Comparative Analysis and Empirical Study of Prefabrication Rate Calculation Methods for Prefabricated Buildings in Various Provinces and Cities in China

Abstract

As an important part of the prefabricated building standard system, the evaluation standards for prefabricated buildings play an important guiding role in the construction and development of prefabricated buildings. However, at present, the national evaluation standards for prefabricated buildings are highly extensive and general, and some of their contents are not well considered, while local standards based on the national standard have been formulated in accordance with the actual situation in their respective regions, which makes the evaluation of prefabricated buildings in various regions more confusing, which also causes differences when calculating the prefabrication rate, restricting the development of prefabricated buildings. In order to promote the construction of a complete evaluation standard system for prefabricated buildings in China, this paper combs through the methods used for the calculation of the prefabrication rate of prefabricated buildings in 28 provincial-level administrative regions in China, conducts a comparative analysis and empirical research on the calculation of the prefabrication rate under different standards in four dimensions, and applies t-tests and simulated annealing algorithms to optimize the projection pursuit model to analyze the differences in the total scores of the prefabrication rate under different standards, as well as the key factors that affect them. The study shows that (1) the same building may have different prefabrication rates under different standards for prefabricated buildings, and the way of calculating the prefabrication rate and the scoring criteria of the evaluation items will result in significant differences in the calculated prefabrication rate. (2) Depending on the value of the optimal projection direction vector, it was found that among the evaluation criteria, the enclosure wall and the internal partition wall have the greatest influence on the total score value, while the main structure has the least influence on the total score value. (3) There are similarities as well as differences in the evaluation criteria of prefabricated buildings in each province. On this basis, by analyzing the reasons for these differences, corresponding suggestions are made for governments needing to formulate or revise local standards.

1. Introduction

1.1. Background of the Study

With the current increasingly serious resource consumption and environmental pollution, energy conservation and emissions reduction have become important issues in international and domestic societies [1]. Data from the China Building Energy Consumption Research Report (2022) show that in 2020, the total energy consumption for building and construction was 2.27 billion tce nationally, accounting for 45.5% of the total national energy consumption, and the total carbon emissions for the entire process of construction was 5.08 billion tCO2 nationally, accounting for 50.9% of the national carbon emissions [2]. As an industry with high energy consumption and high emissions, accelerating the transformation and sustainable development of the construction industry has become an inevitable trend for the development of the construction industry [3]. The climate issue has also become the most critical topic in the world in recent years, especially after the Paris Agreement came into effect in 2016 [4] and the double carbon target proposed by China at the United Nations General Assembly in 2020 [5]. Compared with traditional cast-in-place buildings, prefabricated buildings have many advantages such as high efficiency, short construction period, controllable quality, environmental protection, reduced labor, etc. [6]; moreover, with their advantages of factory production and assembly, prefabricated buildings have become an important way of achieving sustainable development and low-carbon green transformation in the construction industry, and are also a key link to achieving high-quality development of the construction industry [7]. The 14th Five-Year Plan for the Development of the Construction Industry clearly proposes that the proportion of prefabricated buildings among new buildings is to reach more than 30% by 2025. Therefore, prefabricated buildings have become a trend in the development of the construction industry and are a key factor in realizing sustainable building development [8].

1.2. Literature Review

1.2.1. Prefabricated Buildings

The development of prefabricated buildings started earlier in other countries, and the technical systems supporting the production of prefabricated buildings have been perfected to a greater degree. German prefabricated buildings originated in the middle of the 19th century, and a large number of multi-story assembled residential buildings were established in Germany after World War II [9]. German prefabricated buildings represent a high-standard, high-quality, commercialized assembled housing construction system, conforming to the DIN system in terms of design, thus promoting the modularization and standardization of German residential components [10], and the AB system in terms of construction technology, with construction methods including block structure technology, guide rod rising plate structure technology, and prefabricated building technology [11], while the assessment standards mainly consist of the DGNB assessment system, which focuses on energy saving, environmental protection, and the sustainable use of buildings [12]. In recent years, Germany has vigorously developed zero-energy passive buildings and is the country with the most rapidly decreasing energy consumption from buildings [13]. France is among the countries, globally, that promoted the application of prefabricated buildings earlier, and French prefabricated buildings are mainly made of concrete structures, supplemented by steel and wood structures, with the most commonly applied and technologically mature technical system being the Sequence system [14]. This system avoids complicated construction processes such as pre-burial and welding, has the characteristics of fast construction, low cost, and low environmental pollution, and has wide adaptability for application in general industrial buildings [15]. There are a wide variety of codes and standards for prefabricated building design in the United States, including the PCI Design Manual, IBC 2006, ACI 1318-05, ASCE 7-05, etc. [16]. Prefabricated buildings in large cities in the United States are mainly concrete and steel structures with highly standardized and commercialized components and parts, which are highly versatile; the suburban areas of cities and towns are dominated by light steel and wood building systems [17]. In recent years, the main research direction of prefabricated buildings in the United States has been towards green and low-carbon energy-saving assembly technology [18]. In summary, the development of foreign prefabricated buildings is more mature; in particular, structural technology is more advanced. Compared with developed countries, the development of prefabricated buildings in China started slowly, the technology related to prefabricated buildings is relatively backward, and the industrial chain and evaluation standards for buildings are not perfect [19], so it is extremely important to improve the level of assembly technology in China and cultivate a perfect and mature assembly industry chain by conducting research on prefabricated buildings.

1.2.2. Evaluation Criteria for Prefabricated Buildings

An important part of standard systems for prefabricated buildings is the evaluation standard, which is used to evaluate buildings’ degree of prefabrication. The evaluation of prefabricated buildings is not only a grade certification of the prefabricated building, but can also play a guiding and direction-giving role in the development of the construction of prefabricated buildings. The evaluation standard for prefabricated buildings is an important guarantee in promoting the healthy development of prefabricated buildings and realizing the industrial production of buildings, so the establishment of a scientifically valid and well performing evaluation system for prefabricated buildings is especially important. The evaluation systems used for foreign prefabricated buildings are better developed, with Germany adopting the national standard DGNB to evaluate prefabricated buildings, which contains 10 thematic areas: ecological quality, environmental quality, energy-saving quality, economic quality, functional quality, social quality, design and planning quality, technical quality, engineering quality and base quality. The degree of compliance with the standard is calculated through scoring, and the degree of compliance not only reflects the compliance of prefabricated buildings, but also serves as the basis for the economic design of building energy efficiency and sustainability programs. The evaluation system employed for industrially produced buildings in Japan is more complete and mature, and evaluates the construction technology, economic benefits, social benefits, environmental benefits and use functions in a comprehensive manner [20]. The U.S. Department of Housing and Urban Development (UHD) promulgated the National Manufactured Housing Construction and Safety Standards (NHMCS), which regulated this industry [21]. Singapore’s prefabricated buildings do not emphasize prefabrication rate, but focus on ease of construction, and the national standard Code of Practice on Build ability was promulgated, which applies a “building ease of construction score” to buildings with total floor areas of 2000 m² or more, where ease of construction refers to the degree to which the design of a building is conducive to construction, and the level at which the technologies and methods used affect construction productivity [22]. Thus, it can be seen that foreign evaluation criteria for assembly do not deliberately pursue high or low prefabrication rates, but mainly focus on quality, green credentials, environmental protection, and energy efficiency, mainly because, in foreign countries, no subsidies are received for the use of assembly construction [23].

