by Abstract: in order to more reasonably design, manufacture and use the prefabricated component mold of the prefabricated building, this paper combines the design experience and actual production experience for many years, based on the component production efficiency, product quality and mold cost, puts forward new ideas for the modular design, structural optimization design and combination design of the mold, and provides reference for the mold design and production personnel.
1 introduction prefabricated buildings are the main internal customers of green development, circular development and low-carbon development of the construction industry.
They are important means to stabilize growth, promote reform and adjust structure.
Compared with traditional construction methods, prefabricated buildings can achieve the goals of energy saving, water saving, material saving, time saving, labor saving, greatly reducing construction waste and dust, and environmental protection; The prefabricated building mainly carries out the assembly of prefabricated components on the site.
Compared with the traditional cast-in-place mode, it moves a large number of high-intensity operations on the construction site to the “workshop where the working environment can be controlled manually” for modern production, which improves the working conditions of workers, reduces labor intensity, improves the production accuracy of components, shortens the construction period, reduces construction noise, reduces construction waste during wet operation, and greatly improves the level of green construction.
As an important part of the prefabricated building industry, the precision, durability and cost of the mold are particularly important.
At present, the mold design and manufacturing generally have the problems of low standardization and modularization, unreasonable structure and high cost.
With the increasing number of prefabricated components and the continuous improvement of product accuracy requirements, the mold problem has restricted the high-quality development of the prefabricated building industry to a certain extent, There is room for improvement and improvement.
2 current status of prefabricated building mold design 2.1 residential projects with low degree of standardization are characterized by diversity, different house types and storey heights, and different ideas and habits of each engineer for splitting prefabricated components, resulting in different sizes, reinforcement and spacing of prefabricated components, and different molds.
In addition, due to the high precision requirements of the molds, most of the molds cannot be reused in the next project through restructuring.
After the completion of the project, the molds can only be scrapped, resulting in great waste and high mold costs.
2.2 the mold structure design is unreasonable.
Most of the engineers of the mold manufacturing enterprises have no experience in the production of prefabricated components, which makes it difficult to assemble and dismantle many of the designed molds, and even it is impossible to dismantle the molds from time to time, which seriously affects the production efficiency and product quality of the components.
For example, the air conditioning board mold in Fig.
1, the lower rib hole of the left mold is a round hole, and the left mold needs to be withdrawn to remove the mold, However, the bending bar of the component leads to insufficient withdrawal space of the mold, which makes it impossible to remove the mold.
In addition, the beam reinforcement of some wallboards belongs to bending anchor, and the mold needs to be lifted up for formwork removal.
The other positions belong to straight reinforcement, which needs to be pulled out during formwork removal.
The direction of formwork removal is different.
At present, bolt connection is generally used for formwork assembly in the design, and the molds at both ends need to be separated during formwork removal.
As shown in Figure 2, the efficiency of formwork removal is very low.
2.3 insufficient fineness of mold design at present, due to the uneven technical level of mold design practitioners and the manufacturing level of production units, the mold design and manufacturing generally have insufficient fineness.
Common problems include improper consideration of concrete plugging at the reinforcement hole, inconsistent specification of mold connecting bolts affecting efficiency, deformation of mold top plate affecting the finishing effect, etc.
2.4 the prefabricated building project without material selection based on the number of mold turnover includes both super high-rise buildings and low-rise residential buildings.
The use times of the molds of the two buildings are quite different.
However, at present, most mold design and production units do not consider the number of mold turnover and service life.
The thickness of the steel plate and the specification of the profile are designed and produced according to the same standard.
The molds of high-rise buildings have been used for many times, and the strength and rigidity are insufficient, resulting in serious deformation and damage in the later stage, which affects the quality of prefabricated components.
However, the molds of low-rise buildings have less turnover times, and the strength and rigidity are excessive, resulting in waste.
3 suggestions for design improvement 3.1 modular design due to the low degree of standardization of prefabricated components, resulting in the low universal rate of molds, it is impossible to carry out standardized design.
In view of this situation, modular design can be carried out.
For example, many stair molds are equipped with integrated ladders and walkways, as shown in Fig.
3.
These ladders and platforms can be removed from the mold, and the ladders and platforms can be made separately and put in the workshop for common use, which can not only save costs, but also effectively save plant space, as shown in Fig.
4.
In addition, the size of the base in the stair mold remains unchanged, and the original welding method can be changed to bolt connection.
After the completion of the project, the base will be used for the next project, so as to realize the universality of the stair mold base, as shown in Figure 5.
In addition, the window mold can also be modularized.
The window mold is generally composed of 8 units, as shown in Fig.
6.
Among them, four window corners can be used as general molds, and the lengths of four straight section molds can be designed as 600mm, 800mm, 1000mm, etc.
according to the common sizes of windows.
After reasonable combination, the size requirements of most window openings can be realized, so as to save costs and shorten the production cycle.
3.2 design of composite mold prefabricated composite plate generally refers to the prefabricated bottom plate of the floor slab.
In the later stage, it is combined with the upper cast-in-situ concrete layer through truss reinforcement to form a whole.
It is a better structural form combining prefabricated and cast-in-situ concrete.
It has the characteristics of fast construction, large overall rigidity and good seismic resistance.
Prefabricated components can be embedded in advance with wire boxes and reserved pipe openings.
Laminated plate is widely used in prefabricated buildings, and almost every prefabricated building has adopted it.
It accounts for a large proportion of prefabricated components, high mold cost and long production cycle..
