Link points to Internet Archive / others. Not hosted by InfraLens. Details
IS 1785:2000 (Part 1) is the Indian Standard (BIS) for plain hard-drawn steel wire for prestressed concrete, part 1: cold-drawn stress-relieved wire. This standard covers the requirements for the manufacture, supply, and testing of plain, cold-drawn, stress-relieved steel wire used in prestressed concrete. It defines the necessary chemical composition limits, mechanical properties (such as tensile strength and proof stress), and mandatory tests like the relaxation and reverse bend tests to ensure wire ductility and strength.
plain hard-drawn steel wire for prestressed concrete, Part 1: Cold-drawn stress-relieved wire
! Prestressing steel wires must be stored in extremely dry conditions and protected from ground contact to prevent pitting corrosion, which severely limits fatigue life.
! Welding, heating, or brazing of the wire at the construction site is strictly prohibited as it destroys the high-tensile properties achieved through cold drawing.
! Care should be taken during handling to prevent mechanical damage such as notching or severe bending, which act as stress concentrators.
ISO 6934-2:2021International Organization for Standardization (ISO), International
HighCurrent
Steel for the prestressing of concrete — Part 2: Cold-drawn wire
Covers cold-drawn round steel wire (plain, indented, or patterned) for prestressing concrete.
ASTM A421/A421M-21American Society for Testing and Materials (ASTM), USA
HighCurrent
Standard Specification for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete
Specifies requirements for uncoated, stress-relieved, high-carbon steel wire for prestressed concrete.
BS 5896:2012British Standards Institution (BSI), UK
MediumCurrent
Steel for the prestressing of concrete. Specification for high tensile steel wire and strand for the prestressing of concrete
Broader scope covering both wire and strand, but its requirements for wire are similar.
EN 10138-2:2009European Committee for Standardization (CEN), Europe
HighWithdrawn
Prestressing steels - Part 2: Wire
Previous European standard for prestressing wire, now harmonized under the ISO framework.
Key Differences
≠IS 1785 specifies two types: plain and indented wire. Modern international standards like ISO 6934-2 also include patterned (e.g., chevron) wires.
≠IS 1785 defines a single class for relaxation. In contrast, ISO 6934-2 defines three classes: Class 1, Class 2 (normal relaxation), and Class 3 (low relaxation), which is the modern default for most applications.
≠Chemical composition in IS 1785 is prescriptive with defined ranges (e.g., Carbon 0.75-0.85%). ASTM A421 and ISO 6934-2 often allow for more flexibility, providing 'heat analysis' ranges and allowing composition to be optimized by the manufacturer to meet performance criteria.
≠IS 1785 specifies proof stress at 0.1% non-proportional elongation. Many international standards, including ASTM A421, may also use or refer to yield strength determined at 1% total extension under load, and ISO 6934-2 also uses 0.1% proof stress (f_p0,1).
Key Similarities
≈All standards are based on the same manufacturing process: cold-drawing high-carbon steel rod followed by a continuous stress-relieving heat treatment.
≈The fundamental purpose and application are identical: to provide a high-strength tensioning element for inducing and maintaining compressive forces in prestressed concrete structures.
≈Core mechanical tests are similar, including tensile strength, proof/yield strength, elongation, and some form of ductility test (e.g., bend test).
≈All standards require the material to be free from defects like seams, splits, or surface imperfections that could be detrimental to its performance in service.
Parameter Comparison
Parameter
IS Value
International
Source
Tensile Strength (UTS) - 7 mm wire
1725 N/mm² (for Grade 1725)
1770 MPa (for Grade Y1770C)
ISO 6934-2:2021
0.1% Proof Stress (min)
85% of specified UTS
1560 MPa (approx. 88% of UTS for Grade Y1770C)
ISO 6934-2:2021
Elongation at fracture (min)
4% (on 200 mm gauge length)
4% (on 10 in. / 254 mm gauge length)
ASTM A421/A421M-21
Relaxation at 1000h (70% initial load)
Max 2.5%
Max 2.5% (for Low Relaxation / Class 3 wire)
ISO 6934-2:2021
Phosphorus (P) content, max
0.040%
0.040%
ASTM A421/A421M-21
Sulphur (S) content, max
0.040%
0.050%
ASTM A421/A421M-21
Reverse Bend Test (5mm wire)
Minimum of 3 bends without failure
Minimum of 2 bends without failure
ISO 6934-2:2021
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
max carbon content0.85%
max sulphur content0.050%
max phosphorus content0.050%
min proof stress85% of specified minimum tensile strength
max relaxation at 1000 hrs5% (at 70% initial stress)
elongation at ruptureMinimum 4% on a gauge length of 200 mm
What is the permissible relaxation of stress for these wires?+
The relaxation of stress at 1000 hours shall not exceed 5% when initially loaded to 70% of the specified minimum breaking load.
What are the restrictions on chemical composition?+
Carbon should not exceed 0.85%, while Sulphur and Phosphorus are strictly limited to a maximum of 0.050% each to prevent brittleness.
What is the requirement for proof stress?+
The 0.2 percent proof stress must not be less than 85 percent of the specified minimum tensile strength.
Can cold-drawn stress-relieved wire be galvanized?+
No, this standard is for plain wire. Galvanizing involves heat that may alter the mechanical properties achieved during the cold-drawing and stress-relieving process.