Wire Ropes Under Tensile Load - Wire Ropes: Tension, Endurance, Reliability - page 171

2.7.2.3 Rope Termination

The calculation of the allowed range of specific force for wire ropes under fluc-
tuating forces described here is based on test results relating to wire ropes ter-
minating in resin sockets. For ropes with other terminations, the allowed range of
specific forces can be calculated in the same way. In this case the constant a G has
to be estimated with ( 2.109a )or( 2.109b ).

2.7.3 Discard Criteria

Wire ropes always have a limited working life. Prior to rope breakage, the rope has
to be discarded and replaced. It is necessary to have safety inspections to ascertain
the state of the wire rope, i.e. the state at which the wire rope should be discarded.
The discarding state of stay wire ropes will be indicated by damage near the
terminations as well as wire breaks or corrosion on the free rope length. The inner
wires of ropes with tensile loads are always stressed to a greater degree than the
outer wires. This means that in wire ropes suffering under fluctuating tension, it is
the wires in the inner rope in particular which break. Therefore the wire rope has to
be inspected by magnetic methods Feyrer and Wehking ( 2006 ).
In any case, wire breaks in or close to the sockets are promoted by transverse
vibrations of the ropes, Hobbs and Smith ( 1983 ), Oplatka and Roth ( 1991 , 1993 ),
Brevet and Siegert ( 1996 ), Siegert et al. ( 1997 ), Gourmelon ( 2002 ) and Siegert and
Brevet ( 2005 ). Gabriel and Nürnberger ( 1992 ) pointed out that in the most cases,
the stay wires rope has to be discarded because of damage near the terminations or
corrosion but not because of wire breaks on the free length.
The transversal vibration of stay ropes should be minimised by dampers,
Gourmelon ( 2002 ). However these vibrations that induce wire breaks in the
sockets cannot totally avoided. As Oplatka and Roth ( 2000 ) stated, there is no
method found that can show in field-test the condition of the rope even in resin
sockets with sufficient accuracy. Therefore the transversal vibration should be kept
away from the sockets. The wire rope should be hold by a fastening in front of the
socket on that the transversal vibration ends. This fastening should be removable
so that the wire rope can be inspected in this region with magnetic methods.

References

Alani, M., Raoof, M.: Effect of mean axial load on axial fatigue life of spiral strands. Int.
J. Fatigue 19(1), 1-11 (1997)
Andorfer, K.: Die Zugkraftverteilung in schwingend beanspruchten geraden drahtseilen.

Universität Graz, Diss Techn (1983)
Becker, K.: On the fatigue strength of wire ropes. OIPEEC Round Table, Luxembourg, Chaps.
1-3 (1977)