Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 170

the smallest required number of load cycles N 1 = 20,000, the force range is
restricted by the maximum allowed specific force. This maximum allowed specific
force for spiral ropes in steel constructions is about S max /d 2 = 400 N/mm 2 . For
open spiral ropes (in contrast to Warrington-Seale ropes) the influence of the
lower force is relatively low.

Example 2.17: Allowed specific force range

Data:

Required number of load cycles N 1 = 5,000,000 at which with a certainty of 95 %
at most 1 % of the wire ropes are broken.
Spiral rope 1 9 61, lubricated
d = 20 mm, strength R 0 = 1,770 N/mm 2
Rope length L = 120 m, L/d = 6,000
Lower rope force S lower = 30kN, S lower /d 2 = 75 N/mm 2
Resin sockets

Results:
According to ( 2.111 ), the specific force range for the limiting number of load
cycles N D1 = 2 9 10 6

is

lg 2S aD1
d 2

¼ lg 2 ; 000 ; 000
3 : 910

1
3 : 910

14 : 774 þ 0 : 00118 75 0 : 0000037 75 2

0 : 793 lg 20 þ 0 : 399 lg 61 þ lg 0 : 763 Þ

2S aD1 = d 2 ¼ 118 N/mm 2 :

For the required number of load cycles N 1 = 5,000,000, the specific force range
according to ( 2.114 )is

1 = 2 3 : 910 þ 1

ð Þ

5 ; 000 ; 000
2 ; 000 ; 000

2S a1 = d 2 ¼ 118

2S a1 = d 2 ¼ 103 : 2 N/mm 2

and the force range and the stress range are

2r a1 ¼ 175 N/mm 2 : 2S a1 ¼ 41 : 3 kN and