China’s evaluation standards for prefabricated buildings developed late, and in 2015 the Ministry of Housing and Construction officially released the Industrialized Building Evaluation Standards (GB/T51129-2015) [24], which for the first time put forward the concepts of “industrialized building” and “prefabrication rate”, and the concept of “precast rate” was introduced for the first time; the evaluation system and method of assembly were clarified, thus promoting the development of the industrialization of China’s construction [25]. The precast rate refers to the ratio of the volume of concrete used in the prefabricated part to the total concrete used in the corresponding part in the main structure and envelope above the outdoor footprint of the industrialized building; the prefabrication rate refers to the ratio of the number (or area) of prefabricated components and building parts in the prefabricated building to the total number (or area) of similar components or parts. In order to accommodate the development of prefabricated buildings, the Ministry of Housing and Urban–Rural Development promulgated the Evaluation Standard for Prefabricated Buildings (GB/T51129-2017) (hereinafter referred to as the Housing and Construction Standard) in 2017 [26], which established prefabrication rate as the only index for evaluating the degree of prefabrication of civil buildings, and the prefabrication rate was withdrawn from the evaluation system in the national standard, while the Industrialized Building Evaluation Standard was also abolished [27]. As an important part of the evaluation criteria for prefabricated buildings, the prefabrication rate is of great significance in the construction industry. A high prefabrication rate means that more components and modules are prefabricated in the factory, thus reducing waste on site, reducing construction time and labor costs on site, and avoiding risks and accidents on site, while the prefabricated assembly process is usually more standardized and precise, and can provide more consistent product quality. Although the Housing and Construction Standard regulates the measurement of different degrees of assembly of prefabricated buildings across the country, the development of prefabricated buildings is uneven across China [28], and the national standard does not differentiate between different structural systems, different regions, and different component forms without making mandatory requirements, making it difficult to apply the national standard uniformly in all regions and increasing the difficulty of promoting its application [29]. At the same time, taking into account the geographical characteristics of each province, climate and economic development inconsistencies, local standards based on the national standard have been developed to meet the regional reality [30]. However, this has resulted in confusion regarding the evaluation of prefabricated buildings in each region, and the prefabrication rate, as an important part of the evaluation criteria for prefabricated buildings, is calculated differently in each standard, which to some extent restricts the development of prefabricated buildings in China [31].

1.3. Main Contributions

In summary, in order to solve the current problems related to evaluation standards for prefabricated buildings, it is necessary to understand the development level and potential of each province with respect to prefabricated building evaluation, and to build a complete prefabricated building evaluation standard system in China with the aim of promoting the development of prefabricated buildings. In this paper, we consider the assembly evaluation standards of 28 provincial-level administrative regions (excluding Hong Kong, Macao and Taiwan, while Tibet, Qinghai and Inner Mongolia have not introduced relevant policies at the present time), and perform a comparative analysis of the prefabrication rate calculation using each evaluation standard on the basis of four dimensions (the main structure, the enclosure walls and internal partition walls, the decoration and equipment pipelines, and extra credit), analyze the reasons for the differences in the prefabrication rates calculated under different standards, and combine this knowledge with practical cases to conduct empirical research. The main contributions of this paper are as follows: (1) At present, scholars have performed little research into and interpretation of the evaluation standards for prefabricated buildings, while the evaluation standards for prefabricated buildings play an important guiding role in the construction and development of prefabricated buildings, and it is therefore crucial to perform research on them. (2) The research object in this paper constitutes all of the provincial administrative regions in China that have already introduced policies, and at the same time, the evaluation covers all of the contents of those regions’ evaluation standards for prefabricated buildings, making the analysis results comprehensive and integrated. (3) This paper combines this with empirical research of actual cases, and analyzes the differences between the evaluation standards for prefabricated building from a practical point of view, thus giving the research in this paper practical significance.

2. Comparative Analysis of Prefabrication Rate

In order to promote the development of prefabricated buildings and standardize the evaluation of prefabricated buildings, provinces have one after another developed regional evaluation standards for prefabricated buildings [32]. Assembly evaluation criteria are the basis for evaluating the degree of prefabrication of buildings, and are the main basis of government encouragement and support for the development of prefabricated buildings. Each province’s evaluation criteria for prefabricated buildings define whether a building can be considered a prefabricated building by limiting the range of acceptable scores for the decoration and prefabrication rate, with the evaluated level of a building’s prefabrication being determined by the prefabrication rate value [33]. The prefabrication rate, as an important index in evaluation systems for prefabricated buildings, can be calculated using different methods, leading to differences in the resulting prefabrication rate. One method evaluates the prefabrication rate on the basis of the proportion of prefabricated components in terms of weight, while another method uses the proportion of the installed area accounted for by prefabricated components as a measure [34]. In addition, the prefabrication rate is defined in the Evaluation Criteria for Prefabricated buildings (GB/T51129-2017): it is the total proportion of the main structure, enclosure walls and internal partitions, and decoration and equipment piping above the outdoor floor level of a single building that consists of prefabricated components. Due to there being different evaluation standards for prefabricated buildings in each province, the national standard and the provincial standards highly confusing, and the lack of systematic and insufficient coordination among the standards in the different provinces causes the calculation methods for prefabrication rate and their results to also differ. In addition, the traditional construction assembly thinking in the industry mostly equates the promotion of the process of building industrialization with increasing the prefabrication rate of component factories [35]. Therefore, in order to solve the current problems related to the evaluation standards for prefabricated buildings, so that governments around the world can formulate local standards that are more in line with the level of regional development, in this paper, the methods for calculating the prefabrication rate in the evaluation standards employed in each province are compared and analyzed, along with their impact on the evaluation results of prefabricated buildings.

