GB/T 28900-2022 Test methods of steel for reinforcement of concrete
1 Scope
This document specifies test methods for the tensile test, bending test, reverse bending test, axial fatigue test, chemical analysis, geometric measurement, determination of relative rib area, determination of weight deviation and cyclic inelastic load test of steel for reinforced concrete.
This document applies to steels for reinforced concrete.
This document does not apply to prestressed steels.
2 Normative references
The contents of the following documents constitute essential provisions of this document through the normative references in the text. Among them, note the date of the reference documents, only the date of the corresponding version applies to this document; do not note the date of the reference documents, the latest version (including all the revision of the list) applies to this document.
GB/T 228.1 Metallic Materials - Tensile Testing - Part 1: Room Wet Test Method (GB/T 228.1-2021, ISO 6892-1: 2019, MOD)
GB/T 232 Metallic Materials Bending Test Method (GB/T232-2010, ISO 7438:2005, MOD)
GB/T 4336 Carbon Steel and Medium Low Alloy Steel Determination of Multi element Content Spark Discharge Atomic Emission Spectrometry (Conventional Method)
GB/T11170 Stainless Steel Determination of Multielement Content Spark Discharge Atomic Emission Spectrometry (Conventional Method)
GB/T 12160 Calibration of Extensometer System for Uniaxial Testing of Metallic Materials (GB/T 12160-2019, ISO 9513:2012, IDT)
GB/T 16825.1 Testing of Static Uniaxial Testing Machines - Part 1: Testing and Calibration of Force Measuring Systems for Tensile and/or Pressure Testing Machines (GB/T 16825.1-2008, ISO 7500-1: 2004, IDT)
GB/T 25917.1 Uniaxial Fatigue Test System Part 1: Dynamic Force Calibration (GB/T 25917.1-2019, ISO 4965-1:. 2012, IDT)
GB/T 25917.2 Uniaxial Fatigue Test System Part 2: Instruments for Dynamic Calibration Device (GB/T 25917.2:2019, ISO 4965-2: 2012, IDT)
GB/T 38937 Terminology of Steel for Reinforced Concrete (GB/T 38937 - 2020, ISO 16020: 2005, MOD)
3 Terms and definitions
The terms and definitions defined in GB/T 38937 apply to this document.
4 Symbols and descriptions
The following symbols and descriptions (see Table 1) apply to this document.
5 General provisions for specimens
5.1 Preparation
Unless otherwise agreed between supply and demand or specified in the product standard, specimens shall be taken from steel in the delivered condition.
5.2 Straightening
For specimens taken from coils (coils or wire), a simple bend shall be made to straighten the specimen and ensure minimum plastic deformation prior to any test. The manner of straightening of the specimen (manual, mechanical) shall be recorded in the test report.
Note 1, for room temperature tensile tests, axial fatigue tests, cyclic inelastic loading tests, bending tests, reverse bending tests and weight deviation determinations, the straightening of the specimen is essential.
Note peal: excessive straightening can easily cause changes in mechanical and technological properties, by using rubber hammers, wooden hammers or special devices for straightening, on the basis of ensuring minimum plastic deformation, try to make the axis of the specimen coincide with the line of action of the force or in the same plane.
5.3 Artificial ageing
Determination of room temperature tensile test, bending test, reverse bending test, axial stress fatigue test and cyclic inelastic load test performance indicators, according to the requirements of the product standard for straightened specimens for artificial aging.
When the product standard does not specify the artificial aging process, the following process conditions can be used: heating the specimen to 100 ℃, holding at 100 ℃ ± 10 ℃ for 60 min ~ 75 min, and then in the still air natural cooling to room temperature.
Note: Different test conditions (including the number of specimens, specimen size and type of heating equipment) heating time is also different, it is generally believed that the heating time of not less than
The best results are obtained when the heating time is at least 40 min.
If manual ageing is carried out on the specimen, the conditions of the manual ageing process should be recorded in the test report.
6 Tensile test
6.1 Specimens
In addition to the general provisions given in Chapter 5, the parallel length of the specimen shall be sufficiently long to meet the requirements for the determination of elongation after break (A) or total elongation at maximum force (Apx>) as described in 6.3.
When measuring elongation after break (A) by hand, the specimen should be marked with the original distance according to the provisions of GB/T 228.1.
7 Bending test
7.1 Specimen
Specimens in accordance with the provisions of Chapter 5. 7.2 Test equipment
7.2.1 bending device should be used to test the principle shown in Figure Peal.
8 Reverse bending test
8.1 Specimen
Specimens in accordance with the provisions of Chapter 5.
8.2 test equipment
8.2.1 bending device
The bending device specified in 7.2 shall be used.
