Keywords

1 Introduction

If a nation is to be rich and prosperous, the countryside must be revitalized. The rural revitalization strategy calls for promoting an integrated development of urban and rural areas, advancing the modernization of agriculture and rural areas, fully making a scientific and rational use of natural landscape resources, effectively protecting the ecological environment and governing and beautifying the rural living environment, so that the rural areas can become ecologically livable and beautiful.

Prefabricated and modular buildings are widely used around the world with the continuous improvement of ecological protection. An assembled building is a building made of prefabricated components assembled at a construction site [1]. Compared to traditional construction methods, prefabrication has changed the way buildings are produced, for it has many advantages including increasing productivity, improving quality, reducing on-site labor, waste and greenhouse gas emissions and saving energy [2, 3]. Studies have shown that the use of green concrete materials in the precast process can reduce total greenhouse gas emissions by 2.83–12.05% [4]. As a result, assembled buildings play a significant role in environmentally sustainable development [5].

2 Status of Assembly Building Development

Gradual scale-up of assembled buildings. In 2021, the floor area of China’s new assembled buildings was 740 million m2, accounting for about 24.5% in that of the total new buildings, achieving an increase of 18% over 2020. In Shanghai, Beijing, Hainan, Zhejiang, Jiangsu, Hunan, Tianjin, Shandong and Sichuan, the assembly type buildings accounted for more than 30% in their total buildings. The floor area of new assembled buildings throughout the country is increasing rapidly year by year, as shown in Fig. 1.

Fig. 1.
figure 1

Floor area of new assembled buildings nationwide, 2013–2021 (million m2)

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Assembly concrete structures and steel structures are developing rapidly. In 2021, 490 million m2 of assembled concrete structures were constructed, accounting for 67.7% of the new assembled buildings. 210 million m2 of steel structures were constructed, accounting for 28.8% of the new assembled buildings. The floor area of steel structure buildings was 210 million m2, accounting for 28.8% in the new assembled buildings. In 2021, the country's floor area of the new assembly steel structure buildings was 15.09 million m2, achieving an increase of 25% over the previous year. The new assembly building structure types in 2020 and 2021 are shown in Fig. 2.

Fig. 2.
figure 2

Structural Types of New Assembly Buildings in 2021 vs. 2020

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Standard specifications for assembled buildings are gradually being improved. Until now, 102 national standards have been issued, of which 38 are for general and concrete structures, 34 for steel structures and 30 for wood structures; 56 industry standards have been issued, of which 20 are for general and concrete structures, 30 for steel structures and 6 for wood structures.

The technology system is being continuously optimized. The technology systems of assembled concrete structures, steel structure residences, wood structures and so on have been better developed and applied. Assembled monolithic shear wall structures, frame structures, frame-shear wall structures and stacked shear wall structures, etc. are more and more frequently used in projects all over the world.

Industrial capacity continues to increase. In 2021, the designed capacity of assembled precast concrete components reached 240 million m3, 16.5% higher than that of the previous year. The design capacity of assembled steel structural components in 2021 reached 72.31 million tons, with an increase of 15.7% than the previous year. The capacity utilization reached 58.2%. The number of assembly component manufacturers from 2019 to 2021 is shown in Fig. 3.

Fig. 3.
figure 3

2019–2021 Number of Assembly Component Manufacturers

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Assembly renovation has been effective. Assembled decoration was 45.25 million m2 in 2019 and 71.87 million m2 in 2020, representing an increase of 58.7% over the previous year. The interior part system, the part R&D capability and the production quality have been significantly improved and assembled decoration was stepping into the fast lane of development.

Thus, with the implementation of rural revitalization strategy and “Dual carbon” work, our country's prefabricated building is developing rapidly.

3 Feasibility Analysis of Assembly Buildings in New Rural Construction

3.1 Advantages of Rural Assembly

The use of assembled buildings in rural construction helps to improve the quality of rural dwellings, raise the level of energy conservation and emission reduction, improve the appearance of farm buildings, speed up construction and improve living comfort.

The use of on-site wet work in the construction of assembled houses can effectively address the quality risks posed by the construction site, improve the quality of rural housing, reduce pollution to the environment, reduce the emission of construction waste and improve local energy conservation and emission reduction. Assembled buildings can fully utilize the local historical and humanistic characteristics, which can help to improve the rural landscapes and create the appearance of characteristic towns in the new period. Assembled buildings in rural areas can be more targeted to the reasonable design of the buildings, so that the buildings are better adapted to the rural environment and the layout can reflect more characteristics of the countryside and greatly improve the living comfort of rural housing.

