This module includes advance functionality for geometric non-linear analysis such as cables and membranes.
A cable element is an element with no bending stiffness.
Two types of cable elements can be modelled:
- straight cable (pre-stressed element)
- slack cable.
Only the pre-stressing force must be input for a straight cable.
Initial deformation is calculated immediately based on cable self-weight, estimated applied load and prestressing force. The cable shape is determined prior to FE analysis itself and visualized. Calculations are carried out on the "deformed" structure: the final deformation of a cable is calculated from this "slack" shape and not from the ideal straight shape of 1D member.
This module offers the possibility to use membrane elements. Membrane elements are defined as shell elements with no flexural stiffness and no axial compression stiffness. Membrane elements can thus be used to model canvas, nets, etc. that are subjected to axial tension.
Differences in the results between membrane and standard element
The difference in the obtained results stemming from the application of the membrane behaviour can be best demonstrated on a simple example. Let us assume a rectangular plate made of a very thin sheet of steel. The left-hand side of the figures below shows the results obtained for a standard 2D element. The right-hand side then contains the results for the membrane elements.
Note: Membrane elements can only be modelled in a General XYZ environment. Due to the fact the flexural rigidity is zero, no ribs, no prestressed tendons, orthotropic parameters or physical non-linear data can be input on a membrane element. Since a membrane element has no axial compression stiffness, no concrete calculation nor CDD can be performed on this type of element.