Strengthening of reinforced concrete structures: general
Strengthening of concrete structures is a common practice in construction, which helps to significantly extend the life of components and buildings in general. We will talk about the methods of such amplification and consider their features, as well as methods for implementing the basic technologies.
Reinforcement of reinforced concrete structures
General information
Мероприятия по усилению конструкций из железобетона направлены на повышение их несущей способности и срока эксплуатации, а также позволяют восстанавливать и реставрировать различные ЖБИ после длительного износа или потери технических качеств в силу каких-либо причин (читайте также статью «Минимальная температура застывания бетона – особенности бетонирования в зимнее время»).
These works include a whole range of measures and actions that are aimed at achieving different results.
| Increasing the cross section of beams, columns, trusses, beams, belts and other elements of reinforced concrete structures | It is achieved by layer-by-layer concreting using an arm-carcass, spraying concrete at high speed from special guns, injecting the solution into formwork and other means |
| Reinforcing parts and carriers by adding new parts | It is performed by redistributing loads and reducing the impact on the reinforced element due to the inclusion of additional beams, jumpers, consoles, ribs, crossbars, etc. in the design. |
| Unloading and redistribution of efforts to other elements of the building | It is performed by including additional consoles or changing the interaction of old units and their parts, as well as by replacing heavy elements with lighter ones, replacing heavy equipment, insulation and other building systems |
| Improving the technical characteristics of concrete products by adding external metal and reinforced concrete reinforcing structures | Achieved by arranging frames, crimping shirts and clips, including additional reinforcement, channels, belts, steel strips and sheets, anchors, prestressed elements and concrete layers |
| Device of underground concrete piles and various stops, strings, soles | Here diamond drilling of holes in concrete and further in the ground is used, which are then reinforced and filled with mortar to create drill-injected piles and additional supports to increase the stability of the underground parts of the supporting structures |
Note! As you can see, we are talking about serious construction procedures that require an appropriate approach and a fairly high qualification of designers and contractors.
Also, additional procedures may be included in the work package, such as elimination of defects and cracks by injection, gluing, other measures to restore the integrity and solidity of products and their parts.
Measures to strengthen the supporting structures of buildings are of increased complexity and are considered more responsible than building from scratch. This is due to the fact that in the case of restoration we cannot accurately calculate all the processes, because the initial data are insufficient and inaccurate.
Moreover, the work is connected with old buildings, and we do not know the state of the internal and hidden units, the reinforcement, the actual distribution of loads and other important parameters. In addition, such work is dangerous and requires strict adherence to safety regulations and a variety of safety measures.
It should also be noted the special conditions of construction, under which one has to work in cramped spaces, without stopping the activities of the object or enterprise where the work is being done, with limited access to special equipment and other inevitable restrictions. This imposes certain difficulties and requires special training of builders.
Finally, the work, most often, is limited in time and does not tolerate delays or changes in terms and schedules. It also complicates the process and requires a serious organization of work, a proven methodology and experienced installers.
Considering all the listed difficulties and problems, it is not surprising that such activities are controlled by public services and require high responsibility of contractors, designers, labor protection specialists and other participants in the process. Projects go through several stages of coordination and should be drafted as competently and correctly as possible.
Note! After a preliminary study and calculation taking into account everything, including the economic aspects of the upcoming events, serious work should be done to strengthen the carrying concrete goods. Of course, do it yourself is unreal.
It is also important to pay attention to the fact that most modern amplification technologies involve the participation of special construction and lifting equipment, whose price exceeds the budget of any independent master. Therefore, it should be understood that the work of this level are performed by serious accredited construction organizations.
Note! It is impossible to predict with precision the nature of the processes and the difficulties associated with this; therefore, the work is carried out under the constant supervision of the design organization and independent specialists. Often there are situations when you need to quickly make responsible decisions and eliminate unforeseen difficulties.
Indications for use
Комплекс мер по улучшению состояния и технических характеристик бетонных сооружений проводится только в случае наличия достаточных оснований или необходимости для их применения. «На всякий случай» подобные мероприятия не производят (см.также статью «Пенополистиролбетон – все, что нужно знать о данном материале»).