3.2 Problems in the Application of Assembly Buildings in New Rural Construction

Industrialized thinking needs to be strengthened. The villagers have a low acceptance of prefabricated building. The assembled building has yet to be adopted on a large scale in rural areas and is not accepted by villagers.

The level of standardization needs to be further improved. Assembled buildings are designed using secondary disassembly, with arbitrary dimensions and a wide variety of types. The components can not be fixed after they are produced, the utilization rate of the production line is low and the amortization of the molds is high.

Capacity building of the teams needs to be improved. Few design organizations are experienced in assembly building design and even there are fewer assembly building construction organizations.

The cost of rural assembled building still needs to be reduced further. The production, transportation and technical level of the components are about 25% more expensive than traditional construction, which is beyond the reach of most villagers and hinders the large-scale and widespread application of rural assembled building.

3.3 Application of Assembly Buildings in New Rural Construction

Technology system of assembled farm house.The technology system of assembled house can be divided into precast reinforced concrete, light steel frame, cold-formed thin-wall steel system, new bamboo-wood structure system and EPS cavity module system [6].

Precast reinforced concrete structure is composed of precast reinforced concrete members of the building structure system. The prefabricated components of assembled farm house are large in size and weight, but their technical level is mature, construction efficiency is high, and the standardized repetition rate can reduce the cost.

The technology content of light steel frame structure assembling farm house is on the high side, and there are few enterprises that can carry out whole set production. The technical system is basically mature and the development space is large.

Cold-formed thin-wall steel (Keel) assembly type farm house needs skilled workers to install, building main body and poor flexibility of pipeline transformation. But it has the advantages of beautiful appearance, integrated decoration, thermal insulation, components are easy to transport, convenient construction and so on, has formed a large market size.The structure used in the construction of assembled passive houses in rural areas of our country is mainly steel structure system. Compared with the current national energy-saving design standard, the energy saving rate reaches more than 90% [7]. Under the influence of the background of China's vigorous promotion of rural revitalization, assembled passive houses have been better applied in China's rural areas and many areas in China have also carried out a series of research work on the construction technology related to assembled passive houses [8, 9].The assembled public rest rooms can shorten the construction period, reduce the construction waste, save the heating cost, reduce the electric energy consumption and have sound absorption function and good inflaming retarding effect. Most of the light steel materials are used to reduce the load bearing, which makes the whole assembled structure enhanced with flexible connection to achieve high seismic grade [10].

The new bamboo-wood structure system has good thermal insulation and seismic resistance, and is easy to transport and install on site. It is eco-friendly and carbon-recycled, so it is suitable for use in assembled building.In terms of structure and function, the bamboo assembled houses adopt light steel frame structures and bamboo bundle veneer composite materials as the enclosure structures and are equipped with solar-assisted power supply system and hydraulic control system for opening and closing the wall. Under the trend of “National Rural Revitalization Strategy”, bamboo and wooden assembled buildings will be very useful in the future in characteristic towns, temporary quick-fit rooms, public green buildings, etc. [11].

EPS Cavity Module Assembly type farmhouse is poor in fire resistance, durability and permeability, but its thermal insulation, seismic performance is good, convenient for construction, cost is reasonable, suitable for the construction of low-rise buildings.

Moreover, the development of assembled building in the construction of a new rural construction should be encouraged from the policy perspective to guide the development of rural housing along the road of Assembly, encourage enterprises and R & D personnel to continuously explore new technologies and new materials, to make assembly production more efficient and diversified, to strengthen the training of relevant professionals, and to provide enough talent reserve for the transformation from traditional extensive rural housing construction to assembly.

4 Concluding Remarks

By promoting the application of assembled buildings in the construction of rural revitalization, actively exploring livable model assembled farmhouses that are pleasing to villagers, modern in function, safe in structure and economical in cost and adopting assembled building technology to construct leisure farms, public rest rooms and other public service facilities for rural tourism, ecologically livable new buildings may be created, which can improve the living environment and the design and construction technology of farmhouses. They are green and may take the regional landscapes into account. Thereby a new pattern of rural revitalization can be established.

5 Fund Projects

Supported by youth project of science and technology research program of Chongqing Education Commission of China. (No. KJQN202303905).