Some standard content:
GB/T5224—2003
This standard is a revised version of GB/T5224—1995, corresponding to the international standard ISO6934-4:1991 "Steel for prestressed concrete Part 4 Steel strand". The consistency between this standard and ISO6934-4:1991 is non-equivalent, and the main differences are as follows: added varieties and strength levels, adjusted specifications; - cancelled Class I relaxation steel strand;
- improved strength ratio;
added Appendix A fatigue test and Appendix B deflection tensile test; cancelled 1×19 structural steel strand.
This standard replaces GB/T5224—1995 "Steel strand for prestressed concrete". Compared with GB/T5224-1995, this standard has the following main changes: added varieties, specifications, and strength levels; cancelled the I-level relaxed steel strand;
-cancelled the provisions of the 10h relaxation test;
-improved the yield strength ratio;
added Appendix A fatigue test and Appendix B deflection tensile test; added Appendix C new and old standard mechanical properties name and symbol comparison. Appendix A and Appendix B of this standard are normative appendices, and Appendix C is an informative appendix. This standard was proposed by the former State Bureau of Metallurgical Industry. This standard is under the jurisdiction of the National Steel Standardization Technical Committee. The drafting units of this standard are: Tianjin No. 1 Prestressed Steel Wire Co., Ltd., Xinhua Metal Products Co., Ltd., Tianjin Gaoli Prestressed Steel Strand Co., Ltd., Metallurgical Construction Research Institute, Metallurgical Industry Information Standards Research Institute. The main drafters of this standard are: Mao Aiju, Zhang Xiufeng, Duan Jianhua, Feng Wenhua, Li Peixun, Tang Lan, Wei Ming. This standard was first issued in July 1985 and revised for the first time in October 1995. 1 Scope
Steel strand for prestressed concrete
GB/T 5224--2003
This standard specifies the classification, size, shape, quality and allowable deviation, technical requirements, test methods, inspection rules, packaging, marking and quality certificate of steel strand for prestressed concrete. This standard applies to steel strand for prestressed concrete structure twisted from cold-drawn round steel wire and notched steel wire (hereinafter referred to as steel strand).
2 Normative references
The clauses in the following documents become the clauses of this standard through reference in this standard. For dated references, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For undated references, the latest versions shall apply to this standard. GB/T228 Room temperature tensile test method for metallic materials GB/T5223 Steel wire for prestressed concrete
GB/T10120—1996 Test method for stress relaxation of metals GB/T17505 General technical requirements for delivery of steel and steel products YB/T146 Hot rolled wire rod for prestressed steel wire and steel strand Non-alloy steel wire rod for wire making
YB/T 170
3 Terms and definitions
The following terms and definitions apply to this standard. 3.1
Standard steel strand
standard strand
Steel strand made by twisting cold-drawn round steel wire. 3.2
Indented strand
Steel strand made by twisting notched steel wire.
Compact strand
Stranded strand after twisting and then cold drawing.
