Under the Connections object in the tree, a Connection Data object is automatically added. Under this object, you can insert definitions for various types of Catenary Sections, Catenary Joints, and Tether/Riser Sections that can be used to create Catenary Cables and Tethers/Risers.
To define the properties of a Catenary Section:
Select the Connection Data object in the tree view.
Right-click on the Connection Data object in the tree and select Insert Connection Data > Catenary Section, or click on the Catenary Section icon in the Connection Data toolbar.
Select the Catenary Section object in the tree and enter the following information:
The mass per unit length (Mass / Unit Length) of the section of the composite mooring line.
The Equivalent Cross Sectional Area of the mooring line. It is often more convenient, especially with wire lines, to specify this parameter so the buoyancy of the line may be calculated and subtracted from the structural weight to give the 'weight in water'. This parameter may also be specified as zero if the mass per unit length is input as the mass of the line LESS the mass of the displaced water per unit length (this does not apply to the cases when cable dynamic analysis is required, for which a non-zero equivalent cross section area must be defined).
The stiffness of the line (Stiffness, EA), specified in terms of
, where 
is Young’s modulus and 
is the cross sectional area of the line. The default value is chosen to
give a typical value based on the mass/unit length. Clearly this may be in error if the
mass per unit length specified includes buoyancy effects. The Maximum Expected Tension, which is the highest value of tension that should be used in the database created for this composite mooring line. It is important that this is a realistic value. If a very high value is input the database will cover a very large range of tensions, and the accuracy in the actual working range may be reduced. If a very small value is input the database will only cover a small range of tensions, and constant tension may occur for larger strain values, i.e. no extrapolation is carried out. If cable dynamics is utilized this limiting value is not applied.
The Axial Stiffness Coefficients (k1, k2, k3). A cable may have nonlinear axial stiffness. The stiffness is calculated using the formula:
or
where:
= 
as a function of strain
= the stiffness value input above
= Nonlinear axial stiffness coefficients
= linear strain 
= strain at 
= maximum tension specified above
For Cable Dynamics analyses the following optional additional data may be input.
The Bending Stiffness (EI). The Bending Stiffness is specified in terms of EI, where E is Young’s modulus and I is the 2nd moment of area of the line. The default value is zero.
The Added Mass Coefficient (Ca). Added mass is calculated by ρ*Ca*A per unit length in which ρ is the water density and A is the equivalent cross section area. In other words, the added mass is equal to the displaced mass of water multiplied by Ca. For cable dynamic analysis, the equivalent cross section area A must NOT be omitted. The default is 1.0.
The Transverse Drag Coefficient (Cd). Transverse drag force is calculated by 0.5*ρ*Cd*V²*De per unit length where V is the relative transverse velocity. The default is 1.0
The Equivalent Diameter (De) for drag. This allows the drag to be based on a different diameter from the added mass.
The Longitudinal Drag Coefficient (Cx). Inline drag force is calculated by 0.5*ρ*Cx*V²*De per unit length where V is the relative inline velocity. The default is 0.025.
You can insert either a buoy or a clump weight between catenary cable sections (however, you do not need to specify a joint). Intermediate buoys always have the same buoyancy and do not "know" where the surface is. Therefore they may float above the water surface.
To define the properties of a Catenary Joint:
Select the Connection Data object in the tree view.
Right-click on the Connection Data object and select Insert Connection Data > Catenary Buoy or Catenary Clump Weight, or click on the Catenary Buoy or Catenary Clump Weight icon in the Connection Data toolbar.
Select the Catenary Joint object in the tree and enter the following information:
Section Joint Type should be set to Buoy or Clump Weight based on your menu selection when adding the object.
Specify the Structural Mass of the buoy or clump weight. This must be smaller than the mass of displaced water for a buoy, or larger for a clump weight. This can be positive, zero or negative.
Specify the mass of water displaced (Displaced Mass of Water), i.e. the buoyancy/gravity. This can be positive, zero or negative.
Specify the total (constant) Added Mass; i.e. not the added mass coefficient. Applicable to Cable Dynamics only.
Specify the Drag Coefficient * Area (cable dynamics only); drag will be in the direction of the relative velocity of the fluid, VR. The magnitude of the force is given by FD = 0.5 * ρ * CDA * VR * |VR| where CDA = Drag coefficient * projected area.
To define the properties of a Tether/Riser Section:
Select the Connection Data object in the tree view.
Right-click on the Connection Data object and select Insert Connection Data > Tether/Riser Section, or click on the Tether/Riser Section icon in the Connection Data toolbar.
Select the Tether/Riser object in the tree and enter the following information:
The Density of the material of which this section is composed.
The Young's Modulus of the material of which this section is composed.
The Outer Diameter of this section of the Tether/Riser.
The wall Thickness of this section of the Tether/Riser.
The Added Mass Coefficient (
). Added mass is calculated as 
per unit length, where 
is the water density and 
is the cross-sectional area. In other words, the added mass is equal to
the displaced mass of water multipled by 
. The default is 1.0.The Transverse Drag Coefficient (
). Transverse drag force is calculated as 
per unit length, where 
is the relative transverse velocity and 
is the outer diameter. The default is 0.75.