(1) According to the situation of raw materials in the regional market, different proportion tests shall be carried out to ensure the timely adjustment of proportion in the construction process.
three-phase five wire power cable, is adopted in the center of the power line power supply system directly grounded at the special center point on the construction site.
(2) Adjust the construction mix proportion of the laboratory mix proportion in combination with the water content and mud content of raw materials to ensure the actual universality of the laboratory mix proportion.
Design measures (1) “Setting out” measures: set up permanent expansion joints; Separate joints shall be reserved at appropriate positions on the outer wall.
Track and record the measures taken for maintenance and on-site maintenance, find problems in time and ensure the effectiveness of maintenance.
At the same time, combined with internal and external control, the vertical projection error of high-rise buildings can be reduced to the minimum.
(3) Scaffolding and protective railings: the construction layer shall be fully paved, and the dense mesh safety net shall be fully closed.
According to the standard for inspection and evaluation of concrete strength (gbj107), the concrete strength shall be inspected and evaluated in batches.
(3) Distribution box and switch box: three-level distribution and two-level protection shall be adopted, and the two-level leakage protectors shall be matched..
So how to overcome and control the strength of concrete? Proportion selection before the commencement of the project, the concrete with different strength grades shall be prepared according to the design requirements, and the grading test shall be conducted at the legal test institution.
(5) Unloading platform: there shall be calculation sheet and erection scheme, with independent support system.
(2) In the process of verticality control, the laser instrument weighting hammer is used for double comparison, so as to increase the accuracy of verticality.
Hanging two lines and pouring the shear wall are the key to the process line control.
Control of building cracks it can be seen from table 3.3.4 of code for design of concrete structures (GB50010-2002) that the crack width has different control standards for different concrete structures under different environments, and the maximum allowable crack is 0.2mm ~ 0.4? 50.
(4) Material: steel pipe Q235 (3# steel), with outer diameter of 48mm and inner diameter of 35mm.
(2) Support system: construction details shall be prepared after sufficient calculation.
(4) During the construction process, strengthen the monitoring of pit wall, and deal with abnormalities in time.
(3) Measures of combining “release” and “resistance”: reasonably set the post cast strip, adopt corresponding shrinkage compensating concrete technology, and mix cellulose in the concrete.
The “three lines” control axis, elevation and perpendicularity of high-rise buildings are similar to the meridians of buildings.
(3) Drainage measures shall be taken for the side and inside of the foundation pit.
Construction electricity (1) must be provided with electricity room, two-level protection, three-level power distribution, and construction machinery to achieve “four ones”; TN-S system, i.e.
How to control the quality and safety of high-rise buildings because the investment of high-rise buildings is relatively large, the construction period is long, the amount of concrete pouring is large, and the project quality and safety have its particularity.
However, as for crack control, it should focus on pre control, and then remedy when the crack is opened and the crack is increased, which is a last resort.
A warning line shall be set during demolition and supervised by a specially assigned person.
Here, the safety management is summarized as follows: foundation pit support (1) Before foundation pit excavation, the support scheme shall be determined according to the soil condition, foundation pit depth and environment.
Strict maintenance system, pumping concrete is mostly used in high-rise buildings.
In the process of high-rise building construction, the scaffold and the construction layer move upward synchronously, resulting in the inability to measure from some peripheral datum points.
(2) Connection between frame and building structure: two steps and three spans, rigid connection or flexible hardtop.
Strengthen the concrete strength evaluation.
(2) Strengthen the supervision during the curing period.
Control of elevation line (1) locate the elevation at least at four openings of the pre control axis on each floor, recheck the sum of multi-layer elevations, and then level with a level gauge to recheck whether these four points are on the same horizontal plane to ensure the accuracy of elevation.
(2) Among them, the accuracy of the elevation of the four openings is required to be improved.
The control of “three lines” is a major difficulty in high-rise buildings.
After the masonry, the interval shall be at least one week, and it shall be filled and compacted after 15 days; Reasonable joint and block construction; It is advisable to pour and tamp in layers at variable sections such as columns, beams and wallboards.
After the grading report is issued, the mix proportion test (laboratory proportion) shall be conducted according to the grading, which shall be carried out in the actual construction.
Due to formwork, pouring, loading and other reasons in the construction process, the elevation of the openings may lose its benchmark function.
(3) Set up storey height and cumulative storey height review points at the four corners and surrounding areas of the building where conditions are met, and each floor is attached with this position for review to prevent excessive cumulative error.
Axis control (1) axis transmission.
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(4) The removal of formwork shall be carried out according to the procedures specified in the scheme, and the non bearing part shall be removed first.
Strength control of high-rise buildings due to the large amount of concrete, long construction period and many influencing factors of climate and working conditions, sometimes the concrete strength is discrete and even unqualified.
(2) “Anti” measures: avoid stress concentration caused by sudden change of structural section: pay attention to the configuration of structural reinforcement; For lightweight walls such as small concrete hollow blocks, structural columns with a spacing of ≯ 3M shall be added, and a concrete waist beam with a thickness of 120mm and the same width as the wall shall be added in the middle of each wall height; Structural columns shall be added at the unconstrained end of masonry; The reserved door and window openings are reinforced with reinforced concrete frames; The junction of two different substrates shall be treated with steel wire mesh (overlapping ≮ 150mm on each side); Reasonable setting of roof insulation layer and air barrier, etc.
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In the prevention of concrete cracks, the early maintenance of fresh concrete is particularly important.
The concrete of an acceptance batch shall be composed of concrete with the same strength grade, the same age and basically the same production process conditions and proportion.
The safety management of high-rise buildings has prominent safety problems due to the long construction cycle of high-rise buildings, many open-air high-altitude operations, poor working conditions, and the concentration of a large number of personnel intensive work in a limited space, with great mutual interference.
(2) Safety protection measures shall be taken around the deep foundation pit (H ≥ 2m), and heavy objects are not allowed to be stacked within 1.2m from the pit.
Verticality control (1) controlling verticality is not only the basis to ensure the quality of high-rise buildings, but also one of the key links.
For high-rise buildings, displacement or inaccuracy often occur due to wide coverage and difficult operation.
(3) Measures combining “release” and “resistance”.
Scaffold (1) the scaffold of high-rise building shall be fully calculated, and the scaffold scheme prepared according to the characteristics of the project and construction technology shall be attached with calculation sheet.
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(3) The installation of formwork shall comply with the construction scheme, and measures shall be taken to maintain the temporary stability of formwork during the installation process.
Malleable cast iron is used for welded steel pipe and fasteners.
(1) There shall be a curing scheme for the concrete poured in a large volume, and a special person shall be responsible from the beginning of curing to the end of curing, and have sufficient understanding of curing from the subjective consciousness.
Pumping concrete can not only shorten the construction period, but also improve the construction performance of concrete.
Construction measures (1) ‘placing’ measures: the infilled wall shall be built close to the beam bottom, and a certain height shall be reserved.
Formwork engineering (1) construction scheme: it shall include the construction procedures for the design, fabrication, installation and removal of formwork and support, and formulate targeted measures for pumping concrete and seasonal construction.
(2) Control of process line.
(2) “anti” measures: ① try to avoid using cement with early strength and high strength, actively use admixtures and concrete admixtures, and reduce the amount of cement (preferably < 450kg / m3).
For the pouring of shear wall, 18mm thick high-quality plywood should be used, the large formwork should be combined and fixed on the periphery of the outer wall, and the combined formwork should be numbered by bulk disassembly of the inner wall.
(2) Grounding and neutral protection system: ensure that the resistance value is less than the specification.