2.1. Evaluation Method in the Housing and Construction Standard

The Evaluation Standard for Prefabricated Buildings (GB/T51129-2017) takes the prefabrication rate as the final assessment index for prefabricated buildings, and the evaluation system is divided into three dimensions: the main structure, the enclosure walls and internal partitions, and the decoration and equipment piping, and the calculation method used to determine the prefabrication rate is given based on these three dimensions. By analyzing the evaluation system in this standard, it can be seen that “prefabricated components, non-masonry, integration and full decoration” are the main components of the evaluation criteria in the national standard. Although the national standard specifies general directions for the evaluation standards for prefabricated buildings, it is a rough standard with broad and general provisions, and the development of prefabricated buildings in different provinces is not balanced, so it is difficult to apply the national standard uniformly, and some of the contents of the national standard are not well considered, making its promotion and application more difficult.

2.2. Comparative Analysis of Prefabrication Rate Calculation in Different Provinces

The development of local standards in each province based on the national standard needs to take into account many influencing factors, such as economic, climatic and geological characteristics. In terms of the economy, there are differences in the level of economic development among Chinese provinces, and the level of development of prefabricated buildings is higher in provinces with more extensive economic development, such as Jiangsu Province, Zhejiang Province, and Beijing [36]. In terms of climate, due to the vast size of China, each province in the country can be considered to belong to one of five climate zones: severe cold, cold, hot summer and cold winter, hot summer and warm winter, and mild, and different climate zones will result in there being differences in the focus of prefabrication evaluation criteria, which will focus on building insulation in severe cold regions and more on building energy consumption in hot summer and warm winter regions in the east [37]. Geologically, China is located between the Pacific seismic zone and the Eurasian seismic zone, and is extruded by the Pacific plate, the Indian plate, and the Philippine plate, with very active seismic fault zones; therefore, provinces located on the seismic zone may focus on the bearing capacity of buildings and the application of seismic reduction and seismic protection technologies [38]. From the above analysis, it is clear that there are differences among the evaluation criteria for prefabricated buildings employed in different provinces as a result of numerous and complex influencing factors. However, in order to build a complete evaluation system for prefabricated buildings and promote the development of prefabricated buildings in China, it is crucial to address the assembly evaluation system and compare the building prefabrication rates in each province. In this paper, the method for calculating the prefabrication rate of prefabricated buildings is mainly derived from existing management methods for calculating prefabrication rates at the provincial level. By reviewing the prefabrication rate calculations in 28 provincial-level administrative regions (excluding Hong Kong, Macao and Taiwan, while Tibet, Qinghai and Inner Mongolia have not yet issued relevant policies), we summarize and evaluate the consistent methods for calculating the prefabrication rate on this basis; the results are shown in

Table 1. Prefabrication rate calculation summary table.

Serial Number	Computing System	Prefabrication Rate Calculation	Source of Information
1	Scoring Method	$P=\frac{Q_1+Q_2+Q_3}{100-Q_4}$	National Standards
2		$P=\frac{Q_1+Q_2+Q_3}{100-Q_4}+\left(\frac{Q_5}{100}\right)$	Beijing, Jilin Province, Heilongjiang Province, Ningxia Hui Autonomous Region, Gansu Province, Xinjiang Uygur Autonomous Region, Yunnan Province, Guizhou Province, Guangxi Province, Henan Province, Anhui Province, Jiangxi Province, Guangdong Province
3		$P=\frac{Q_1+Q_2+Q_3+Q_5}{100-Q_4}$	Zhejiang Province, Liaoning Province, Tianjin City, Hebei Province, Hubei Province, Shanxi Province, Shaanxi Province, Shandong Province, Hunan Province, Hainan Province, Chongqing City
4		$P=\frac{Q_1+Q_2+Q_3+Q_5}{100}$	Sichuan Province, Fujian Province
5	Weighting Method	$Z={\alpha }_1{Z}_1+{\alpha }_2{Z}_2+{\alpha }_3{Z}_3$	Jiangsu Province
6		$\begin{array}{l}\mathrm{Building} \mathrm{prefabrication} \mathrm{ratio}=\mathrm{Precast} \mathrm{ratio}+\\ \mathrm{Interior} \mathrm{weighting} \mathrm{factor}\times \\ {\displaystyle \sum \left[\mathrm{Interior} \mathrm{parts} \left(\mathrm{technology}\right) \mathrm{correction} \mathrm{factor}\right.}\\ \times \left.\mathrm{Interior} \mathrm{parts} \left(\mathrm{technology}\right) \mathrm{correction} \mathrm{ratio}\right]\end{array}$	Shanghai, China
7		$\begin{array}{l}\mathrm{Building} \mathrm{prefabrication} \mathrm{ratio}=\mathrm{Precast} \mathrm{ratio}\\ +C\mathrm{omponent} \mathrm{prefabrication} \mathrm{ratio} \\ +\mathrm{Additional} \mathrm{industrialization} \mathrm{technology}\end{array}$	Zhuhai, China

Notes: P in the formula represents the prefabrication rate; Q₁, Q₂, Q₃ represent the score values of main structure, envelope and internal partition wall, and decoration and equipment piping, respectively; Q₄ represents the total score of the evaluation items missing from the project; Q₅ represents the score value for extra credit. For the prefabrication rate, Z₁, Z₂ and Z₃ represent the proportion of prefabricated components in the main structure, the wall area of the envelope and internal partition wall components, and the horizontal projection area of the industrialized internal parts, respectively; α₁, α₂ and α₃ represent their weight coefficients, respectively. pi represents the prefabrication rate value of components, ai represents the weight of components, and Si the proportion of the same type of prefabricated components and their degree of prefabrication. () indicates extra credit that may be excluded from the calculation depending on provincial regulations.

below.

From Table 1, it can be seen that the calculated prefabrication rate results are determined using the method for calculating the prefabrication rate on the basis of the score for each evaluation item. For example, category 1 does not specify additional points for buildings, and categories 2, 3, and 4 have different evaluation items for the numerator and denominator of the prefabrication rate calculation. Different categories can lead to differences in the calculation of the prefabrication rate for the same prefabricated building due to the different calculation methods. However, methods can be divided, on the basis of their calculation method, into scoring methods and weighting methods. Calculation categories 1–4 in the table are scoring methods, which involve the scoring of each evaluation item in the evaluation criteria to calculate the prefabrication rate according to the calculation formula. Categories 5–7 in the table are weighting methods. Weighting methods calculate the prefabrication rate by multiplying the application rate of each part of the evaluation criteria by the weighting coefficient. When applying a scoring method, the evaluation criteria for the prefabricated building will set a minimum score for the evaluation items, thus making them somewhat mandatory. When applying a weighting method, there is no restriction on the minimum score, thus weakening the boundary between the evaluation items and promoting the integrated development of prefabricated buildings. In summary, the different ways of calculating the prefabrication rate will have a direct impact on the calculation results of the prefabrication rate, which is one of the reasons for the great deal of confusion with respect to the standards.

