In-depth analysis of Japan's experience in the development of construction industrialization

After the Second World War, there was a general shortage of housing in Japan. In order to solve the problem of "housing shortage", the Japanese government formulated a series of housing construction plans. Its planning specifications and implementation effects are worth learning.

The first stage .

From 1955 to 1964, new ways of living were popularized and community development began.

In order to solve the urgent problem of housing shortage at that time, large-scale collective housing construction began. With the progress of industrial technology, a series of construction methods (SPH, HPC) were formed in the 1950s and 1960s, which greatly improved the construction efficiency.

The second stage .

From 1965 to 1974, large-scale development and mass supply.

This period was a period of high economic growth in Japan, and a large number of people were concentrated in cities. Industrialized production has completed the construction quantity increased during the period of high economic growth and solved the shortage of labor force.

The third stage .

From 1975 to 1984, the residential environment was comprehensively developed to meet the diversified needs.

During this period, the trend of population concentration in large cities slowed down. It began to carry out diversified design according to the individual needs of society and regional environment. From the "standard parts for public housing" (KJ parts) system to the "good parts (BL) certification system".

The fourth stage .

From 1985 to 1994, it returned to the urban area from the community and built a comprehensive multi-functional new city.

During the economic bubble period in Japan, urban functions were readjusted, many large factories moved out of the city, and the number of super high-rise residential buildings with 30 to 50 stories increased rapidly in major cities. The structural form was pure frame structure or tube structure composed of beams and columns, without shear wall. The equipment is designed to eliminate the restriction of upper and lower floors by means of drainage on the same floor, so as to realize free residential division and indoor layout.

The fifth stage .

From 1995 to 2004, create the future city.

During this period, Japanese society entered the era of old age and low birth rate, and began to pay attention to the supporting facilities of old people's homes and kindergartens, and popularized universal design and barrier-free design.

The sixth stage .

Since 2005, it has moved from urban construction to urban regeneration.

The four fields of urban regeneration, residential environment regeneration, disaster recovery and suburban environment are put forward, and the policy of urban reconstruction is put forward.

SPH and NPS Standard Design

After 1950, Japan experienced a period of economic recovery after World War II and then entered a period of rapid growth. The shortage of housing is increasingly becoming a serious social problem in big cities. Due to the serious shortage of housing quantity, Japan has emerged and implemented a standard design scheme with government-led public housing and public group housing as the core, standardized standard design as the basis, and industrialized construction ideas, gradually forming the development of universal and standardized housing parts, which not only reduces production costs, but also improves the quality of housing.

With the further development of housing parts industry in the 1950s, it laid the foundation for the industrialization of housing supply. The standard design method based on the production mode of mass production has completed the construction quantity increased in the period of high economic growth, met the long-term shortage of housing construction, and solved the shortage of labor force.

SPH (Standard of Public Housing) based on large-scale PCa construction method was developed on the basis of effective utilization of large-scale PC version housing industrialization construction technology in the 1950s, and large-scale construction was carried out in Japan.

In 1964, the Housing Corporation established a mass production test site, developed the factory manufacturing technology of using horizontal steel formwork and steam curing, and began to vigorously promote the PCa construction method. In order to develop to high-rise buildings, the HPCa construction method of combining PCa plate with H-shaped steel (I-shaped steel) was also developed.

Industrialization of collective housing includes the componentization of each part that constitutes the whole house. Only through the integration of all the components of housing, can problem of rationalization of housing production be fundamentally solved.

As the number of housing tends to be saturated, in public housing, there are loose standard design methods such as NPS (New Planning System) diversification series. Japan has begun to explore ways to improve the quality of housing construction from various directions.

After the oil crisis, the era of mass construction was over and the SPH was replaced by the more flexible NPS. SPH is a standardized house type, while NPS is a design rule, which can not only maintain the effectiveness and production efficiency of PCa, but also fully respond to various specific requirements.

The NPS's standardized approach to public housing design, developed after the 1970s, provides important modular sizing rules. Revise the practice of national unification. From uniformity to diversification, from multi-quantification of single products to multi-variety of small quantities, this idea has continued to this day.

At the same time, the types of household types and the supply of household variability are promoted as the highlights of technology development. When designing, we should pay attention to the variability after occupancy and the renewal and interchangeability of equipment and residential parts.

Since the 1980s, great changes have taken place in the purpose and method of PCa construction method. Different from the pure shear wall PCa construction method, the PCa construction method of high-rise residential buildings is not a complete set of fixed construction method, but according to the time, place and the characteristics of the building, the specific construction methods of beams, columns, floors and other parts are selected.

The form of prefabricated parts is mostly semi-PCa, leaving the cast-in-place part is conducive to ensuring the integrity of the building. This is quite different from the production mode of pure shear wall with few varieties and large quantities.

Another feature is that the precast assembly method is not limited to reinforced concrete structures, but can also be used for steel reinforced concrete structures and prestressed concrete structures. At present, the prestressed assembly method (PCPCa method) has also been developed, which does not require connecting steel bars or steels between components, and ensures the strength and integrity of the structure through the prestress applied by steel cables.

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CHS Residence.

CHS (Century Housing System) was proposed and developed by the Ministry of Construction (now the Ministry of Land, Infrastructure and Transport) of Japan in 1980 as an important part of the "Development Project for Improving Residential Functions", and the "Recognition of Century Housing System" was started in 1988 and has continued to this day.

