by What is a precast building? How are precast buildings produced? How is the site constructed? What about the cost? What are the advantages over other materials? What is a precast building? Have you ever played LEGO (it’s OK to have seen it).
We can imagine the components made in advance such as beams, plates, columns and walls as Lego blocks, and just put them together at the construction site.
Like Toledo, precast buildings prefabricate some or all components in the factory and then transport them to the construction site for assembly.
“Assembly” is not just “erection”.
After the precast components are transported to the construction site, the reinforced concrete will be overlapped and poured, so the assembly room is very safe.
Therefore, such “industrialized” and “industrialized” buildings have been widely used in Europe, America and Japan.
There is no love for no reason in the world.
Why are these developed capitalist countries so keen on precast buildings? 1.
It is conducive to improve the construction quality.
The precast components are precast in the factory, which can maximally improve the common quality problems such as wall cracking and leakage, and improve the overall safety grade, fire resistance and durability of the residence.
2.
It is conducive to accelerating the progress of the project.
Efficiency is return.
The progress of precast buildings is about 30% faster than that of traditional methods.
3.
It is conducive to improve the construction quality.
Hyaluronic acid in the construction industry can make the construction products long-term and young.
After the indoor fine decoration is industrialized, express delivery can be received at home, that is, disassembly and installation, which is fast and good.
4.
It is conducive to regulating the supply relationship, improving the listing speed of real estate, slowing down the current situation of insufficient market supply, and there is no need to queue up all night to buy a house.
After the popularization of the industry, the construction cost can be reduced and the house price can be effectively restrained.
5.
It is conducive to civilized construction and safety management.
There are a large number of workers on the traditional operation site.
Now, a large number of site operations are moved to the factory.
Only a small number of workers need to be left on the site, which greatly reduces the incidence of on-site safety accidents.
6.
It is conducive to environmental protection and resource conservation.
There are few original cast-in-situ operations on site, and the health does not disturb the residents.
From then on, we bid farewell to “gray”.
In addition, the reuse rate of steel formwork can be improved, and garbage, loss and energy saving can be reduced by more than half.
How to produce cast components? How are they produced? Taking the cast building slab as an example, the production process is: steel formwork fabrication → reinforcement binding → concrete pouring → demoulding.
Holes shall be reserved during reinforcement binding.
During reinforcement binding, the hook shall be embedded in the concrete for pouring.
After demoulding in the assembly line, the cast components of the finished cast slab shall be cast and stacked in the factory temporarily, It can be ready to be transported to the construction site.
Taking the precast frame structure as an example, after the construction of the first floor is completed, the columns of the upper floor are hoisted first, and then the main beam, secondary beam and floor slab are hoisted.
After the hoisting of precast components is completed, the reinforcement at the connection part shall be bound, and finally the node and the cast-in-situ layer of beam and slab shall be poured.
What is the most technically demanding of the above steps? The answer is the hoisting of cast components.
In order to ensure the smooth lifting, after the cast components are transported to the site, the stacking site needs to be reasonably arranged to facilitate the lifting.
Just like moving, we usually arrange the goods handling sequence to reasonably reduce the workload.
How is the most important lifting step operated? The dressing mirror is prepared for the hoisting of the cast column.
The lower space is narrow and inconvenient for observation.
Through the reflection principle of the small dressing mirror, it is convenient to plug the reserved reinforcement in the lower layer into the hole of the upper cast column.
The construction site brother is very smart, handsome.
The hoisting of cast composite beam and cast composite plate can also be pre assembled on site or build a cast display area for the parts with great hoisting difficulty.
After the pre assembly of the frame structure girder and the hoisting of the display area of the shear wall residence, bind the reinforcement of the cast-in-situ layer and prepare to pour the cast-in-situ layer concrete.
In order to increase the connection between the cast members and the cast-in-situ layer and ensure the reliability and safety of the structure, the surfaces of the cast members are left with keyways or roughened.
How can so many components not make mistakes? Fabricated component number!! In order to ensure that workers will not make mistakes, reduce construction errors and speed up the progress of the project, we have applied for ID cards for each component, which have their own unique ID number to facilitate seating.
Walls, slabs, stairs and other cast components have their own unique numbers.
Cost management} is it right now that the clouds have been cleared for precast buildings and the sun has risen.
However, these are not enough for developers.
Cost control and design management are the finishing point of the implementation process of precast buildings.
Knock on the blackboard and draw the key points: precast buildings have two important indicators, the proportion of assembly area and prefabrication rate.
Assembly rate = implemented assembly area ÷ total floor area.
Prefabrication rate = total volume of cast members ÷ total concrete volume.
Shanghai is in the forefront of the country in precast buildings, and is gradually improving the requirements of prefabrication rate and assembly rate.
The higher the prefabrication rate, the higher the cost.
According to preliminary statistics, the cost increment is about 150 yuan for every 10% increase in prefabrication rate.
First of all, the assembly range should be avoided in the first opening area as far as possible.
According to the requirements of assembly area in the transfer contract, the project cycle can be balanced through phased development.
Due to the cooperation of precast components with factories in advance and the limited production capacity of these factories, there is a great pressure on the time cost of the first phase of development.
Secondly, it is necessary to split the structural components and select the monomer with high repetition rate of precast components.
Generally, the repetition rate of components is recommended to be greater than 100.
The more you repeat, the better..