2.3. Comparative Analysis of Evaluation Standards for Prefabricated Buildings in Different Provinces

The results of calculating the prefabrication rate under the different calculation methods selected for prefabricated buildings, i.e., the scoring rules of the scoring method and the weight distribution of the weighting method, are mainly determined by the score values for each of the evaluation items. The evaluation criteria for prefabricated buildings in each province are divided into four main dimensions according to the components being evaluated: the main structure, the enclosure walls and internal partitions, the decoration and equipment piping, and extra credit. In order to investigate the influence of the score values of the various evaluation criteria on the calculation results of prefabrication rate, in this paper, the prefabrication evaluation criteria used in different provinces adopting the weighting method and the scoring method are compared in four dimensions—the main structure, the envelope and internal partition walls, decoration and equipment piping, and extra credit—in order to analyze the differences between the criteria while identifying the reasons for such differences. Since there are many provinces that employ calculation methods 2–4, Beijing, Zhejiang Province and Sichuan Province are selected as representative provinces for analysis in this paper.

2.3.1. Comparative Analysis of Evaluation Methods for the Main Structure

The main structure ensures the stability and safety of the building structure, and the main structure score accounts for a large proportion of the total score in the evaluation criteria for prefabricated buildings, while different methods for evaluating the main structure make differences in the scoring value of the main structure, which will have a direct and significant impact on the resulting prefabrication rate; therefore, it is important to consider the evaluation methods of the main structure, and analyzing the differences that exist in the results obtained for the main structure using different standards is extremely important [39]. When scoring methods are used to calculate the score of the main structure, the corresponding evaluation criteria set specific scores for the types of components included in the main structure and other related requirements. Evaluation criteria that employ weighting methods do not set specific scores for the calculation of the score for the main structure, but assign different weights to different types of components incorporated in the main structure. In order to further analyze the similarities and differences among the scoring rules and the weights assigned to each evaluation criterion, the distribution of scores and weights was drawn as shown in Figure 1.

From Figure 1, it can be seen that the standards in the horizontal components do not have set refinement items in common; the differences are mainly reflected in the setting of each item and the score of the evaluation for the main structure. The reason for this difference is that it is necessary for the evaluation of each standard item to consider various starting points. For example, the Zhejiang Standard sets refinement items for vertical members according to the characteristics of prefabricated members with a high design difficulty and a low tolerance rate; the Fujian Standard takes into account that Fujian is in the Pacific seismic zone, with higher frequency and probability of earthquakes, and the standardization of the prefabricated members belonging to the main structure will have an impact on the bearing capacity of the prefabricated members as well as structural stresses; therefore, horizontal members have higher scores. The evaluation items include the standardization, generalization and application of seismic protection technology.

From Figure 2, it can be concluded that there are differences in the scope of the main structural components, the classification method, and the corresponding weights of different categories, which are mainly caused by the different focus of each standard with respect to the components. From the weights assigned, it can be seen that the Jiangsu Standard and Shanghai Standard focus on the prefabrication of vertical elements, while the Zhuhai Standard focuses more on the application of floating windows, air conditioning panels and other elements, in consideration of the fact that the use of floating windows and other elements will expand the space and increase the actual usable area of consumers, thus promoting the sales of buildings.

2.3.2. Comparative Analysis of Enclosure Walls and Internal Partition Walls

As an important component of the structural system in prefabricated buildings, enclosure walls and internal partition walls can improve the safety and overall performance of buildings, and they account for a large proportion in prefabricated buildings, and the scoring values of enclosure walls and internal partition walls should not be neglected [40]. For enclosure walls and internal partition walls, the evaluation criteria for the scoring method set specific scores for enclosure walls and internal partition walls and their corresponding integration, while weighting methods exhibit large differences in the calculation of enclosure wall and internal partition wall scores, as shown in Figure 3 and Figure 4.

On the basis of Figure 3, it can be concluded that there are common features in the setting of the enclosure wall and internal partition wall, as well as the total score for each standard, and there are differences in the setting of the integration of technology into the enclosure wall and internal partition wall, which is mainly due to the differences in the level of economic development and the maturity of the technology processes in each region. The production cost of the factory integration of the decorative layer of the enclosure wall and the accuracy of the on-site construction in the region are necessarily high, and the integration of heat insulation into the internal partition wall rejects the score of rough rooms, but rough rooms are still the main sales channel in third- and fourth-tier cities; therefore, the Zhejiang Standard and Fujian Standard take into account the actual situation of the region in order to set refinements for the integrated technology in order to increase the promotion of prefabricated buildings.

From Figure 4, it can be seen that the calculation method and the calculation range of the weighting method are slightly different for each evaluation standard of the enclosure wall and the internal partition wall. In the calculation method employed in the Jiangsu Standard, the sum of the area of prefabricated enclosure and internal partition wall is compared with the total area accounted for by enclosure and internal partition wall, while in the Shanghai Standard and the Zhuhai Standard, the proportion of parts and their corresponding weights are calculated, and the weights in the Shanghai Standard can be modified according to different technical processes; in the calculation scope, the enclosure wall is calculated as part of the main structure in the Shanghai Standard and the Zhuhai Standard.

2.3.3. Comparative Analysis of Decoration and Equipment Piping

Decoration and equipment piping are directly related to the use effect and safety of the house, and have a great influence on the use effect and comfort of the house, playing an important role in the evaluation criteria of prefabricated buildings. In scoring methods, the evaluation criteria for decoration and equipment piping mainly involving setting specific scores for the included evaluation items, while in weighting methods, corresponding weights are assigned to the evaluation items, which are analyzed as shown in Figure 5 and Figure 6 below.

