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GB/T 5224-2023 PDF in English


GB/T 5224-2023 (GB/T5224-2023, GBT 5224-2023, GBT5224-2023)
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GB/T 5224-2023: PDF in English (GBT 5224-2023)

GB/T 5224-2023
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.65
CCS H 49
Replacing GB/T 5224-2014
Steel Strand for Prestressed Concrete
(ISO 6934-4:2020, Steel for the Prestressing of Concrete - Part 4: Strand, NEQ)
ISSUED ON: AUGUST 6, 2023
IMPLEMENTED ON: MARCH 1, 2024
Issued by: State Administration for Market Regulation;
Standardization Administration of the People’s Republic of China.
Table of Contents
Foreword ... 4
1 Scope ... 7
2 Normative References ... 7
3 Terms and Definitions ... 7
4 Classification, Code and Labeling ... 8
4.1 Classification and Code ... 8
4.2 Labeling ... 8
5 Order Content ... 9
6 Dimensions, Cross-sectional Shape, Weight and Allowable Deviations ... 10
7 Technical Requirements ... 15
7.1 Manufacturing ... 15
7.2 Mechanical Properties ... 16
7.3 Surface Quality ... 21
7.4 Straightness of Steel Strands ... 21
7.5 Fatigue Properties, Deflection Tensile Properties and Stress Corrosion Properties... 21
8 Test Methods ... 21
8.1 Surface Inspection ... 21
8.2 Inspection of Overall Dimensions ... 21
8.3 Measurement and Calculation of Enlargement Ratio of Center Steel Wire Diameter of
1  7 Structured Steel Strands ... 22
8.4 Tensile Test ... 22
8.5 Straightness ... 23
8.6 Measurement and Calculation of Nominal Weight Deviation per Meter ... 23
8.7 Test of Stress Relaxation Properties ... 24
8.8 Fatigue Test ... 24
8.9 Deflection Tensile Test ... 25
8.10 Stress Corrosion Test ... 25
8.11 Numerical Rounding ... 25
9 Inspection Rules ... 25
9.1 Classification of Inspection ... 25
9.2 Delivery Inspection ... 26
9.3 Eigenvalue Inspection ... 27
10 Packaging, Marking and Quality Certificate ... 27
10.1 Packaging ... 27
10.2 Marking ... 28
10.3 Quality Certificate ... 28
Appendix A (normative) Eigenvalue Inspection Rules ... 29
A.1 Test Batch ... 29
A.2 Sampling and Inspection Quantity per Batch ... 29
A.3 Evaluation of Test Results ... 29
Bibliography ... 31
Steel Strand for Prestressed Concrete
1 Scope
This document specifies the classification, code and labeling, order content, dimensions, cross-
sectional shape, weight and allowable deviation, technical requirements, test methods,
inspection rules, packaging, marking and quality certificate of steel strand for prestressed
concrete.
This document is applicable to steel strand for prestressed concrete structures twisted from cold-
drawn round steel wires, indented steel wires and helical rib steel wires (hereinafter referred to
as the “steel strand”).
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 5223 Steel Wire for Prestressing of Concrete
GB/T 21839 Test Methods of Steel for Prestressing 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 standard strand
The steel strand twisted from cold-drawn round steel wires.
3.2 indented strand
The steel strand twisted from steel wires containing indentations.
3.3 helical rib strand
The steel strand twisted from steel wires containing helical ribs.
3.4 compact strand
The steel strand that is twisted, and then, cold-compacted.
3.5 nominal diameter
The nominal dimension of the diameter of the circumscribed circle of the steel strand.
3.6 stabilizing treatment
In order to reduce stress relaxation during application, the steel strand is subject to heat
treatment under a certain tension for a short period of time.
4 Classification, Code and Labeling
4.1 Classification and Code
The general structure of the steel strand is classified into the following 9 categories, and the
structure codes are:
a) Standard steel strand twisted from two cold-drawn round steel wires 1  2
b) Standard steel strand twisted from three cold-drawn round steel wires 1  3
c) Indented steel strand twisted from three steel wires containing indentations 1  3I
d) Standard steel strand twisted from seven cold-drawn round steel wires 1  7
e) Indented steel strand twisted from six steel wires containing indentations and one
cold-drawn round center steel wires 1  7I
f) Helical rib strand twisted from six steel wires containing helical ribs and one cold-
drawn round center steel wires 1  7H
g) Compact strand twisted from seven cold-drawn round steel wires, and then, cold-
compacted (1  7)C
h) 1 + 9 + 9 Seale steel strand twisted from nineteen cold-drawn round steel wires 1 
19S
i) 1 + 6 + 6/6 Warrington steel strand twisted from nineteen cold-drawn round steel
wires 1  19W
4.2 Labeling
The labeling of products delivered in accordance with this document shall include the following
content:
a) Prestressed steel strand;
b) Structure code;
c) Nominal diameter;
d) Strength level;
e) Serial No. of this document.
