Reinforcement is an important component of reinforced concrete structures, designed to take heavy loads. It can be said that the reliability and operational characteristics of structures largely depend on the strength and endurance of these steel rods. Reinforcement classes reflect mechanical, chemical and physical properties, technology of rolling, methods of post-rolling processing, corrosion resistance, as well as a number of other parameters of these load-bearing elements of any modern structure.
It is known that the construction of a building is constantly experiencing various types of loads: from the mass of equipment, machines or furniture in the building to the total weight of people and structural elements of the structure itself. Moreover, all types of loads have a different effect on the bearing elements. They can compress, stretch or bend. The strength of these loads is also different.
All classes of fittings, possessing individual qualities, are designed to make different efforts. For example, working reinforcement can withstand even the most unfavorable loads for a building - tensile forces created by external factors and the own mass of reinforced concrete structures. In such building elements as columns and supports, this type of reinforcement perceives the main compressive forces. However, only this type of steel rods is not enough to give the building the necessary strength.
Therefore, along with working fittings, the design of most modern buildings uses distribution, designed to evenly distribute the force between the rods, and mounting, which performs the function of combining individual steel elements into a single rigid frame. To prevent the formation of oblique cracks, additional high-strength rods, shaped clamps and hooks are introduced into the structure.
All classes of reinforcement are indicated by an alphanumeric index from A-1 to A-6. The higher this designation, the stronger the rods themselves. The scope of application of these elements of building structures depends on this. For example, class A1 reinforcement is a hot-rolled smooth steel bar. It is used mainly in buildings that are not subject to high loads and stress. The fittings of this class serve as mounting, structural and transverse elements. It has good weldability.
Other classes of reinforcement, starting with A-2 and above, are hot-rolled rod elements of a periodic profile. As a rule, such rods are subjected to thermochemical processing after rolling, which increases their strength. The application of class A-2 is almost the same as A-1. With the exception of rods made of steel St 5 and having a diameter greater than 32 mm, since when welding such rods, they do not provide a sufficiently reliable welded joint.
Class A3 reinforcement is widely used in the manufacture of standard reinforced concrete structures, where it serves as a working component. It also has good weldability. Class A-4 has much greater strength than the previous ones, and, accordingly, is used as a tensile (bearing) element. The weldability of such reinforcement is considered satisfactory, although somewhat inferior to the previous classes. Therefore, the rods of this category are joined in a manner called a compressed clip. Reinforcing bars of classes A-5 and A-6 are extremely strong structural elements. They are used in long building structures with a span of at least twelve meters. Such fittings can withstand very large loads and forces.