From Figure 5, it can be concluded that the standards are the same for the setting of decoration and equipment pipeline evaluation items, but there are differences in the setting of evaluation scores and refinement items as a result of differences between the actual situations of each region. For example, in terms of pipeline separation, the Beijing Standard takes into account the interlocking underground pipelines and the phenomenon of complex ownership in Beijing, and sets the pipeline separation score higher, dividing it into electrical pipelines, water supply and drainage pipelines, and heating pipelines for the purposes of scoring, making the development of underground pipelines in Beijing more standardized and ownership more clear, while for the Zhejiang Standard, the above-mentioned situation does not pertain, so it is divided into vertical arrangement and horizontal arrangement, depending on the direction of the pipelines.

From the values of the weights in Figure 6, it can be concluded that each evaluation standard attaches a great deal of importance to full renovation, while the other evaluation items have their own focus, mainly considering the difficulty of promoting the corresponding technical process. Full renovation not only helps to reduce the management cost, but also helps to reduce the cost of work surface expansion, waste cleaning, etc., and also can avoid the noise pollution caused by alternate renovation; in particular, the management of noise pollution resulting from people’s social lives is very severe in Shanghai; therefore, the standards promote full renovation to a greater extent. The Zhuhai Standard takes into account the high construction difficulty and the long construction period of the dry method, and does not make corresponding provisions for the dry method, while the dry method in Jiangsu Province is more mature, so it receives greater focus.

2.3.4. Comparative Analysis of Extra Credit

Extra credit represents additional points given for specific good performance, or the implementation of advanced technology or innovative measures, in addition to meeting the specified basic requirements. Extra credit can encourage innovation in and development of prefabricated building technology, improve building quality and level, promote green and sustainable development, and enhance market competitiveness and corporate image. The Housing and Construction Standard, the Shanghai Standard, and the Zhejiang Standard focus more on the degree of prefabrication of the prefabricated building itself relative to the use of advanced technology in prefabricated buildings, so extra credit is not specified in the evaluation criteria, while other standards set extra credit in order to promote the use of prefabricated buildings and the application of innovative technologies, with scores as shown in Figure 7.

From the analysis of extra credit presented in Figure 7, it can be concluded that: in terms of value, the extra credit of each standard vary greatly; in terms of content, extra credit can be divided into three main aspects, informationization, greening, and standardization, but each standard will allocate extra credit according to the actual local conditions. For example, in Fujian Province, which is a “hot summer and warm winter” region, the application of a standard “exterior windows + east–west facade” can reduce energy consumption, so extra credit focuses more on the application of standardized exterior windows.

A comparative analysis of the provincial assembly evaluation criteria along four dimensions—main structure, envelope and internal partition walls, decoration and equipment piping, and extra credit—shows that there are differences in the evaluation content and evaluation scores among provinces that affect the calculation of the prefabrication rate for prefabricated buildings. The differences in the content and score of the evaluation criteria arise due to the influence of many factors, including the economic, climatic and geological characteristics of each region; therefore, the differences in each province’s own situation will give focus to the evaluation criteria for prefabricated buildings, and the specificity of each province’s regional situation makes the development of evaluation criteria diverse, making the coordination between the standards and the system poor.

In summary, the results of the calculation of prefabrication rate are mainly determined using the calculation method for determining prefabrication rate on the basis of the scoring criteria of the evaluation items described in the evaluation standard for prefabricated buildings. Methods for calculating the prefabrication rate can be divided into two categories, scoring methods and weighting methods, and evaluation items are mainly scored along four dimensions: the main structure, the enclosure wall and internal partition wall, decoration and equipment piping, and extra credit. The calculation of the prefabrication rate of prefabricated buildings may differ among provinces due to differences in regional economic development, climate characteristics, geological characteristics and the level of development of the construction industry. Therefore, in order to improve the standard systems for prefabricated buildings, improve the level of prefabrication technology in China, and cultivate a mature prefabrication industry chain, it is necessary to consider both the commonalities in the development process at the national level and the differences from the perspective of each province and region in the development of prefabricated building standards.

3. Empirical Analysis

By analyzing the evaluation criteria for prefabricated buildings in each province, we found that the different evaluation criteria have an impact on the results of the prefabrication rate calculation, and these differences cannot be perceived intuitively by comparing the individual criteria alone. Therefore, in this paper, actual engineering cases are selected for empirical analysis, through which empirical evidence can be provided to verify the extent of the differences in prefabrication rates obtained under different standards for prefabricated buildings, and the main factors influencing the differences. These case studies reveal the differences in the scores obtained for the same building under different evaluation standards for prefabricated buildings on the basis of detailed data and facts, and provide a reliable empirical basis for the standardization and development of evaluation standards for prefabricated buildings. At the same time, the case studies serve to summarize the knowledge gained regarding the evaluation for prefabricated buildings, analyze the key factors and the main reasons for the differences that arise, and provide reference and guidance for the development and promotion of prefabricated building evaluation.

3.1. Project Overview

The project is a residential apartment project with a prefabricated concrete shear wall structure. The residential project has 22 floors, of which floors 1–2, the roof, and the roof of the machine room are cast-in-place concrete floors, while the rest of the floors are precast concrete structures, and the floors are the same as those used in standardized household types. The height of the first floor of the building is 4 m, the height of the second floor is 3.5 m, and the height of each floor above the second floor is 3 m; the thickness of the wall is 0.2 m, and the building height is 67.5 m. The data relevant to the structural components of the building are shown in

Table 2. Data sheet of structural elements.

Types of Components	Floor	Length	Types of Components	Floor	Horizontal Projection Area	Thickness
Length of prefabricated shear wall facade	3–22	25 m	Laminated floor slabs	3–22	263.42 m2	130 mm
Prefabricated shear wall inner wall length	3–22	44.6 m	Staircase slab	3–22	18.7 m2	120 mm
Length of precast edge members	3–22	15.1 m	Balcony panels	3–22	23.4 m2	120 mm
Length of cast-in-place concrete wall line	1–22	71 m	Air conditioning slab	3–22	16.9 m2	100 mm
Length of concrete in post-cast zone meeting conditions	3–22	3.2 m	Cast-in-place concrete floor slab	1–22	84.32 m2	120 mm
Length of non-masonry wall of non-load-bearing enclosure wall (Area occupied by beams is 15.46 m2)	3–22	62.5 m	Non-masonry length of internal partition wall	3–22	87.57 m	-
Length of wall line of enclosure wall with heat insulation and decorative integration	3–22	96 m	Length of internal partition wall	1–22	112.93 m	-
Length of wall line of enclosure wall	1–22	141.7 m	Length of wall line with pipe integration	3–22	68.32 m	-

. The building has been fully renovated; the proportion of floors produced using dry working methods is 75.62%, the proportion of integrated kitchen application is 80.31%, the proportion of integrated bathroom application is 85.69%, and the proportion of the separation of pipes in the pipeline is 63.87%. Information technology was applied throughout the whole process of building construction, and the building received two stars for its green building evaluation; furthermore, the seismic reduction and anti-vibration technology applied meets the national standard.