nominal diameter
Nominal diameter
The nominal size of the diameter of the circumscribed circle of the strand. 3.5
Stabilizing treatmentShort-term heat treatment of the strand under a certain tension to reduce stress relaxation during application. 4 Classification and marking
4.1 Classification and code
GB/T5224-2003
Steel strands are divided into 5 categories according to their structure. Its codes are: Steel strand made of two steel wires
Steel strand twisted with three steel wires
Steel strand twisted with three notched steel wires
Standard steel strand twisted with seven steel wires Steel strand twisted with seven steel wires and then drawn 4.2 Marking
4.2.1 Marking content
The marking of products delivered in accordance with this standard shall include the following contents: prestressed steel strand, structure code, nominal diameter, strength grade, standard number. 4.2.2 Marking examples
(1×7)C
Example 1: The standard push-type steel strand with a nominal diameter of 15.20 mm and a strength level of 1860 MPa is marked as: Prestressed steel strand 1×7-15.20-1860-GB/T52242003Example 2: The steel strand with a nominal diameter of 8.74 mm and a strength level of 1670 MPa is marked as: Prestressed steel strand 1×3I-8.74-1670-GB/T5224-2003Example 3: The standard push-type steel strand with a nominal diameter of 15.20 mm and a strength level of 1860 MPa is marked as: Prestressed steel strand 1×3I-8.74-1670-GB/T5224-2003Example 4: The standard push-type steel strand with a nominal diameter of 15.20 mm and a strength level of 1860 MPa is marked as: Prestressed steel strand 1×3I-8.74-1670-GB/T5224-2003Example 5: The standard push-type steel strand with a nominal diameter of 15.20 mm and a strength level of 1860 MPa is marked as: Prestressed steel strand 1×3I-8.74-1670-GB/T5224-2003Example 6: The standard push-type steel strand with a nominal diameter of 15.20 mm and a strength level of 1860 MPa is marked as: Prestressed steel strand 1×3I-8.74-1670-GB/T5224-2003Example 7: The standard push-type steel strand with a nominal diameter of 15.20 mm and a strength level of 1860 MPa is marked as The steel strand made of seven steel wires with a diameter of 2.70mm and a strength level of 1860MPa, twisted and die-drawn, is marked as:
Prestressed steel strand (1×7) C-12.70-1860-GB/T5224--20035 Ordering content
The contract for ordering according to this standard should include the following main contents: a) Product name;
Structure (code)
c) Dimensions;
Strength level:
This standard number;
Quantity;
Purpose;
Other requirements proposed by the purchaser.
6 Dimensions, shape, mass and allowable deviation
6.1 The dimensions, allowable deviation and reference mass per meter of 1×2 structural steel strand shall comply with the provisions of Table 1, and the shape is shown in Figure 16.2 The dimensions, allowable deviation and reference mass per meter of 1×3 structural steel strand shall comply with the provisions of Table 2, and the shape is shown in Figure 2.6.3 The dimensions, allowable deviation and reference mass per meter of 1×7 structural steel strand shall comply with the provisions of Table 3, and the shape is shown in Figure 3.6.4 Steel strands with specifications other than those in Table 1 and Table 3 may be provided upon negotiation between the supplier and the buyer. 6.5 Coil weight: The mass of each coil of steel strand shall not be less than 1000kg, and 10% of the coils are allowed to be less than 1000kg? But not less than 300kg.
6.6 Coil diameter: The inner diameter of the steel strand coil shall not be less than 750mm, and the coil width shall be 750mm±50mm, or 600mm±50mm. The supplier shall indicate the coil size in the quality certificate.
Steel strand
Steel strand
Figure 11×2 schematic diagram of structural steel strand
Table 11×2 structural steel strand dimensions and allowable deviations, reference nominal diameter per meter
Steel strand diameter
Steel wire diameter
Steel strand diameter
Allowable deviation/mm
Reference cross-sectional area of steel strand
Figure 21×3 structural steel strand Schematic diagram
Table 21×3 structural steel strand dimensions and allowable deviations, reference mass per meter Nominal diameter
Steel strand diameter
Wire diameter
Steel strand measurement dimensions
Measurement dimensions A
Allowable deviation/mm
Steel strand reference
Cross-sectional area
GB/T5224—2003
Steel strand per meter| |tt||Reference mass/(g/m)
Steel strand per meter
Reference mass/(g/m）
GB/T52242003
Steel strand
(1×7)C
7 Technical requirements
Figure 3 Schematic diagram of the appearance of 1×7 structural steel strand
Table 3 Dimensions and allowable deviations of 1×7 structural steel strand, reference mass per meter 7.1 Brand and chemical composition
Diameter allowable
Deviation/mm
Steel strand reference
Cross-sectional area
Steel strand per meter
Reference mass/(g/m）
Center wire diameter d
Enlargement range/%
Not less than
The steel used to manufacture steel strand shall be determined by the supplier according to the product specifications and mechanical properties. The brand and chemical composition shall comply with the provisions of YB/T146 or YB/T170, and other brands may also be used for manufacturing. The composition is not a delivery condition. 7.2 Manufacturing
7.2.1The wire rod used to manufacture steel strand shall be a sorbitized wire rod, which is twisted into steel strand after cold drawing. The steel wire used to make notched steel strand shall comply with the provisions of the corresponding clauses in GB/T5223.
