SOLVERS Home: Case Dependence

Description

Freedom Case

Selects the freedom case to be used in the Linear Buckling and Natural Frequency solvers.

For both of these solvers, one freedom case at the time is considered.

Load Case for Node Temperature

Selects the load case that defines the fixed nodal temperatures for the Transient Heat solver.

A model may contain any number of load cases but only one of these can be used to define the fixed nodal temperature distribution in the Transient Heat solver.

Property Temperature Dependence

Material properties such as modulus of elasticity and thermal expansion coefficient can vary as a function of temperature by associating them with Factor vs Temperature tables in the property dialog.

Active Stage

The active stage dropdown list contains all the stages defined in the model in addition to the option <All groups active>. Depending on the solver, a stage may be selected for analysis. If <All groups active> is selected, all elements in the model are used in the analysis.

Cable Inertia Case

If the model contains cable elements, the cable inertia case dropdown list may become available for the linear solvers. This lists all the load cases in the model, from which one case is selected. The selected case is used to define the catenary, and hence stiffness matrix, of the cables for assembly into the global stiffness matrix.

This is required because the stiffness of a cable element depends on its catenary shape, which is determined by the applied inertia loads acting on the mass of the cable together with the stiffness of the structure to which the cable ends are attached.

In reality, the cable element is a geometrically nonlinear element, and solving for this nonlinearity becomes part of any geometric nonlinear analysis, so no special considerations are required in those solvers. But if geometric nonlinearity is not considered because the analysis in a linear one, a cable stiffness has to be calculated by using some assumptions. In Strand7 the assumptions are that the cable shape (catenary) is set by the inertia load applied in the selected load case, based on the assumed cable free length. The cable pre-load attributes in the selected load case will affect the cable free length. Furthermore, it is assumed that the ends of the cable do not move while this catenary shape is formed.

Cable Pre-load Case

This applies only to the Linear Transient Dynamic solver.

It selects the load case that defines the cable pre-load (i.e., pre-strain and temperature applied to the cable). These attributes alter the free length and therefore the stiffness of the cable.

The control is not provided for the other linear solvers because in those solvers, a single load case defines both the inertia and the free length of the cable.

The control is not provided for the nonlinear solvers because the pre-load applied in the nonlinear solvers becomes part of the nonlinear analysis.

See Also