Prestressed steel strand is a stranded steel cable composed of 2, 3, 7 or 19 high-strength steel wires, which has been stress relieved (stabilized) and is suitable for prestressed concrete or similar purposes.
The main characteristics of prestressed steel strand are high strength and good relaxation performance. In addition, it is relatively straight when it is unfolded. The common tensile strength grades are 1860 MPa, and 1720, 1770, 1960, 2000, 2100 MPa. The yield strength of this steel is also very high.
In most post tensioned and pretensioned prestressed projects, plain steel strand is the most widely used prestressed steel. Die drawing steel strand is mainly used for lifting engineering, but also for nuclear power and other projects. Galvanized steel strand is often used in tie bar, cable and external prestressed engineering of bridge. The application of epoxy coated steel strand is similar to that of galvanized prestressed steel strand.
1. It is strictly prohibited to use any form of heating deformation measures in the use of prestressed steel strand to avoid reducing the mechanical properties of prestressed steel strand.
2. Welding is strictly prohibited in use, because the strength of the welding spot is much lower than that of the steel itself, which is easy to cause wire breakage at the welding spot during tensioning.
3. Toothless saw (grinding wheel) shall be used for the division of prestressed steel strand. It is easy to damage the surrounding surface of steel by electric welding or gas welding. At the same time, it causes local overheating at the end, which leads to the decrease of mechanical properties.
4. When the prestressed steel wire is distributed circularly, its folding radius shall not be less than three times of its diameter.
5. The steel strand without axial roll packaging shall be tapped from the inner shaft for setting out in the vertical state, and the extracted steel strand shall be spring type and automatically straightened. Takeout direction: after takeout, the spiral direction of the spring type is consistent with the twist direction of the strand, otherwise, it will be scratched or disordered.
6. The lay direction of prestressed steel strand is generally left lay, which shall be indicated in the contract when right lay is adopted, otherwise it will directly affect the connection between prestressed steel strand and anchorage.
7. The quality of prestressed steel wire pier head is not directly related to the quality of steel wire itself, but the high strength will not be conducive to the quality of steel wire pier head, so when you choose pier head anchoring, you should explain to the steel strand manufacturer in the ordering.