CN117027038A - Construction method of ultra-long large-volume bearing platform for large aircraft test - Google Patents

Abstract

The invention discloses a construction method of an ultra-long large-volume bearing platform for a large aircraft test, which comprises the following steps of: s1: pouring foundation piles; s2: measuring and lofting, excavating a foundation pit, treating the pile head of a foundation pile, and pouring a cushion layer; s3: setting up a template, binding reinforcing steel bars, performing first layer bearing platform concrete pouring, adopting C30 micro-expansion compensation type concrete within the 1m range of the bearing platform end, adding 10% of expansion agent, burying a cooling pipe and a temperature measuring element, and performing maintenance and foundation pit backfilling; s4: measuring and lofting again, roughening the surface of the concrete of the first layer of bearing platform, brushing cement slurry interface agent, standing templates, binding reinforcing steel bars, installing high-strength reinforcement net, performing concrete pouring of the second layer of bearing platform, adopting compensating concrete, adding 16% of expansion agent, embedding cooling pipes and temperature measuring elements, and curing. Has the advantages of stable structure and high strength.

Description

A construction method for an ultra-large volume platform used for large aircraft testing

Technical field

The invention relates to the technical field of building construction, and in particular to a construction method of an ultra-large volume platform used for large aircraft testing.

Background technique

The large aircraft ground dynamics test platform is the first test platform in related fields in China. It is of great significance and has far-reaching influence. After completion, it will test various aircraft tires, wheel brakes, and landing gear systems. The high-speed dynamic characteristics and performance on different road surfaces will be tested. Dynamic characteristics of large slip angles under real runways, collecting basic data, breaking foreign monopoly on basic data of key technologies, and filling a domestic gap.

The test platform is located in Hunan, where there are large temperature differences throughout the seasons. Since the cap platform is a very large volume concrete structure, it is easy for cracks to appear in the concrete structure of the cap platform due to temperature changes, destroying the stability of the main structure. At the same time, the test platform uses a test bench to simulate A large aircraft conducts dynamic ground testing. The test rig is very fast and will impose a huge load on the platform. The strength requirements for the concrete structure of the platform are very high.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the shortcomings of the existing technology and provide a construction method of an ultra-large volume platform for large aircraft testing with stable structure and high strength.

In order to solve the above technical problems, the present invention adopts the following technical solutions:

A construction method for an ultra-large-volume cap platform used for large aircraft testing. The cap platform is cast in separate molds and includes the following steps:

S1: Pouring foundation piles;

S2: Measure and set out, excavate the foundation pit, process the foundation pile heads, and then pour the cushion;

S3: After the cushion strength reaches the design requirements, the formwork is erected, the steel bars are tied, and then the first layer of concrete is poured for the cap. C30 micro-expansion compensating concrete is used within 1m of the end of the cap, and 10% expansion agent is added to the concrete. Cooling pipes and temperature measuring elements are buried in the middle, and maintenance and foundation pit backfilling are carried out after the pouring is completed;

S4: After the strength of the first layer of platform reaches the design requirements, measure and stake out again, chisel the concrete surface of the first layer of platform, apply cement slurry interface agent, then erect the formwork, tie the steel bars, install high-strength reinforcement mesh, and then proceed. The concrete for the second floor cap is poured using compensating concrete with 16% expansion agent added. Cooling pipes and temperature measuring elements are buried in the concrete. After the pouring is completed, maintenance is carried out.

As a further improvement of the above technical solution:

In step S3, the formwork is made of bricks and the concrete mix ratio is C30.

The limited expansion rate of the expansion agent in water for 14 days is ≥0.030, and the limited expansion rate of the expansion agent in air for 28 days is ≥-0.030.

In step S4, the formwork adopts a shaped steel formwork, and reinforced mesh is installed on the sides and top of the second layer of platform. The reinforced mesh is a high-strength reinforced mesh with a diameter of 2mm and a grid size of 50×50mm.

In step S4, the compensating concrete mix ratio is set to: cement: water: sand: gravel: fly ash: water reducing agent: expansion agent = 1: 0.48: 2.48: 3.32: 0.19: 0.041: 0.226.

The limited expansion rate of the expansion agent in water for 14 days is ≥0.040, and the limited expansion rate of the expansion agent in air for 28 days is ≥-0.020.

In steps S3 and S4, an appropriate amount of admixture is added to the concrete.

In steps S3 and S4, a post-cast expansion reinforcement belt is set between each mold cap. The closing time of the post-cast expansion reinforcement belt is controlled to be the lowest temperature on the day of construction 28 days after the construction of each mold cap.

In steps S3 and S4, after the concrete pouring is completed, the heat preservation and moisturizing time is not less than 42 days.

