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).

IS 14268

: 1995

Uncoated stress relieved low relaxation seven-ply strand for prestressed concrete -

CurrentFrequently UsedSpecificationBIMStructural Engineering · Concrete Reinforcement (Steel)

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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.

Uncoated stress relieved low relaxation seven-ply strand for prestressed concrete -

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 %

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.