In recent years, the construction industry has been in a recession; in the situation, a new architectural structure which is called assembly structure appeared just in time.
Prefabricated rate must be mentioned when talks about assembly, the simplest way to measure the industrialization at the design stage is to calculate the prefabricated rate, which is the ration for the volume (or value) of the prefabricated component to the volume (or volume) of the entire building components.
The use of volume ratio is applicable when the component material and the value of unit volume is nearly the same. If use the steel structure to replace the traditional reinforced concrete structure, the unit price of the former is much higher than that of the latter, and the volume is smaller; thus the volume ration cannot reflect the actual situation.
When takes value ratio, it covered the tendency that the price for some prefabricated unit is on the high side; such as the unit price for precast reinforced concrete wall panel is much higher than the price for masonry wall; it made the precast ratio tends to be quite high in certain situations, it is not true. Therefore, it is necessary to illustrate the significance of the precast rate when expressing the industrialization degree of construction with precast rate.
The assembly structure has grown rapidly with the help of government support. Shanghai is one of the fastest growing cities in China and the city with highest requirements; the preproduction rate requires reaching 40%, this is quite high, here is an example: a project conducted in Shanghai recently takes shear wall structure, the bottom reinforcement area, the upper roof part, roof layer and the edge components of the wall adopt the whole cast-in-place structure, the remaining layers take assembly structure.
The assembly type generally adopts the following components, the composite beams, laminated plates, and wholly-prefabricated laminated plates. At the beginning of the design process, designers took normal casting structure to place the shear wall and beam; finally the problem came, how to deal with the insufficient prefabrication rate.
The house type has been decided, and the cast-in-place part cannot be reduced, how to deal with it? The only solution is taking shear walls at all the places that could adopt shear walls, this resulted in many places took shear walls to replace original partition, the floor also became much thicker, finally reached 40% prefabrication rate.
The purpose for China to encourage assembly structure is saving energy and protecting environment; however, in order to meet the related standard, it could cause huge waste from time to time; does the design must submit to the prefabrication rate? These problems may be solved in the future, but it is still waiting for further cooperation.
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