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GB 13788-2024: Cold rolled ribbed steel bars
GB 13788-2024
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.15
CCS H 44
Replacing GB/T 13788-2017
Cold Rolled Ribbed Steel Bars
ISSUED ON: JUNE 25, 2024
IMPLEMENTED ON: SEPTEMBER 25, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 3
1 Scope ... 4
2 Normative References ... 4
3 Terms and Definitions ... 4
4 Designation ... 5
5 Dimensions, Shape, Weight and Allowable Deviations ... 5
6 Raw Materials and Properties ... 10
7 Test Methods ... 11
8 Inspection Rules ... 13
9 Packaging, Marking and Quality Certificate ... 13
Appendix A (normative) Hot-rolled Wire Rods for Cold-rolled Ribbed Steel Bars ... 15
Cold Rolled Ribbed Steel Bars
1 Scope
This document specifies the designation, dimensions, shape, weight and allowable deviations,
raw materials and properties, test methods, inspection rules, packaging, marking and quality
certificate of cold rolled ribbed steel bars (hereinafter referred to as the steel bars).
This document is applicable to cold rolled ribbed steel bars for ordinary reinforced concrete,
manufacturing welded mesh and prestressing concrete.
2 Normative References
The contents of the following documents constitute indispensable clauses of this document
through the normative references in the text. In terms of references with a specified date, only
versions with a specified date are applicable to this document. In terms of references without a
specified date, the latest version (including all the modifications) is applicable to this document.
GB/T 222 Permissible Tolerances for Chemical Composition of Steel Products
GB/T 2101 General Requirement of Acceptance, Packaging, Marking and Certification for
Section Steel
GB/T 2103 General Requirements for Acceptance, Packaging, Marking and Quality
Certification of Steel Wire
GB/T 17505 Steel and Steel Products - General Technical Delivery Requirements
GB/T 21839 Test Methods of Steel for Prestressing Concrete
GB/T 28900 Test Methods of Steel for Reinforcement of Concrete
YB/T 081 Rule for Rounding off of Numerical Values and Judgement of Testing Values for
Technical Standards of Metallurgy
3 Terms and Definitions
The following terms and definitions are applicable to this document.
3.1 cold rolled ribbed steel bars
Steel bars with transverse ribs evenly distributed along the length direction on their surface after
hot-rolled round wire rods are subjected to cold rolling.
3.2 nominal diameter
The diameter of a circle equal to the nominal cross-sectional area of the steel bars.
3.3 specific projected rib area
The ratio of the projected area of a transverse rib on a plane perpendicular to the axis of the
steel bars to the product of the nominal perimeter of the steel bars and the rib spacing.
3.4 rib spacing
The chord length of the discontinuous part of the transverse rib on the circumference of the
steel bars projected on a plane perpendicular to the axis of the steel bars.
4 Designation
There are five designations for the steel bars: CRB550, CRB600H, CRB650, CRB800 and
CRB800H. CRB550 and CRB600H are steel bars for ordinary reinforced concrete, while
CRB650, CRB800 and CRB800H are steel bars for prestressing concrete.
C, R, B and H are respectively the first letters of the words “Cold rolled”, “Ribbed”, “Bars” and
“High ductility”; the figures represent the characteristic value of tensile strength.
5 Dimensions, Shape, Weight and Allowable Deviations
5.1 Nominal Diameter Ranges
The nominal diameter range of CRB550 steel bars is 4 mm ~ 12 mm, the nominal diameter
range of CRB600H steel bars is 4 mm ~ 16 mm, and the nominal diameters of CRB650 steel
bars and above are 4 mm, 5 mm and 6 mm.
5.2 Shape
5.2.1 Shape requirements
CRB600H shall have two-sided ribs (see Figure 1), CRB550 and CRB650 shall have three-
sided ribs (see Figure 2). Upon negotiation between the supply-side and the demand-side,
CRB800 and CRB800H are allowed to adopt other shapes.
5.2.2.4 The bevel angle  on both sides of the transverse ribs of the steel bars with two-sided
ribs and three-sided ribs and the surface of the steel bars shall not be less than 45.
5.2.2.5 The sum of the transverse rib spacings of the steel bars with two-sided ribs and three-
sided ribs shall not be greater than 20% of the nominal circumference (fi  0.2d).
5.2.2.6 The specific projected rib area fr shall be determined in accordance with Formula (1):
Where,
K = 2 (two-sided ribs) or 3 (three-sided ribs);
FR---the longitudinal cross-sectional area of one rib, expressed in (mm2);
---the included angle between the transverse rib and the axis of the steel bar, expressed in ();
d---the nominal diameter of the steel bar, expressed in (mm);
l---the transverse rib interval, expressed in (mm).
If the geometric parameters of the steel bars are known, the specific projected rib area can be
calculated using Formula (2):
Where,
d---the nominal diameter of the steel bar, expressed in (mm);
fi---the sum of the spacings between each row of transverse ribs on the circumference of the
steel bar, expressed in (mm);
h---the midpoint height of the transverse rib, expressed in (mm);
h1/4---the height at 1/4 of the transverse rib, expressed in (mm);
l---the transverse rib interval, expressed in (mm).
NOTE: the calculation results of Formula (2) are approximate values.
5.3 Dimensions, Weight and Allowable Deviations
The dimensions, weight and allowable deviations of the steel bars with two-sided ribs and three-
sided ribs shall comply with the stipulations of Table 1.
supply-side and the supply-side, it is allowed to be replaced by the inspection data of the same
designation continuously produced with the same raw materials and the same process.
7.2 Mechanical Properties
The nominal cross-sectional areas listed in Table 1 are used to calculate the strength of the steel
bars.
7.3 Stress Relaxation Test
7.3.1 During the test, the ambient temperature of the specimen shall be maintained at 20 C 
2 C.
7.3.2 Mechanical straightening is allowed on the specimen, but any heat treatment or other cold
machining shall not be carried out.
7.3.3 The initial test force applied onto the specimen is 70% of the nominal tensile strength of
the specimen multiplied by the nominal cross-sectional area of the specimen.
7.3.4 The loading speed is 200 MPa/min  50 MPa/min. The loading of the initial load shall be
completed within 3 ~ 5 minutes. After maintaining the load for 2 minutes, start recording the
relaxation value.
7.3.5 The length of the specimen is not less than 60 times the nominal diameter.
7.3.6 It is allowed to use test data of at least 120 h to extrapolate the 1,000-h relaxation rate
value.
7.4 Dimensional Measurements
7.4.1 The height of the transverse ribs is measured by measuring the height of each row of
transverse ribs of the same section and taking the average value; the rib interval is measured by
measuring the average interval, that is, measure the distance between the centers of the 1st and
11th transverse ribs in the same row and divide it by 10, which is the average interval between
the transverse ribs.
7.4.2 Dimensional measurements are accurate to 0.02 mm.
7.5 Measurement of Weight Deviations
When measuring the weight deviations of the steel bars, the length of the specimen shall not be
less than 500 mm. The length measu...