In addition, the "Centennial Housing Construction System Recognition Benchmark" has been formulated, which not only requires the design, structure and materials to achieve longevity, but also requires the planning of maintenance management and the establishment of a one-stop system from design, production, supply and after-sales service.

The Centennial Housing Construction System Identification Standard is mainly composed of six main points: the principle of variability, the principle of connection, the principle of independence and separation, the principle of durability, the principle of maintenance and inspection, and the principle of environmental protection. These principles play a very important leading role in defining the necessary performance of housing and promoting the longevity of housing.

CHS residential system attaches great importance to durability, emphasizes modular size rules and variability of component interchangeability, and sets interface rules according to the level of component service life. CHS residence is a kind of residence system which emphasizes the separation of main body, equipment and interior decoration, requires the maintenance of residence and the renewal of parts and equipment, and pursues the long-term use of residence.

SI residential system.

SI (Skeleton Infill) housing refers to a form of housing in which the skeleton is completely separated from the interior during the construction process, which can also be called variable housing, open housing and so on.

The framework of SI residential system mainly refers to the structural part of the residence, and the filling body mainly refers to the equipment pipeline and interior decoration. The external structure is made of high-durability materials, which can significantly prolong its service life; the internal filling bodies such as partition walls, various pipelines, floors, kitchens and bathrooms inside the house can be produced in factories and supplied on a large scale through standardization and serialization.

The building frame part of the SI residence is independently constructed, and the internal components are installed after factory production. This residential form minimizes the on-site manufacturing part of residential construction, and the reduced part is manufactured in the factory and installed only on site, which improves the construction efficiency of the whole residence, enhances the level of dry operation, and also realizes the changeable internal space. At the same time, it avoids the waste caused by the secondary decoration of traditional residential buildings, and can be changed with the change of household lifestyle and living habits.

Development process.

The development of components is closely related to the collective housing. The 1960s was the era of component development, the 1970s was the era of integration, and the 1980s was the era of serialization.

In the 1960s, the component manufacturers that began to mature were the main force to develop the components. In 1966, the Ministry of Construction of Japan pointed out in the "Industrialization Conception of Housing Construction" that in order to successfully achieve the five-year plan of housing construction, it is necessary to vigorously promote the industrialization of housing construction and realize the factory production of materials and components. In 1969, the Industrial Technology Institute of the Ministry of Construction of Japan began to implement the Five-Year Plan for Promoting the Standardization of the Housing Industry, and in the same year, the Five-Year Plan for Promoting the Standardization of the Housing Industry was formulated. Up to now, the product standards for industrialized and socialized production of various residential components (components, fittings, products and equipment) in Japan have been very complete, accounting for more than 80% of the total number of standards, and the size and function standards of components have also formed a system. Each manufacturer produces components and fittings and various standard products according to the standard, which can be used in the assembly of buildings.

The 70's was a period of change from quantity to quality in housing construction. The production and types of decoration and equipment components increased sharply, and the scale of components tended to be large-scale and integrated. Established in 1974, the certification system of excellent housing parts (BL parts) promotes the development of private enterprises by adopting private parts through the certification of their performance.

In the 1980s, with the improvement of the overall affluence of the society, the demand for housing and parts became more diversified, and the parts tended to be systematic and serialized, with an increase in types. The sales volume of unit bathroom has exceeded the sales volume of single bathtub, and now 100% of new residential buildings and 90% of single-family residential buildings adopt unit bathroom.

With the implementation of the Quality Assurance Law in 1999, not only the requirements for the quality of parts have been raised, but also the performance level must be clearly expressed. The focus of the market has shifted to the renovation of old houses, energy saving, environmental protection and meeting the adaptability of the elderly, which have become the new requirements for the development of parts. The development of digital technology has also put forward new requirements for multi-function and intellectualization.

Relevant policies .

(1) In 2009, the system of defect insurance for the sale of existing residential buildings and the system of performance expression of existing residential buildings were formulated, and the popularization of this system was promoted;

(2) In 2010, the circulation activation of existing residential buildings and other undertakings were implemented. In the sale of existing residential buildings, if the defect insurance for the sale of existing residential buildings is added and the resume information of residential buildings is registered, the subsidy for the inspection fee and the fortification fee for renovation and renovation can be obtained;

(3) In order to provide information related to the sale of existing residential buildings, real estate sales information was provided on the Internet in 2007, and information such as residential resumes can be logged in and consulted;

(4) In 2005, the special clause of tax reduction for residential loans was amended, and the policy coverage was expanded to existing residential buildings with certain seismic performance, regardless of the construction life.

Transformation technology .

① Energy-saving renovation of residential buildings: renovation carried out by owners to reduce energy consumption of residential buildings, such as replacing ordinary single-layer glass with double-layer glass.

② Transformation of barrier-free facilities of residential buildings: For the sake of the elderly and other residents with special needs, the residential buildings are transformed to facilitate the lives of the elderly, such as setting slopes at the steps, setting handrails, and transforming the common corridors, stairs and elevators into barrier-free facilities to facilitate access.

③ Disaster prevention and transformation of residential buildings: transformation of fire prevention, waterproofing and theft prevention of residential buildings.