7.2.2 The twisting distance of steel strands is 12 to 16 times the nominal diameter of steel strands. The twisting distance of die-drawn steel strands should be 14 to 18 times the nominal diameter of steel strands. There should be no broken, transverse cracks or crossed wires in the steel strands. 7.2.3 The twisting direction of steel strands is generally left (S) twist, and right (Z) twist should be indicated in the contract. 7.2.4 After twisting, the steel strands should be continuously stabilized. 7.2.5 The finished steel strands should be cut with a grinding wheel saw. They should not be loose after cutting. If they leave their original position, they can be restored to their original position by hand. 4
7.2.6 The finished steel strands are only allowed to retain the welding points before drawing. 7.3 Mechanical properties
7.3.1 The mechanical properties of 1×2 structural steel strands shall comply with the provisions of Table 4. 7.3.2 The mechanical properties of 1×3 structural steel strands shall comply with the provisions of Table 5. 7.3.3 The mechanical properties of 1×7 structural steel strands shall comply with the requirements of Table 6. Table 4 Mechanical properties of 1×2 structural steel strands
Tensile strength of steel strands
Steel strands
Nominal diameter Rm/MPa
Not less than
Maximum force of the entire steel strand
Not less than
Specified non-proportional
Elongation force
Not less than
Maximum force total elongation
(L=400 mm)
Not less than
For all specifications
Note: The specified non-proportional extension force Fo.2 value shall not be less than 90% of the nominal maximum force Fm of the entire steel strand. GB/T5224-2003
Stress relaxation performance
Initial load is equivalent to the stress relaxation rate after 1000h. Percentage of the nominal maximum force/%
For all specifications
Not greater than
For all specifications
GB/T 5224-2003
Steel strand
Steel strand
1×3 1Www.bzxZ.net
Nominal diameter
Tensile strength
Rm/MPa
not less than
Table 51×3 structural steel strand mechanical properties
whole steel strand
Specified non-proportional
maximum force
not less than
Elongation force
not less than
Total elongation at maximum force
(L.400 mm)
not less than
For all specifications
Note: The value of the non-proportional extension force Feo.: shall not be less than 90% of the nominal maximum force Fm of the whole steel strand. 6
Stress relaxation performance
Initial load is equivalent to
percentage of nominal maximum force/%
For all specifications
Stress relaxation rate after 1000h
Not greater than
For all specifications
Steel strand
(1×7)C
Steel strand
Nominal diameter
Tensile strength
Rm/MPa
Not less than
Table 61×7 structural steel strand mechanical properties
Entire steel strand
Specified non-proportional
maximum force
Not less than
Elongation force
Fpo.2 /kN
Not less than
Total elongation at maximum force
(I≥500 mm)
Not less than
For all specifications
Note: The value of non-proportional elongation n.2 is not less than 90% of the nominal maximum force F of the whole steel strand. 7.3.4
GB/T5224--2003
Stress relaxation performance
The initial load is equivalent to the percentage of the nominal maximum force/%
For all specifications
The actual strength of each batch of steel strand delivered by the supplier shall not be higher than its tensile strength level by 200MPa. 7.3.5
The elastic modulus of steel strand is (195±10)GPa, but it is not a delivery condition. According to the supply agreement, steel strands with strength levels other than those in Table 4, Table 5 and Table 6 can be provided. 7.3.6
It is allowed to use the extrapolation method to determine the relaxation rate after 1000h (see 8.5.6)7.3.7
7.4 Surface quality
The stress relaxation rate after 1000h
is not greater than
For all specifications
7.4.1 Unless the purchaser has special requirements, there shall be no oil, grease or other substances on the surface of the steel strand. The steel strand is allowed to have slight floating rust, but there shall be no visible rust pits.
7.4.2 The tempering color is allowed on the surface of the steel strand. 7.5 Straightness of steel strand
Take a steel strand with a chord length of 1m and place it on a plane. The maximum natural rise between the chord and the inner side of the strand shall not exceed 25mm. GB/T 5224.---2003
7.6 Fatigue performance and deflection tensile performance
After negotiation between the supply and demand parties and with the above information specified in the contract, fatigue performance tests and deflection tensile tests may be carried out on the products. 8 Test methods
8.1 Surface inspection
The surface quality shall be visually inspected.
