little understanding of steel strand

1. Storage 
Prestressed steel strands are stored in dry warehouses. For outdoor and on-site storage, sleepers should be placed on the ground. Direct contact with wet ground is strictly prohibited, and tarpaulins or rain-proof sheds should be added to shorten the storage period as much as possible. Rust-proof packaging should be used in special environments. The rust on the surface of the prestressed steel strand will not affect the use, but the rust that becomes visible (pits) will affect its mechanical properties.
2. Hoisting
The hoisting of the steel strands should be hoisted in sequence, and the stacking should be orderly and leave gaps. The unbonded prestressed steel strand should be hoisted in parallel with three brown rope buttonholes. It is strictly forbidden to directly hoist the steel wire rope. The coiled prestressed steel strand should be hoisted with a forklift or special lifting tool to prevent it from breaking and causing loose packages.
3. Use
1. It is strictly forbidden to use any form of heating deformation measures in the use of prestressed steel strands so as not to reduce the mechanical properties of the prestressed steel strands.
2. Welding is strictly prohibited during use because the strength of the welding spot is much lower than that of the steel itself, and it is easy to cause wire breakage at the welding spot during tensioning.
3. The cutting of the prestressed steel strand should be done with a toothless saw (grinding wheel). Cutting by electric or gas welding is easy to cause damage to the surrounding surface of the steel. At the same time, local overheating of the end is caused, resulting in a decrease in mechanical properties.
4. When using circulating reinforcement, the bending radius of the prestressed steel wire must be at least three times its diameter.
5. The Tianjin steel strand packaged in rolls without a shaft should be tapped and paid off from the inner shaft in the vertical state, and the drawn steel strand will be spring-shaped and straightened automatically. The helix direction of the spring type after tap is the same as the twist direction of the stranded wire, otherwise it will be twisted or twisted.
6. The twist direction of the prestressed steel strand is generally left-twisted. When using the right twist, it should be indicated in the contract of the steel strand company, otherwise it will directly affect the connection with the anchorage.
7. The quality of the prestressed steel wire pier head is not directly related to the quality of the steel wire itself, but too high strength will be detrimental to the quality of the steel wire pier head. Strand manufacturer’s instructions.

4. Acceptance 
1. The acceptance of prestressed steel should be carried out in accordance with the relevant national standards, and the experimental instruments should be legal measuring instruments of the state and comply with the test standards.
2. If quality problems occur during acceptance, attention should be paid to checking whether the project meets the requirements.
(1) whether the most recent national standards and test methods are accepted. Whether the tonnage of the selected testing machine is appropriate, whether the measurement is standard, whether the steel fracture is stuck, and whether the nominal area is used to calculate the strength.
(3) Whether the bending bayonet of the bending testing machine meets the national standard, as well as whether the surface finish of the bayonet, the height of the pull-out hole, and the pattern’s bending angle meet the standard. (4) The measurement of the elongation of the steel should be done using a sharp, standard marking distance tool, and there should be no damage to the surface just now.
Whether the steel itself has serious corrosion and man-made surface damage caused by storage.
Five, make a payment. The prestressed steel strand must be paid off with a payoff machine when it is used.