# Boundary Condition Changes in Simulation Steps

**URL:** https://calculix.discourse.group/t/boundary-condition-changes-in-simulation-steps/2151
**Category:** Uncategorized
**Created:** [March 14, 2024, 12:34pm UTC](https://calculix.discourse.group/t/boundary-condition-changes-in-simulation-steps/2151 "2024-03-14T12:34:19Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![Bhavita](https://avatars.discourse-cdn.com/v4/letter/b/b782af/32.png) [@Bhavita](https://calculix.discourse.group/u/Bhavita)
#### Post date: [March 14, 2024, 12:34pm UTC](https://calculix.discourse.group/t/boundary-condition-changes-in-simulation-steps/2151/1 "2024-03-14T12:34:19Z")

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Hello,

Is it possible to alter the boundary conditions between simulation steps?  
For example, I have two step in first step I fix Set\_TOP-Layer2 as fixed but for step 2 I want to free the Set-Top-Layer2 and want to fixed the Set-Top-Layer3. How can I achieve this?  
Any guidance on this would be helpful.

\*STEP, NLGEOM  
\*STATIC

\*BOUNDARY  
Set-Ground, 1  
Set-Ground, 2  
Set-Ground, 3  
Set-Top-Layer-2,1  
Set-Top-Layer-2,2  
Set-Top-Layer-2,3

\*TEMPERATURE  
Part-2, 201

\*MODEL CHANGE, TYPE=ELEMENT, ADD  
Part-2

\*\* Outputs → frd file  
\*NODE FILE  
U  
\*EL FILE  
S, E, PEEQ  
\*\* outputs → dat file  
\*\* reaction forces for Constraint fixed  
\*NODE PRINT, NSET=ConstraintFixed, TOTALS=ONLY  
RF  
\*END STEP

\*STEP, NLGEOM  
\*STATIC  
\*BOUNDARY  
Set-Ground, 1  
Set-Ground, 2  
Set-Ground, 3  
Set-Top-Layer-3,1  
Set-Top-Layer-3,2  
Set-Top-Layer-3,3

\*TEMPERATURE  
Part-3, 201

Thanks,  
Bhavita

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<div class="post-metadata">

### Author: ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)
#### Post date: [March 14, 2024, 12:37pm UTC](https://calculix.discourse.group/t/boundary-condition-changes-in-simulation-steps/2151/2 "2024-03-14T12:37:25Z")

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Just use `*BOUNDARY, OP=NEW` and respecify only those BCs that should stay in the second step. Of course, you can also add new ones.

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<div class="post-metadata">

### Author: ![Bhavita](https://avatars.discourse-cdn.com/v4/letter/b/b782af/32.png) [@Bhavita](https://calculix.discourse.group/u/Bhavita)
#### Post date: [March 14, 2024, 12:50pm UTC](https://calculix.discourse.group/t/boundary-condition-changes-in-simulation-steps/2151/3 "2024-03-14T12:50:23Z")

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@Calc_em Thank you, It worked as intended.