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GB/T 28900-2012 English PDF (GBT28900-2012)

GB/T 28900-2012 English PDF (GBT28900-2012)

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GB/T 28900-2012: Test methods of steel for reinforcement of concrete

This standard specifies the test methods for tensile, bending, reverse bending, axial fatigue, chemical analysis, geometric measurement, measurement of relative rib area, determination of weight deviation, metallographic inspection of steel, for reinforcement of concrete. This standard applies to steel products for reinforcement of concrete.
GB/T 28900-2012
GB
NATIONAL STANDARD OF THE
PEOPLE REPUBLIC OF CHINA
ICS 77.140.60
H 44
Test methods of steel for reinforcement of concrete
(ISO 15630-1:2010, Steel for the reinforcement and prestressing of
concrete - Test methods - Part 1: Reinforcing bars, wire rod and wire,
MOD)
ISSUED ON: NOVEMBER 05, 2012
IMPLEMENTED ON: MAY 01, 2013
Issued by: General Administration of Quality Supervision, Inspection and Quarantine of PRC;
Standardization Administration of PRC.
Table of Contents
Foreword ... 4
1 Scope ... 6
2 Normative references ... 6
3 Symbol description ... 6
4 General requirements for specimens ... 8
4.1 Preparation ... 8
4.2 Straightening ... 8
4.3 Artificial aging ... 8
5 Tensile test ... 9
5.1 Specimen ... 9
5.2 Test equipment ... 9
5.3 Test procedure ... 9
6 Bending test ... 11
6.1 Specimen ... 11
6.2 Test equipment ... 11
6.3 Test procedure ... 11
6.4 Judgment of test results ... 12
7 Reverse bending test ... 12
7.1 Specimen ... 12
7.2 Test equipment ... 12
7.3 Test procedure ... 13
7.4 Judgment of test results ... 14
8 Axial fatigue test ... 14
8.1 Test principle ... 14
8.2 Specimen ... 15
8.3 Test equipment ... 15
8.4 Test procedure ... 15
9 Chemical analysis ... 17
10 Dimension measurement ... 17
10.1 Specimen ... 17
10.2 Test equipment ... 17
10.3 Test procedure ... 18
11 Determination of relative rib area (fR) ... 20
11.1 Overview ... 20
11.2 Determination ... 20
11.3 Calculation of fR ... 21
12 Determination of weight deviation ... 22
12.1 Specimen ... 22
12.2 Accuracy of measurement ... 22
12.3 Test procedure ... 22
13 Metallographic inspection method of steel bars ... 23
13.1 Specimen ... 23
13.2 Test procedure ... 23
Appendix A (Informative) Technical differences between this standard and ISO 15630-1:2010 as well as the reasons ... 24
Test methods of steel for reinforcement of concrete
1 Scope
This standard specifies the test methods for tensile, bending, reverse bending, axial fatigue, chemical analysis, geometric measurement, measurement of relative rib area, determination of weight deviation, metallographic inspection of steel, for reinforcement of concrete.
This standard applies to steel products for reinforcement of concrete.
This standard does not apply to prestressed steel.
2 Normative references
The following documents are essential to the application of this document. For the dated documents, only the versions with the dates indicated are applicable to this document; for the undated documents, only the latest version (including all the amendments) is applicable to this standard.
GB/T 228.1-2010 Metallic materials - Tensile testing - Part 1: Method of test at room temperature (ISO 6892-1:2009, MOD)
GB/T 232-2010 Metallic materials - Bend test (ISO 7438:2005, MOD)
GB/T 4336 Carbon and low-alloy steel - Determination of multi-element
contents - Spark discharge atomic emission spectrometric method (routine method)
GB/T 12160 Calibration of extensometers used in uniaxial testing (GB/T
12160-2002, ISO 9513:1999, IDT)
GB/T 13298 Metal - Inspection method of microstructure
GB/T 16825.1 Verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Verification and calibration of the force-measuring system (GB/T 16825.1-2008, ISO 7500-1:2004, IDT)
3 Symbol description
The symbols used in this standard are as shown in Table 1.
