What's the prefabricated building?
What are its advantages?
How exactly are prefabricated building made?
How was the construction done?
Let's take a look
01
What's the prefabricated building
As with Lego, the prefabricated building will have some or all of the components prefabricated in a factory and then shipped to a construction site for assembly.
“Assembly” is not just“Build”, prefabricated components to the construction site, will be reinforced concrete lapping and pouring, so the assembly room is very safe. This“Industrialization”, “Industrialization” of the building in Europe, the United States and Japan has been widely used.
First of all, the external wall is this kind of lock-type splicing, but also some of the steel frame docking. Then fill, and finally join the sealing strip seam sealant.
When building the inner wall, first install the skeleton, and then directly splice, both convenient and fast, but also to facilitate subsequent demolition.
It is not unreasonable for the state to promote prefabricated building prefabricated building, which is faster and easier to build than traditional methods, and also saves manpower and materials.
These small prefabricated panels are the most important part of the construction process. Although they look simple, they require accurate data to ensure the stitching is successful, so they need to be painted with extra care.
02
What are the advantages of prefabricated building?
Why are these advanced capitalist countries so prefabricated building?
The reasons are as follows:
1, to improve the quality of construction
The fabricated components are prefabricated in the factory, which can improve the common quality defects such as wall cracking and leakage to the maximum extent, and improve the overall safety level, fire resistance and durability of the residence.
2, to speed up the progress of the project
Efficiency is a return, prefabricated building about 30% faster than the traditional approach.
3, to improve the quality of construction
Hyaluronic acid in the construction industry, can make the construction products long-term, eternal youth. After the factory interior decoration, can be achieved at home delivery, that is, disassembly is installed, fast and good.
4. It helps to adjust the supply relationship
Increase the speed of the listing of real estate, slow the current situation of insufficient supply of the market, buy a house from now on do not have to wait in line all night. After the popularization of the industry, can reduce construction costs, can effectively curb housing prices.
5, is advantageous to the civilization construction, the safety management
Traditional job site has a large number of workers, now a large number of site work to the factory, the site only a small number of workers on the line, greatly reducing the site safety accident rate.
6. Environmental Protection and Resource Conservation
On-site original cast-in-place operations rarely, health does not disturb the people, from now on bid farewell to“Grey Misty.”. In addition, steel formwork and other re-use rate, waste, loss, energy-saving can be reduced by more than half.
03
How are components produced?
Taking the prefabricated building plate as an example, the production process is: steel mold making → steel bar binding → concrete casting → mold release.
Holes should be left in the steel bar for binding.
The hook should be embedded when the steel bar is tied.
Concrete casting, assembly line operation.
After demoulding, the finished assembly board and the Assembly components are finished, and then they are sorted and stacked in the factory for the time being, ready to be transported to the construction site.
The finished assembled components are loaded on the road and transported to the site.
04
Construction process
Take the prefabricated frame structure as an example, after the construction of the first floor is completed, the first floor column is hoisted, followed by the main beam, secondary beam, floor slab.
After the hoisting of the precast members is finished, the reinforcing bars at the connecting parts are bound, and the joints and the cast-in-place floor of the beam and slab are poured at last.
What is the most technically demanding of the above steps?
The answer is the Assembly of components hoisting.
In order to ensure the smooth lifting, the assembly of components to the scene, the need to arrange a reasonable stacking site, convenient lifting. Just like moving house, the order of moving goods is usually arranged to reduce the workload reasonably.
How does this most important lifting step work?
Assembled column hoisting
The mirror above is prepared for the assembly of the column lifting, the lower space is narrow, not easy to observe, through the small mirror reflection principle, to facilitate the lower reserved steel bar and the upper assembly of the column hole plug.
Assembled composite beam hoisting
Assembly type plywood hoisting
For the parts that are difficult to be lifted, they can also be pre-assembled on the spot or build an assembly-type display area to play an exemplary role.
The frame structure of Kaifeng's prefabricated and shear wall residential display area
After hoisting, tie down the steel bars of the cast-in-place layer and prepare to pour the cast-in-place layer concrete.
In order to increase the connection between the fabricated component and the cast-in-place layer and ensure the reliability and safety of the structure, the surface of the fabricated component is left with keyway or rough treatment.
There are many kinds of connections between the assembled members. Currently, the floor slab is usually in the form of 7 + 8(70mm thick precast floor slab + 80mm thick cast-in-place floor) . Taking the connection of primary and secondary beams as an example, this paper shows the variety of connection treatment methods between assembled members:
Primary and secondary beam connection side node-the main beam reserved groove
In the connection of primary and secondary beams, the post-cast section of the main beam is reserved
Primary and secondary beam connection-the main beam with bracket
How can so many components not go wrong?
That is to number the assembled components!
In order to ensure that workers do not make mistakes, reduce construction errors, speed up the progress of the project, to each component of the ID card, they have their own unique ID number, easy to seat.
Walls, panels, staircases and other fabricated components have their own unique number.
05
Cost control
Cost control and design management are the Zhang Sengyou of the prefabricated building implementation process.
There are two important prefabricated building, the proportion of assembly area and the prefabrication rate.
Assembly rate = total floor area for the implementation of assembly.
Prefabrication rate = total volume of assembled components total concrete volume.
The higher the prefabrication rate, the higher the cost, preliminary statistics, prefabrication rate per 10% increase in cost increment of about 150 yuan.
Therefore, cost control is one of the key control points in the prefabricated building implementation process.
First of all, the assembly type to avoid the scope of choice in the first open area. According to the requirement of assembly area in the transfer contract, the project cycle can be balanced by developing in stages. The time cost of the first phase of development is under pressure due to the advance coordination of prefabricated components with plants and the limited capacity of these plants.
Secondly, the structural components need to be split to select the high repetition rate of prefabricated components monomer, the general component repetition rate is recommended to be greater than 100. The more you repeat, the better.
With so many assembled components, how do you choose which ones to split?
A. The size of prefabricated components should follow the principle of less specification/more combination.
C. The position of precast shear wall joint is chosen where the structure bears less stress.
D. When the long members are split, the symmetrical center can be considered.
Don't. Considering the influence of demoulding/stacking/transportation/hoisting, the weight of single member should be as close as possible, and the height should not exceed 6t, and the length should not exceed 6m.
Compared with the traditional cast-in-place building, the fabricated building requires higher degree of cooperation among the various specialties, and needs the participation of various specialties as early as possible:
A. Major in architecture
To consider the external facade style, thermal insulation form, drop plate area, stair floor practice, embedded window frames, tiles, stone reverse impact.
B. Major in equipment
Involving the pre-fabricated components of the pre-hole, pre-embedded pipe, drawing refining workload is very large.
C. Major in interior design
Involves the electromechanical point to raise funds, the intervention time is greatly advanced.
D. Construction
Need the total package, hoisting unit, component manufacturers are involved in advance.
At the same time, BIM simulation is also carried out in the design process, considering the position relationship and connection between the prefabricated steel bar and the cast-in-place steel bar, and greatly reducing the dislocation and collision of the members in the construction process.
The prefabricated building has had a different impact on many existing building practices, most notably on the thermal insulation of external walls and stone facades.
Our prefabricated building industry is at an early stage and needs the government to set targets, tasks, support policies, incentives and push forward and guide the development of the industry. Even so, the prefabricated building has encountered many difficulties in the short term, such as rising costs, extension of construction period, developers wait and see, construction experience, lack of technical reserves, the system to be improved and so on. In the future, this will change dramatically, and as the prefabricated building gets bigger, eventually the market will gain new momentum.