In repair and construction work, technical operations with columns are performed quite often. This is due to the large loads that fall on this structural element, wearing out its structure. The most common repair and restoration operation of this type can be called reinforcing columns, for which a wide range of methods is used.
In what cases is reinforcement of the barrel required?
The need for additional strengthening of building structures usually arises after the formation of defects. The column is mainly used as a supporting architectural and construction element, so it is characterized by various kinds of damage. The most common problems are:
- Cracks. The most common type of damage to the column structure, which can have different forms and manifestations. As for the reasons, deformation cracks can occur as a result of shrinkage of the building, increased loads, corrosion of reinforcement in the barrel, decrease in concrete strength, etc.
- Chips. No less dangerous defect, the formation of which can be associated with mechanical or fire impacts on the structure, as well as with the loss of the original properties of the metal bearing rods.
- Exfoliation. Such damage also occurs due to fire, corrosion of reinforcement and pressure of neoplasms - ice crust or alkalis.
- Peeling. As a rule, it is a consequence of contact with aggressive media. Cyclic wetting / drying or freezing / thawing processes usually result in complete structural failure.
Structural deformation factors can influence the choice of tactics for repair and restoration measures. But most often, column reinforcement technologies are selected based on the physical and operational qualities and parameters of the barrel. Before you begin to review specific methods for solving the problem, it is worth familiarizing yourself with the universal rules for organizing work.
General advice of specialists during the work
In reinforcing technical operations that are carried out in relation to load-bearing structures and structures, various supports, overlays and angular support elements are often involved. Using such devices, it is important to consider two rules:
- The number of levels or layers of reinforcing bandage should not be less than three. The transverse binding is completely superimposed in four layers.
- An overlap of about 20-30 cm is maintained. Butt joints are generally excluded.
If you plan to use methods of strengthening columns with surface treatment of the barrel with composite agents and polymers, then the following conditions should be taken into account initially:
- The moisture content of concrete should be at least 4%. This coefficient is checked by a moisture meter.
- Condensation must be removed from the surface of the column.
- Before laying the polymer directly, a layer of epoxy is applied to the barrel.
- The temperature of the structure should vary in the range of +10 ... + 45 ° . This is the normal mode for working with polymer compositions.
Regardless of the method used to strengthen the barrel, you should clean and dedust the surface. It should be free from dirt, grease stains, and cement lotion. Similar tasks are solved with a grinding tool - manual or machine, depending on the area.
Clip reinforcement technology
The use of a combined holder to strengthen the trunks of columns allows you to ensure the durability of the structure, both in front of dynamic and static loads. The standard version of this method is considered to be reinforcing the columns with a metal cage, but experts recommend initially calculating the addition of the frame with reinforced concrete inserts with closed steel clamps.
Before performing installation operations, notches should be made in the structure of the trunk to a depth of 5 mm. The surface of the column is also cleaned of foreign particles and protected against corrosion. The basis of the cage frame will be a structure of transverse slats and longitudinal metal corners. The longitudinal components are seated on a cement-sand mortar and clamped with clamps. Further along the entire length of the barrel to the corners, it is necessary to weld the transverse strips by spot welding, maintaining a step of the order of 50-60 cm.
The advantages of reinforcing columns with steel clips include mounting speed and structural flexibility of the mounting scheme. Immediately after the installation of the frame is completed, the trunk will be ready to accept the calculated loads, and later, if necessary, the frame can be modified by introducing additional fasteners. But the main task of reinforcing the cage can only be accomplished if the screeds and planks with corners are snug against the surface of the column. The quality of fixation is determined by the smoothness of the barrel and its geometry.
Section extension technology
A typical construction of a construction column consists of two structural parts - concrete and reinforcing elements. If the reinforcement of the columns with clips is oriented towards increasing the rigidity of the supporting metal skeleton of the barrel in an external way, then increasing the cross section aims to expand the area of the bearing surface. The main concrete mass is increasing, which makes the structure more stable and more durable.
This method is used in cases where, in principle, the possibility of increasing the technical zone at the place of operation of the column is allowed. The best way can be a one-sided cross-sectional growth - in width, length or depth of the structure. From a technological point of view, the main task of the master will be to ensure a sufficiently strong connection between the new concrete layer and the old one. For this, methods of reinforcing columns with metal clips are used. But the frame in this case does not perform the function of an independent supporting element, but acts as an auxiliary reinforcing crate, which will allow you to connect two concrete levels. The same longitudinal reinforcement is mounted with notches and corners. Ideally, if possible, it should be welded to the main reinforcement in the barrel with metal shorts. Then, direct masonry of the concrete mortar is performed.
Composite reinforcement technology
Today, in many areas of construction and production, metal parts are replaced by products from composites and carbon fiber. This option of reinforcing columns is advantageous in that with a lower mass and size of the element allows you to provide the same functional tasks. Lightweight carbon fiber in itself does not overload the column (especially important for the construction of dilapidated cultural monuments), but it is resistant to loads like steel. Moreover, the tensile strength of some composites is 4-5 times higher than that of reinforced concrete reinforcement.