3.2. Calculation of the Prefabrication Rate Using Different Criteria

This paper uses the prefabricated building evaluation standards of each province to calculate the prefabrication rate of this actual engineering project, and on this basis, the analysis of the differences between the standards has good reliability, validity and applicability. The prefabrication rate of the building can be calculated objectively and accurately using the evaluation standards for prefabricated buildings, and the results of this study can be used to improve the evaluation standards for prefabricated buildings so that they provide a theoretical reference for construction projects in real life. At the same time, in order to better reflect the differences between the evaluation standards applicable in each province, while simplifying the variables and the prefabrication rate calculation process, thereby making the research more accurate, effective and reliable, the following assumptions were made regarding the calculation of the prefabrication rate in this paper:

(1) Since the case selected in this paper is a concrete shear wall structure, the vertical members of the main structure used in this paper mainly consist of wall members, including precast shear exterior walls, precast shear interior walls, precast edge members, and cast-in-place concrete walls. The horizontal components, we mainly consider slab members, including laminated floor slabs, stair slabs, balcony slabs, air conditioning slabs, etc. Other vertical and horizontal members present in the project are not considered in the calculation.

(2) Depending on the provisions of the evaluation standard for prefabricated buildings employed, the area of doors, windows and reserved openings can be deducted or not when calculating the application rate of integrated walls, wall insulation, and decoration; areas corresponding to doors, windows and reserved openings are not deducted during the calculation in this paper.

The prefabrication rate of the project evaluated in this paper is calculated on the basis of these assumptions regarding the calculation of the prefabrication rate, and the scores of the prefabrication rate calculated under each of the different prefabricated building evaluation standards are shown in

Table 3. Prefabrication rate score table under each standard.

	Main Structure	Enclosing Walls and Internal Partitions	Decoration and Equipment Piping	Extra Credit	Total Score
Housing and Construction Standard	35.21	13.34	27.29	-	75.84
Beijing Standard	34.18	13.34	22.51	5	75.03
Zhejiang Standard	35.21	14.66	24.29	-	74.16
Fujian Standard	31.06	25.73	21.98	7	85.77
Jiangsu Standard	25.56	18.81	26.16	18	88.53
Shanghai Standard	58.42	7.49	16.44	-	82.35
Zhuhai Standard	61.54	12.69	16.84	0.18	91.25

, below.

The score values obtained for the project using different prefabricated building evaluation criteria are shown in Table 3. For example, under the Housing and Construction Standard, the project scored 35.21 points for the main structure evaluation item, 13.34 points for the enclosing wall and internal partition wall, 27.29 points for decoration and equipment piping, and 0 points for the extra credit item, making a total score of 75.84 points. The scores obtained using different criteria were similar. From Table 2, it can be concluded that there can be differences in the prefabrication rates obtained for the same building when using different evaluation criteria, and the score for the main structure accounts for the largest proportion of the total score for prefabrication rate, while the extra credit account for the smallest proportion. With respect to the main structure score, the weighting method scores higher than the scoring method, which is mainly due to the fact that the main structure contains more different types of construction, especially the outer parapet walls, thus causing the weighting method to score more highly for the main structure and lower for the parapet walls and inner partition walls. In terms of extra credit, some provinces do not pay enough attention to innovative technologies related to prefabricated buildings and either do not set or have low scores in the extra credit category. In order to confirm the differences in the calculated results of prefabrication rate under the evaluation criteria of each province, in this paper, the t-test is used to analyze the differences in the prefabrication rate scores from a statistical point of view. Analysis of the data using statistical methods can reveal inherent patterns and correlations. By establishing mathematical models and making statistical inferences, a quantitative assessment of the factors influencing the building prefabrication rate can be derived in order to improve the scientificity and accuracy of the study.

The t-test is a test used to determine the degree of difference between the means of small samples, and it uses the theory of the t-distribution to determine the probability of a difference occurring, and thus whether the difference between two means is significant [41]. T-tests can be divided into three types: one-sample t-tests, paired-samples t-tests, and independent-samples t-tests [42]. There are differences in the scope of application between different types of t-test; the one-sample t-test is used to compare whether there is a difference between the sample data and a specific value, the independent-samples t-test is used to analyze the difference between definite class data (X) and quantitative data (Y), and the paired-samples t-test is used to analyze the comparative relationship between the differences between paired quantitative data [43]. Combined with the actual situation of the case study, in this paper, the one-sample t-test is used to investigate the differences between the evaluation criteria.

The use of the one-sample t-test has the basic prerequisite that the data used for the test are quantitative and obey or approximately obey a normal distribution. Therefore, in this paper, IBM SPSS Statistics 22 is used to test the normality of the evaluation item scores and the total scores of the assembly evaluation criteria. The normality test is a non-parametric test, and the original hypothesis is that “the sample comes from a total that is not significantly different from the normal distribution, that is, it conforms to the normal distribution”, that is, p > 0.05 indicates that the data conform to a normal distribution. Usually, there are two tests for normal distribution; one is the Shapiro–Wilk test, which is applied to small data samples (sample size ≤ 5000), and the other is the Kolmogorov–Smirnov test, which is applied to large data samples (sample size > 5000) [44], so in this paper, the Shapiro–Wilk test was employed, and the results are shown in

Table 4. Normality test and one-sample t-test table.

	Shapiro–Wilk			One-Sample t-Test
Evaluation Items	Statistics	Df	Sig	t	df	Sig	Mean Difference	Difference 95% Confidence Interval
								Lower Limit	Upper Limit
Main Structure	0.813	7	0.055	7.606	6	0.000	40.17	27.25	53.09
Enclosing walls and internal partitions	0.913	7	0.417	6.999	6	0.000	15.15	9.85	20.45
Decoration and equipment piping	0.909	7	0.392	13.853	6	0.000	22.22	18.29	26.14
Extra credit	0.736	7	0.009	1.707	6	0.139	4.31	−1.87	10.49
Total score	0.948	7	0.707	27.016	6	0.000	81.14	73.79	88.49

, below.

