What Are Prestressed Steel Strands? 

Prestressed steel strands are high-strength steel wires twisted together to form a cable or strand, commonly used in the construction of prestressed concrete structures. They typically consist of 7 wires — one central wire surrounded by six helical wires — and are either uncoated or galvanized, low-relaxation or normal-relaxation, depending on the application.

Principle of Prestressing

The basic concept behind prestressing is to pre-load the concrete structure using tensioned steel strands before it is subjected to external loads. This method introduces a compressive force into the concrete, which helps counteract the tensile forces that occur under service loads.

How It Works:

Tensioning the Strands: Steel strands are stretched (tensioned) using hydraulic jacks.

Anchoring to Concrete: The stretched strands are anchored at both ends of a concrete element.

Transferring Stress: Once the concrete has reached sufficient strength, the tension in the strands is gradually released, transferring the force to the concrete.

Result: The concrete is compressed, improving its ability to resist tension, cracking, and deflection.

Key Properties

High Tensile Strength: Typically around 1860 MPa (or more).

Excellent Bonding with Concrete (especially when indented or with a rough surface).

Low Relaxation: Maintains tension over long periods.

Durability: Can be galvanized or epoxy-coated for corrosion protection.