Use Soft Spring to Stabilize Model
Check this option to instruct the program to add soft springs attached
to the ground to prevent instability. If you apply loads to an unstable
design, it will translate and/or rotate as a rigid body. You should apply
adequate restraints to prevent rigid body motion.
If you cannot stabilize the design by applying adequate restraints,
turn on this flag and rerun the analysis. Animating the resulting deformed
shape will show you excessive motion in one or more directions. You can
then apply additional restraints to prevent rigid body motion. Repeat
the analysis without activating this flag after fixing the problem.
In general, you should not activate this flag unless you ran the analysis
and the program tells you that the constraints are not adequate, or you
know that you have not specified adequate restraints.
This option is automatically applied for
contact problems solved by the Direct Sparse solver.