EXAMPLE 1: standard steel strand twisted from seven cold-drawn round steel wires, with a
nominal diameter of 15.20 mm and a tensile strength of 1,860 MPa is labeled as:
prestressed steel strand 1  7-15.20-1,860-GB/T 5224-2023
EXAMPLE 2: indented steel strand twisted from three steel wires containing indentations, with a
nominal diameter of 8.70 mm and a tensile strength of 1,860 MPa is labeled as:
prestressed steel strand 1  3I-8.70-1,860-GB/T 5224-2023
EXAMPLE 3: helical rib steel strand twisted from six steel wires containing helical ribs and one
cold-drawn round center steel wire, with a nominal diameter of 21.60 mm and a
tensile strength of 1,770 MPa is labeled as: prestressed steel strand 1  7H-21.60-
1,770-GB/T 5224-2023
EXAMPLE 4: compact steel strand twisted from seven cold-drawn round steel wires, then, cold-
compacted, with a nominal diameter of 12.70 mm and a tensile strength of 1,860
MPa is labeled as: prestressed steel strand (1  7)C-12.70-1,860-GB/T 5224-2023
EXAMPLE 5: Seale steel strand twisted from nineteen cold-drawn round steel wires, with a
nominal diameter of 21.8 mm and a tensile strength of 1,860 MPa is labeled as:
prestressed steel strand 1  19S-21.8-1,860-GB/T 5224-2023
5 Order Content
The order content includes, but is not limited to the following:
a) Serial No. of this document;
b) Product name;
c) Strength level;
d) Structure code;
e) Dimensions, length (or coil diameter) and weight (or quantity or coil weight) of the
steel strands;
f) Purpose.
7.3 Surface Quality
7.3.1 Unless the user has special requirements, there shall be no oil, grease and other substances
on the surface of the steel strands.
7.3.2 There shall be no detrimental defects that may affect the performance on the surface of
the steel strands. Axial surface defects are allowed, but their depth shall be less than 4% of the
diameter of a single steel wire.
7.3.3 Slight rust on the surface of the steel strands is allowed. There shall be no visible rust pits
on the surface.
7.3.4 Tempering color is allowed on the surface of the steel strands.
7.4 Straightness of Steel Strands
The straightness of the steel strands shall not be greater than 25 mm.
7.5 Fatigue Properties, Deflection Tensile Properties and Stress Corrosion
Properties
Through negotiation between the demand-side and the supply-side, and statement in the
contract, axial fatigue test, deflection tensile test and stress corrosion test can be carried out.
8 Test Methods
8.1 Surface Inspection
Conduct visual inspection on the surface quality.
8.2 Inspection of Overall Dimensions
8.2.1 The diameter of the steel strands shall be measured with a measuring tool with a division
value of not greater than 0.02 mm. The distance between the measurement position and the end
shall not be less than 300 mm.
8.2.2 The diameter of the 1  2 structured steel strands shall be measured as the Dn value shown
in Figure 1; the diameter of the 1  3 structured steel strands shall be measured as the A value
shown in Figure 2; the diameter of the 1  7 structured steel strands (excluding 1  7I and 1 
7H structures) shall be based on the two opposite outer layer steel wires crossing the diameter
direction and measured as the Dn value shown in Figure 3; the diameter of the 1  19 Warrington
steel strands shall be based on the two opposite outer layer steel wires crossing the diameter
direction and measured as the Dn value shown in Figure 4.
8.2.3 The diameter of the 1  19 Seale steel strands shall be measured as the diameter of the
circumscribed circle of the steel strands, as the Dn value shown in Figure 5. To measure the
diameter of the circumscribed circle, use a wide-mouth caliper. The width of the jaws must span
at least two adjacent steel wires. The jaws respectively clamp the highest points of the upper
and lower steel wires. This measured value is the diameter of the circumscribed circle of the
steel strands, as shown in Figure 7.
Figure 7 -- Schematic Diagram of Circumscribed Circle Diameter Measurement of 1 
19 Structured Seale Steel Strands
8.2.4 To measure the diameter of steel strands of different structures, measure three times in
different directions around the circumference. The average value of the three measurements is
the actual measured diameter of the steel strands.
8.3 Measurement and Calculation of Enlargement Ratio of Center Steel Wire
Diameter of 1  7 Structured Steel Strands
To calculate the enlargement ratio of the center steel wire diameter of the 1  7 structured steel
strands, the diameter of the six outer layer steel wires of the steel strands shall be measured first
and take the average value. The difference between the diameter of the center steel wire and the
average value is divided by the average value. The percentage of the calculated result is the
enlargement ratio of the center steel wire diameter.
8.4 Tensile Test
8.4.1 General requirements
In accordance with the stipulations of GB/T 21839, anchor clamps for prefabricated field-
tensioned steel strands shall not be used for the tensile test on the steel strands.
The design of the clamping device shall ensure that during the test, the load is distributed along
the entire clamping length, and the minimum effective clamping length shall not be less than
one lay length of the steel strands. If the specimen breaks within the chuck or within 2 times
the nominal diameter of the steel strands from the jaws and fails to satisfy the performance
requirements of this document, this test shall be deemed as invalid, and additional samples shall
be tested, until valid test data is obtained.
