Name
case — Analysis case block
Synopsis
case id
attributes
end
Description
The case command specifies all
ingredients needed for the analysis case identified by
id
(a positive and unique integer
number), in particular the boundary conditions, the initial
conditions, and the solution strategy parameters.
The analysis case that will be solved must be specified
by the case
attribute of the adir command.
Attributes
The attributes enumerated in this section pertain to most types of analyses and concern the specification of initial conditions, boundary conditions, and constraints. Solverspecific attributes are explained in the chapter Solvers.
analysis
t

Specifies the type of analysis for the present analysis case. The string
is one oft
linear

Linear static (stationary) analysis (default).
nonlinear

Nonlinear static (stationary) analysis.
linearised_prebuckling

Bifurcation buckling analysis with linear prestress (solid mechanics).
free_vibration

Free vibration analysis (solid mechanics).
dynamic_nonlinear

Nonlinear dynamic (transient or nonstationary) analysis.
frequency_dependent_free_vibration

Frequencydependent free vibration analysis.
atemperatures
id
[sfactors
sfunction "function_string
"]
Specifies the ambient temperatures set
to be included for certain types of analysis, like heat analysis.id
In linear analysis, the optional parameter
sfactor
specifies a scale factor
by which the set is multiplied, the default value being 1.0.s
In nonlinear direct analysis and in incremental analysis, the set is scaled by the load factor (static analysis) or by the time (dynamic analysis). The optional parameter
sfactor
specifies an additional scale factor
by which the set is multiplied, the default value being 1.0. Alternatively, the optional parameters
sfunction
specifies a function which is being evaluated at each load or time increment and by which the set is multiplied. component
name
type
"argument
" [sfactors
sfunction "function_string
"]
Specifies a component to be used in the current analysis case. Components are extensions to B2000++. They implement specific natural boundary conditions, essential boundary conditions, initial conditions, or sets of constraints.^{[4]}.
The
andname
parameters are used to identify the component^{[5]}, while thetype
parameter is given to the component at the start of the analysis (stage).argument
In linear analysis, the optional parameter
sfactor
specifies a scale factor
by which the values returned by the component are multiplied, the default value being 1.0.s
In nonlinear direct analysis and in incremental analysis, the values returned by the component are scaled by the load factor (static analysis) or by the time (dynamic analysis). The optional parameter
sfactor
specifies an additional scale factor
by which the values returned by the component are multiplied, the default value being 1.0. Alternatively, the optional parameters
sfunction
specifies a function which is being evaluated at each load or time increment and by which the values returned by the component are multiplied. dof_initdofdot_init
id

Specifies the initial conditions set
for the current analysis case.id
ebc
id
[sfactors
sfunction "function_string
"]
Adds the essential boundary conditions set
to the current analysis case. Note that essential boundary conditions are not cumulative, i.e. if several essential boundary condition sets are specified, all values of common degreesoffreedom must be equal.id
In linear analysis, the optional parameter
sfactor
specifies a scale factor
by which the set is multiplied, the default value being 1.0.s
In nonlinear direct analysis and in incremental analysis, the set is scaled by the load factor (static analysis) or by the time (dynamic analysis). The optional parameter
sfactor
specifies an additional scale factor
by which the set is multiplied, the default value being 1.0. Alternatively, the optional parameters
sfunction
specifies a function which is being evaluated at each load or time increment and by which the set is multiplied. field_transfer
id

Adds the field_transfer set
to the current analysis case. Note that a field_transfer set with anid
of 0 is automatically added to all analysis cases.id
Alternatively, several or all
field_transfer
sets may be specified:field_transfer
ilist
field_transfer allIt is required to specify a constraint method other than the default
reduction
method for which the accuracy of the calculated solution cannot be always ensured whenfield_transfer
conditions are active. See also Imposing Constraints. join
id

Adds the join set
to the current analysis case. Note that a join set with anid
of 0 is automatically added to all analysis cases.id
linc
id