Let's consider the reasons that may be grounds for making a decision on the production of the described procedures:
- Aging of structures and their loss of design strength due to fatigue of materials, corrosion, chemical changes and other natural causes, which could not be avoided due to certain circumstances;
- Changes in the number of floors of buildings and the associated increase in loads on the foundation, columns, floors and other elements of the structure, which may entail destruction and other undesirable or dangerous consequences;
- Redevelopment of buildings with changes in the configuration of load-bearing walls, columns, beams, consoles, trusses and other structural elements involved in the transfer and redistribution of loads in the building and its nodes;
- Soil movements, which lead to a change in the operating conditions of the foundations, an increase in external pressure on their walls, and a disruption of the established balance of forces in the systems of underground supports and supporting structures;
- Changing the purpose of buildings or re-equipment of workshops, which leads to the emergence of new types of wear, including vibration loads, significant point forces, thermal or chemical effects, etc .;
- Violation of integrity or destruction of individual parts, components, systems and structures as a whole as a result of accidents, earthquakes, natural disasters of various kinds, man-made disasters or military actions;
- Elimination of errors in the design or performance of work on the construction of structural bearing elements.
Note! Here are only the main situations in which a decision can be made to work on reinforcing reinforced concrete structures. Such a decision can be made for other reasons and depends on the specific problem and the arsenal of means to solve it.
In order to make a verdict on the feasibility and necessity of holding these or other events, a mandatory survey is carried out. This survey should determine the actual characteristics of the materials of the parts or assemblies to be strengthened, the limits of their strength and the expected or existing loads.
On the basis of the survey, calculations are made and the working drawings of structural components are developed taking into account design and actual loads, loading schemes, the effect of the application of amplification technologies and their contribution to improving the overall reliability of the building. Expenses and economic effect are also calculated taking into account the shutdown of enterprises at the time of repair and reconstruction.
The calculation of the reinforcement of reinforced concrete columns, floors, walls, foundations and other building systems is a complex and demanding work that only experienced, high-level specialists can do. Most often, this task is performed by entire departments or design organizations.
Ways of amplification
There are many ways to strengthen reinforced concrete structures; we will consider only the main ones.
In certain situations, these methods are used to improve the structural quality of parts, components and load distribution systems in buildings:
- Perform repair plaster to restore the integrity of the part and the integrity of its surface, as well as to protect the fittings from corrosion and eliminate various surface defects;
- Injection of concrete solution into cracks, cavities, voids and other defects to repair and restore the integrity of the body parts;
- Gunning concrete products with concrete using special guns, which are applied to the surface of concrete with high speed, which allows it to compact and gain considerable strength. It is used separately and together with other methods of amplification;
- Reinforcement of reinforced concrete beams, columns, walls and floors through the construction of special clips and shirts, which use external reinforcement and concreting by forcing the solution into formwork, shotcrete and layer-by-layer concreting with vibration;
- Strengthening of the foundation with reinforced concrete yoke, belts, anchor ties and other metal and reinforced concrete structures;
- Strengthening beams, beams, struts, columns, supports and piles with composite materials such as carbon fiber, Kevlar, carbon fiber and other similar materials;
- Changing the nature of mating parts from moving to hard;
- Adding unloading parts: strut, struts, consoles and other;
- Unloading of structures by introducing new units and elements, changing single-span overlaps by multi-span, adding new supports and columns, applying cords and pre-stressed reinforcement, steel belts and shirts.
It is obvious that the methods and related works are so diverse that a specific description of them all will take several volumes. However, there is also a general instruction, or rather a set of recommendations that are valid for almost all events.
They boil down to the general rules of surface preparation and installation of steel reinforcement and include applying notches to the concrete surface, jointing and cleaning the reinforcement from corrosion (using cutting of reinforced concrete with diamond circles or machining with perforators), a bunch of external frame with internal reinforcement or a concrete body. Be sure to perform cleaning and moistening of the surface with the help of water cannons and other devices.
Also, the rules may describe a bundle of rods of the outer frame between them, preheating the plates to create tension, and other generally applicable procedures.
Note! It should be remembered that there are no universal instructions and a general set of rules, since they are prescribed separately for each specific type of work.
Conclusion
With the help of reinforcement of reinforced concrete structures, it is possible to prolong the service life of buildings, eliminate or prevent an emergency, prepare the structure for redevelopment or superstructure. These activities are related to a complex type of work and require a serious approach; you can see this through the video in this article (find out here how concrete hardens).