The construction being designed should be fixed in the space, so the user should select the nodes to be fixed and the directions they should be fixed. These operations are performed using the Restraints on nodes dialog box; to open it, click the button
- Restraints from the Stiffness and Restraints panel on the Create and Edit tab (Fig. 1.).
Fig. 1. "Restraints on nodes" dialog box
The dialog box that appeared on the screen allows the assignment of restraints for the spatial node (6 restraints in accordance with 6 degrees of freedom of rigid node in the spatial problem).
In the global system of coordinates restraints X, Y, Z means fixation of the node in the direction of the homonymous axes of the general system of coordinates.
Restraints UX, UY, UZ means fixation of the node from rotations around the specified axes of the global system of coordinates.
In the models with the number of degrees of freedom less than 6 (e.g. flat trusses, flat frames, etc.), the Model Type
is used. There are seven Model types are used in Lira-SAPR (Type 6 +++ same as in the Type 5, but with one additional degree of freedom W - the deplanation of the bar section; Type 15 +++ general form spatial models with 1 degree of freedom per node +++ temperature t (Heat transfer problem
To set the necessary restraints, check the corresponding flags in the dialog box. Then run a command
- Add restraints at selected nodes. For example, table 1 shows which restraints are set on the nodes in the case of model type 2 +++ three degrees of freedom per node (displacement along axis X and Z and rotation around axis Y). Deleting of restraints is done similarly by clicking the button
- Delete restraints from selected nodes.
Table 1. Types of restraints
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