5 Tensile test
5.1 Specimen
In addition to the general provisions given in Chapter 4, the parallel length of the specimen shall be long enough, to meet the requirements for elongation determination in 5.3.
When determining the elongation at break (A), the specimen shall be marked with the original gauge length L0, in accordance with the provisions of GB/T 228.1.
When measuring the total elongation at maximum force Fm, (Agt), by manual method, the equal division mark shall be marked on the parallel length of the specimen. According to the diameter of the steel bar product, the distance between the equal division marks shall be 10 mm; it may also be 5 mm or 20 mm, according to the needs.
5.2 Test equipment
The testing machine shall be checked and calibrated, according to GB/T
16825.1, at least up to level 1.
When using an extensometer to determine ReL or Rp0.2, the accuracy of the extensometer shall reach level 1 (see GB/T 12160). When determining Agt, it may use an extensometer with level 2 accuracy (see GB/T 12160).
The extensometer, which is used to determine the total elongation at maximum force Fm, (Agt), shall have a gauge length of at least 100 mm. The gauge length shall be recorded in the test report.
5.3 Test procedure
The tensile test shall be carried out in accordance with GB/T 228.1. For the determination of Rp0.2, if the elastic straight section of the force-extension curve is short OR not obvious, one of the following methods shall be used:
a) Recommended procedures in Chapter 15 and Appendix K of GB/T 228.1-
2010;
b) The straight-line segment of the force-extension curve shall be regarded as the line segment, connecting the two points 0.2Fm and 0.5Fm.
temperature of 10 ??C ~ 35 ??C.
Note: For the test at low temperature, if the agreement does not specify the test conditions, it shall use a temperature deviation of ??2 ??C. The specimen shall be immersed in the cooling medium AND kept for sufficient time, to ensure that the entire specimen reaches the specified temperature (for example, at least 10 min for liquid media and at least 30 min for gaseous media). The bending test shall be carried out, within 5 s after the specimen being removed from the medium. Moving the specimen shall ensure that the temperature of the specimen is within the allowable temperature range.
The specimen shall be bent on the bending core.
The bending angle (??) and bending core diameter (D) shall comply with relevant product standards.
6.4 Judgment of test results
The bending test shall be judged, according to the provisions of the relevant product standards.
When the product standard does not specify, if the bending specimen has no visible cracks, the specimen is judged to be qualified.
7 Reverse bending test
7.1 Specimen
The specimen shall meet the general requirements of Chapter 4.
7.2 Test equipment
7.2.1 Bending device
The bending device, which is specified in 6.2, shall be used.
7.2.2 Reverse bending device
Reverse bending can be performed on the bending device, as shown in Figure 2. Another optional reverse bending device diagram is as shown in Figure 3. described in 7.3.2; c - The position after the operation as described in 7.3.4. Figure 4 -- Legends of the reverse bending test procedure
7.3.2 Bending
The bending step shall be carried out, at a temperature of 10 ??C ~ 35 ??C. The specimen shall be bent on the bending core.
The bending angle (??) and bending core diameter (D) shall meet the
requirements of relevant product standards.
The specimen shall be carefully inspected, for cracks and fractures, by visual inspection.
7.3.3 Manual aging steps
The temperature and time of artificial aging shall meet the requirements of relevant product standards.
When the product standard does not specify any aging treatment method, it may refer to the recommended process in 4.3.
7.3.4 Reverse bending steps
After being naturally cooled to 10 ??C ~ 35 ??C in still air, make sure to bend the specimen back, at the angle (??) specified by the relevant product standard, at the bending origin (the midpoint of the arc segment with the largest radius of curvature).
7.4 Judgment of test results
The reverse bending test shall be determined, according to the relevant product standards.
When the product standard does not specify, if the reverse bending specimen has no visible cracks, the specimen is judged to be qualified.
8 Axial fatigue test
8.1 Test principle
The axial fatigue test is to make the specimen bear an action of the axial tension, which has a sinusoidal periodic variation at the fixed frequency f (as shown in Figure 5), within the range of elastic deformation; make the test shall be within 10 ??C ~ 35 ??C; in order to ensure that the test is carried out under controllable conditions, the test temperature shall be (23 ?? 5) ??C.
