# Alert for "Compression only support" **URL:** \ **Category:** Feature Requests\ **Created:** [May 30, 2024, 4:18am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776 "2024-05-30T04:18:59Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![andrea.starnini](https://avatars.discourse-cdn.com/v4/letter/a/46a35a/32.png) [@andrea.starnini](https://prepomax.discourse.group/u/andrea.starnini)\ **Post date:** [May 30, 2024, 4:18am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/1 "2024-05-30T04:18:59Z")
Using only compression support could be useful to have an alert about to activate NL geom - The evaluation of the rection forces will be completely wrong with NL geom off…see third picture - Default parameter on both cases - RF2 reaction due to a washer under screw head - preliminary evaluation ![immagine](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/0/04a659d5a47fb30d9058aed94b34ebae79c620da.jpeg) ![immagine](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/9/9fa2681f1a64fba196e00a86cae9b41c6ffe7754.jpeg) ![immagine](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/4/4083d4acfebbfd14537bfe956daab8adcdbf50c8.jpeg) ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [May 30, 2024, 7:20am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/2 "2024-05-30T07:20:11Z")
I think we had this discussion already in the past. The problem with Nlgeom is that it takes into account large displacements. But maybe somebody would like to neglect these large displacements and still perform a nonlinear analysis with the compression-only supports. I decided to add an additional option when defining compression-only support. This option will turn on or off the nonlinear analysis by adding a fictitious nonlinear material to the input file. To turn on the nonlinear analysis, a fictitious non-linear material or a fictitious contact must be added to the input file. But, I think adding material is easier. Any thoughts? ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [June 2, 2024, 9:33am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/3 "2024-06-02T09:33:10Z")
I have added the described non-linear switch: ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/2/24336ae3b932a78d7ac298a1eb5800ed168c66a5.png) ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [June 3, 2024, 6:13am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/4 "2024-06-03T06:13:24Z")
The request was a user warning, but now an on/off switch was added. Do you think the warning is still necessary? ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [June 3, 2024, 6:50am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/5 "2024-06-03T06:50:28Z")
I would just add a note to Non-linear that switching it from the default Yes to No is risky (the results can be different than what one expects). ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [June 3, 2024, 7:48am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/6 "2024-06-03T07:48:24Z")
Currently, the default value is No. I selected it as default since it does not introduce convergence issues. ---
**Author:** ![FEAnalyst](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/feanalyst/32/688_2.png) [@FEAnalyst](https://prepomax.discourse.group/u/FEAnalyst)\ **Post date:** [June 3, 2024, 8:08am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/7 "2024-06-03T08:08:30Z")
Ok, then such a note under this option is even more needed and maybe a warning should be considered as well. ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [June 4, 2024, 5:47am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/8 "2024-06-04T05:47:54Z")
I added the following note: ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/5/55841521dc891f26460af51130d832b35d218e39.png) ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [June 4, 2024, 5:48am UTC](https://prepomax.discourse.group/t/alert-for-compression-only-support/1776/9 "2024-06-04T05:48:10Z")
Closed on June 4, 2024, 5:48am UTC