The technique of reinforcing columns in this case will consist in bonding composite or carbon fiber lamellas perpendicular to the surface of the barrel. Typically, the calculation is made to alleviate vertical loads with an emphasis on bending moment. To achieve this effect, the reinforcement plates are glued along the line of action of the load moment. As for the adhesive composition, polymer building mixtures can be used, which will also perform auxiliary tasks of external reinforcement of the structure, moisture protection and heat resistance - the set of adhesive properties will depend on the conditions of its use. Among the advantages of this method, the absence of structural changes in the column, the possibility of decorating the barrel by painting lamellas and durability are highlighted.
Reinforcement of reinforced concrete columns
For architectural trunks of this type, it is recommended to use methods of reinforcing a steel jacket. Since this is a massive structure with a large mass, the reinforcing frame must fit tightly into the structure of the column. At the same time, it is undesirable to overload the bearing barrel, as this will cause a higher effect of mechanical fatigue not only for the column, but also for the lower floor. Optimal is the use of a steel cage with corners on a cement-sand mortar. As in the classical scheme, reinforcement of reinforced concrete columns is carried out with transverse trims and adapter inserts welded to the internal reinforcement of the barrel.
Before welding, it is important to consider one technological trick. Experts recommend heating the wallpaper strips to 100-120 ° C, and only after that proceed with the connection. When the element cools down, its size will become smaller, which will provide a positive effect of prestressing. Also in the reinforcement of reinforced concrete structures it will not be amiss to use additional safety devices. It is most convenient to mount spacers formed by two channel corners. They are connected by slats and fastened by the principle of support with tension bolts.
Heated clamp reinforcement
If the columns do not experience large design loads and do not require capital reinforcement of the structure, then it is possible to dispense with the optimized technique of lining strips made of strip steel. It turns out a kind of strapping collars that are mounted along the entire height of the trunk. As a result, building materials with fittings are saved, and the column structure remains untouched. The technological complexity of this solution lies in the preliminary heating of the metal strips and the correct crimping of the column. Theoretically, clamps can be used in reinforcing reinforced concrete columns with a round, rectangular and square section. But in each case there will be its own crimp pattern, for which the appropriate method of stripping is selected.
Blanks for linings are heated in a furnace or burner to about 300 ° C. Further, using a special conductor or clamps, it is necessary to tightly squeeze the barrel with a hose clamp in a previously installed zone. Some time after tying, the clamp will cool down, and the metal as a result of temperature reduction will be pressed even denser against the surface of the column. Again, the end result is not so much an independent reinforcing frame as an auxiliary reinforcement.
Reinforcement of metal columns
Compared to reinforced concrete shafts, all- metal structures exclude the possibility of monolithic building up of the structure by means of a carcass or concrete masonry. Therefore, braces, puffs, spacers and prestressed devices are more often introduced. A very practical and functional option is the option of reinforcing a steel column by expanding or hardening the structural shoe adjacent to the ceiling or foundation. On the lower tier, the possibility of creating a concrete screed is just allowed, which will increase the vertical stability of the column.
Small barrel structures are recommended to be reinforced with prestressed elements. As such, inventory and telescopic trusses with rigid struts are used, the parameters of which can be changed depending on the current load. By the way, such reinforcement of reinforced concrete columns will be difficult due to insufficient structural rigidity, but metal trunks allow the use of jacking tools. That is, the user can change the height and position of the structure, wedging and connecting it with the clamps.
Slots and grooves are made in the supporting sections for additional insurance, and restrictive temporary plates with circular slots for reinforcement are also mounted. After this, a reinforcing rod is installed, and the supporting zone is concreted. When the cast screed has gained enough strength, the reinforcement bar is strained with anchor hardware and bolts - they can be built into the holes from the side of the lower faces. It turns out a capital way of structural reinforcement of the columns, which is used only when the technical feasibility of rebuilding the adjacent site.
Strengthening Compressed Columns
The eccentrically compressed trunks are strengthened by a combination of technical means, including reinforcing bandages, profile metal corners and transverse trims. Integrated reinforcement allows in this case to provide cramped deformation and mutual operation of the elements of the harness with the ceilings. That is, the load moments are not redistributed, but are directly transferred from the upper concrete structure to the lower one.
The basis of the reinforcing system is formed by several transverse bandages, which are interspersed with single reinforcing inserts made of steel or carbon fiber. But if the reinforcement of the column with a reinforced concrete cage is made with the addition of sand-cement mortar, then the bandage with overlays is calculated only on hardware fasteners. In particular, the same concrete is replaced by anchoring with longitudinal elements through floors. The main difficulty in mounting such a system comes down to the necessity of maintaining axial symmetry when installing longitudinal gripping and fastening elements.
Conclusion
The nature of the application of one or another method of strengthening the vertical architectural structure will largely depend on the characteristics of the parts of the structure associated with it. For example, reinforcement of reinforced concrete columns at high loads may include the installation of a metal frame with concrete expansion, and the installation of spacers. But only if this allows you to perform the lower overlap - the restriction may be due to excess design load weight. Especially acute are such limitations in situations of amplification of group column compositions. As a rule, massive and heavy weight frames and screeds are not allowed in such cases, and the developers of a technical project are faced with the task of detailed calculation of additional connections by integrating rigid prestressed supports.