What is the minimum grade of concrete required for prestressed poles?

The minimum grade of concrete shall be M 40.

What is the required minimum cover for prestressing steel?

The minimum clear cover to prestressing steel should be 20 mm.

What is the primary mechanical test required for acceptance?

The transverse strength test, which checks the failure load against the ultimate design breaking load.

Can splicing of prestressing wires be done?

No, splicing of tensioned wires is generally not permitted within the length of the pole.

IS 1678

: 1998

Prestressed concrete poles for overhead power, traction and telecommunication lines

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This standard prescribes the requirements for the design, materials, manufacture, and testing of prestressed concrete poles used for overhead electrical power transmission, traction, and telecommunication lines.

Prestressed concrete poles for overhead power, traction and telecommunication lines

Quick Reference Values

minimum concrete gradeM 40

minimum cover to prestressing steel20 mm

tolerance on overall length±15 mm

tolerance on cross sectional dimensions+3 mm / -3 mm

minimum factor of safety against ultimate failure2.0 or 2.5 (as specified by purchaser)

minimum clear spacing between wires15 mm or 3x wire dia

Practical Notes

Poles must be clearly marked with the manufacturer's name, year of manufacture, and designated working load.

Lifting and handling points must be strictly adhered to; improper handling can induce bending moments that exceed the cracking moment of the pole.

Curing must be thorough, and transfer of prestress should only occur once the concrete has reached the specified transfer strength to avoid bursting cracks.