Fixing nodes at the deformed position from a previous load step using SPC FIXED OPTION
Altair EmployeeThe purpose of this topic is to show how to fix the displacement applied to a previous load step, additionally to apply an enforced displacement to another set of nodes using the option FIXED in the SPC CARD. This option is used in conjunction with the CNTNLSUB entry to retain the deformed boundary resulting from a preceding nonlinear subcase. This is supported for both analysis and optimization runs.
In the model file attached, a force is applied to load step 1. In load step 2 the node where was applied the load is fixed after the structure is deformed. Finally, an enforced displacement is applied to another set of nodes.
Figure 1: Sequence of load steps of the model
For load step 1 a concentrated force is applied to the independent node of the rbe2 (on the right side). An SPC is applied to another rbe2 on the left side of the model, constraining DOF123456.
Figure 2: Load step 1 - Applying concentrate force
For load step 2 a concentrated force is removed, however, an SPC with the FIXED option is applied to the same independent node of this rbe2 (on the right side) to retain the deformation of load step 1. Finally, another SPC with enforced displacement is applied to the independent node of the rbe2 on the left side of the model.
Figure 3: Load step 2 - Using the SPC FIXED option and applying enforced displacement
Figure 4 below shows how to apply the FIXED SPC option in HW v2022. (1) First, choose the node it has to be restrained from the previous nonlinear subcase. (2) Check the option FIXED, (3) constrain the appropriated DOF, and (4) click create. Don't forget to choose the right SPC load collector before creating SPCs.
Figure 5: How to apply the FIXED option in SPC CARD