Steel strand is a kind of steel used in prestressed concrete structure, which is twisted by cold-drawn round steel wire and notched steel wire, and consists of multiple steel wires. Zinc plating layer, zinc-aluminum alloy layer, aluminum-clad layer, copper plating layer and epoxy resin can be added to the surface as required.
Second, classification
There are three kinds of steel strand: standard steel strand, engraved steel strand and die-drawn steel strand. Standard steel strand is a steel strand twisted by cold-drawn round steel wire; Notched steel strand is a steel strand twisted by nicked steel wire; Die-drawn steel strand is a kind of steel strand that is twisted first and then cold-drawn.
Our common joints are standard steel strands twisted by seven steel wires with high strength and low relaxation prestress diameter of 15.20mm and strength grade of 1860MPa, with the label: prestressed steel strand1× 7-15.20-1860-.
5224-2003。
Third, the characteristics and applications
High strength and low relaxation prestressed steel strand is mainly used for prestressed reinforced concrete in bridges, especially in bridges. The tension of steel strand is the force opposite to the load direction before the beam bears the load. When the load acts, the load must first offset this part of prestress, and then the beam is stressed, thus increasing the bearing capacity of the bridge, reducing the dead weight and increasing the span of the beam.
Steel strand has the advantages of high strength, good bond with concrete, large cross-sectional area, few strands, convenient arrangement and placement in the structure, and easy anchoring. It can also be used for rock and soil anchorage, and is often used for slope protection and reinforcement of expressways.
High-strength and low-relaxation prestressed steel strands and unbonded steel strands (which can be called bare wires) are covered with a layer of grease and plastic sheath. In engineering construction, the unbonded steel strand in concrete is free to loosen due to grease and sheath outside, and the steel strand is isolated from concrete, so it is called unbonded steel strand.