Rebar classes: general information

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Reinforcement is an important component of reinforced concrete structures, designed to accept heavy loads. It can be said that the reliability and performance of structures largely depend on the strength and endurance of these steel rods. Reinforcement classes reflect mechanical, chemical and physical properties, rolling technology, post-rolling treatment methods, corrosion resistance, as well as a number of other parameters of these load-bearing elements of any modern structure.

It is known that the structure of a building constantly experiences various types of loads: from the mass of equipment, machines or furniture located 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 them. The strength of these loads is also different.

All classes of reinforcement, having individual qualities, are designed to accept different efforts. For example, working reinforcement perfectly withstands even the most unfavorable loads for a building - tensile forces created by external factors and the own weight of reinforced concrete structures. In building elements such 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 structure the necessary strength.

Therefore, along with the working reinforcement in the design of most modern buildings, distribution reinforcement is used, 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, curly 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 these elements of building structures also depends on this. For example, class A1 rebar is hot-rolled smooth steel bars. It is used mainly in buildings that are not subject to heavy loads and stress. The fittings of this class serve as mounting, structural and transverse elements. It has good weldability.

Other classes of rebar,starting from A-2 and above, are hot-rolled bar elements of a periodic profile. As a rule, such rods are subjected to thermochemical treatment after rolling, which increases their strength. The application of class A-2 is practically the same as that of 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 rebar 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 stressed (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 way that is called a crimped 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 are able to withstand very high loads and forces.