What are the symbols of grade one, grade two and grade three steel bars?

The symbols of the first, second and third grades of steel bars are as follows:

2400kg/cm tensile strength is 1 grade steel bar, which is indicated by Ф on the drawing.

The tensile strength of 2800kg/cm square is also 1 grade steel bar, and two vertical rings are indicated by Ф on the drawing.

16Mn steel with tensile strength of 3400kg/cm ~ 2 belongs to Grade 2 steel bar, which is indicated by Ф on the drawing and marked with a cross.

25MnSi steel with a tensile strength of 3800kg/cm square belongs to Grade 3 steel bar, which is indicated by Ф in the middle on the drawing, and there are two vertical lines and one horizontal line below.

Each kind of steel bar should be inspected according to the bill of materials to see if it meets the requirements. After these two inspections, the samples should be released according to the bill of materials, and mass production can only be carried out after the trial production is qualified. Processed steel bars should be listed and stacked neatly.

The unit of measurement for calculating the theoretical weight of steel is kilogram (kg). Its basic formula is:

W (weight, kg )=f (cross-sectional area was) × l (length, m)×ρ (density, g/cm3) ×11000.

Extended data:

Hook or bend of reinforcement:?

(1) steel hook. There are three forms, namely semi-circular hook, straight hook and inclined hook. After the steel bar is bent, the endothelial contraction, skin extension and axial length at the bend remain unchanged, and the bend forms an arc. The size after bending is not greater than the blanking size, so the bending adjustment value should be considered. ?

The bending center diameter of steel bar is 2.5d, and the straight part is 3d. The theoretical calculation value of reinforcement hook length increase is 6.25d for counter-rotating semi-circular hook, 3.5d for straight hook and 4.9d for oblique hook. ?

(2) Bending steel bar. The bending diameter d of the middle bend should not be less than 5 times the diameter of the steel bar. ?

③ Stirrups. The end of stirrups should be hooked, and the hook form should meet the design requirements. Stirrup adjustment, that is, the difference or sum of the increase length of the hook and the bending adjustment value, depends on the outer package size or inner package size of the stirrup. ?

(4) The blanking length of steel bar shall be specified according to the component size, the thickness of concrete protective layer, the adjustment value of steel bar bending and the increase length of hook. ?

Cutting length of straight steel bar = member length-protective layer thickness+hook increase length?

B blanking length of bending steel bar = straight bending length+oblique bending length-bending adjustment value+hook increase length?

C. Stirrup blanking length = stirrup inner diameter+stirrup adjustment value+hook increase length?

References:

Baidu encyclopedia-rebar symbol