How many levels of reinforcement strength are there? What are the strength grades of rebar?

grade reinforcement (235 370 grade); grade reinforcement (335 510 grade); Grade bars (370 570) and grade bars (540 835).

The steel bars used in construction are mainly divided according to the tensile strength.

1. The tensile strength of 240MPa is called grade 1 steel bar, which is represented on the drawing;

2. The tensile strength of 280MPa is also a grade 1 steel bar, which is represented by two vertical circles in the drawing;

3. The 16mn steel with a tensile strength of 340MPa belongs to grade 2 steel bars, and the drawings are represented by adding a horizontal one below;

4. The 25mnsi steel with a tensile strength of 380MPa is a grade 3 steel bar, which is represented by two vertical in the middle and one horizontal in the drawing.

Rebar

Rebar refers to steel for reinforced concrete and prestressed reinforced concrete, which has a circular cross-section and sometimes a square with rounded corners. Including round steel bars, ribbed steel bars, and torsion steel bars.

The strength grade of the reinforcement is divided according to the standard value of yield strength, not according to the value of tensile strength, and it is not graded.

Reinforcement for ordinary concrete:

HPB300 grade (hot-rolled round).

HRB335 grade (hot-rolled ribbed).

HRB400 grade (hot-rolled ribbed).

HRB500 (ditto).

How to classify the grade of reinforcement.

A: Reinforcement grade:PressYield strengthEigenvalue grading. Classification: HPB, HRB, RRB, HRBF.

The grades and symbols of ordinary steel bars are shown in the following table (extracted from the "Code for Design of Reinforced Concrete" GB50010-2010):

The symbol of ordinary steel bar in the code for reinforced concrete design GB50010-2010 only represents the grade of ordinary steel bar. The meaning of the composition of the grade (excerpted from "Steel for Reinforced Concrete Part I: Hot Rolled Round Steel Bar":

Hot Rolled Round Bar Grade: HPB300 Composition Meaning: Composed of HPB yield strength eigenvalues (300MPa).

Meaning of the English letters: HPB - the abbreviation of hot rolled plain bars. Design Symbols:

Steel for Reinforced Concrete Part 2: Hot-rolled ribbed steel bar.

Ordinary hot-rolled ribbed steel bar grades: HRB335, HRB400, HRB500; Composition meaning of grade: Composed of characteristic values of HRB yield strength (335MPa, 400MPa, 500MPa).

On the rebar, the grade markings are denoted by . English letter meaning: HRB - the English abbreviation of hot rolled ribbed bars.

Fine-grained hot-rolled steel bar grades: HRBF 335, HRBF400, HRBF 500;Composition meaning of grade: Composed of HRBF yield strength eigenvalues (335MPa, 400MPa, 500MPa).

On the rebar, the grade mark is C3, C4 and C5 respectively. HRBF English letter meaning: HRB - the abbreviation of hot rolled ribbed bars (hot rolled ribbed bars) followed by the first letter of "fine".

Waste heat treated ribbed steel bar grade: RRB400, the composition meaning of the grade: It is composed of the characteristic value of RRB yield strength (400MPa). RRB - Waste heat treatment of ribbed steel bars in English (Remainedheat Treatment

Ribbed Steel Bars).

Bars

Ribbed

Remained

According to the GB50010-2010 table of the "Code for the Design of Reinforced Concrete", the steel bar only has grades, symbols, standard values of yield strength and standard values of ultimate strength.

Steel for Reinforced Concrete Part I: Hot Rolled Round Steel Bar and Steel for Reinforced Concrete

Part 2: Hot Rolled Ribbed Steel Reinforcement Look,Rebar is no longer called "grade".Only the category, grade, according to the yield strength characteristic value grade.

China's hot-rolled steel bars can be divided into four grades according to their strength:

1.grade reinforcement.

Its strength class is 24 38 kg and is made of calm, semi-calm or boiling steel.