Adds the linear constraints set
to the current analysis case. Note that a linc set with anid
of 0 is automatically added to all analysis cases.id
nbc
id
[sfactors
sfunction"function_string
"]
Adds the natural boundary conditions set
to the current analysis case. Natural boundary conditions are cumulative, i.e. if several natural boundary condition sets are specified the resulting natural boundary condition forid
is the sum of all natural boundary condition sets multiplied by their respective scaling.id
In linear analysis, the optional parameter
sfactor
specifies a scale factor
by which the set is multiplied, the default value being 1.0.s
In nonlinear direct analysis and incremental analysis, the set is scaled by the load factor (static analysis) or by the time (dynamic analysis). The optional parameter
sfactor
specifies an additional scale factor
by which the set is multiplied, the default value being 1.0. Alternatively, the optional parameters
sfunction
specifies a function which is being evaluated at each load or time increment and by which the set is multiplied. rcfo_restrict
list

Specifies to which nodes the calculation of reaction forces shall be restricted in postprocessing (this directive is ignored by the b2000++ processor). If not specified, b2browser and baspl++ will loop over all nodes of the model to calculate the reaction forces.
epatch
id
p1p8e1e12f1f6b
When the discretization of a part of the discretization was created by means of the epatch command, a number of predefined nodelists are available. The epatch is identified by
.id
Individual patch vertex nodes are specified with
p1
top8
.The collection of nodes that are located at a patch edge are specified with
e1
toe12
.The collection of nodes that are located at a patch face are specified with
f1
tof6
.The collection of nodes of the whole patch body are specified with
b
. nodelist
name

Specifies the name of the node list.
nodeset
name

Specifies the name of the node set.
stage
id
[sfactors
sfunction "function_string
"]
Specifies the analysis stage
to be activated for the current analysis case. One or more stages can be defined for the current case. If more than one stage is specified, the solver will solve for one stage after the other in the order stages have been entered. Ifid
stage
is specified for a given analysis case, no boundary conditions (such asebc
ornbc
), no constraints, and no initial conditions that analysis case.In linear analysis, the optional parameter
sfactor
specifies a scale factor
by which the conditions of the referenced stage are multiplied, the default value being 1.0.s
In nonlinear direct analysis and in incremental analysis, the conditions of the referenced stage are scaled by the load factor (static analysis) or by the time (dynamic analysis). The optional parameter
sfactor
specifies an additional scale factor
by which the set is multiplied, the default value being 1.0. Alternatively, the optional parameters
sfunction
specifies a function which is being evaluated at each load or time increment and by which the set is multiplied. temperatures
[sfactorid
s
sfunction"function_string
"]
Specifies the temperatures set
to be included for certain types of analysis, like thermal stress analysis.id
In linear analysis, the optional parameter
sfactor
specifies a scale factor
by which the set is multiplied, the default value being 1.0.s
In nonlinear direct analysis and in incremental analysis, the set is scaled by the load factor (static analysis) or by the time (dynamic analysis). The optional parameter
sfactor
specifies an additional scale factor
by which the set is multiplied, the default value being 1.0. Alternatively, the optional parameters
sfunction
specifies a function which is being evaluated at each load or time increment and by which the set is multiplied. title
'...text...'

Optional title describing the case.
PerStage Commands in Multistage analysis
In nonlinear analysis, it is often necessary to split the loading path into a series of stages. Example:
stage 1 ebc 1 nbc 1 end stage 2 ebc 2 step_size_init 0.05 step_size_max 0.05 end case 3 analysis nonlinear residue_function_type artificial_damping stage 1 stage 2 end adir case 3 end
In this example, case 3 is executed, which consists of two stages (defined by stages 1 and 2). To ensure convergence of the nonlinear solver in the presence of buckling (loadcontrolled by default), artificial damping is performed to stabilise the problem.
The b2000++ program initializes many of its internal procedures and data structures on a percase basis, not on a perstage basis. The commands for the various methods are interpreted only during this initialization phase. Specification of commands like residue_function_type inside of stages 1 or 2 will be ignored. Instead, they must be placed in the definition of case 3 and, consequently, they will be active for both stages.
On the other hand, commands controlling the step size and the tolerances for the residual, solution, etc., can be defined inside a stage.
^{[4] }For example, a component can implement a weaklycoupled fullynonlinear aeroelastic toolchain. In this case, the values taken by the component are the current (nodal) displacements (calculated by B2000++), and the values returned by the component are the (nodal) forces. To this end, at each Newton iteration (or each x^{th} Newton iteration), the component invokes the spatial coupling tool, the CFD mesh deformation tool, the CFD solver, and again the spatial coupling tool.
^{[5] }Under this identifier, the component is registered.