Specifications and Models of Prestressed Unbonded Steel Strands
What is an unbonded steel strand?
The unbonded prestressed steel strand is made by applying a layer of grease on the basis of an ordinary steel strand and then wrapping it with a plastic protective sheath. Because of the effect of grease and sheath, the steel strand has no direct contact with the concrete during use and can expand and contract freely, and the stress is completely conducted by the anchor, so it is called an unbonded prestressed steel strand.
Specifications and models of unbonded prestressed steel strands
It is represented by the specification and model of the steel strand. For example, 1*7-15.2-1860 means that a steel strand is stranded by 7 steel wires with a diameter of 5mm. The diameter of the steel strand is 15.2mm, and the tensile strength is 1860Mpa. Common stranded wire numbers are 2, 3, 7, and 19. Commonly used steel strand diameter specifications are 15.2mm, 12.7mm, and 15.7mm. The tensile strength is 1860Mpa, 1720Mpa, 1770Mpa, 1960Mpa, 2000Mpa, 2100Mpa.
Theoretical weight of unbonded prestressed strand
The weight of the steel strand in meters (kg/m) = the square of the single diameter (mm) of the stranded steel wire * 0.785 * the number of steel wires * 1.01 (twisting coefficient) * 7.8/1000. The theoretical weight of the unbonded prestressed strand is based on the strand weight plus the weight of the grease and plastic sheath.
In actual transactions, the meter weight is usually obtained by looking up the meter or measuring by weighing.