GB/T 38818-2020Steel wire ropes for hanger of suspension bridge (English PDF)

4.1 Classification

4.1.1 Classification follows the principles laid down in GB/T 8706. Steel wire ropes are divided into single-layer round strand ropes, single strand ropes and locked coil (sealed) ropes; the detail is given in Table 1 to Table 3.

Table 1 covers single-layer round strand ropes. Classes 6 x 19, 6 x 36 and 6 x 61 all have 6 strands, 6 outer strands and 1 strand layer; classes 8 x 19, 8 x 36 and 8 x 61 all have 8 strands, 8 outer strands and 1 strand layer. For the 19 classes the outer strand has 15 to 26 wires, 7 to 12 outer wires and 2 to 3 wire layers; for the 36 classes, 29 to 57 wires, 12 to 18 outer wires and 3 to 4 wire layers; for the 61 classes, 61 to 85 wires, 18 to 24 outer wires and 3 to 4 wire layers. In every case the strand is of parallel lay.

Table 2 covers single strand ropes. Class 1 x 91 has 90 to 125 wires, 29 to 34 outer wires and 5 to 6 wire layers; class 1 x 127 has 126 to 167 wires, 35 to 40 outer wires and 6 to 7 wire layers; class 1 x 169 has 168 to 215 wires, 41 to 46 outer wires and 7 to 8 wire layers; class 1 x 217 has 216 to 269 wires, 47 to 52 outer wires and 8 to 9 wire layers; class 1 x 271 has not fewer than 270 wires, not fewer than 53 outer wires and not fewer than 9 wire layers.

Table 3 covers locked coil ropes: the double-layer fully locked coil rope has 2 layers of Z-shaped wire, the triple-layer fully locked coil rope has 3 layers and the four-layer fully locked coil rope has 4 layers.

4.1.2 Classified by the direction and the type of lay, single-layer round strand ropes are divided into right ordinary lay (sZ) and left ordinary lay (zS), and single strand ropes and locked coil ropes are divided into right lay (Z) and left lay (S).

4.2 Designation

The designation of the steel wire rope follows GB/T 8706; the structural arrangement of the strands is marked from the centre outwards. Examples of rope designations are given in Figure 1.

Example a), for a locked coil rope, reads 60 n1Z-n2Z-n3Z - WSC 1470 A Z, where the fields are in order the nominal diameter, the rope structure, the core structure, the rope grade, the surface condition of the wire and the direction of lay of the rope.

Example b), for other ropes, reads 46 6 x 36WS-IWRC 1770 AB sZ and 42 1 x 91 1570 A Z, where the fields are in order the nominal diameter, the rope structure, the core structure, the rope grade, the surface condition of the wire and the type and direction of lay of the rope.

6.1 Wire for rope making

6.1.1 Round steel wire for rope making, including the centre wires, the filler wires and the core wires, shall comply with the provisions for wire for important applications in YB/T 5343-2015.

6.1.2 The coating weight of shaped steel wire for rope making shall comply with Table 4, and the remaining indexes shall comply with the provisions for wire for static applications in YB/T 4643-2018.

6.1.3 The surface condition and the nominal tensile strength grade of round steel wire for rope making shall comply with Table 5.

6.1.4 In a steel wire rope, the range of the tensile strength grade of the wire before closing, corresponding to the rope grade, shall comply with Table 6. Wires of the same nominal size in the same layer shall be of the same tensile strength grade; the remaining wires shall be within the range given in Table 6, but the minimum breaking force of the rope, or the sum of the minimum breaking forces of the wires, shall in every case satisfy Table A.1 to Table A.10 of Annex A.

6.1.5 In a coated steel wire rope, the coating class and coating type of wires of the same diameter in the same layer shall be the same.

Table 4 gives the minimum coating weight of shaped wire for rope making in g per square metre, by nominal wire height h in mm: 4.0 mm, 115 for class AB and 165 for class A; 5.0 mm, 130 and 180; 6.0 mm, 145 and 195; 7.0 mm, 145 and 195; 8.0 mm, 145 and 195.

Table 5 gives the nominal tensile strength grades in N per square millimetre available for each surface condition. A class AB coating is available in 1 270, 1 370, 1 470, 1 570, 1 670, 1 770, 1 870, 1 960, 2 060 and 2 160; a class A coating in 1 270, 1 370, 1 470, 1 570, 1 670, 1 770, 1 870, 1 960 and 2 060.

Table 6 gives the rope grade and the corresponding range of nominal tensile strength grade of the wire before closing, in N per square millimetre. For single-layer round strand ropes and single strand ropes: rope grade 1 570 corresponds to wire of 1 370 to 1 770; rope grade 1 770 to wire of 1 570 to 1 960; rope grade 1 960 to wire of 1 770 to 2 160; rope grade 2 160 to wire of 1 960 to 2 160. For locked coil ropes: rope grade 1 470 corresponds to wire of 1 270 to 1 670; rope grade 1 570 to wire of 1 370 to 1 770; rope grade 1 670 to wire of 1 470 to 1 870; rope grade 1 770 to wire of 1 570 to 1 960. Note 1: the minimum breaking force of the rope is calculated from the rope grade and not from the tensile strength grade of the individual wire. Note 2: by agreement between supplier and purchaser, wire of other grades may also be used. Note 3: grade 2 160 should not be used for single strand ropes.

6.2 Dimensions, shape and permitted deviations

6.2.1 Nominal diameter: the nominal diameter is the nominal size of the rope stated in the contract. The nominal diameters listed in Table A.1 to Table A.10 are the recommended diameters; the supplier and the purchaser may also contract on other nominal diameters.

6.2.2 Measured diameter: the measured diameter of the rope is the diameter obtained by the method specified in 7.1.1.

6.2.3 Permitted deviation of the diameter and out-of-roundness: measured by the method of 7.1, the permitted deviation of the rope diameter and the out-of-roundness shall comply with Table 7. For single-layer round strand ropes with a steel core, a nominal diameter D from 40 mm up to but not including 60 mm has a permitted deviation of plus 5 per cent to 0 and an out-of-roundness of not more than 4 per cent of D; a nominal diameter D of 60 mm and above has a permitted deviation of plus 4 per cent to 0 and an out-of-roundness of not more than 4 per cent of D. For single strand ropes and locked coil ropes with a steel core, a nominal diameter D of 40 mm and above has a permitted deviation of plus 4 per cent to 0 and an out-of-roundness of not more than 3 per cent of D.

6.3 Closing of the rope

6.3.1 The strands of the rope shall be closed evenly, tightly and without slackness; the slackness property is not assessed for single strand ropes or for single-layer round strand ropes of nominal diameter greater than 80 mm.

6.3.2 The core shall give sufficient support for the outer layer of strands (or wires) to be closed evenly around it, and the gaps between adjacent outer strands (or wires) shall be reasonably uniform.

6.3.3 Unless agreed between supplier and purchaser, there shall be no joint in an outer wire of the rope over any independently used length or working length.

6.4 Surface quality of the rope

There shall be no manufacturing defects as defined in GB/T 21965 on the surface of the rope. Unless agreed between supplier and purchaser, the rope shall not be greased.

6.5 Rope structure

The rope shall be of one of the structures given in Table A.1 to Table A.10. By agreement between supplier and purchaser other structures may also be used.

6.6 Rope core

The core is normally an independent wire rope core (IWRC) or a wire strand core (WSC); the purchaser may specify another type of core.

6.7 Rope grade

The rope grade shall comply with Table A.1 to Table A.10. By agreement between supplier and purchaser, ropes of other grades meeting the requirements may also be supplied.