ASTM-A475:03(2020) pdf free download – Standard Specification for Zinc-Coated Steel Wire Strand.
6. Stranding
6.1 Unless otherwise specified, strand shall have a left lay. A left lay is defined as a counter-clockwise twist away from the observer. All wires shall be stranded with uniform tension. Stranding shall be sulliciently close to ensure no appreciable reduction in diameter when stressed to 10 % of the minimum breaking strength.
6.2 The 3-wire strand shall consist of three wires concentrically twisted with a uniftwm pitch of not less than 14 nor more than 20x the specified nominal diameter of the strand.
.3 The 7-wire strand shall consist of a center wire with a 6-wire layer concentrically twisted over it with a uniform pitch of not more than 16x the specified nominal diameter of the strand.
6.4 The 19-wire strand shall consist of a center wire with a 6-wire layer concentrically twisted over it, having a right lay and a uniform pitch of not more than 16x the nominal diameter of this 7-wire core. The nominal diameter of this 7-wire core shall be considered to be 3x the nominal diameter of the wires. A 12-wire outer layer, having a left lay shall be concentrically twisted over the 7-wire core and shall have a uniform pitch of not more than 1 6x the specified nominal diameter of the strand.
6.5 The 37-wire strand shall consist of a center wire with a 6-wire layer concentrically twisted over it, having a left lay and a uniform pitch of not more than 16x the nominal diameter of this 7-wire inner core. The nominal diameter of this 7-wire inner core shall he considered to he 3x the nominal diameter of the wire. An intermediate layer of 12 wires having a right lay shall be concentrically twisted over this 7-wire core and shall have a uniform pitch of not more than 16x the nominal diameter of this 19-wire core. The nominal diameter of this 19-wire core shall be considered as 5x the nominal diameter of the wires. An 18-wire outer layer. having a left lay shall be concentrically twisted over the 19-wire core and shall have a uniform pitch of not more than 16x the specified nominal diameter of the strand.
6.6 All wires in the strand shall lie naturally in their true positions in the completed strand and, when the strand is cut, the ends shall remain in position or be readily replaced by hand and then remain in position. This may be accomplished by any means or process, such as preforming, post forming, or form setting.
7. Breaking Strength and Weight
7.1 The approximate weight per unit length of strand and the minimum breaking strength of the fInished strand shall be as specified in Table I.
7.2 A test in which the breaking strength is below the minimum specified and which may have been caused by the slipping of the specimen in the jaws of the testing machine, by breaking within the jaws or within 1 in. (25.4 mm) of the jaws, or by the improper socketing of a specimen shall he disregarded and another sample from the same coil or reel shall he tested. Tests shall he made on lengths of strand that do not contain wire joints or splices.
8. Elongation
8.1 The elongation of the strand in 24 in. (610 mm) shall be not less than that specified in Table 3.
8.2 The elongation shall he determined as the percent increase in separation between the jaws of the testing machine from the position after application of the initial load to the position at the initial failure in the test specimen. The separation of the jaws of the testing machine shall be approximately 2 ft when under an initial load equal to 10 % of the required minimum breaking strength of the strand. The elongation values shall be recorded only for specimens which break over I in. from the jaws of the testing machine. Additional samples shall be taken from the same coil or reel when the previous tests are to he disregarded.