Table 3 shows results of the normality test and the one-sample t-test for the prefabricated building evaluation criteria. As can be seen from Table 3, the significance of the main structure, the enclosure and interior partition walls, the decoration and equipment piping, and the total score are all greater than 0.05, indicating that the data conform to a normal distribution, while the significance of the extra credit is lower than 0.05, indicating that the normal distribution of the data for the extra credit is not significant according to the Shapiro–Wilk test. In order to further explore the significance of the extra credit, a histogram is plotted for the extra credit data, as shown in Figure 8, below.

From Figure 8, it can be seen that the distribution of the data for the extra credit obeys an approximately normal distribution, so it is also possible to conduct a one-sample t-test to determine the differences. The one-sample t-test for each evaluation item shows that sig > 0.05 for the extra credit indicates that the differences between extra credit scores for prefabricated buildings among provinces are not significant, which is mainly due to the fact that some provinces do not pay enough attention to innovative technologies related to prefabricated buildings, and therefore do not make provisions for extra credit, or assign small values to the extra credit. The evaluation items other than the extra credit are sig < 0.05, which means that the differences are more significant, especially regarding the total score. Therefore, the t-test analysis shows that the use of different evaluation criteria for prefabricated buildings can cause significant differences in the results when calculating the prefabrication rate. In order to study the specific scores for the evaluation items of each evaluation criterion, in this paper, the specific scores of each criterion are presented in multi-layer circular pie charts, as shown in Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15.

Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15 present multi-layer circular pie charts of the specific scoring values of the evaluation criteria for prefabricated buildings, which are divided into three layers representing, from the inside to the outside, the total scoring value, the scoring value of the evaluation items, and the scoring value of the evaluation item refinement items, respectively. Taking the Housing and Construction Standard as an example, the total score value is 75.54 points, while the evaluation of the main structure, the decoration and equipment piping, and enclosure walls and internal partition walls scored values of 35.21 points, 27.29 points, and 13.34 points, respectively. For the main structure, the refinement items corresponding to vertical components and horizontal components scored 23.15 points and 12.06 points, respectively. The other criteria are presented similarly. From the analysis of the detailed scores of the above evaluation criteria, it can be seen that the vertical members and the internal partition walls in the main structure account for the largest proportion of the total score, while the scores for the green building rating and application of BIM information technology account for the highest proportion of extra credit; meanwhile, the decoration and equipment piping scores were more evenly split. Therefore, for the prefabricated building to obtain a higher prefabrication rate, the application rate of vertical members and internal partition walls should be focused on more, as well as the application of information technology and green technology.

In order to further explore the evaluation items that have the greatest impact on the total score value for prefabrication rate under different evaluation criteria for prefabricated buildings, in this paper, the simulated annealing optimization projection pursuit model is adopted to evaluate the evaluation items for prefabricated buildings. The projection pursuit method is a sample-data-driven data analysis method. The main principle is to project the data scattered in high-dimensional space onto low-dimensional subspace in some combination, find the projection that reflects the structure or characteristics of the high-dimensional data, and analyze the structural characteristics of the data with reference to the projection value [45,46]. As an objective evaluation method that does not need to set weights, the projection pursuit method (PP) is widely used in the evaluation and optimization of multiple factors [47]. In this paper, the simulated annealing algorithm is chosen to optimize the objective function of the projection pursuit method in order to identify the projection that is best able to reflect the original data. The simulated annealing algorithm (SA) is a simulation of the thermodynamic process of high-temperature metal cooling, and the simulated annealing algorithm has a good global search ability, can jump out of local optima by receiving the probability of deteriorating solutions, and has good solution efficiency and convergence. Therefore, in this paper, the simulated annealing algorithm is established to optimize the projection pursuit model with the aim of analyzing the evaluation items under the evaluation standards for prefabricated buildings.

Using the scores of the evaluation items obtained under different prefabricated building evaluation standards presented in Table 2, with reference to the relevant evaluation data, in combination with the actual situation of the project, the simulated annealing algorithm is used to optimize the projection pursuit model to perform the evaluation. The initial parameters of the algorithm are set as follows: initial temperature T₀ = 1000, termination temperature T_end = 0.0001, number of iterations N = 150. The data are first normalized, and the results are as follows:

$$x=\left[\begin{array}{cccc}0.2682& 0.3207& 1& 0\\ 0.2396& 0.3207& 0.5594& 0.2778\\ 0.2682& 0.3931& 0.7235& 0\\ 0.1529& 1& 0.5106& 0.3889\\ 0& 0.6206& 0.8959& 1\\ 0.9133& 0& 0& 0\\ 1& 0.2851& 0.0369& 0.0100\end{array}\right]$$

The simulated annealing algorithm is used to optimize the projection pursuit model solution based on the data normalization process. In order to verify the suitability and feasibility of the model for the analysis of the evaluation terms, and whether it can converge quickly during the running process, it is necessary to determine the convergence of the model. We used MATLAB.2019b software to run the simulated annealing algorithm optimized projection pursuit model, and its convergence curve was plotted as shown in Figure 16.

Figure 16 shows the relationship between the objective function value and the number of iterations, presenting the objective function value for the prefabricated building evaluation standard corresponding to each iteration of the simulated annealing optimization projection pursuit model. From the figure, it can be seen from the convergence curve that, with the increasing numbers of iterations, the convergence trend gradually becomes obvious, while the convergence curve also gradually becomes smooth, indicating that the simulated annealing optimization projection pursuit model has good feasibility for analyzing the evaluation items of the evaluation criteria for prefabricated buildings, and the algorithm operates with high efficiency and good convergence. After applying the simulated annealing algorithm to optimize the solution obtained using the projection pursuit model, the maximum projection target value in the running results is 0.5515, the projection eigenvalues under different prefabricated evaluation criteria are z* = [1.3261, 1.1326, 1.1220, 1.8591, 2.4065, 0.0210, 0.3534], and the optimal projection direction is shown in Figure 17 below.

In Figure 17, the horizontal coordinate represents the evaluation items in the evaluation standards for prefabricated buildings, and the vertical coordinate represents the value of the optimal projection direction vector, from which it can be seen that the optimal projection direction vector of the enclosure wall and the internal partition wall is 0.9986 at its maximum, and the optimal projection direction vector of the main structure is 0.0229 at its minimum. The size of the best projection direction vector reflects the degree of influence of a given evaluation item for prefabricated buildings on the total score; thus, it can be judged that the enclosure wall and internal partition wall have the greatest influence on the total score, and the main structure has the least influence on the total score. This is mainly due to the fact that the evaluation criteria for prefabricated buildings usually focus on overall performance and quality, and that enclosure walls and internal partition walls have a greater impact on the indicators designating the safety, comfort, and energy efficiency of the building. Therefore, in the evaluation criteria, enclosure walls and internal partition walls assume a greater functional role in prefabricated buildings. In contrast, the main structure has less influence on the total score of the evaluation criteria for prefabricated buildings, mainly because the main structure is mainly related to the overall stability and load-bearing capacity of the building, and is less related to the overall performance of the prefabricated building. Although the main structure plays a load-bearing role in prefabricated buildings, other functional aspects are mainly considered in the evaluation criteria.

