Civil Engineering Reference
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• The mean breaking number of bending cycles N.
• The breaking number of bending cycles N 10 at which with 95 % certainty, not
more than 10 % of the wire ropes break.
• The mean discarding number of bending cycles N A .
• The discarding number of bending cycles N A10 at which with 95 % certainty
not more than 10 % of the wire ropes have to be discarded.
These numbers of bending cycles are:
• Simple bendings , calculated with the tensile force S,( 3.85 ) and
• Combined fluctuating tension and bendings
, calculated with the equiva-
lent tensile force S equ ( 3.87 ).
Table 3.14a Endurance factors f d ,f L and f C
Rope diameter, Feyrer ( 2011 )
b þ 1
b þð d = d E Þ a ¼
0 : 52
0 ; 48 þð d = 16 Þ 0 : 3
f d ¼
f L ¼ b þ 1
1 : 49
Bending length, Feyrer ( 2011 )
b þ z a ¼
0 : 14
l = d 2 : 5
57 : 5
2 : 49
Rope core and number of strands
Number of strands
8 strands
6 strands
Fibre core, Wolf ( 1987 )
FC
f C = 1.0
f C = 0.94
Steel core, independent
IWRC
f C = 1.0
f C = 0.81
Steel core, parallel
PWRC
f C = 1.86
f C = 1.51
Steel core, polymer covered
ESWRC
f C = 2.05
f C = 1.66
Steel core, fibre enveloped
EFWRC
f C = 1.06
f C = 0.86
The breaking number of bending cycles N is reached if the rope or at least one
strand has broken. The discarding number of bending cycles is reached if the
number of wire breaks B 30 or B 6 —not defined by Technical Rules but according to
( 3.83 ) and ( 3.84 )—have been found on a reference length of the rope. For lang lay
ropes and spiral round strand ropes, there is no reliable appearance of outside wire
breaks so that the discard numbers of wire breaks generally have to be detected
with magnetic devices. For cross lay ropes, which are rarely used today, no dis-
carding numbers of bending cycles have been evaluated.
3.4.3.2 Correction of the Number of Bending Cycles
The number of bending cycles calculated with Eq. ( 3.55 ) can be corrected for
other conditions with the help of endurance factors f Ni . With these endurance
factors—listed in Table 3.15 —the corrected number of bending cycles is
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