26. Wire rope cable properties
The identification tag for this tutorial is PDS-AAQ. Pregenerated input files for this tutorial are found in the folder named PDS-AAQ in the provided tutorial input files.
26.1. Tutorial overview
This tutorial covers:
- Determining DCableSegment feature properties for wire rope
26.2. Wire rope
Note
- Wire ropes, made from various types of steel are frequently used for a variety of mooring and marine applications. Several wire rope manufacturers provide property for their ropes online (found here) that can be used to set the cable properties in the DCableSegment feature in ProteusDS.
- The following tutorial reviews how to set DCableSegment feature properties for a 1 inch 6x19 classification steel wire-rope, the properties of which are given in Fig. 26.1.

Fig. 26.1 Wire rope properties.
26.3. Size and buoyancy
Note
- Wire ropes do not have a uniform cross section, and they may contain small air gaps that entrain water when used in subsea applications. The DCableSegment feature properties must be set in ProteusDS to correctly model this.
- The
$Diameter
property is always used to specify the nominal diameter for ropes and cables; this diameter is used for drag and added mass calculations.
- For a 1” nominal diameter wire rope the
$Diameter
is 0.0254 m.
Note
- The mass per unit length in air is provided in the rope specifications. The mass per unit length for fiber core 1” wire rope is 1.68 lbs/ft, or 2.5 kg/m.
- The
$Density
can be calculated from the nominal diameter and the mass in air using the equation:
\(\rho = \frac{4M_l}{\pi d^2}\)
where \(M_l\) is the mass per unit length in air in kg/m and \(d\) is the nominal diameter in m.
- The
$Density
is calculated to be 4934 kg/m3.
Note
- The
$BuoyancyDiameter
property is used to set the distributed buoyancy force per unit length of the cable. - To calculate buoyancy diameter for a 1” wire rope with no mass per unit length in water or specific gravity provided, the specific gravity must be calculated using the material density.
- Assuming a material density of 7800 kg/m3 for steel, the specific gravity can be calculated using the following equation, where \(\rho_{cm}\) is the material density.
\(SG_{cm} = \rho_{cm} / 1000\)
- Using this equation, the specific gravity of steel wire rope is 7.8.
Note
- To calculate the buoyancy diameter, use the following equation from the ProteusDS User Manual:
\(d_b = \sqrt{\frac{4 M_l}{\pi \cdot 1000 \cdot SG_{cm}}}\)
- Using this equation, the
$BuoyancyDiameter
is calculated to be 0.0202 m.
26.4. Mechanical properties
Note
- The axial stiffness of wire ropes can be calculated using elongation properties if provided by the manufacturer, similar to fiber ropes as performed in the fiber rope properties tutorial. In cases where elongation properties are not provided, the axial stiffness must be calculated using an assumed elastic modulus based on literature.
- For this example, no elongation properties are provided by the manufacturer and therefore an elastic modulus must be assumed.
- For stranded wire rope, an elastic modulus of 7.0e10 N/m2 can be assumed (Based on properties provided in the ProteusDS User Manual).
- The area of the wire rope can be calculated using the equation:
\(A = \pi d^2 / 4\)
- Calculating area using the nominal diameter yields an area of 5.07e-4 m2.
- The axial stiffness is the product of the elastic modulus and the cross sectional area. An axial stiffness
$EA
of 3.55e7 N is calculated.
Note
- Bending and torsional stiffness (
$EI
and$GJ
) are calculated for wire rope using the area moment of inertia (\(I\)) and the polar moment of inertia (\(J\)). - The area moment of inertia (\(I\)) for a wire rope can be calculated using an equation from the ProteusDS User Manual:
\(I = \frac{\pi}{64}d^4\)
- For 1” wire rope, the area moment of inertia is calculated to be 2.04e-8 m4.
- The bending stiffness is the product of the elastic modulus and the area moment of inertia. A bending stiffness
$EI
of 1430 Nm2 is calculated.
Note
- The polar moment of inertia (\(J\)) for a wire rope can be calculated using an equation from the ProteusDS User Manual:
\(J = \frac{\pi}{32}d^4\)
- The polar moment of inertia for a 1” wire rope is calculated to be 4.08E-8 m4.
Note
- The shear modulus (G) of a material is not usually available, however, an assumption can be made to use a shear modulus that is 50% of the elastic modulus.
- Assuming a shear modulus that is 50% of the elastic modulus, the shear modulus is 3.5e10 N.
- The torsional stiffness is the product of the shear modulus and the polar moment of inertia. A torsional stiffness
$GJ
of 1430 Nm2 is calculated. - Wire rope has high compressive elasticity, therefore the compressive elasticity property
$CE
should be left as 1.
26.5. Drag and added mass properties
Note
- The added mass coefficient
$CAc
for most ropes and cables can be 1.0, represented as long cylinders. - The drag coefficient
$CDc
for spiral wire without sheathing is specified in the ProteusDS User Manual as between 1.4 - 1.6. In this situation 1.5 will be chosen. - The tangential drag coefficient
$CDt
can be left as the default value of 0.01 for all wire ropes.
- The rope properties for a 1 inch wire rope may be set as:
// Axial Rigidity
$AxialRigidityMode 0
$EA 3.55E7
// Fluid loading
$CDc 1.5
$CDt 0.01
$CAc 1
// Mechanical
$EI1 1430
$EI2 1430
$GJ 1430
$Diameter 0.0254
$BuoyancyDiameter 0.0202
$Density 4934
$AxialDampingMode 1
$AxialReferenceDampingRatio 0.5
$BCID 0
$TCID 0
$CE 1
// Strain Limit
$ElongationLimitMode 0