9 Axial fatigue test
9.1 Test principle
Axial fatigue test is the specimen in the elastic deformation range, so that it is subjected to a fixed frequency ( f) sinusoidal curve cycle changes (see Figure 5) of the role of axial tension, and make the test has been carried out until the test Bin broken you or reach the relevant product standards cycle cycle times and no damage to the specimen.
10 Chemical analysis
In general, the chemical composition is determined by spectroscopic methods of analysis GB/T4336 or GB/T 11170. In the event of a dispute over the results of the analysis, the chemical composition should be arbitrated using the chemical analysis method.
11 Dimensional measurements
11.1 Specimens
Specimens should comply with the provisions of Chapter 5.
The length of the specimen shall meet the measurement requirements of 11.3.
11.2 Test equipment
The geometrical accuracy of the measuring equipment shall meet at least the following requirements:
--- 0.01 mm for measuring the height of the cross or longitudinal ribs up to 1 iem;
--0.02 mm for measuring the height of a cross or longitudinal rib greater than 1 mm;
-0.05 mm for measuring the distance between two adjacent ribs;
---0.05 mm for measuring the width of a cross rib;
---0.5 mm for measuring the spacing between cross ribs (see 11.3.3>);
-- 1° for measuring the angle between the axial direction of the cross-rib and the axial direction of the reinforcement or the oblique angle of the rib side. When in dispute, conventional direct reading instruments such as calipers, depth gauges etc. should be used.
11.3 Test procedure
11.3.1 Height of the cross-rib
11.3.1.1 Maximum value (h max)
The maximum height of the cross-rib (h .m.x) shall be obtained by measuring at least three maximum values in each row of the cross-rib and calculating the average value; these cross-ribs for measurement shall not bear the product identification of the reinforcement.
If there are different angles (β) between the axial direction of the cross-rib and the steel axis in a row, each β shall be measured at least three times for a single cross-rib.
12 Determination of the relative rib area (f x)
12.1 Overview
The adhesion between the steel and the concrete allows for the transfer of shared loads.
The main factor influencing the adhesion comes from the shear adhesion created by the ribs on the surface of the concrete steel. When the steel for reinforced concrete has ribs, the bonding properties can be determined by various methods: a) determination of the geometry of the ribs
b) measurement of the adhesion between concrete and concrete steel in a pull-out test or beam test. On the basis of the geometrical data, the coefficient of adhesion, also known as the relative rib area (fR), is calculated. 12.2 Measurement
The relative rib area (f x>) shall be determined using the geometrical results measured in chapter 11.
13 Determination of weight deviation
13.1 Specimens
The determination of the weight deviation shall be carried out on a specimen with a vertical cut end, the location, number and length of which shall be in accordance with the relevant product regulations.
13.2 Accuracy of measurement
The length of the specimen shall be measured to an accuracy of 1 mm and the weight shall be measured to an accuracy of not less than 1%.
14 Cyclic inelastic load test
14.1 Test principle
The cyclic inelastic load test is performed by subjecting the specimen to 5 complete symmetrical hysteresis cycles under the conditions given in Table 2 and Figure 7. The test is completed when the specimen fails or completes the specified number of cycles before reaching 14.
14.2 Specimens
In addition to the general provisions given in Chapter 5, the free length of the specimen shall be as specified in Table 2.
The specimens shall be representative, undamaged and of sufficient length to meet the length requirements between fixtures as given in Table P.C. The surface of the free length between fixtures shall not be subjected to any form of surface treatment.
14.3 Test equipment
The force detection system of the test machine shall be calibrated and calibrated in accordance with GB/T 16825.1 and shall have a static accuracy rating of at least Class 1. For each cyclic inelastic load testing machine, the test conditions (initial force, clamping force, test control of the free length between fixtures) and the necessary specimen length should be recorded for each nominal diameter of the steel.
Note: Refer to GB/T 228.1 for provisions relating to initial force and beam separation rate control.
14.4 Test procedures
14.4.1 on the specimen provisions
The specimen should be clamped in the test equipment in order to transfer the load axially.
The fixture used should ensure that the specimen does not bend during the test. The clamping force perpendicular to the test axis shall be the minimum to ensure that the specimen will not be displaced.
Appendix A (informative) Comparison table of the structure of this document with ISO 15630-1:2019
Appendix B (Informative) Technical differences between this document and ISO 15630-1:2019 and the reasons for them
contents
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and descriptions
5 General provisions for specimens
6 Tensile test
7 Bending test
8 Reverse bending test
9 Axial fatigue test
10 Chemical analysis
11 Dimensional measurements
12 Determination of the relative rib area (fx)
13 Determination of weight deviation
14 Cyclic inelastic load test
14.4.1 on the specimen provisions
Appendix A (informative) Comparison table of the structure of this document with ISO 15630-1:
Appendix B (Informative) Technical differences between this document and ISO 15630-1:2019 and the reasons for them