8.4.7 Test termination
If the specimen is destructed before the specified number of cycles is reached, OR when the specified cycle number is reached but the specimen is not broken, the test shall be terminated.
8.4.8 Validity of test
If the damage occurs in the clamping part OR within 2d from the clamping part, OR if the damage is caused by abnormal characteristics of the specimen, the test may be deemed invalid.
9 Chemical analysis
Under normal circumstances, use the GB/T 4336 spectral analysis method, to determine the chemical composition.
In the event of a dispute over the analysis method, the chemical composition shall be arbitrated, by the chemical analysis method.
10 Dimension measurement
10.1 Specimen
The specimen shall meet the general requirements of Chapter 4.
The length of the specimen shall ensure the measurement requirements of 10.3.
10.2 Test equipment
The size measurement equipment shall have at least the measurement
accuracy, as shown below:
- For horizontal ribs or longitudinal ribs less than or equal to 1 mm, the measurement accuracy is 0.01 mm;
- For transverse ribs or longitudinal ribs greater than 1 mm, the height accuracy is 0.02 mm;
- For two rows of adjacent transverse ribs, the spacing accuracy is 0.05 mm; - The measurement accuracy of transverse ribs (see 10.3.3) is 0.5 mm;
- The angle, between the axial direction of the transverse rib and the axial direction of the steel bar, is 1??; the measurement accuracy of the rib's lateral inclination angle is 1??.
When disputes arise, traditional reading devices, such as two-foot gauges, wire gauges, etc., shall be used.
10.3 Test procedure
10.3.1 Transverse rib height or notch depth
10.3.1.1 Maximum value (hmax)
The maximum height of the transverse rib (hmax) shall be obtained by calculating the average value, after measuring at least 3 maximum values, in each row, on the transverse rib. These transverse ribs used for measurement shall not bear the product identification of the steel bar.
10.3.1.2 Value of a given position
The height of the transverse rib, at a given position, such as at 1/4 point, 1/2 point or 3/4 point, is defined as h1/4, h, h3/4, respectively. It shall be obtained, by calculating the average value, after measuring at least 3 values, at this position on this row of different transverse ribs. These transverse ribs, which are used for measurement, shall not have the product identification of the steel bar. 10.3.2 Longitudinal rib height (h1)
The height of the longitudinal ribs (h1) shall be the calculated average value, which is obtained by measuring each longitudinal rib, at least 3 times, at three different positions of the product.
10.3.3 Spacing of transverse ribs (l)
The transverse rib spacing (l) shall be the measured length divided by the number of ribs in the length.
The measured length is considered to be the distance, from the center of one rib to the center of another rib, on the same row of ribs, at a straight line parallel to the center line of the product. The measured length shall have at least 10 rib spacings.
10.3.4 End clearance of transverse ribs (??ei)
The end clearance of the transverse ribs (??ei) shall be the sum of the average Where:
?? - An empirical coefficient. For a special steel profile, it shows the relationship between fR and h/l.
The values of h1/4, h, h3/4 can be determined according to 10.3.1.2.
??ei can be determined according to 10.3.5.
11.3.3 Calculation formula of fR
The formula, which is used to calculate fR, shall be specified in the relevant product standards AND recorded in the test report.
12 Determination of weight deviation
12.1 Specimen
The weight deviation shall be measured on a specimen, which has a vertical end face. The number and length of the specimens shall comply with the
requirements of the relevant product.
12.2 Accuracy of measurement
The length of the specimen is measured to an accuracy of 1 mm. The weight measurement accuracy shall be at least ??1%.
12.3 Test procedure
When measuring the weight deviation of the steel bars, the specimens shall be taken from different steel bars; the number is not less than 5; the length of each specimen is not less than 500 mm. The length shall be measured one by one, accurate to 1 mm. When measuring the total weight of the specimen, it shall be accurate to no more than 1% of the total weight.
The deviation, between the actual weight of the steel bar and the theoretical weight, is calculated according to formula (9):
Weight deviation = [Actual total weight of the specimen - (Total length of the specimen ?? Theoretical weight)] / (Total length of the specimen ?? Theoretical weight) ?? 100% ?€??€??€??€??€??€??€??€??€??€?.?€??€?(9)

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