Prestressed steel strand is a stranded steel cable composed of 3, 7, or 19 high-strength steel wires, and has undergone stress-relief treatment (stabilization treatment), suitable for prestressed concrete or similar purposes. The pre-stressed concrete steel strands should be adjusted in quota to better meet the standards required for construction. The following is the quota adjustment method of the specific parameters of the prestressed concrete steel strand
1. Specifications: The common steel strand is made of 7 steel wires with a circular cross-section, centered on one steel wire, and the other 6 steel wires are spirally twisted around it. The commonly used specifications are 9.0mm (7φ3), 12.0mm (7φ4), 15.0 mm (7φ5), and other 3 types.
2. Root (or wire): It refers to a steel wire.
3. Strand: It refers to a steel strand composed of several steel wires, such as a steel strand composed of 7 steel wires with diameters of 9.0mm, 12.0mm, 15.0mm, etc.
4. Bundle: The number of stranded wire bundles seen in the cross-section of the prestressed component (the same as the number of holes), each bundle is equipped with 2 anchors.
5.Bundle length: It refers to the length of one stretch.
6. XX holes: It refers to the number of holes in the anchor used. When selecting the quota, the number of holes should be greater than or equal to the number of holes specified by the design icon (not necessarily all holes are used).
7. XX bundles per ton: It refers to how many bundles per ton of steel strands are folded into within the standard tensile length.
Method of quota adjustment
1. The beam length and the number of holes should conform to the actual tension length and the number of anchorage holes in the design or construction plan.
2. Calculate the number of strands of the designed steel strand: find the number of strands per ton, and then adjust it according to the given amount. The weight/length given in the drawing = the number of bundles, and a similar quota are applied according to the calculated number of bundles. If the calculated number of bundles is different from the fixed number of bundles, the quota needs to be adjusted.
3. The number of strands per ton should be adjusted to the number of strands given in the design drawings. For example: design a steel strand with a length of 16m, using a steel strand with a diameter of = 15.24mm (7φ5) and 7-hole anchorage, as a unit of steel strand The weight is 1.102Kg/m, then: 1000Kg/(7*16*1.102)=8.102 bundles, applying the quota 4068022 (stranded wire bundle length 20m, 7 holes per t11.65 bundle), 11.65-8.102=3.448 bundles, so it needs Adjust the quota to: 4068022-23*3.448.
4. Another example: X bridge box girder longitudinal prestressed steel strands are φ15.24-19, that is, each bundle has 19 strands, each with 7 wires, a total of 240 strands. With a total length of 8106.2m and a total weight of 169419.6Kg, the steel strand per ton = 240 strands/169.42 tons=1.417 strands/ton, and the average design strand length = 8106/240=33.775m. Considering the construction tensioning length, the selected quota is 4068036 (steel strand length 40m, 19 holes per t2.05 bundle), the quota adjustment is 2.05-1.42=0.63, and the quota adjustment is 4068036-4068037*0.63.
The quota adjustment of the parameters of the prestressed concrete steel strands must not only be based on the standards of the design drawings but also must be combined with the construction conditions on-site. If you want to get more knowledge about prestressed concrete steel strands after reviewing the above, you can get a comprehensive solution by contacting us.
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