Reinforcement technology helps to achieve optimal building strength in modern construction. The methods for its implementation are diverse and the choice of a particular one depends on a number of parameters of the object being strengthened. Reinforcement received the greatest distribution as an element of the foundation - it is thanks to metal rods that a high-strength building component called reinforced concrete is formed. At the same time, the integration of the rods into the concrete base must be strictly calculated, otherwise all efforts to create a reliable platform will be in vain.
Parameters for the calculation of reinforcement
The calculation of the volume and parameters of the metal "skeleton" is impossible without knowledge of the required properties relative to the building itself. Based on its characteristics, reinforcement for the foundation is selected . The calculation is made according to several indicators that determine the technical and operational qualities of the structure.
The list of base values includes the following parameters:
- weight of rods used;
- the length of each element;
- total weight of the frame;
- diameter and ribbing;
- number of rods.
It would seem that the use of the maximum possible number of fittings will allow to achieve the highest technical and operational qualities of the building foundation. But this is not so, since improper distribution of loads on the foundation can lead to the opposite effect, weakening the structure.
Calculation for a slab foundation
One of the popular types of foundation is slab. In this case, ribbed rods with a diameter of at least 1 cm are used. The choice of thickness depends on the planned mass of the house and the characteristics of the soil. For example, if a wooden structure is being erected, then the calculation of reinforcement for a slab foundation may assume the minimum permissible thickness. In the case of a stone or brick house, this figure is an average of 1.5 cm. Based on these data, the optimal volume of reinforcing material is selected.
Rebar pitch
The number of rods, as well as their size, must be calculated according to the grid pitch. So, if it is planned to reinforce on a slab foundation 6x6 m, then the gap will be 20 cm. That is, you will need to install 31 bars along and across. Accordingly, the calculation of the amount of reinforcement for the foundation in this case shows the need to use 62 rods. But this is not all - since two belts are formed on the slab, the primary result is multiplied by two - as a result, 124 units are obtained. The total length of the material, provided that one rod has a length of 6 m, will be 744 m.
Connecting fittings will also be required. It is calculated individually and based on the width of the belt - these are coupler rods several decimeters long. In the case of the described foundation, the total length of the auxiliary reinforcement will be about 100 m.
Calculation for the strip foundation
When constructing a tape base for the house, reinforcement with a diameter of 10-14 mm is also used. But there is one difference that determines the specificity of the consumption of rods in such foundations. The fact is that the concrete construction of the tape type is more resistant to bending, so the thickness will initially be underestimated when compared with the slab counterpart.
For longitudinal reinforcement, brand A3 rods are used. Their function is to receive a direct load on the foundation, which determines the need to use rods with a ribbed surface. Less high loads fall on the vertical and transverse elements, so they can be smooth - A1 grade. Typically, the calculation of reinforcement for a strip foundation involves the installation of four rods in the longitudinal direction - two for each belt. If the requirements for reliability increase due to the instability of the soil or the characteristics of the building itself, then an increase in the number of rods is possible.
Calculation for a column foundation
This type of foundation involves the use of reinforcing rods with the smallest thickness - a diameter of 1–1.2 cm is common. The main load is taken up by ribbed vertical rods A3, while elements of the horizontal direction (0.6 cm thick) perform only the ligament function .
As an illustration of the reinforcement, you can take a column with a length of 2 m and a diameter of 40 cm. Four elements with a diameter of 1.2 cm are required here, between which a pitch of 20 cm is maintained. Smooth rods of 6 mm diameter will perform their fastening. Regarding the length, the calculation of the reinforcement of the column foundation can be represented as follows: four vertical bars of 2 m in total will amount to 8 m.
Reinforcement schemes
The shape of the metal frame in the concrete base depends on the selected reinforcement scheme. The latter, in turn, will determine the effectiveness of the configuration used - in each case it can be different.
The main rule in choosing a scheme for forming a structure from metal rods is a bias towards the correct shapes. The installation of reinforcement elements in the form of a rectangle or square, as practice shows, provides the highest reliability of the building. However, other solutions for the construction of the reinforcing cage are not ruled out if the design of the house itself deviates from the standards.
The arrangement of the rods in the concrete structure must take into account additional reinforcement, which, however, is not so necessary if the foundation of the slab is being built . Calculation of reinforcement with reinforcement is usually used in tape reinforced concrete tabs when angles and joints are formed.
Fittings
Even the correct calculation of reinforcement will not provide reliability and durability of the foundation if the unsuccessful method of fixing the rods is chosen. Usually, welding is used to connect metal structures and parts, but in the case of reinforcement, it is advisable to stay on wire fastening - the structure of the material will retain its original qualities, reliably strengthening concrete.
For this, a knitting wire and a special hook are used, which allows you to create knots. Optimum strength of the frame is possible only with a uniform connection of the sections of the convergence of the rods - exceptions apply to corner sections that require reinforcement. Additionally reinforced reinforcement for the foundation, the calculation of which takes into account the "problem" places of joints and turns, will protect the structure from physical influences.
On average, about 25 cm of knitting wire is spent on each joint. You can increase the reliability of the nodal connection by double strapping, and then use a crochet hook.
Reinforcement errors
The best way to insure against the wrong choice and installation of valves is to follow the design documentation steadily. Ignoring the established construction parameters may be due to the desire to save, the lack of the necessary material, etc. Each of these cases poses a risk to the safety of the facility under construction. It is also not recommended to forget about the technological rules by which reinforcement is selected for the foundation. Calculation of it will optimize further installation, but the primary quality of the material will make the main contribution to the success of the project.
In addition, in the organization and the reinforcement itself, it is necessary to prevent the following errors:
- Use of inappropriate fittings. Smooth rods will not be able to replace analogues with a ribbed surface, as well as one category of material - another.
- Unprepared metal surface. The presence of grease, corrosion and dirt is unacceptable, since it reduces the adhesive quality of the material.
- Errors in the calculation of the intervals in accordance with which the reinforcement for the foundation is laid. The calculation of the step from one rod to another should not be less than 2 cm - this is unjustified from the point of view of the reliability of the design and the proportional distribution of loads.
- The connection of reinforcement in places of tension of the concrete base. If the length of the reinforcement is not enough, a lining method is used. Although there are times when such a technique is allowed, it is advisable to avoid unnecessary attachment points.
Features of the calculation of fiberglass reinforcement
The advantages of the composite analogue of metal rods have made it popular. In terms of diameter and weight, the calculation of fiberglass reinforcement for the foundation is somewhat different. Firstly, innovative material is several times lighter than steel - for example, the mass of a 100-meter reinforcing wire made of fiberglass is 8 kg. Secondly, the composite increases the strength properties of concrete, which reduces the thickness of the reinforcement elements. For example, if metal rods with a diameter of 1 cm are declared in the project, then you can limit yourself to a 0.8-centimeter diameter.