# Reaction Moment at boundary condition **URL:** \ **Category:** General Questions\ **Created:** [June 8, 2022, 9:37pm UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231 "2022-06-08T21:37:17Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![FEM-Roc](https://avatars.discourse-cdn.com/v4/letter/f/0ea827/32.png) [@FEM-Roc](https://prepomax.discourse.group/u/FEM-Roc)\ **Post date:** [June 8, 2022, 9:37pm UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/1 "2022-06-08T21:37:17Z")
Hello, does anybody know how the reaction moment at the boundary condition can be evaluated? I can only find the reaction forces (RF). Thank you for your support ---
**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 8, 2022, 10:10pm UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/2 "2022-06-08T22:10:16Z")
You can read reaction moments only from reference points with applied BCs since nodes of solid elements don’t have rotational DOFs and you can’t get moment from them. ---
**Author:** ![FEM-Roc](https://avatars.discourse-cdn.com/v4/letter/f/0ea827/32.png) [@FEM-Roc](https://prepomax.discourse.group/u/FEM-Roc)\ **Post date:** [June 9, 2022, 7:40am UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/3 "2022-06-09T07:40:32Z")
Good Morning, I cannot find Information on how to Read the Moment at the reference Point. Do you have any advice? Thanks ---
**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 9, 2022, 7:45am UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/4 "2022-06-09T07:45:32Z")
You have to create a History output request for such a point and select RF (reaction forces) variable. Then, in the Results tab, you will see a list of outputs including reaction forces and moments for that point. Of course, you have to apply proper BCs to the point and connect it to the rest of the model using rigid body constraint to get output for it. ---
**Author:** ![FEM-Roc](https://avatars.discourse-cdn.com/v4/letter/f/0ea827/32.png) [@FEM-Roc](https://prepomax.discourse.group/u/FEM-Roc)\ **Post date:** [June 9, 2022, 9:59am UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/5 "2022-06-09T09:59:48Z")
Thank you, this was exactly what I was looking for ---
**Author:** ![FEM-Roc](https://avatars.discourse-cdn.com/v4/letter/f/0ea827/32.png) [@FEM-Roc](https://prepomax.discourse.group/u/FEM-Roc)\ **Post date:** [July 11, 2022, 11:44am UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/6 "2022-07-11T11:44:39Z")
Re-Opening this topic: Reaction Forces / Moments for rigid Body constraints seem not to work with Shell Elements (result is unrealistic small RF / RM). There were already discussions on issues of Shell Elements with rigid Body constraints with CalculiX. Does anybody know a workaround to determine reaction forces/Moments at boundary conditions (edges, Surfaces) with Shell Elements? Thanks! ---
**Author:** ![Matej](https://avatars.discourse-cdn.com/v4/letter/m/a698b9/32.png) [@Matej](https://prepomax.discourse.group/u/Matej)\ **Post date:** [July 11, 2022, 3:37pm UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/7 "2022-07-11T15:37:39Z")
I have no idea but maybe instead of using a rigid body, you cod try to use the kinematic coupling (not yet supported in the PrePoMax but it can be added using the keyword editor). ---
**Author:** ![acal](https://avatars.discourse-cdn.com/v4/letter/a/e79b87/32.png) [@acal](https://prepomax.discourse.group/u/acal)\ **Post date:** [October 1, 2025, 3:31pm UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/8 "2025-10-01T15:31:35Z")
I have a rigid-body constraint from a surface to a ref. point, and another rigid-body constraint from that ref. point (RP) to another surface. In other words the two surfaces are made rigid and connected. If I ask a history output for the reaction forces on the RP I get a zero, because there are no forces between the RP and the “ground”. If I ask for a history output on one of the two surfaces I get only force. How can I get the moment transferred between the two surfaces (linked to the RP)? Ansys, for example, creates directly the two sets of equations and allows to get all forces and moments that are transferred between the two surfaces. ---
**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:** [October 1, 2025, 4:09pm UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/9 "2025-10-01T16:09:15Z")
One rigid body constraint assigned to both surfaces should suffice. But you will get reactions only from nodes with applied boundary conditions in the corresponding degrees of freedom. To get moments on a surface, you could use the \*SECTION PRINT keyword (via Keyword Editor). ---
**Author:** ![acal](https://avatars.discourse-cdn.com/v4/letter/a/e79b87/32.png) [@acal](https://prepomax.discourse.group/u/acal)\ **Post date:** [October 2, 2025, 10:50am UTC](https://prepomax.discourse.group/t/reaction-moment-at-boundary-condition/231/10 "2025-10-02T10:50:28Z")
> [@FEAnalyst](#): > > \*SECTION PRINT Thank you again. Tested and it works. It could be handy to have it in the PPM UI 😉