Using MODCHG to activate and deactivate contacts and Elements


MODCHG card can be used to activate and deactivate contacts and Elements in subcases.

MODCHG is available for Nonlinear Static and Nonlinear Transient Analysis. It also supports optimization only for contact activation and deactivation.


1.Right click in model browser and create >Property.

2.Select property card as MODCHG.

3.Provide number of contacts and element needed to add/remove. We provided 3 for this tutorial.

4.In MODCHG provide TYPE as contact/element. Select CHANGE as add/remove to activate/deactivate contact/element. In Field CTID(0)  select Group/Element Set.

5.MODCHG card can be reference in subcase.



Consider example with bending of cantilever plate.

The steps followed during analysis:

1.Pretension added. (Contacts are deactivated with MODCHG )

2.Load of 50KN is added in 2nd subcase with STATSUB(PRETENS).

3.Load of 100KN is added in 3rd subcase with CNTNLSUB.

4.Unloading of forces are done with adding pin to restrict full unloading of plate. (Contacts are activated with MODCHG)



Result below shows contact status at pin only at unloading sub case. The plate is allowed to penetrate through pin up to subcase 3.

Please check attached files for animations.