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IS 14268:1995 is the Indian Standard (BIS) for uncoated stress relieved low relaxation seven-ply strand for prestressed concrete -. This standard specifies the requirements for uncoated, stress-relieved, low-relaxation seven-ply steel strands used for prestressing concrete. It covers material properties, manufacturing, dimensions, mechanical characteristics like tensile strength and relaxation, and testing procedures.
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Ensure strands are free from pitting, rust, oil, or grease before use, as these can affect bond with concrete and long-term durability.
! Low-relaxation strands are critical for minimizing prestress losses over time, a key design consideration in long-span structures.
! Always check the manufacturer's test certificate against the requirements of Table 2 and Table 3 to verify compliance with breaking load and relaxation properties.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
prestressed concretesteelprestressing steelstrand
International Equivalents
Similar International Standards
ASTM A416/A416M - 18ASTM International, USA
HighCurrent
Standard Specification for Steel Strand, Uncoated Seven-Wire for Prestressed Concrete
Specifies requirements for uncoated seven-wire low-relaxation steel strand for prestressed concrete.
EN 10138-3:2009CEN (European Committee for Standardization), Europe
HighCurrent
Prestressing steels - Part 3: Strand
Specifies requirements for seven-wire stress-relieved steel strands for the prestressing of concrete.
BS 5896:2012BSI (British Standards Institution), UK
HighCurrent
High tensile steel wire and strand for the prestressing of concrete - Specification
Defines specifications for high tensile steel low-relaxation seven-wire strands for prestressing concrete.
ISO 6934-4:2020ISO (International Organization for Standardization), International
HighCurrent
Steel for the prestressing of concrete — Part 4: Strand
Covers specifications for uncoated seven-wire stress-relieved strands used for prestressed concrete.
Key Differences
≠IS 14268 requires yield strength (at 1% extension) to be not less than 85% of the breaking strength, whereas ASTM A416 specifies a minimum of 90% for low-relaxation strand.
≠The maximum permissible sulfur (S) content in IS 14268 is 0.040%, which is stricter than ASTM A416's limit of 0.050%.
≠IS 14268 specifies nominal strand sizes like 15.2 mm, while ASTM A416 specifies equivalent imperial sizes like 0.600 in (15.24 mm), leading to slight differences in nominal area and mass.
≠While the 1000-hour relaxation test is the benchmark in most standards, IS 14268 explicitly details a 100-hour test as a routine acceptance test, which is not a primary method in ASTM A416.
Key Similarities
≈All standards specify the same fundamental product: a seven-wire strand composed of six outer wires helically wound around a central core wire.
≈The manufacturing process, involving stress-relieving and a final thermal treatment to achieve low-relaxation properties, is a common requirement across all standards.
≈All standards offer similar tensile strength grades, with the most common being approximately 1860 MPa (or its equivalent, 270 ksi in ASTM).
≈A minimum elongation of 3.5% at rupture over a specified gauge length is a consistent ductility requirement in IS 14268, ASTM A416, and other equivalents.
≈All standards require the strand to be uncoated ('bright') and free from deleterious surface imperfections to ensure proper bond with concrete.
Parameter Comparison
Parameter
IS Value
International
Source
Yield Strength (at 1% extension)
≥ 85% of breaking strength (for Grade 1860)
≥ 90% of specified minimum ultimate strength
ASTM A416/A416M
Sulfur (S) Content, max
0.040%
0.050%
ASTM A416/A416M
Breaking Strength of Strand (12.7 mm, ~1860 MPa Grade)
183.7 kN
183.7 kN (41,300 lbf for 1/2 in. Grade 270)
ASTM A416/A416M
Elongation at Rupture, min
3.5% on a 610 mm gauge length
3.5% in a 24 in. [610 mm] gauge length
ASTM A416/A416M
Nominal Steel Area (15.2 mm vs 0.600 in strand)
139 mm² (for 15.2 mm)
140 mm² (0.217 in² for 0.600 in)
ASTM A416/A416M
Relaxation Loss after 1000h (at 70% initial load), max
2.5%
2.5%
ASTM A416/A416M
Grade Nomenclature (Highest Strength)
1860 (MPa)
Grade 270 (ksi)
ASTM A416/A416M
⚠ Verify details from original standards before use
Key Values6
Quick Reference Values
Minimum breaking load for 12.7 mm strand182.4 kN
Nominal steel area for 12.7 mm strand98.7 mm²
Minimum breaking load for 15.2 mm strand259.1 kN
Nominal steel area for 15.2 mm strand139 mm²
Minimum elongation at fracture (gauge length 600 mm)3.5 %
Maximum 1000h relaxation at 70% of breaking load2.5 %
Tables & Referenced Sections
Key Tables
Table 1 - Dimensions and Physical Properties of Uncoated Seven-Ply Stress-Relieved Strands
Table 2 - Mechanical Properties of Uncoated Seven-Ply Stress-Relieved Strands
What are the common sizes of PC strands covered by this code?+
Common nominal diameters are 9.5 mm, 11.1 mm, 12.7 mm, and 15.2 mm (Table 1).
What is the minimum breaking load for a 12.7 mm strand?+
The minimum breaking load is 182.4 kN (Table 2).
What does 'low relaxation' mean?+
It refers to the material's property to lose a minimal amount of stress over time. The maximum loss is specified as 2.5% after 1000 hours at 70% of the initial breaking load (Table 3).
Is welding permitted on these strands?+
No, welding is strictly not permitted on prestressing strands as it severely degrades their mechanical properties and can lead to brittle failure (Clause 4.3).