# Best way to find force in bolted connection **URL:** \ **Category:** General Questions\ **Created:** [February 12, 2024, 11:26am UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498 "2024-02-12T11:26:43Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![jakob](https://avatars.discourse-cdn.com/v4/letter/j/71c47a/32.png) [@jakob](https://prepomax.discourse.group/u/jakob)\ **Post date:** [February 12, 2024, 11:26am UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/1 "2024-02-12T11:26:43Z")
![Screenshot 2024-02-12 082923](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/8/846cd4f146974671b9a7fdd0b414b9b8d8a891fa.png) This connection is a part of a bigger assembly made of welded steel profiles. The two beams in the picture are supposed to be bolted together using two steel plates on the sides and 16 bolts. I already have the whole thing simulated in PrePoMax but now i wonder what the best way would be to find the force that needs to be held by the bolts. My first thought was to create a surface contact on the contact faces and then check the surface contact force with a history output. Is there a better way? ---
**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:** [February 12, 2024, 11:31am UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/2 "2024-02-12T11:31:46Z")
Yes, you could add tied contact there and check the total forces: [Calculation of Shear and Normal Forces on a Cylindrical Contact Surface - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).](https://calculix.discourse.group/t/calculation-of-shear-and-normal-forces-on-a-cylindrical-contact-surface/2029) Or use `*SECTION PRINT` if it’s modeled as a single compound part. Section print is not supported in PrePoMax yet but can be added using the Keyword Editor: [Section print in history outputs](https://prepomax.discourse.group/t/section-print-in-history-outputs/47) ---
**Author:** ![lucas\_bueno](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/lucas_bueno/32/1168_2.png) [@lucas\_bueno](https://prepomax.discourse.group/u/lucas_bueno)\ **Post date:** [February 12, 2024, 1:58pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/3 "2024-02-12T13:58:27Z")
> [@jakob](#): > > Is there a better way? Probably fastening analysis is one of the greatest discussions in the FEM community. You will find lots of ways of doing this, each one with its advantages and disadvantages. Here are some options: - Model the splices and bolts as 3D geometry - Model the connection through interpolation elements + beams - Same as above, but using springs instead of beams - Estimating the flexibility of 5 rows of fasteners using hand calculations - And so on… Using the last option you would find that each fastener takes different loads and the last ones on each side will take the highest load transfer. As @FEAnalyst said, you can use the section force to do this. Be aware that highly loaded joints in bending, torsion, or shear may not be suitable for this uniaxially loaded approach. ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/b/bd15393d1cde7b5993d7d60d42f9fdad3fe2d805.png) If you want, take a look at [Download Composite Programs (espcomposites.com)](https://www.espcomposites.com/software/download.html) where you can find the worksheet eDistribution 3.0 to estimate this. ---
**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:** [February 12, 2024, 2:02pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/4 "2024-02-12T14:02:12Z")
> [@lucas\_bueno](#): > > Model the connection through interpolation elements + beams One important limitation here - in CalculiX, preload with beams results in beam elements being deleted so one cannot check the forces within them. ---
**Author:** ![synt](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/synt/32/4658_2.png) [@synt](https://prepomax.discourse.group/u/synt)\ **Post date:** [February 12, 2024, 2:26pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/5 "2024-02-12T14:26:45Z")
> [@FEAnalyst](#): > > in CalculiX, preload with beams results in beam elements being deleted so one cannot check the forces within them. probably, using shrinkage effect such as thermal load or initial condition type stress/displacement can eliminate this condition. It will be use real beam element with section forces capable instead of imaginary/fictitious preload element. ---
**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:** [February 12, 2024, 2:30pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/6 "2024-02-12T14:30:47Z")
Yes, that could be a workaround. Good old pretension by thermal expansion. ---
