GB/T 5224-2014 English PDF (GBT5224-2014)

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GB/T 5224-2014: Steel strand for prestressed concrete
GB/T 5224-2014
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.15
H 49
Replacing GB/T 5224-2003
Steel strand for prestressed concrete
(ISO 6934-4.1991, Steel for the prestressing of concrete –
Part 4. Strand, NEQ)
ISSUED ON. JUNE 24, 2014
IMPLEMENTED ON. APRIL 1, 2015
Issued by. General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration Committee.
Table of Contents
Foreword . 3 
1 Scope .. 5 
2 Normative references . 5 
3 Terms and definitions . 5 
4 Classification and marks.. 6 
5 Order content . 7 
6 Dimension, shape, weight and allowable deviation . 8 
7 Technical requirements . 12 
7.1 Manufacture . 12 
7.2 Mechanical properties . 13 
7.3 Surface quality . 16 
7.4 Strand straightness .. 17 
7.5 Fatigue properties, oblique tensile properties and stress corrosion properties
. 17 
8 Test methods . 17 
8.1 Surface inspection . 17 
8.2 Inspection of dimensions . 17 
8.3 Tensile test . 17 
8.4 Stress relaxation test .. 18 
8.5 Fatigue test .. 18 
8.6 Oblique tensile test .. 19 
8.7 Stress corrosion test . 19 
8.8 Numerical rounding-off . 19 
9 Inspection rules .. 19 
9.1 Delivery inspection. 19 
9.2 Characteristic value inspection . 21 
10 Packaging, marks and quality certificate .. 21 
10.1 Packaging .. 21 
10.2 Marks . 21 
10.3 Quality certificate . 21 
Annex A (Normative) Characteristic value inspection rules .. 22 
Foreword
This Standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This Standard replaces GB/T 5224-2003 "Steel Strand for Pre-stressed
Concrete". Compared with GB/T 5224-2003, the main changes on technical
content are as follows.
- added the category, specification, intensity level of 19-wire strand;
- added the specification of 7-wire strand;
- specified the maximum value of the maximum force; deleted that the
actual strength of each delivery batch strand of the supplier cannot be
higher than its tensile strength level 200 MPa;
- modified the relaxation test initial force from the characteristic maximum
force percentage to the actual maximum force percentage; added that if
there is no special requirement, only relaxation test with an initial force of
70% of the actual maximum force Fma shall be carried out; deleted the
requirements for original initial force as 60% of the maximum force;
- modified "the 0.2% yield force Fp0.2 is not less than 90% of the nominal
maximum force Fm of the whole strand" to "it shall be within the range of
88%~95% of the actual maximum force Fma of the whole strand";
- added coil diameter of part specifications of strands; added requirements
for weigh deviation;
- added the requirements for characteristic value inspection and delivery
inspection type test;
- added the appendix of strand characteristic value.
This Standard uses redrafting method to modify and adopt ISO 6934-4.1991
"Steel for the prestressing of concrete - Part 4. Strand". The consistency with
Part 4 of ISO 6934 is not equivalent. The main differences in this Standard are
as follows.
- added the strength level; modified the specification;
- added the indented strand variety;
- adjusted the yield ratio range;
- specified the maximum value of the maximum force;
- added Annex A.
Steel strand for prestressed concrete
1 Scope
This Standard specifies the terms and definitions, classification and marks,
order content, dimension, shape, weight and allowable deviation, technical
requirements, test methods, inspection rules, packaging, marks and quality
certificate.
This Standard is applicable to steel strands used for prestressed concrete
structures made from cold-drawn light round steel wire and scored steel wire
(hereinafter referred to as the strand).
2 Normative references
The following referenced documents are indispensable for the application of
this document. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any
amendments) applies.
GB/T 5223, Steel wire for prestressing of concrete
GB/T 21839, Steel for prestressed concrete - Test methods
GB/T 24238, Hot-rolled wire rod for prestressed steel wire and strand
GB/T 24242.2, Non-alloy steel wire rods for conversion to wire - Part 2.
Specific requirements for general purpose wire rod
GB/T 24242.4, Non-alloy steel wire rods for conversion to wire - Part 4.
Specific requirements for wire rod for special applications
YB/T 081, Rule for rounding off of numerical values and judgement of testing
values for technical standards of metallurgy
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1 standard strand
the strand twisted of cold-drawn round wire rod.
d) strength level;
e) standard reference.
4.2.2 Marking example
Example 1. the 7-wire standard strand of which the nominal diameter is 15.20
mm, the tensile strength is 1860 MPa is marked as.
Prestressed strand 1×7-15.20-1860-GB/T 5224-2014
Example 2. the 3-wire indented strand of which the nominal diameter is 8.70
mm, the tensile strength is 1720 MPa is marked as.
Prestressed strand 1×3I-8.70-1720-GB/T 5224-2014
Example 3. the 7-wire compact strand of which the nominal diameter is 12.70
mm, the tensile strength is 1860 MPa is marked as.
Prestressed strand (1×7)C-12.70-1860-GB/T 5224-2014
Example 4. the 19-wire Westwood strand of which the nominal diameter is 21.8
mm, the tensile strength is 1860 MPa is marked as.
Prestressed strand 1×19S-21.80-1860-GB/T 5224-2014
5 Order content
The order contract in accordance with this Standard shall contain the following
information.
a) reference to this Standard;
c) product name;
c) strength level;
d) structure code;
e) strand dimension, length (or coil diameter) and weight (or quantity, or coil
weight);
f) usage;
g) other requirements.
calculating the theoretical weight per meter of the strand.
6.6 The weight of each coil of strand is not less than 1000 kg. When less than
10 coils, it allows 10% of the coil number is less than 1000 kg but not less than
300 kg.
6.7 For the strand of which the diameter is not greater than 18.9 mm, the coil
inner diameter is not less than 750 mm. For the strand of which the diameter is
greater than 18.9 mm, the coil inner diameter is not less than 1100 mm. the coil
width is (750±50) mm, or (600±50) mm.
7 Technical requirements
7.1 Manufacture
7.1.1 The strand can be made with designations specified in GB/T 24238 or
GB/T 24242.2, GB/T 24242.4 or other designations. The manufacturer does not
provide chemical composition.
7.1.2 The strand shall use hot-rolled wire rods as raw materials and is made
through cold-drawing. After twisting, the strand shall be continuously stabilized.
The steel wire for indented strand shall comply with the provisions of
corresponding terms in GB/T 5223. When the nominal diameter of strand is ≤12
mm, the indented depth is 0.06mm ± 0.03mm. When the nominal diameter of
strand is >12 mm, the indented depth is 0.07mm ± 0.03mm.
7.1.3 The twist distance of 1×2, 1×3, and 1×7 structural strands shall be 12 to
16 times the nominal diameter of strand. The twist distance of compact strand
shall be 14 to 18 times the nominal diameter of strand. The twist distance of
1×19 structural strand is 12 to...