Civil Engineering Reference
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(a)
S
s
/S
0
=5
(b)
Parallel lay 8x19
−
IWRC
S
s
/S
0
=3
- sZ -
F
min
/S
0
= 12
a
a
D/d = 40; l/d =1000
(c)
pieces of one rope
1 rope sZ
1 rope zS
oder
S
s
/S
0
=3
(d)
a
1
=1.1a
2
S
s
/S
0
=5
a
1
a
2
a
1
=1.15a
2
(e)
a
1
=1.1a
2
S
s
/S
0
=3
0
50%
100
a
1
a
2
failure probability Q
Fig. 3.78
Failure probability Q and relative impact forceS
s
/S
0
of two parallel bearing wire ropes
(example)
large torque should only be used for relatively low heights because of the great
fluctuating stresses found especially in the steel core and the possible total loos-
ening of the strands on the upper rope end. However wire ropes with special steel
core can be used for larger differences of height for that they are qualified by good
experience or by calculated relative small stresses from rope twist.
3.3.3 Cranes and Lifting Appliances
Because of the wide range of use for cranes and lifting appliances, there are very
different requirements, concerning rope endurance. Cranes and lifting appliances
have therefore been classified according to the conditions of usage as laid down in
ISO 4301/1. Table
3.8
gives the values for c (for the rather unusual nominal rope
strength R
0
= 1.570 N/mm
2
) and the diameter ratio D/d which is used for the eight
classes of mechanism in order to achieve the minimum requirements of ISO 4308/
1 (1986). Parameter c corresponds to the most frequently used specific tensile
force in the following
S
=
d
2
¼ 1
=
c
2
:
In the last column of Table
3.8
, the rope endurance is listed as the number of
hoisting cycles Z
A
10
. This number of hoisting cycles Z
A10
, at which with a certainty
of 95 % at most 10 % of the ropes have to be discarded, has been calculated for
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