Symmetry conditions can be used, if the system behaves symmetrically to one or two axes. Along those symmetry lines not only the geometry must be symmetrically - as well the loading situation!
The benefit of those calculations is to save space and computation time. If the user knows, that the right of a system behaves as the left or additionally the top half as the bottom half - this knowledge can be exploited for the calculation.
As the pendulum impactor can't be divided, pendulum impact simulations can never use this option!
A four point supported glass pane 1600x1000mm shall be calculated. This pane is horizontally arranged and only loaded by face loads (or other loads as point loads in the middle of the pane). The point fixings are all located 100x100mm from the corner.
So, instead of generating the total system, only one quarter can be consider - as we know that the other 3 quarters acts identically in the same way as the one simulated (left as right and bottom as the top half).
For this, the system has now been halved at the symmetry lines.
This will set the conditions that for example in x-direction no deformation (u) can arise and that the rotation (φ) here equals zero.
When doing so for insulated glass units, you have to take care that those symmetry borders don't get spacers! Those borders are located within the pane and not at the sealed outside.
For this example, instead of 5900 unknown to solve, now only 1400 d.o.f. must be regarded. But the resulting stresses and deformations for a quarter section are equal to the full solution.