In steps S3 and S4, the temperature rise of the concrete pouring body based on the mold entry temperature is ≤50°C, the temperature difference between the inside and outside of the concrete pouring body is ≤25°C, the cooling rate of the concrete pouring body is ≤2.0°C/d, and the concrete is poured when the insulation cover is removed The temperature difference between the body surface and the atmosphere is ≤20℃.

Compared with the prior art, the advantages of the present invention are:

The construction method of the ultra-large volume cap for large aircraft testing of the present invention adopts a pile cap structure. The foundation pile and cap are jointly stressed, the load is balanced, and the structural strength is high. The cap is poured in layers, and the concrete Shrinkage-compensating concrete is used, and expansion agents are added to the concrete to further improve the structural strength of the cap platform. Cooling pipes are set up for temperature control to avoid cold joints and ensure the stability of the concrete structure of the cap platform.

Description of the drawings

Figure 1 is a construction flow chart of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and specific examples.

As shown in Figure 1, the construction method of the ultra-large volume cap platform used for large aircraft testing in this embodiment, the cap platform split mold pouring, includes the following steps:

S1: Pouring foundation piles;

S2: Measure and set out, excavate the foundation pit, process the foundation pile heads, and then pour the cushion;

S3: After the cushion strength reaches the design requirements, the formwork is erected, the steel bars are tied, and then the first layer of concrete is poured for the cap. C30 micro-expansion compensating concrete is used within 1m of the end of the cap, and 10% expansion agent is added to the concrete. Cooling pipes and temperature measuring elements are buried in the middle, and maintenance and foundation pit backfilling are carried out after the pouring is completed;

S4: After the strength of the first layer of platform reaches the design requirements, measure and stake out again, chisel the concrete surface of the first layer of platform, apply cement slurry interface agent, then erect the formwork, tie the steel bars, install high-strength reinforcement mesh, and then proceed. The concrete for the second floor cap is poured using compensating concrete with 16% expansion agent added. Cooling pipes and temperature measuring elements are buried in the concrete. After the pouring is completed, maintenance is carried out.

This method uses a pile cap structure. The foundation piles and the cap are jointly stressed. The load is balanced and the structural strength is high. The cap is poured in layers. The concrete is shrinkage-compensating concrete. An expansion agent is added to the concrete to further improve the bearing capacity. The strength of the platform structure is increased, and cooling pipes are installed in the concrete for temperature control to avoid cold joints and ensure the stability of the concrete structure of the platform.

In this embodiment, the total length of the cap platform is 1067m, and it is poured in 38 molds.

In this embodiment, in step S3, the formwork is made of bricks, and the concrete mix ratio is C30. Among them, the first floor cap is 11.2m wide and 0.9m high. The formwork is made of bricks. When tying the steel bars, the steel bars exceeding 25mm are mechanically connected. The concrete within 1m of the end and the ordinary concrete in the middle are poured simultaneously in layers. A truck crane and a hopper are used for pouring, and a truck pump is used for pouring in the middle. The end concrete is made of compensating concrete, with 10% UEA expansion agent added to it. The concrete expansion stress compensates for the shrinkage stress caused by the temperature difference after the structure is closed.

In this embodiment, the limited expansion rate of the expansion agent in water for 14 days is ≥0.030, and the limited expansion rate of the expansion agent in air for 28 days is ≥-0.030.

In this embodiment, in step S4, the formwork adopts a shaped steel formwork, and reinforced mesh is installed on the sides and top of the second-layer platform. It enhances the crack resistance and strength of concrete structures.

In this embodiment, in step S4, the compensating concrete mix ratio is set to: cement: water: sand: gravel: fly ash: water reducing agent: expansion agent = 1: 0.48: 2.48: 3.32: 0.19: 0.041: 0.226. By using cement with small shrinkage, the water-cement ratio and the amount of cement slurry are reduced, the quality of concrete is improved, the final setting temperature of concrete is reduced, and the shrinkage stress of concrete is reduced.

In this embodiment, the limited expansion rate of the expansion agent in water for 14 days is ≥0.040, and the limited expansion rate of the expansion agent in air for 28 days is ≥-0.020.

In this embodiment, in steps S3 and S4, an appropriate amount of admixture is added to the concrete. Adding admixtures can significantly improve the properties of concrete and increase the structural strength of concrete.

In this embodiment, in steps S3 and S4, a post-cast expansion reinforcement belt is set between each mold cap, and the closing time of the post-cast expansion reinforcement belt is controlled to be the lowest temperature on the day of construction 28 days after the construction of each mold cap. Post-cast expansion reinforcement strips are installed to reduce the impact of residual shrinkage deformation of concrete and enhance the crack resistance of concrete.

