Detailed argument: housing industrialization around us

Do you have doubts about the following questions? Let's take a look at the analysis and elaboration of experts.

"What kind of housing is industrial housing?"

"How to evaluate and calculate the degree of industrialization?"

"What different results will different calculation methods bring to enterprises?"

"Steel price and prefabrication of concrete structure, which is the key point?"

Will the pursuit of prefabrication rate become a misunderstanding of housing industrialization

Recently, six pilot projects of housing industrialization have been launched in Shenzhen. In this key step of housing industrialization practice, Shenzhen has encountered many problems mentioned above. At the expert review meeting on technical requirements of Shenzhen housing industrialization pilot project recently held, several national well-known experts conducted professional discussions on these hot topics.

Steel structure vs precast concrete structure

Is housing industrialization equivalent to precast concrete structure (PC).

At the same time, the level of steel structure technology has already developed and matured. In recent years, the steel price has continued to decline. The net profit of a ton of steel has dropped from nearly 1000 yuan a few years ago to 0.43 yuan, the lowest point in the first half of this year. While the industry ridicules that "it's not enough to buy a Popsicle", the "vigorously promoting steel structure housing" is also constantly making sound.

PC or steel structure, is causing hot debate.

Chen Zhenji: the industrialization road we are taking now, and the assembly mentioned, does not jump out of the framework of decades ago. In fact, we should discuss more structural systems, such as steel structures.

The premise of carrying out prefabrication is mass production and mass application, and workers, market, science and technology and government policies should keep up. However, there are many embarrassing situations in the implementation of prefabricated assembly mode in China's residential buildings, which makes the general developers afraid to test the water, which is beyond reproach under the condition of free market economy.

However, in addition to PC, is it industrialization to use mass-produced tool type formwork and cast ready mixed concrete into house parts? Is it industrialization that two or three storey "temporary buildings" in many urban construction sites are completely assembled with factory produced standard plates? Is it industrialization? Is it light steel structure house system that wall plates, floor slabs, roofs, etc. are all manufactured in factories? North 2003 In order to fight against SARS, Beijing built Xiaotangshan Hospital seven days and seven nights, which is known as "the miracle in the history of world medical treatment". It uses factory prefabricated components, but it is not PC. is this industrialization

I have been engaged in the research of concrete structure for more than 50 years. Now there are more and more doubts about whether the construction industrialization is equivalent to the prefabrication and assembly of concrete, and whether this is the only way for the construction industrialization? In China, should we broaden our thinking and seek the industrialization road more suitable for various conditions?

Ma Tao: in my opinion, due to various reasons, there are some inevitable problems in the industrialization in history. The "new construction industrialization" advocated at this stage should be based on the original intention of solving various quality problems in the last round of industrialization, and should be applied to the employment characteristics of fewer and fewer workers. It is no longer based on people, but on quality, standards and machinery To control our industrialization.

In contrast, steel structure has been industrialized for a long time, and there are many cases to analyze. Although there are still problems such as fire prevention, enclosure and maintenance, it seems that it can not be promoted in a big way at this stage.

Just as the industrialization of housing is not equal to industrialization, industrialization is not equal to assembly, but in the process of reality, through a reasonable path to change the existing problems, get the market-oriented construction organization mode, get the appropriate precision products, or the main significance and goal at this stage. Under this goal, all the problems come down to one, the overall level of design and construction personnel needs to be greatly improved, and the concept of industrialization needs to be used for transformation.

Fan Hua: PC, steel structure, steel concrete combination, large formwork system, formwork assembly, etc. should be included in the scope of industrialization. As for the steel structure and PC who will go first, I think they can be combined, but the most important problem is actually market demand.

At a recent meeting held in Shanghai, the relevant person in charge of Shanghai Hyundai Group put forward the concept of "socialization" and proposed that products should be market-oriented. Only when they are accepted by the market can enterprises have motivation, unless the government creates a market at a higher level. If we need to promote PC in affordable housing, it means that we need this product at this stage, which is in line with the demand.

Gu Mingwang: in 2008, he made special research on various structural systems and enterprise technical routes, and the results show that steel concrete combination must be an inevitable trend in the future. Assembly type should include a variety of structural systems, according to the needs of different situations, using different structures to adapt.

Chen Zhenji: no technology should be "monorail driving". We should examine and evaluate the construction industrialization with a broader way of thinking, and treat the construction industrialization and technological innovation with a sea embracing attitude.

Assembly rate vs prefabrication rate

Compared with the dispute over the route, the more important question is, what kind of standard should be used to evaluate and calculate industrialization? This will directly affect the vital interests of the market and enterprises.

In Shanghai, the "Interim Measures on encouraging the construction of prefabricated integrated residential projects" promulgated in 2011 clearly stipulates that only those with a prefabricated assembly rate of more than 15% can meet the conditions of prefabricated integrated residential projects and enjoy the relevant building area exemption. In the real industrialization project, prefabrication rate data is also widely used as the highlight of promotion.

The concept of prefabrication rate seems to have become the general measurement index of housing industrialization. However, the pursuit of prefabrication rate has been questioned repeatedly, and even considered as "a big misunderstanding of housing industrialization".

CEN Yan: at present, there are three main calculation methods for housing industrialization: volume ratio, area ratio and value ratio. As the value ratio is easy to lead to artificial value enhancement, the former two calculation methods are mostly adopted, which correspond to the concepts of prefabrication rate and assembly rate respectively.

Assembly rate refers to the percentage of the area of concrete with prefabricated components in a specific part of the building in the total concrete area, or the percentage of the area of the component without formwork and the area with prefabricated large formwork in the total surface area of the component; while prefabrication rate refers to the percentage of the volume of concrete with prefabricated components in a specific part of the building in the total concrete volume. The calculation of area ratio or volume ratio will lead to different results.

Gu Mingwang: We used to calculate through a group of solid floors and composite floors. According to the assembly rate, the data is the same, but according to the prefabrication rate, half of the composite floors are prefabricated in the factory, half of them need to be cast in situ, and the volume data of concrete is half less than that of solid floors. This raises a new question: why is advanced technology lagging behind in terms of prefabrication rate and "losing money" in terms of data due to technological progress?

The development of concrete structure should be in three directions: prefabrication technology, cast-in-place Technology (industrialized formwork system) and no formwork removal technology. From this point of view, simply emphasizing prefabrication rate is a mistake.

The concept of assembly rate includes more considerations such as template free or industrial template, which is more reasonable. A more scientific way is to set different weights for different means of industrialization.

Ma Tao: in fact, from this point of view, as long as the technology can be exempted from formwork, it should be industrialized products, including formwork free and support free, combined formwork and industrial formwork. The industrialization of construction process is also an important part of new building industrialization. Therefore, it is meaningless to increase the prefabrication rate when the assembly rate is very low.

Fan Hua: if we blindly pursue the prefabrication rate, the components may become very heavy, which will bring unnecessary burden to the production, transportation and installation. Similar cases are common.

So, what can be used as the standard of industrialization evaluation? In foreign countries, there is a "reasonable working hours" index, that is, the proportion of labor in construction and installation from the beginning to the end of a project, which is absolutely an index reflecting the degree of industrialization, but it is still too early for China.

CEN Yan: only technological progress can reduce the labor ratio, which is higher than the volume ratio and area ratio.