No. 3 ordinary carbon steel rolled round steel bar. It is a low-strength steel bar, which has the characteristics of good plasticity, high elongation (δ5 above 25), easy to bend and form, and easy to weld. It has a wide range of applications and can be used as a small and medium-sized reinforced concrete structure.

The main stressed reinforcement, the stirrups of the members.

Tie rods of steel and wood structures, etc. Wire rod rebar can also be used as a raw material for cold-drawn mild steel wire and double rebar.

2.Level. Rebar

Grade steel bars are rolled with low-alloy calmed steel or semi-calmed steel, with silicon and manganese as solid solution strengthening elements. The strength level of the grade steel bar is 34 (32) 52 (50) kg, which has high strength, good plasticity and ideal welding performance. The surface of the steel bar is rolled with long longitudinal bars and uniform distribution.

to strengthen the bond between the reinforcement and the concrete. With grade steel bar as the stressed steel bar of reinforced concrete structure, can save steel 40 50 than using grade steel bar. Therefore, it is widely used in large and medium-sized reinforced concrete structures, such as bridges, dams, port projects and the main reinforcement of housing building structures.

After cold drawing, the grade steel bar can also be used as a prestressed steel bar for the building structure.

3.grade reinforcement.

The main performance of the grade steel bar is about the same as that of the grade bar, and the strength level is 38 58 kg.

4.grade reinforcement.

The strength level of the steel bar is 55 85 kg, rolled with medium carbon low alloy calm steel, in addition to silicon, manganese as the main alloying elements, vanadium or titanium is also added as a solid solution and precipitation strengthening element, so that it can improve the strength while ensuring its plasticity and toughness. The surface of the grade steel bar is also rolled with longitudinal bars and transverse ribs, and it is a house construction project.

The main prestressed reinforcement. Before use, the grade steel bar should be cold-drawn by the construction unit, and the cold-drawn stress is 750 megapascals, so as to improve the yield point, give full play to the inherent potential of the steel, and achieve the purpose of saving steel. The yield point of cold-drawn steel bars is not obvious, so the design is based on the statistical value of cold-drawn stress (cold-drawn design strength).

However, after several months of natural aging or artificial heating of the cold-drawn steel bar, the steel bar will have a short yield step, the value of which is slightly higher than the cold tensile stress, and the steel bar has a tendency to harden, this phenomenon is called "age hardening". Therefore, while ensuring the specified cold tensile stress, the cold tensile length rate should be controlled not to be too large, so as to avoid the brittleness of the steel bar. The carbon content of grade steel bars is high, and the process of flash preheating flash welding or electric heat treatment after butt welding is generally adopted to ensure that the butt welding joint, including the heat-affected zone, does not produce hardened structure and prevents brittle fracture.

The diameter of the grade reinforcement is generally 12 mm, and it is widely used in prestressed concrete slab components and in bundled configurations for large prestressed building components (such as roof trusses, crane beams, etc.). When hot-rolled grade steel bar is used as prestressed steel bar, cold drawing, welding is still needed, and its strength is still low, and further improvement is needed.

According to the performance of the rebar, there are four grades. 1. According to mechanical propertiesgrade reinforcement (300 420 grade); grade reinforcement (335 455 grade); Grade bars (400 540) and grade bars (500 630).

2. According to the size of the diameterSteel wire (diameter 3 5mm), thin steel bar (diameter 6 10mm), thick steel bar (diameter greater than 22mm).

3. According to the production processHot-rolled, cold-rolled, cold-drawn steel bars, as well as heat-treated steel bars made by heat treatment of grade steel bars, the strength is higher than the former.

Formula for calculating the load bearing of rebar.

Flat steel, steel plate, steel strip w = width.

Square steel w = side length

Round bar, wire rod, steel wire w = diameter

Steel pipe w = wall thickness (outer diameter - inner diameter).

Equilateral angle steel w = side thickness (2 side width - side thickness).

Unequal angle steel w = side thickness (long side width + short side width - side thickness) I-beam w = waist thickness [height + f (leg width - waist thickness)].

Channel steel w = waist thickness [height + e (leg width - waist thickness)].