GB/T 40029-2021 (GB/T40029-2021)

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GB/T 40029-2021: PDF in English (GBT 40029-2021)

GB/T 40029-2021
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 77.140.65
CCS H 49
Steel strand for prestressed concrete of LNG
ISSUED ON: APRIL 30, 2021
IMPLEMENTED ON: NOVEMBER 01, 2021
Issued by: State Administration for Market Regulation;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative references ... 4 
3 Terms and definitions ... 4 
4 Symbols ... 5 
5 Codes and marks ... 6 
6 Order content ... 6 
7 Technical requirements ... 6 
8 Test methods ... 11 
9 Inspection rules ... 14 
10 Packaging, labeling, transportation, storage and quality certificate ... 15 
Bibliography ... 17 
Steel strand for prestressed concrete of LNG
1 Scope
This Standard specifies the terms and definitions, symbols, codes and marks,
order content, technical requirements, test methods, inspection rules,
packaging, labeling, transportation, storage and quality certificates for steel
strand for prestressed concrete of LNG (hereinafter referred to as "steel strand").
This Standard is applicable to the steel strand used in prestressed concrete
structure of liquefied natural gas storage tank engineering, and other low
temperature environments.
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 228.1, Metallic materials - Tensile testing - Part 1: Method of test at
room temperature
GB/T 5224, Steel strand for prestressed concrete
GB/T 14370, Anchorage, grip and coupler for prestressing tendons
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
For the purposes of this document, the terms and definitions defined in GB/T
5224 as well as the followings apply.
3.1 cold drawn round wire
smooth round steel wire formed by cold drawing of wire rod
3.2 strand
5 Codes and marks
5.1 Codes
For the strand that is twisted by six cold drawn round wires, around a cold drawn
round wire, according to the same twist direction, the same twist distance, its
structure code is: 1×7.
5.2 Marks
Products are marked with product name, structure code, nominal diameter,
strength level, and file number.
Example:
The steel strand of which the nominal diameter is 15.70mm, tensile strength is
1860MPa, is marked as: prestressed steel strand 1×7-15.70-1860-GB/T 40029-
2021
6 Order content
The contract for ordering according to this Standard shall contain the following
main contents:
a) Number of this Standard;
b) Product name;
c) Intensity level;
d) Structure code;
e) Steel strand size, length and weight (or quantity, or coil weight);
f) Twist direction;
g) Purpose;
h) Other requirements.
7 Technical requirements
7.1 Shape, size, weight and allowable deviation
The size and allowable deviation of the steel strand shall meet the requirements
furnace batch numbers at the most.
7.2.4 The lay length of the steel strand shall be 12 to 16 times the nominal
diameter of the steel strand.
7.2.5 The diameter of the center wire shall not be less than 1.03 times the
diameter of the outer wire.
7.2.6 There shall be no broken, cross-cracked and intersecting steel wires in
the steel strand.
7.2.7 The twist direction of the steel strand is right twist or left twist.
7.2.8 The steel strand shall be cut with a grinding wheel saw. It shall not be
loose after cutting. If it leaves the original position, it shall be manually restored
to the original position.
7.2.9 There shall be no welding points on the steel strand, including the welding
points before drawing.
7.3 Properties
7.3.1 The mechanical properties of steel strand shall meet the requirements of
Table 3.
Table 3 -- Mechanical properties of steel strand
Strand structure
Nominal
diameter
Dn/mm
Tensile
strength
Rm/MPa
Whole
steel
strand
Maximum
force
Fm/kN
Maximum
value of
the
maximum
force of
steel
strand
Fmꞏmax/kN
0.2% yield
strength
Fp0.2/kN
Maximum
force total
elongation
Agt/%
(L0≥500mm)
1×7 15.20 1860 260 288 229 5.0
1×7 15.70 1860 279 309 246 5.0
1×7 17.80 1860 355 391 313 5.0
7.3.2 The steel strand is drawn and fractured. The steel wire fracture shall be
plastic fracture.
7.3.3 The rate of reduction in area Z of the central steel wire of the strand is not
less than 25%.
7.3.4 The elastic modulus E of the steel strand is (195±10) GPa, which cannot
be used as a delivery condition. When requested by the purchaser, the range
value shall be met.
8.3.2 0.2% yield strength
The 0.2% yield strength test of the steel strand is carried out in accordance with
the provisions of GB/T 21839. The 0.2% yield force is the force (Fp0.2) when the
non-proportional extension of the extensometer gauge length (not less than
500mm) reaches 0.2% of the extensometer gauge length. When measuring
Fp0.2, the preload is 10% of the nominal maximum force.
8.3.3 Maximum force total elongation
The determination of the maximum force total elongation Agt is carried out in
accordance with the provisions of GB/T 21839. If it uses a computer to collect
data or use electronic stretching equipment, the extension of the specimen
caused by the preload when measuring the elongation shall be added to the
total extension.
8.3.4 Elastic modulus
The determination of elastic modulus is carried out according to GB/T 21839.
8.3.5 Steel wire section shrinkage rate
The rate of reduction in area of steel wire shall be determined in accordance
with the provisions of GB/T 228.1. After the wire is broken, the diameter of the
wire is measured in two mutually perpendicular directions at the smallest point
of the necking (if necessary, the broken part of the specimen shall be butted
together at the break). Take the average value d1. The rate of reduction in area
of steel wire is calculated according to formula (2):
Where,
Z - Rate of reduction in area, %;
d1 - Average diameter after breaking, in millimeters (mm);
d0 - Original average diameter, in millimeters (mm).
8.4 Stress relaxation performance test
8.4.1 The stress relaxation performance test of steel strand shall be carried out
according to GB/T 21839.
8.4.2 The test gauge length is not less than 60 times of the nominal diameter.
8.4.3 No heat treatment or cold working shall be carried out after specimen
10.1.3 Each coil of steel strands shall be bundled firmly, not less than 6 bundles.
After mutual agreement, moisture-proof paper, linen cloth and other materials
can be added for packaging.
10.2 Labeling
Each steel strand coil shall be attached with a sign, indicating supplier name,
product name, mark, exit-factory number, specification, strength level, furnace
batch number, execution document number, weight and number of pieces.
10.3 Transportation
The steel strand shall be transported in a closed type. Pay attention to
waterproof. Avoid contact with all objects that may cause mechanical or
chemical damage to the steel strand. Be careful when loading and unloading to
prevent damage to the steel strand and its packaging.
10.4 Storage
10.4.1 Steel strands shall be stored indoors. Set up support pads to prevent the
steel strand from contacting the ground.
10.4.2 Pay attention to ventilation during storage of steel strands and prevent
atmospheric corrosion to the steel strands.
10.4.3 During storage, all steel strands shall be protected with water-soluble
anti-rust oil or similar products every 10d~12d if they are unpacked.
10.5 Quality certificate
Each batch shall be accompanied by a quality certificate, indicating the
supplier's name, product name, specification, mark, strength level,
implementation standard, weight, number of pieces, purchaser’s name, test
results, delivery date, and quality inspection department's imprint.
......
 
(Above excerpt was released on 2021-06-30, modified on 2021-06-30, translated/reviewed by: Wayne Zheng et al.)
Source: https://www.chinesestandard.net/PDF.aspx/GBT40029-2021