by [Abstract] compared with traditional buildings, precast buildings have short construction cycle and less pollution.
Therefore, precast buildings have developed very rapidly in recent years.
In the actual construction process of precast buildings, the use of appropriate construction technology will help to further improve the overall performance of precast buildings.
Taking a precast building project as an example, this paper analyzes the construction technology and key and difficult points of precast structure building, in order to provide useful reference for industry staff.
1.
Overview of a precast complex building construction project.
The average floor height of a complex building is 4.32m, the number of floors is 5, and the total building height is up to 21.6m.
It is a concrete precast shear wall structure.
The concrete strength is C30 or above, and the monomer prefabrication rate exceeds 40%.
As in the non seismic area, the seismic fortification intensity is 6 according to the design requirements, and the seismic fortification category is class C.
The design service life is 50 years, the construction engineering grade and fire resistance grade are grade II, and the roof waterproof grade is grade I according to the design specifications.
It is constructed by means of processing and production in the precast component factory and hoisting on the construction site, and precast components such as precast sandwich external wall hanging plate, internal wall plate, PK prestressed concrete laminated plate (hereinafter referred to as laminated plate) and precast stairs are assembled.
2 key and difficult points of project construction 2.1 difficulties in the construction of assembled integral residential PC.
the project is an assembled integral project, in which the floor, exterior wall, balcony plate, composite beam and staircase are precast components.
The following problems must be solved in the assembled integral residential PC project: transportation and stacking of precast components.
Different transportation modes need to be considered for different types of components.
For example, whether the outer wall panel should be transported square or vertically needs to be comprehensively considered after considering factors such as transportation cost, transportation quantity per vehicle, transportation stacking mode, transportation fixation mode and vehicle load limit requirements of transportation vehicles.
Hoisting and fixing of precast components.
According to the maximum weight of a single precast component, combined with the size of the component and the rotation radius of the tower crane, select the appropriate tower crane machinery after selection and comparison.
Improper selection of the lifting method of the component is easy to cause the deformation of the precast component, thus affecting the quality of the precast component.
During the hoisting of precast components, pay attention to the moving speed of the boom to make the components move at a uniform speed.
At the same time, protect the edges and corners of precast components from collision.
When moving close to the installation position, professional personnel need to manually assist the centering and positioning operation.
2.2 different from cast-in-situ buildings, the precast building project site is mainly hoisting, so the project is equipped with a large number of tower cranes, and a building is equipped with at least one tower crane.
The tower crane is fully covered, there are many cross operations, and there are many safety facilities within the operation range of the tower crane.
In the process of lifting the tower crane section, the vertical direction is difficult and the risk factor is high.
The lifting time, installation mode and personnel arrangement of the tower crane section must be implemented in strict accordance with the plan to ensure no conflict with the construction schedule of other floors.
At the same time, affected by the construction period requirements, during the superstructure and decoration construction, a large number of construction materials need to be lifted to the upper construction level for construction in time, which is particularly important for the selection and allocation of vertical transportation machinery.
2.3 the working surface of tower crane is small, the volume of precast components is large, and they are transported to the site in time for reasonable stacking.
A large stacking site is still required.
The reinforcement area of the stacking site is wide, resulting in a small working surface of tower crane.
The working area available for turnover within the construction scope of underground works is small, the number of single-layer precast components in a single building is large, the storage yard of horizontal precast components covers a wide area, the distance between single buildings is close, the construction road for tower crane cross operation is wide, the turning radius is large, and the available area of hoisting site is narrow, which increases the difficulty of tower crane operation.
3 cast building construction technology and technology 3.1 positioning measurement in the construction of new PC residence, positioning measurement should be done well, and the site elevation should be controlled, so as to provide guarantee for construction quality.
The plane can be controlled by the network control method, a square grid is arranged on the site, and 4 pilot points are set in each floor.
During the axis survey, the vertical control points can be arranged on the basement roof according to the building plane shape and with the help of the control network set on the ground to form a cross with the control network.
Attention shall be paid to ensure that the control network can avoid columns, beams and walls in each floor, and good intervisibility shall be maintained between points, which shall not be blocked by core barrel and other structures.
During the pouring of the concrete roof of the basement, the fixed survey points shall be arranged at the intersection points, and after the pouring of the roof, the survey and setting out shall be completed based on the survey points.
In the process of using the high precision theodolite to guide the test, the instrument can be erected at the control points in the middle.
In order to ensure the accuracy of the measurement results, the instrument should be leveled.
The specific survey method is as follows: an operator places the control point on the reserved hole and communicates through the walkie talkie to make the theodolite cross line completely coincide with the receiving target cross line under the condition of continuously adjusting the accuracy.
Then, corresponding marks shall be made at the reserved holes, and cross lines shall be snapped on the concrete, so as to complete the pilot survey of this point.
3.2 PC component hoisting in order to ensure the orderly hoisting of PC components, all PC components in each floor shall be hoisted in place in a counterclockwise direction along the outer facade.
During hoisting, the sequence must be correct to avoid rework.
The relevant technical points are as follows.
Before hoisting, flexible materials can be used to fill the joints of PC wallboard components, including vertical joints and horizontal joints.
After filling, the double-sided adhesive tape can be used for pasting.
In order to ensure the effective bonding of the adhesive tape, the dust, ponding and other sundries at the part where the adhesive tape is pasted shall be cleaned before the formal hoisting of the components of PC wallboard, and the components of PC wallboard shall be hoisted after the adhesive tape is pasted..