**Author:** ![jakob](https://avatars.discourse-cdn.com/v4/letter/j/71c47a/32.png) [@jakob](https://prepomax.discourse.group/u/jakob)\ **Post date:** [February 12, 2024, 2:56pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/7 "2024-02-12T14:56:30Z")
So if I use a tied contact and then get the total forces on the surface and then use those forces for the manual calculation of a bolted connection, that would be accurate? ---
**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:** [February 12, 2024, 3:03pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/8 "2024-02-12T15:03:13Z")
It might be best to use this approach and then compare it with the simplest one of those more advanced (e.g. model the plates and bolts as springs). Otherwise, it’s hard to say how inaccurate the simplified approach will be. ---
**Author:** ![synt](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/synt/32/4658_2.png) [@synt](https://prepomax.discourse.group/u/synt)\ **Post date:** [February 12, 2024, 3:29pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/9 "2024-02-12T15:29:16Z")
external link at CalculiX forum provide is only for example to use \*`Contact Print` with `CF,CFN,CFS` options. In test case attachment using Tied Contact type, to get accurate results of bolt response needed Penalty contact instead. ---
**Author:** ![lucas\_bueno](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/lucas_bueno/32/1168_2.png) [@lucas\_bueno](https://prepomax.discourse.group/u/lucas_bueno)\ **Post date:** [February 12, 2024, 5:21pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/10 "2024-02-12T17:21:14Z")
> [@jakob](#): > > that would be accurate It’s a way of doing it. The responsibility of verifying the most adequate method in each situation is up to the stress engineer. ---
**Author:** ![Gunnar](https://avatars.discourse-cdn.com/v4/letter/g/ed655f/32.png) [@Gunnar](https://prepomax.discourse.group/u/Gunnar)\ **Post date:** [February 13, 2024, 6:45am UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/11 "2024-02-13T06:45:08Z")
> [@jakob](#): > > Is there a better way? Maybe like this? It’s transparent and flexible. > [@Modeling bolt connection with preloaded beam element](https://prepomax.discourse.group/t/modeling-bolt-connection-with-preloaded-beam-element/1412/9): > > Side note, by using solid elements and connecting the bolt head to the shaft with tied contact, you can use the History output to get the summed up normal/shear loads + moments for the slave surface. ---
**Author:** ![lucas\_bueno](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/lucas_bueno/32/1168_2.png) [@lucas\_bueno](https://prepomax.discourse.group/u/lucas_bueno)\ **Post date:** [February 13, 2024, 12:54pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/12 "2024-02-13T12:54:08Z")
> [@lucas\_bueno](#): > > Using the last option you would find that each fastener takes different loads and the last ones on each side will take the highest load transfer. As pointed out by @ANYS, in this case, it is a double-shear problem, but I showed the plot for single-shear. The right one should be 5 fasteners instead of 10 being analyzed. Again, the first and last ones (from each side) must have the highest load transfer. ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/5/56bb8dcce6398f5ef88127160f76b8454e293c96.png) I still need to think a little about them having different magnitudes in the worksheet. My first thought is that they should be equal (symmetric load transfer about the 3rd fastener) 🤔. ![image](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/f/fd7539589f56959731a21d53be6e39cf130582ab.png) I would recommend checking this: [(6) (PDF) Optimal modelling of rivet joints using finite element method (researchgate.net)](https://www.researchgate.net/publication/345015566_Optimal_modelling_of_rivet_joints_using_finite_element_method). ---
**Author:** ![Rick](https://avatars.discourse-cdn.com/v4/letter/r/9f8e36/32.png) [@Rick](https://prepomax.discourse.group/u/Rick)\ **Post date:** [January 15, 2026, 9:00pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/13 "2026-01-15T21:00:05Z")
Has someone documented a workflow for using beam elements without preload to extract bolt forces? ---
**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:** [January 15, 2026, 9:13pm UTC](https://prepomax.discourse.group/t/best-way-to-find-force-in-bolted-connection/1498/14 "2026-01-15T21:13:37Z")
Check the threads referenced here: [UNV import to support line element (beam) - #12 by FEAnalyst](https://prepomax.discourse.group/t/unv-import-to-support-line-element-beam/62/12) This tutorial may also be helpful: [https://youtu.be/AiLCzKAOdx0?si=is62sOoSHkigEcr9](https://youtu.be/AiLCzKAOdx0?si=is62sOoSHkigEcr9) However, in CalculiX, solid and spring elements and even MPCs themselves are more commonly used to model beams than beam elements due to their various limitations/bugs (even though beams are likely the most common choice in other software).