There are different classification methods of templates in stages: according to shape, there are two kinds of templates: plane template and curved template; According to the stress situation, it can be divided into bearing formwork and non-bearing formwork (that is, bearing the weight of concrete and the lateral pressure of concrete); According to the materials, it can be divided into wood formwork, steel formwork, steel-wood composite formwork, gravity concrete formwork, reinforced concrete veneer formwork, aluminum alloy formwork, plastic formwork, etc. According to the structure and use characteristics, it can be divided into two types: detachable and fixed; According to its special functions, there are sliding templates, vacuum sucker or vacuum floppy template, thermal insulation template, steel template trolley and so on.
2. Before 1960s, wooden formwork was mainly used in highway engineering construction in China. Because wood can be easily made into various shapes, some special-shaped structures usually use wooden templates. In modern times, many countries and highway projects still use wooden formwork or steel-wood mixed structure.
At the end of 1970s, China implemented the technical policy of replacing wood with steel, and composite steel formwork was mostly used in foundation, column, beam, slab and wall construction, especially in mass concrete construction of highway engineering, which showed obvious advantages.
Thirdly, the importance of formwork engineering in concrete construction is inseparable from its efforts to improve its work and performance.
First of all, the cost of formwork engineering in concrete construction is relatively large, accounting for about 65,438+05-30% of the total cost of concrete. In mass concrete projects with no reinforcement or less reinforcement, it accounts for about 5-65,438+05%. The labor consumption of formwork production and installation is about 28%-45% (labor in a concrete), and a lot of high-quality steel and wood are consumed. The role of templates is often shown. According to the statistics of some projects, the formwork removal time accounts for about 35% of the total construction period. Template process is the key line in the construction network diagram in many cases, and the improvement of template technology can often speed up the construction progress.
Four, the type and structure of the template sometimes change the concrete pouring process.
The traditional formwork type is to fix the panel with braces, which hinders the warehousing, leveling and tamping of concrete mixture, roughening and cleaning of the surface layer, and construction preparation for pouring the warehouse surface, so it is impossible to carry out mechanized operation.
Cantilever formwork greatly overcomes the shortcomings of traditional formwork types and has great advantages in mechanized construction and reducing labor consumption.
5. In the highway construction projects that our factory participates in, the traditional formwork project is still the main form. Although some new technologies have been introduced (for trial implementation), some problems are still worth discussing.
Our factory has always advocated the construction unit to use steel formwork as much as possible in concrete construction, but in actual construction, only a small amount of steel formwork is used in many parts, which not only wastes a lot of wood, but also greatly reduces work efficiency. According to the successful project summary, the efficiency of steel formwork is 2-4 times higher than that of wood formwork (including comprehensive labor such as installation, formwork removal, electric welding, roughening and platform erection), and the cost of steel formwork (reaching the standard turnover rate) is only half of that of wood formwork. Therefore, it is one of the good ways to improve economic benefits to reasonably replace wood molds with steel molds.
There are many deficiencies in template management in our factory. Mainly in the turnover rate of the template. According to the regulations, the turnover of steel formwork is 50 times, that of large wooden formwork is 15 times, and that of general wooden formwork is 7 times. However, the actual turnover rate of our factory is far from this requirement. Taking the general wooden formwork as an example, the turnover rate of our factory is about 4 times, which greatly increases the construction cost. The solution to this problem is to improve the ideological quality and professional level of workers, and our management level also needs to be improved.
In the introduction and use of new formwork technology in our factory, sliding formwork has a large one-time investment, which is suitable for high-rise concrete pouring, but the benefit is not obvious or no benefit when it is used for low-rise concrete pouring. Therefore, when adopting new technology, we should consider its application scope and link it with economic benefits.
In view of the important role of formwork engineering in reinforced concrete construction, all countries in the world are studying and constantly improving the construction technology and technology of formwork engineering. With the establishment of formwork professional company, formwork engineering will continue to develop in a fast and economical direction.
The development prospect of formwork engineering will focus on how to speed up concrete construction. I think one of the ways to speed up the progress is to seriously study the use of sliding mode. Increase the thickness of pouring layer, reduce horizontal joints, and adopt jack-up formwork. Increase the size of pouring blocks and reduce construction joints to reduce the formwork area.
With the deepening of reform, in order to meet the needs of project bidding, the preliminary work involves the following contents:
Template engineering planning, mainly combined with the construction plan, choose the template system, organize production, choose machines and tools and prepare budget estimates.
Template design, mainly the structural design and process design of the template, is indispensable, and can be entrusted to a professional company or designed by the engineering unit itself.
Consider the comprehensive benefits and management in the use stage.
In a word, formwork engineering plays a very important role in reinforced concrete construction. It is of great significance to do a good job in structural design and technological design of formwork to improve engineering efficiency and speed up construction progress. Different formwork types determine different construction techniques of concrete pouring, and have different effects on concrete quality and engineering benefits. How to improve the template technology is an important topic.
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