8.2 Dimension inspection
The diameter of the steel strand shall be measured with a measuring tool with a graduation value of 0.02mm. The diameter measurement of the 1×2 structural steel strand shall measure the D value shown in Figure 1; the steel strand of the 1×3 structure shall measure the A value shown in Figure 2. The diameter measurement of the 1×7 structural steel strand shall be based on the two opposite outer steel wires in the direction across the diameter, as shown in Figure 3, D, and the average value shall be taken when measuring the meshes in different directions on the same section. 8.3 Measurement of mass per meter
The mass per meter of steel strand should be measured as follows: Take 3 steel strands with a length of not less than 1m, and measure the length of each steel strand to an accuracy of 1mm. Weigh the mass of each steel strand to an accuracy of 1g, and then calculate the mass per meter of the steel strand as follows. M=
Where:
M-mass of steel strand per meter, in grams per meter (g/m); m-mass of steel strand, in grams (g); L-length of steel strand, in meters (m). The measured single weight is the average of the three calculated values. 8.4 Tensile test
8.4.1 Maximum force
The maximum force test of the entire steel strand shall be carried out in accordance with the provisions of GB/T228. If the specimen breaks in the chuck and within 2 times the nominal diameter of the steel strand from the jaws and fails to meet the performance requirements of this standard, the test is invalid. Take the reference cross-sectional area value of the steel strand when calculating the tensile strength. 8.4.2 Specified non-proportional elongation force
The specified non-proportional elongation force of steel strands is the force (F0.2) when the non-proportional elongation of the extensometer gauge reaches 0.2% of the original gauge. In order to facilitate the supplier's daily inspection, the force (Fl) when the specified total elongation reaches 1% of the original gauge can also be measured. The goods can be delivered when the value meets the Fpo.2 value specified in this standard, but Fpo.2 is measured during the arbitration test. When measuring Fpo.2 and Fu, the preload is 10% of the specified non-proportional elongation force.
8.4.3 Total elongation at maximum force
The determination of total elongation at maximum force Agt shall be carried out in accordance with the provisions of GB/T228. When using a computer to collect data or using an electronic stretching device to measure the elongation, the elongation caused by the preload on the sample shall be added to the total elongation. 8.5 Stress relaxation performance test
8.5.1 The stress relaxation performance test of steel strands shall be carried out in accordance with the provisions of GB/T10120. 8.5.2 During the test, the ambient temperature of the sample shall be maintained within 20℃±2℃. 8.5.3 The test gauge length shall not be less than 60 times the nominal diameter. 8.5.4 No heat treatment or cold processing shall be performed after the sample is prepared. 8.5.5 The initial load shall be applied evenly within 3min~5min, and the relaxation value shall be recorded after holding the load for 1min. 8.5.6 It is allowed to use the test data of at least 100h to calculate the relaxation rate value of 1000h. 8.6 Fatigue and deflection tensile test
Fatigue performance test shall be carried out in accordance with the provisions of Appendix A; deflection tensile test shall be carried out in accordance with the provisions of Appendix B. 9 Inspection rules
The inspection rules for steel strands shall be in accordance with the provisions of GB/T17505. 8
9.1 Inspection and acceptance
GB/T 5224--2003
The inspection of products shall be carried out by the supplier's technical supervision department in accordance with the provisions of Table 7, and the purchaser may conduct inspection and acceptance in accordance with this standard. 9.2 Batch rules
Steel strands should be inspected in batches. Each batch of steel strands shall consist of steel strands of the same brand, specification and production process. The quality of each batch shall not exceed 60t.
9.3 Inspection items and sampling quantity
9.3.1 The mechanical properties of steel strands shall be tested according to the corresponding provisions of Table 4, Table 5 and Table 6. The test items and sampling quantity shall comply with the provisions of Table 7.