In this embodiment, in steps S3 and S4, the heat preservation and moisturizing time is not less than 42 days after the concrete pouring is completed.

In this embodiment, in steps S3 and S4, the temperature rise of the concrete pouring body based on the mold entry temperature is ≤50°C, the temperature difference between the inside and outside of the concrete pouring body is ≤25°C, and the cooling rate of the concrete pouring body is ≤2.0°C/d. The demolition When covered with thermal insulation, the temperature difference between the surface of the concrete pouring body and the atmosphere is ≤20°C. . By setting up cooling pipes and other insulation measures, the temperature of the concrete is controlled to prevent cracks and ensure the stability of the concrete structure.

Although the present invention has been disclosed above in terms of preferred embodiments, this is not intended to limit the present invention. Any person familiar with the art can, without departing from the scope of the technical solution of the present invention, use the technical content disclosed above to make many possible changes and modifications to the technical solution of the present invention, or modify it into equivalent implementations with equivalent changes. example. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims (10)

1. A construction method for an ultra-large volume cap used for large aircraft testing. The cap is cast in separate molds and is characterized by: including the following steps: S1: Pouring foundation piles; S2: Measure and set out, excavate the foundation pit, process the foundation pile heads, and then pour the cushion; S3: After the cushion strength reaches the design requirements, the formwork is erected, the steel bars are tied, and then the first layer of concrete is poured for the cap. C30 micro-expansion compensating concrete is used within 1m of the end of the cap, and 10% expansion agent is added to the concrete. Cooling pipes and temperature measuring elements are buried in the middle, and maintenance and foundation pit backfilling are carried out after the pouring is completed; S4: After the strength of the first layer of platform reaches the design requirements, measure and stake out again, chisel the surface of the concrete of the first layer of platform, apply cement slurry interface agent, then erect the formwork, tie the steel bars, and then concrete the second layer of platform. For pouring, the concrete is made of compensating concrete, in which 16% expansion agent is added. Cooling pipes and temperature measuring elements are buried in the concrete. After the pouring is completed, maintenance is carried out. 2. The construction method of an ultra-large volume platform for large aircraft testing according to claim 1, characterized in that in step S3, the formwork is made of bricks, and the concrete mix ratio is C30. 3. The construction method of an ultra-large volume platform for large aircraft testing according to claim 2, characterized in that: the expansion agent has a limited expansion rate of ≥0.030 for 14 days in water and a limited expansion rate of 28 days in air. Rate ≥-0.030. 4. The construction method of an ultra-large-volume platform for large aircraft testing according to claim 3, characterized in that: in step S4, the template adopts a shaped steel formwork, and the sides and top of the second layer of platform are installed and reinforced. Reinforced mesh, the reinforced mesh is a highly reinforced mesh with a diameter of 2mm and a mesh size of 50×50mm. 5. The construction method of an ultra-large volume platform for large aircraft testing according to claim 4, characterized in that: in step S4, the compensating concrete mix ratio is set to: cement: water: sand: Crushed stone: fly ash: water reducing agent: expanding agent = 1: 0.48: 2.48: 3.32: 0.19: 0.041: 0.226. 6. The construction method of an ultra-large volume platform for large aircraft testing according to claim 5, characterized in that: the expansion agent has a limited expansion rate of ≥0.040 for 14 days in water and a limited expansion rate of 28 days in air. Rate ≥-0.020. 7. The construction method of an ultra-large volume platform for large aircraft testing according to claim 1, characterized in that: in steps S3 and S4, an appropriate amount of admixture is added to the concrete. 8. The construction method of an ultra-large volume cap for large aircraft testing according to claim 7, characterized in that: in steps S3 and S4, post-cast expansion reinforcement strips are provided between each mold cap. The closing time of the post-cast expansion reinforcement belt is controlled to be the lowest temperature on the day of construction 28 days after the construction of each mold cap. 9. The construction method of an ultra-large volume cap platform for large aircraft testing according to claim 8, characterized in that: in steps S3 and S4, after the concrete pouring is completed, the thermal insulation and moisturizing time is not less than 42 days. . 10. The construction method of an ultra-large volume platform for large aircraft testing according to claim 9, characterized in that in steps S3 and S4, the temperature rise of the concrete pouring body is ≤50 based on the mold entry temperature. ℃, the temperature difference between the inside and outside of the concrete pouring body is ≤25℃, the cooling rate of the concrete pouring body is ≤2.0℃/d, and the temperature difference between the surface of the concrete pouring body and the atmosphere is ≤20℃ when the insulation cover is removed.