8.4.2 Maximum force
The maximum force test of the whole steel strands shall be carried out in accordance with the
stipulations of GB/T 21839. When calculating the tensile strength, take the nominal cross-
sectional area value of the steel strands.
8.4.3 Yield force
The yield force of the steel strands of the force (Fp0.2) when the non-proportional extension of
the extensometer gauge length (not less than one lay length) reaches 0.2% of the extensometer
gauge length. In order to facilitate the supply-side’s routine inspection, the force (Ft1), at which,
the total extension reaches 1% of the original gauge length can also be determined. When its
value complies with the Fp0.2 value specified in this document, it can be delivered, but Fp0.2 shall
be determined during the arbitration test. When determining Fp0.2 and Ft1, the preload is 10% of
the nominal maximum force.
8.4.4 Total elongation of maximum force
The total elongation Agt of the maximum force is determined in accordance with the stipulations
of GB/T 21839. If a computer is used to collect data or an electronic tensile equipment is used,
when measuring the elongation, the elongation caused by the preload on the specimen shall be
added to the total elongation.
8.4.5 Elastic modulus
The elastic modulus is determined in accordance with the stipulations of GB/T 21839.
8.5 Straightness
The straightness measurement of the steel strands shall be carried out in accordance with the
stipulations of GB/T 21839.
8.6 Measurement and Calculation of Nominal Weight Deviation per Meter
8.6.1 Take three steel strands with a length of not less than 1 m. The specimens shall be
vertically cut from the end of the steel strands. The length of each steel strand shall be measured
accurately to 1 mm. The general requirements for the specimens shall comply with the
stipulations of GB/T 21839.
8.6.2 Weight the weight of each steel strand, accurate to 1 g. Then, in accordance with Formula
(1), calculate the weight per meter of the steel strands.
Where,
M---the weight per meter of the steel strands, expressed in (g/m);
m---the weight of the steel strands, expressed in (g);
L---the length of the steel strands, expressed in (m).
8.6.3 The measured unit weight is the average value of three calculated values.
8.6.4 To calculate the nominal weight deviation per meter, the difference between the average
measured unit weight of the specimens and the corresponding nominal weight per meter
provided in this document shall be divided by the corresponding nominal weight per meter. The
percentage of the calculation result is the nominal weight deviation per meter.
8.7 Test of Stress Relaxation Properties
8.7.1 The test of stress relaxation properties of the steel strands shall be carried out in
accordance with the stipulations of GB/T 21839.
8.7.2 The test gauge length shall not be less than 60 times the nominal diameter.
8.7.3 After specimen preparation, no heat treatment or cold working shall be carried out.
8.7.4 It is allowed to use at least 120 h of test data to reckon the relaxation rate of 1,000 h. The
correlation coefficient of reckoning the relaxation rate shall not be less than 0.98. If the
correlation coefficient is less than 0.98, it is allowed to use 240 h of test data to reckon. If the
correlation coefficient is still less than 0.98, the test shall be continued to 1,000 h.
8.8 Fatigue Test
8.8.1 The specimens used for the fatigue test are specimens taken directly from the finished
steel strands. The length of the specimens shall ensure that the distance between the two clamps
is not less than 500 mm or twice the lay length (whichever is the larger value).
8.8.2 General-purpose steel strands shall be able to withstand 2  106 times of 0.7Fma ~ (0.7Fma
 Fr) pulsating load without breaking.
Round steel strands: Fr/Sn = 190 MPa;
Indented steel strands: Fr/Sn = 170 MPa;
Helical rib steel strands: Fr/Sn = 170 MPa.
Where,
Fma---the actual maximum force of the steel strands, expressed in (N);
Fr---the equivalent load value of the stress range, expressed in (N);
Sn---the nominal cross-sectional area of the steel strands, expressed in (mm2).
8.8.3 The steel strands used for stay cables shall be able to withstand 2  106 times of 0.45Fm ~
(0.45Fm  Fr) pulsating load without breaking.
Round steel strands: Fr/Sn = 300 MPa;
Where,
Appendix A
(normative)
Eigenvalue Inspection Rules
A.1 Test Batch
The test batch can be determined based on actual requirements and is generally the contractual
batch consisting of product batches.
A.2 Sampling and Inspection Quantity per Batch
A.2.1 For the properties test specified in this Appendix, 15 specimens (if applicable, 60
specimens) shall be taken from different coils of steel strands for the tensile test.
A.2.2 Take 2 specimens for the 120-h relaxation test.
A.2.3 Take 2 specimens for the fatigue test.
A.2.4 Take 10 specimens for the deflection tensile test.
A.2.5 Take 12 specimens for the stress corrosion test.
A.3 Evaluation of Test Results
A.3.1 Parameter inspection
In order to inspect the specified properties, such as the characteristic parameters Fm and Fp0.2,
the following parameters shall be determined:
a) All individual values of 15 specimens Xt (n = 15);
b) Mean m15 (n = 15);
c) Standard deviation S15 (n = 15).
If all properties satisfy the conditions given by Formula (A.1), then, the test batch complies
with the requirements.
Where,
fk---the required eigenvalue;
2.33---the value of the acceptance coefficient k when n = 15, at 90% confidence level, and a
failure rate of 5%.
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.