Bending of helically twisted cables under variable ... - Pfisterer

The tensional stress in the wire is then:
where:
is the strain stiffness of the cable.
2.2. The secondary stress
The The derivations derivations below are based on on the the work work by Leider (1973, (1973, 1975), 1975), who who has has made major contributions
to to the the bending bending of cables. For For a a better better overview, overview, they they are are applied applied in in part part to a a single single layer, layer, 7-wire 7 helically
twisted cable – i.e. a cable with a core wire surrounded by a helical layer of 6 wires. It is further assumed
that the wires in the layer do not touch each other circumferentially – an assumption which is generally
true for the cables without fillers investigated here and for ACSR high voltage overhe overhead ad conductors.
This This can can be be achieved achieved through through a a slight increase increase of of the diameter of of the core wire wire over over that of the wires in
the layer [Leider, 1975, Feyrer, 1990].
The tensile forces ZL in in the the individual individual wires of of the cable layer layer create a radial force force on on the layers
underneath, or the core wire, corresponding to a radially oriented distributed load pL. p . This load is:
where ρL is the curvature radius of a wire helix of the layer and rrL
is the coil radius of this layer. Fig. 2.4
shows the parameters in the cable.
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