Above, the similarities present in the differences among the main structure, enclosure walls and internal partition walls, decoration and equipment piping, and extra credit obtained under different prefabricated building evaluation standards were analyzed. On this basis, in order to analyze the differences in prefabrication rate between different prefabricated building evaluation standards and analyze the reasons for those differences, a line graph of the prefabrication rate and evaluation item scores for each standard is drawn, as shown in Figure 18.

It can be seen from Figure 18 that the Zhuhai Standard has the highest score for the main structure, mainly because the weighting method is used for calculation, the main structure contains more prefabricated component types, and the vertical component weight is also greater; therefore, the score is higher. For the enclosure wall and internal partition wall, the Fujian Standard has the highest score value; this is, on the one hand, because of its higher total score, while, on the other hand, the Fujian Standard incorporates decorations of the internal partition wall. For the decoration and equipment pipeline, the residential construction standards scored the highest, mainly because in the residential construction standards, separation of the pipeline score is easier and higher. For extra credit, the Jiangsu standard scored the highest, mainly because in the Jiangsu standard, the extra credit involve a broader range of aspects, and the score set is also higher.

Therefore, the above analysis shows that the reasons for the differences in the prefabrication rate under different evaluation standards include: (1) the use of different systems for calculating the prefabrication rate; using the scoring method as opposed to the weighting method will lead to differences in the calculation results, where the weighting method will score higher on the main structure, while the scoring method will score higher on the enclosure walls and internal partition walls; (2) the setting of the refinement items in each standard will have a greater impact on the score of buildings with general assembly; (3) the different settings for the total score of each standard, especially the setting for the extra credit and the high and low scores, have a great impact on the prefabrication rate score.

4. Conclusions and Recommendations

With the current situation of resource consumption and environmental pollution becoming increasingly serious, prefabricated buildings are a current trend in building development, research into prefabricated buildings into China has made great achievements, but there is still a large gap compared with developed countries. As an evaluation standard for prefabricated buildings, China adopts the assembly index. This is due to the relatively backward national situation of China’s prefabricated building industry. In this paper, the evaluation criteria for prefabricated buildings in different provinces are analyzed in terms of their method for calculating the prefabrication rate and the scoring criteria for the evaluation items, which can significantly impact the calculation results of the prefabrication rate. In addition, by using actual cases, the prefabrication rates of prefabricated buildings were calculated under different standards, and the differences in the total score values and the degree of influence of various factors on the total score values were studied by means of t-tests and multiple linear regression analysis; the reasons for the differences in prefabrication rates calculated under different standards were analyzed, and conclusions were obtained as follows:

(1)

There are similarities and differences in the evaluation standards for prefabricated buildings in each province. There are similarities in the evaluation criteria for the horizontal component refinement items, the evaluation items for decoration and equipment piping, and the scores for enclosure walls and internal partition walls, while other evaluation and score items differ due to the level of economic development, climatic and geological conditions, maturity of technology and different starting points for consideration in each region.

(2)

Different prefabrication rates can be obtained for the same building under different prefabricated building standards, and the method for calculating the prefabrication rate and the scoring criteria of the evaluation items can cause significant differences in the prefabrication rate results.

(3)

Among the rating items of prefabricated buildings, the main structure, the enclosure wall and internal partition wall, and extra credit have the most significant influence on the total score value, among which the main structure has the greatest influence, while the decoration and equipment piping have a weaker effect on the total score.

(4)

The methods for the calculation of the prefabrication rate in each province can be divided into scoring methods and weighting methods, with the main difference between the two systems being whether the outcome is a specific score; additionally, there are differences in the scores for different evaluation items between the two systems.

After analysis, it became clear that there are significant differences between the evaluation standards of each province, which can lead to problems such construction quality being unguaranteed and difficult to compare, the market competition being unfair, and the development of the construction industry being unbalanced, which is not conducive to the sustainable development of China’s prefabricated buildings in the long run. Therefore, it is necessary for the state to strengthen standardization and improve the evaluation standard system. In this paper, the limitations and shortcomings of the national standard are combined with the advantages of local standards to provide several recommendations for governments needing to develop or revise their local standards, as follows:

(1)

Appropriate prefabrication rate calculation methods should be chosen in different regions in accordance with the actual situation in the region. The weighting method can be used in provinces with high levels of prefabricated building development, thus weakening the boundaries between the evaluation items and making the choice more flexible. In provinces with a low level of prefabricated building development, the scoring method can be chosen, which makes their construction mandatory by setting a minimum score, thus increasing the application rate of prefabricated buildings.

(2)

The evaluation requirements for the main structure in each standard should be investigated as appropriate, and the scoring range widened in order to avoid the abandonment of vertical components due to their high requirements. Additional points should be added, and appropriate points should be given to buildings using information technology and industrialization technology, etc. The setting of the additional points can be flexible, and should be suitable while promoting plurality. This will encourage the development of prefabricated buildings.

(3)

Different scoring rules should be set for different structural systems and types of structure, so that different criteria can be used when evaluating different buildings to increase the rationality of the evaluation.

(4)

A flexible and variable evaluation system should be set up for interior decoration to avoid a significant decrease in the prefabrication rate due to interior decoration and to stimulate the development of prefabricated decoration.

The research in this paper focuses on a comparative analysis of the evaluation standards for prefabricated buildings in various provinces in China. Although the research on prefabricated buildings in China has made great achievements, there is still a large gap compared with developed countries. As an evaluation standard for prefabricated buildings, China adopts the prefabrication rate index to measure prefabricated buildings, which is different from the evaluation systems used in all other countries, and is determined by the relatively backward national situation of China’s prefabricated building industry. Therefore, there is a lack of mature evaluation standards for prefabricated buildings, which form the research object of this paper, compared with in other countries, also serving as a direction for future research. By analyzing the evaluation standards and comparing them with those of different foreign countries, it is possible to introduce advanced assembly technology from abroad and digest and re-innovate it in combination with China’s national conditions, so as to improve the level of assembly technology in China and cultivate an improved and mature industrial assembly chain.