Assembly-Related Cards

The initial assembly related cards are:

Skip Initial Joint Assembly

    <card> ::= skip initial joint assembly ;

This directive inhibits the execution of the initial joint assembly. Note that for a model to behave correctly, the initial joint assembly should always succeed. A correct model succeeds with 0 iterations, i.e. it intrinsically satisfies the constraints from the beginning. However, the initial joint assembly is more than a simple compliance test; it represents a static preprocessor for models. See the directives use in Section 5.1.2 and initial stiffness in Section 5.1.3 for more details on performing appropriate initial joint assembly.

Use

    <card> ::= use : <item_list> , in assembly ;
    <item_list> ::= <item> [ , <item_list> ]
    <item> ::= { rigid bodies 
               | gravity
               | forces
               | beams
               | aerodynamic elements
               | loadable elements }

joints are used by default, and cannot be added to the list. beams are used by default, too, but can be added to the list essentially for backwards compatibility.

Initial Stiffness

    <card> ::= initial stiffness : <position_stiffness>
                                   [ , <velocity_stiffness> ] ;

This directive affects the stiffness of the dummy springs that constrain the position and the orientation (<position_stiffness>) and the linear and angular velocity (<velocity_stiffness>) of the structural nodes (either static or dynamic) during the initial assembly; the default is 1.0 for both. Note that each node can use a specific value; see Section 6.1 for details.
Note that the same value is used for the position and the orientation, so this stiffness is dimensionally inconsistent; It should really be intended as a penalty coefficient. The same considerations apply to the penalty value for linear and angular velocities.

Omega Rotates

    <card> ::= omega rotates : { yes | no } ;

Sets whether the imposed angular velocity should be considered attached to the node or fixed in the global system during the initial assembly.

Tolerance

    <card> ::= tolerance : <tolerance> ;

The tolerance that applies to the initial joint assembly; this tolerance is used to test the norm 2 of the residual, because it is very important, for a correct start of the simulation, that the algebraic constraints be satisfied as much as possible. The alternate statement initial tolerance is tolerated for backwards compatibility.

Max Iterations

    <card> ::= max iterations : <max_iterations> ;

The number of iterations that are allowed during the initial assembly. The alternate statement max initial iterations is tolerated for backwards compatibility.