The application of jump BIN method.
According to the project response, the later pouring effect of the post cast strip is often not ideal, and the post cast strip itself is often found to be cracked in the acceptance; 5) The turnover of formwork is seriously affected.
In 2013, Beijing began to prepare Beijing local standards, and formally implemented DB11 / t1200-2015 technical specification for jump BIN method for super long mass concrete structures in August 2015.
(the total length of box raft equipment foundation is 686m) and Shanghai Baosteel (the total length of box equipment foundation is 912m), Professor Wang tiemeng adopted the jump BIN method for overall construction without leaving post pouring belt, achieved good results and accumulated practical experience.
The basic principle of the skip BIN method is “the combination of resistance and release, release first and then resistance”.
For the first two problems, designers usually set expansion joints or expansion post cast strips and other measures, such as adding reinforcement, adding expansion agent, adding fiber, strengthening maintenance, etc; In view of the latter problem, the measures of setting settlement joint or settlement post pouring belt are usually adopted.
Subsequently, the jump BIN method was gradually popularized in civil engineering all over the country, and the structural crack control center was established in many places and departments (jump BIN method is one of the important measures).
However, everything has its advantages and disadvantages.
Three problems need to be solved for super long and super large basement: first, the shrinkage of concrete in the setting process; Second, the stress problem of super long and super large concrete in use; Third, the vertical deformation difference caused by the height difference of superstructure, foundation form and foundation bearing layer.
Because the plates on both sides, two bottom forms and supports of the post cast strip (referring to the floor) cannot be removed, a large part of the formwork cannot be turnover for a long time, especially the post cast strip cannot be removed for several months or even 1 ~ 2 years; 6) Impact on construction progress: grade separation operation affecting electromechanical and decoration; Affect the stacking and hoisting of components; 7) Before the settlement post pouring belt is closed, the backfill of the basement roof cannot be backfilled, and the site cannot be leveled and used, resulting in unsmooth roads and great difficulties for the whole site construction.
In the 1970s, during the construction of Wuhan Iron and Steel Co., Ltd.
On November 28, 2019, China Engineering Construction Standardization Association issued T / cecs640-2019 technical specification for jump BIN method of super long mass concrete structure.
The idea of “release” is the same as the principle of post cast strip construction, which is to cut the structure to release the shrinkage stress.
Aiming at the problems mentioned in Section 2, it has evolved to the third generation of “jump bin method (seamless block resistance method)”.
Therefore, the current mainstream trend is to try not to set joints if the post cast strip can solve the problem.
The rust removal of reinforcement is not only laborious, but also not suitable for cleaning, which affects the quality; 2) The long-term existence of post cast-in-place settlement belt (generally closed only after the main building is capped) is easy to cause potential safety hazards, especially for deep foundation pit; 3) The post cast-in-place belt of settlement exists for a long time, and the high water level area (especially confined water) must be dewatered for a long time, which seriously affects the construction, high construction cost and waste of water resources, which not only does not comply with the green construction, but also may affect the safety of surrounding buildings; 4) During the concrete pouring of the post cast strip, the structure at this place has long been closed, so the concrete transportation is very difficult and the pumped concrete cannot be used.
During this period, the concrete stress is relaxed, the tensile performance is improved, the stress of front and rear bins is superimposed, the tensile stress is reduced, which is conducive to controlling the temperature shrinkage stress and harmful cracks, Permanent deformation joints and post cast strips shall be avoided.
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Before the post cast strip is closed and poured, the basement is always in a water leakage state, and rainwater, sundries and various forms of garbage enter the post cast strip, causing pollution and corrosion of reinforcement.
At this time, there are more than 60 projects constructed by jump BIN method in Beijing and more than 150 projects in China.
In fact, even if we open article 13.9.7 of jgj3-2010, “the construction of super large volume concrete can be carried out by retaining deformation joint, post cast strip construction or jumping warehouse method”.
Jump BIN method originated in the field of industrial construction.
The skip BIN method is to divide the structure into bins according to the non cracking length, and adopt the skip bin pouring method for mass concrete structure according to the concrete supply conditions.
The concept of skip warehouse method is very simple and has many benefits for project management.
It can be seen that the skip BIN method is a mature measure to control the cracks of super large volume concrete in both application practice and code provisions.
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3.
We should not only pay attention to the advantages of the jump position method, but also see its shortcomings.
It mainly starts from controlling the performance of concrete raw materials and optimizing the concrete mix proportion, including controlling the particle size, gradation and mud content of aggregate, minimizing the amount and water consumption of cementitious materials, controlling the molding temperature and slump of concrete, and “good beating” of concrete Ensure the homogeneity and compactness of concrete.
Solution – active crack control technology is adopted for super large volume concrete in jump bin France, which has evolved from the first generation of “permanent deformation joint method” to the second generation of “post cast strip method”.
As the setting of joints in the basement has a great impact on the later use, it is inevitable to have problems such as water leakage.
If we search the relevant literature of jump position method, there are almost all praise words.
The regulation was implemented on April 1, 2020.
Application examples include: underground commercial street of Xiamen Wucun bus station, Xiamen Baolong first city, Xiamen Strait Exchange Center Phase II, resettlement house of unit a in xiongdong area of xiong’an new area, Shenzhen Qianhai zhoudafu financial building project, Guangzhou Knowledge tower project, Haikou Meilan Airport, Hangzhou World Expo Center project, etc.
With the increasing number of civil projects with super long and deep foundation pits, some large civil projects have tried the jump warehouse method, such as the floor of Guiyang Airport, the floor of Shenyang Wanda, the floor of Xiamen International Conference Center, the floor of Strait Exchange Center, etc.
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The warehouse jumping method is to change two joints of the post cast strip method into one joint (construction joint), in which a steel plate waterstop is set.
Problems of skip warehouse method.
NOCITCE changed the push rule because of WeChat official account.
Schematic diagram of skip warehouse method construction 5.
The idea of “resistance” is to improve the tensile strength of concrete as much as possible without increasing the amount of cementitious materials.
The hydration heat release rate of cementitious material (cement) is fast, reaches the peak in 1D ~ 3D, then decreases rapidly, and approaches the ambient temperature in 7d ~ 14d.
2.
Only manual transportation can be used for slow pouring, and special personnel shall be assigned for curing for 14 days, which is scattered and difficult to manage.
It takes a lot of labor to clean up.
The interval time of adjacent bins is 7d.
Let’s recall, what is the problem of the jump BIN method compared with the post pouring belt? The jump BIN method speeds up the closure time of concrete.
According to the high standard, the closing time of post cast strip is 45d; The concrete closure time of jump BIN method is about 7 days..
However, there are still many problems in setting the post cast strip: 1) construction is difficult and quality is difficult to guarantee.
1, in the actual structural design, we often encounter super long and large basement (including floor, floor, basement wall, etc.), the largest size is usually above 200m.
