Civil Engineering Reference
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1,00
0,98
0,96
0,94
0,92
0,90
N/mm
2
0
100
200
300
400
specific tensile force S / d
2
Fig. 2.19
Relative rope diameter d/d
0
of 8-strand ropes with steel core
Relative rope diameters d/d
0
deviate to a great extent. The most important
influences are due to wires and strands loosening and to variations in core density.
An unexpectedly small diameter reduction can result from the strands arching.
Such arched strands reduce the working life of running ropes and should therefore
be avoided. For the fibre-core wire ropes normally used for rope ways, the regu-
lations therefore recommend that up to half of the wire rope breaking force the
rope diameter should be at least 3.1 times the strand diameter for 6-strand ropes
and 3.8 times the strand diameter for 8-strand ropes.
2.4 Torque and Torsional Stiffness
2.4.1 Rope Torque from Geometric Data
If a wire rope is loaded by a tensile force, a rope torque will occur due to the helix
structure of the rope. The torque can be calculated if the geometric data of the wire
rope and the rope tensile force are known. Heinrich (
1942
) was the first to
investigate the torque of a strand by consistently taking any changes in the strand
diameter and the lay length into account. Costello and Sinha (
1977a
,
b
), Costello
and Miller (
1979
) have also arrived at this derivation. In contrast, most authors
such as Dreher (
1933
), Hruska (
1953
), Unterberg (
1972
) and Haid (
1983
) made
use of a practical calculation which neglected minor influences. Engel (
1957
,
1958
) calculated the torque and the torsional stiffness as well.
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