Cable

The Elastic Catenary Cable element is based on the analytical solution derived from a state subjected to self-weight and can be used to model cables in long-span bridges. Similar to truss elements, it can only transmit axial forces, and while it considers geometric nonlinearity, the material model is assumed to be linearly elastic.

The cross-section of the Cable element is defined as a Beam cross-section. In the first analysis step where the element is used, the unstressed length must be defined using the *Field, Type=CableLength command.

If the Cable element is positioned in equilibrium with the gravity direction, the solution will not converge. Additionally, if the unstressed length is too large or too small, the solution may not converge, so careful use is recommended.

Fig. 4.4-1. Cable element

Precautions when using Cable elements

1. The cross-section of the Cable element uses a Beam cross-section with elastic material properties. Variable cross-sections cannot be applied, and only the area value is used in the formulation.
2. GravityLoad must be applied.
3. The initial value of the unstressed length must be specified when the element is created (CableLength field).
4. Currently, Cable elements do not support mass matrices and can only be used in static analysis.
5. Cable elements are geometric nonlinear elements, and nonlinear analysis will be performed if included in the analysis.

Example

*Material, Type=IsoElasticity, Name=mat
 210E9, 0, 0, 1E5

*SECTION, TYPE=Beam, NAME=cable
*Cell, TYPE=Value, Mat=cable 
 0.01    # area, ...

*Element, Type=Cable, ELSet=CableSet
 1001, 1001, 1002, S=cable

*Load, TYPE=Gravity, Name=gr
 101, 0, 0, -9.8

...
*Step
...
*Field, Type=CableLength
 1, 200.

*Element, Type=Cable

Defines a cable element.

*Element, Type=Cable, ELSet=elset
 id, n1, n2, S=section
 ...

Specifications

• No. of nodes: 2
• Fields: BSF=[Nx], BSE=[Ex], uniaxial model response at element center
• Compatible section: CableSection
• Active DOFs: X,Y,Z