Table 7 Routine inspection items and sampling quantity for supplier's delivery Sequence
Inspection items
Overall dimensions
Straightness of steel strand
Maximum force of the whole steel strand
Specified non-proportional elongation
Total elongation at maximum force
Stress relaxation performance
Sampling quantity
By coil
3 pieces/batch
3 pieces/batch
3 pieces/batch
Not less than 1 piece/contract batch [Note]
Release position
Inspection method
According to the provisions of 8.2 of this standard
With a graduation value of 1 mm measuring tool measurement
According to the provisions of 8.4.1 of this standard
Intercepting at any
end of each (any) coil
According to the provisions of 8.4.2 of this standard
Heat-driving according to the provisions of 8.4.3 of this standard
According to the provisions of 85 of this standard
Note: The contract batch is the total amount of a purchase contract. In special cases, the relaxation test can be replaced by the factory continuous inspection to provide data with the same raw materials and the same production process.
9.3.21000h stress relaxation performance test, fatigue performance test, deflection tensile test are only type inspections, and are only inspected when there are major changes in raw materials, production processes, equipment, and new products are produced or production is resumed after suspension. 9. 4 Re-inspection and judgment rules
When the inspection results specified in 9.3.1 do not meet the requirements of this standard, the coil shall not be delivered. And take double the number of samples from the untested steel strand coils of the same batch to retest the unqualified items. If even one sample fails the retest, the entire batch of steel strands shall not be delivered, or they shall be delivered after passing the reel-by-reel inspection. The supplier has the right to re-batch the unqualified products for acceptance. 10 Packaging, marking and quality certificate
10.1 Packaging
Each coil of steel strand shall be firmly tied, with no less than 6 bundles. With the agreement of both parties, moisture-proof paper, linen and other materials may be used for packaging. 10.2 Marking
Each coil of steel strand shall be hung with a sign, which shall indicate the supplier's name, trademark mark, product mark, quantity, factory number, specification, strength level, implementation standard number, etc.
10.3 Quality Certificate
Each contract batch shall be accompanied by a quality certificate, which shall indicate: supplier name, address and trademark, specifications, strength level, purchaser name, contract number, product mark, quality, number of pieces, implementation standard number, test results, inspection and delivery date, and technical supervision department stamp. GB/T5224—2003
Appendix A
(Normative Appendix)
Fatigue Test
A, 1 The specimen used for fatigue test is the specimen directly cut from the finished steel strand, and the specimen length shall ensure that the distance between the two clamps is not less than 500 mm.
A.2 The steel strand shall be able to withstand 2X106 times of 0.7Fm～(0.7Fm2△F.) pulsating load without breaking. 2△Fa/S, =195MPa
Where:
F.--Nominal maximum force of steel strand, in Newton (N); 2△F. ——Equivalent load value of stress range (twice stress amplitude), in Newton (N); S, a reference cross-sectional area of steel strand, in square millimeters (mm2). A.3 During the whole process of the test, the static measurement error of the maximum stress of pulsating tension to maintain a constant stress should not be greater than 1%. A.4 The stress cycle frequency cannot exceed 120Hz. A.5 All stresses are transmitted to the specimen along the axial direction, and there should be no influence of jaws and notches, and there should be a corresponding device to limit any slippage of the specimen in the chuck.
A.6 The test is invalid when the specimen breaks in the chuck and the clamping area (2 times the nominal diameter of the steel strand) due to the influence of notches or local overheating.
A.7 During the test, the temperature of the specimen shall not exceed 40℃, and the ambient temperature of the test room shall be between 18℃ and 25℃. 10
B.1 Test principle
Appendix B
(Normative Appendix)
Deflection tensile test
GB/T 5224--2003
This test is applicable to steel strands with a diameter greater than or equal to 12.5 mm. The steel strand is fixed on a deflection device at an angle of 20° to the straight line for tensile test until at least one single wire breaks, and the ratio of its breaking force to the maximum axial tensile force is measured. B.2 Samples and specimens
B.2.1 The specimens used for deflection tensile test shall be cut from the samples with qualified mechanical properties at a time, with a length equivalent to 12 specimens. One strand is taken from each end for axial tensile test to determine the maximum force of the steel strand. The rest are cut into 10 strands for deflection tensile test. Note: The deflection coefficient can be calculated with 7 valid test results, but considering the invalid test situation, at least 10 specimens shall be taken. B.2.2 The specimen length shall be sufficient for the specimen to be stretched and anchored. B.2.3 The specimen shall not be processed in any way except for cutting. B.3 Test equipment
B.3.1 Overview
The testing machine shall have a rigid frame to meet the test requirements specified in this standard. The testing machine includes a fixed can clamp and a movable anchor clamp with a force measuring device, a loading device and a grooved spindle. B.3.2 Test equipment dimensions
The dimensions of the test equipment shall comply with the provisions of Figure B.1 and Table B.1. L, 750 mm
Codes and descriptions of each part f—Spandrel;
-Fixed end;
b Anchor clamp.
