technical research on steel structure thermal insulation, fire resistance, flame retardancy, waterproof corrosion, and wind and earthquake resistance, overcome construction and wall panel supporting technologies, develop unique steel materials with relatively reasonable prices and excellent quality, and develop integrated design and production, installation, and decoration are integrated into steel structure residences that are comfortable, environmentally friendly, thermally insulated, and have beautiful exterior facades. Meeting residents' requirements for improved housing is the main direction for development in the future.
3. Intelligence, digitization, and platform empower the intelligent construction of prefabricated steel structure residences
New-generation technologies such as intelligence, digitalization, networking, and platformization play an essential role in the entire life cycle of prefabricated steel structure residences. For example, Shenzhen City carries out artificial intelligence drawing reviews for buildings, significantly improving the reviews' quality. Applying artificial intelligence and big data technologies, such as industrial robots and intelligent assembly in construction, can reduce the large number of construction workers and improve the modernization level of enterprises. For example, the entire life cycle application of BIM technology in prefabricated steel structure residences has dramatically enhanced the informatization level of construction management. Intelligent digital platforms and other technologies with steel structures as the main body will provide new development momentum for the construction industry.
4. Reconstruct the entire industry chain system of steel, steel structure, and real estate industries
The upstream and downstream enterprises of prefabricated steel structure housing coordinate and interact to build a unified market, eliminate internal barriers, realize the customization of steel structure housing products, industrialize production, form a new model of the construction industry chain, and maximize overall benefits. The industrial concentration of my country's steel structure enterprises is not high. Under constant guidance, strong steel structure enterprises will enter the prefabricated housing market, integrate the upstream and downstream industrial chains, and form an independent enterprise with advantages in technology research and development, scale production, and independent development. A leading enterprise with innovation, capital, and brand advantages, it promotes technological upgrading and high-quality development of steel structure housing.
In summary, prefabricated steel structure residences will be widely promoted and applied in the future due to their advantages of environmental protection and energy saving, green recycling, excellent wind and earthquake resistance, lightweight and high strength, and fast construction speed. In the process of promotion and application, prefabricated steel structure housing will continue to innovate and develop. New methods, materials, artificial intelligence, digital technology, etc., will be continuously applied to engineering construction. Government departments, industry associations, and enterprises attach great importance to developing and promoting steel structure housing. Therefore, they must constantly improve relevant design, production specifications, and standard requirements, strengthen the promotion of the advantages of steel structure housing and the cultivation of talents, and guide the transformation of housing models. Upstream and downstream enterprises must coordinate and cooperate to reconstruct the entire industrial chain system, promote the development of steel structure housing, and meet the needs of green and low-carbon economic growth.
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