How to Check And Accept Pre-stressed Strands?

Pre-stressed steel strand acceptance sampling standards

1. inspection items: surface quality, dimensional deviation, twist distance, tensile test, bending test, relaxation test.

2. Sampling methods and quantities.

2.1 Steel strand for prestressing concrete shall be accepted in batches, each batch consisting of the same grade, the same specification, the same production process made of steel strand, and the weight of each batch shall not be greater than 60 tons.

2.2 From each batch of steel strand, any 3 plates shall be taken for surface quality, diameter deviation, twist distance, and mechanical properties test. If each batch is less than 3 discs, the inspection shall be carried out disc by disc. Yield strength and relaxation tests shall be carried out quarterly on a sample basis, no less than one strand at a time.

2.3 One 750mm sample from the normal part of the end of the selected outline strand of each tray shall be intercepted for testing.

3. The results of the judgment and processing: technical performance has special provisions, test results such as a failure, the unqualified disc scrapped. Then from the untested strand to take double the number of the unqualified items of re-inspection, if there is still a failure, the batch is judged to be unqualified. (All specifications)

Prestressing strand tensile strength design value?

According to the provisions of the national specification GB50010-2010.

Prestressing steel strand tensile strength design value of fpy = 1110, 1220, 1320, 1390MPa four.

TIP: Prestressing force: Prestressing force is a pre-applied force applied to a structure during construction to improve its performance in service. Prestressing force: Prestressing force is pre-applied compressive stress applied to a structure during construction. The pre-application of compressive stresses during the service life of a structure can fully or partially counteract the tensile stresses caused by the load. It prevents structural damage. Commonly used in concrete structures. It is the pre-application of pressure to a concrete structure before it is subjected to a load. It causes compressive stresses in the concrete in the tension zone during external loading. This is used to counteract or reduce the tensile stresses generated by the external load. This allows the structure to be used without cracking or to crack later under normal conditions.

Prestressing strands are stranded steel cables consisting of 2, 3, 7, or 19 high-strength steel wires that have been stress relieved (stabilized) and are suitable for prestressed concrete or similar applications.

The number of wires in a strand can be divided into 2-wire strands, 3-wire strands, 7-wire strands, and 19-wire strands. The surface form can be divided into glossy strand, scored strand, molded strand (compact), galvanized strand, epoxy coated strand, etc. They can also be classified according to diameter, strength level, or standard.

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