1==700mm
α =20*±0, 5*
Figure B, 1 Deflection tensile test device
Table 8.1 Displacement of the clamp
Percentage of maximum force
From 0% to breaking
From 50%Fm to breaking
Note: The wedge-shaped clamp should be ground before the test. B.3.3 Clamp
Maximum allowable displacement
The axial centerline of the two ends of the specimen should be perpendicular to the bearing plane of the anchor clamp. Incorrect design size and positioning will result in erroneous test results.
The anchor clamp should meet the following requirements:3 Quality Certificate
Each contract batch shall be accompanied by a quality certificate, which shall indicate: supplier name, address and trademark, specifications, strength level, purchaser name, contract number, product mark, quality, number of pieces, implementation standard number, test results, inspection and delivery date, and technical supervision department stamp. GB/T5224—2003
Appendix A
(Normative Appendix)
Fatigue Test
A, 1 The specimen used for fatigue test is the specimen directly cut from the finished steel strand, and the specimen length shall ensure that the distance between the two clamps is not less than 500 mm.
A.2 The steel strand shall be able to withstand 2X106 times of 0.7Fm～(0.7Fm2△F.) pulsating load without breaking. 2△Fa/S, =195MPa
Where:
F.--Nominal maximum force of steel strand, in Newton (N); 2△F. ——Equivalent load value of stress range (twice stress amplitude), in Newton (N); S, a reference cross-sectional area of steel strand, in square millimeters (mm2). A.3 During the whole process of the test, the static measurement error of the maximum stress of pulsating tension to maintain a constant stress should not be greater than 1%. A.4 The stress cycle frequency cannot exceed 120Hz. A.5 All stresses are transmitted to the specimen along the axial direction, and there should be no influence of jaws and notches, and there should be a corresponding device to limit any slippage of the specimen in the chuck.
A.6 The test is invalid when the specimen breaks in the chuck and the clamping area (2 times the nominal diameter of the steel strand) due to the influence of notches or local overheating.
A.7 During the test, the temperature of the specimen shall not exceed 40℃, and the ambient temperature of the test room shall be between 18℃ and 25℃. 10
B.1 Test principle
Appendix B
(Normative Appendix)
Deflection tensile test
GB/T 5224--2003
This test is applicable to steel strands with a diameter greater than or equal to 12.5 mm. The steel strand is fixed on a deflection device at an angle of 20° to the straight line for tensile test until at least one single wire breaks, and the ratio of its breaking force to the maximum axial tensile force is measured. B.2 Samples and specimens
B.2.1 The specimens used for deflection tensile test shall be cut from the samples with qualified mechanical properties at a time, with a length equivalent to 12 specimens. One strand is taken from each end for axial tensile test to determine the maximum force of the steel strand. The rest are cut into 10 strands for deflection tensile test. Note: The deflection coefficient can be calculated with 7 valid test results, but considering the invalid test situation, at least 10 specimens shall be taken. B.2.2 The specimen length shall be sufficient for the specimen to be stretched and anchored. B.2.3 The specimen shall not be processed in any way except for cutting. B.3 Test equipment
B.3.1 Overview
The testing machine shall have a rigid frame to meet the test requirements specified in this standard. The testing machine includes a fixed can clamp and a movable anchor clamp with a force measuring device, a loading device and a grooved spindle. B.3.2 Test equipment dimensions
The dimensions of the test equipment shall comply with the provisions of Figure B.1 and Table B.1. L, 750 mm
Codes and descriptions of each part f—Spandrel;
-Fixed end;
b Anchor clamp.
1==700mm
α =20*±0, 5*
Figure B, 1 Deflection tensile test device
Table 8.1 Displacement of the clamp
Percentage of maximum force
From 0% to breaking
From 50%Fm to breaking
Note: The wedge-shaped clamp should be ground before the test. B.3.3 Clamp
Maximum allowable displacement
The axial centerline of the two ends of the specimen should be perpendicular to the bearing plane of the anchor clamp. Incorrect design size and positioning will result in erroneous test results.
The anchor clamp should meet the following requirements:3 Quality Certificate
Each contract batch shall be accompanied by a quality certificate, which shall indicate: supplier name, address and trademark, specifications, strength level, purchaser name, contract number, product mark, quality, number of pieces, implementation standard number, test results, inspection and delivery date, and technical supervision department stamp. GB/T5224—2003
Appendix A
(Normative Appendix)
Fatigue Test
A, 1 The specimen used for fatigue test is the specimen directly cut from the finished steel strand, and the specimen length shall ensure that the distance between the two clamps is not less than 500 mm.
A.2 The steel strand shall be able to withstand 2X106 times of 0.7Fm～(0.7Fm2△F.) pulsating load without breaking. 2△Fa/S, =195MPa
Where:
F.--Nominal maximum force of steel strand, in Newton (N); 2△F. ——Equivalent load value of stress range (twice stress amplitude), in Newton (N); S, a reference cross-sectional area of steel strand, in square millimeters (mm2). A.3 During the whole process of the test, the static measurement error of the maximum stress of pulsating tension to maintain a constant stress should not be greater than 1%. A.4 The stress cycle frequency cannot exceed 120Hz. A.5 All stresses are transmitted to the specimen along the axial direction, and there should be no influence of jaws and notches, and there should be a corresponding device to limit any slippage of the specimen in the chuck.
A.6 The test is invalid when the specimen breaks in the chuck and the clamping area (2 times the nominal diameter of the steel strand) due to the influence of notches or local overheating.
A.7 During the test, the temperature of the specimen shall not exceed 40℃, and the ambient temperature of the test room shall be between 18℃ and 25℃. 10
B.1 Test principle
Appendix B
(Normative Appendix)
Deflection tensile test
GB/T 5224--2003
This test is applicable to steel strands with a diameter greater than or equal to 12.5 mm. The steel strand is fixed on a deflection device at an angle of 20° to the straight line for tensile test until at least one single wire breaks, and the ratio of its breaking force to the maximum axial tensile force is measured. B.2 Samples and specimens
B.2.1 The specimens used for deflection tensile test shall be cut from the samples with qualified mechanical properties at a time, with a length equivalent to 12 specimens. One strand is taken from each end for axial tensile test to determine the maximum force of the steel strand. The rest are cut into 10 strands for deflection tensile test. Note: The deflection coefficient can be calculated with 7 valid test results, but considering the invalid test situation, at least 10 specimens shall be taken. B.2.2 The specimen length shall be sufficient for the specimen to be stretched and anchored. B.2.3 The specimen shall not be processed in any way except for cutting. B.3 Test equipment
B.3.1 Overview
The testing machine shall have a rigid frame to meet the test requirements specified in this standard. The testing machine includes a fixed can clamp and a movable anchor clamp with a force measuring device, a loading device and a grooved spindle. B.3.2 Test equipment dimensions
The dimensions of the test equipment shall comply with the provisions of Figure B.1 and Table B.1. L, 750 mm
Codes and descriptions of each part f—Spandrel;
-Fixed end;
b Anchor clamp.
1==700mm
α =20*±0, 5*
Figure B, 1 Deflection tensile test device
Table 8.1 Displacement of the clamp
Percentage of maximum force
From 0% to breaking
From 50%Fm to breaking
Note: The wedge-shaped clamp should be ground before the test. B.3.3 Clamp
Maximum allowable displacement
The axial centerline of the two ends of the specimen should be perpendicular to the bearing plane of the anchor clamp. Incorrect design size and positioning will result in erroneous test results.
The anchor clamp should meet the following requirements:
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