# Pretension shear/tensile resistance **URL:** \ **Category:** Uncategorized\ **Created:** [February 13, 2024, 5:31pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091 "2024-02-13T17:31:26Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [February 16, 2024, 8:56am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/21 "2024-02-16T08:56:11Z")
i have posted two simple example cases, one using initial condition type stress and the other is sliding at nut wall surfaces and reversed loads. It seems the latter approach is more generic, surface behavior (contact) can be changed within a step. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 16, 2024, 10:19am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/22 "2024-02-16T10:19:46Z")
> [@xyont](#): > > i have posted two simple example cases Thanks, Xyont. I will keep those options present. (Where could I find them?). In the meantime, I will try to go deeper in the understanding of the pretension card , its limitations and discarding any possible wrong set up from my side. > [@jbr](#): > > This is the standard way in Abaqus, as mentioned by @Calc_em 's cat. We may need to evaluate if a flag for “follower force” is required in the cases of large displacement. A follower force would be nice in case Nonlinear pretension is active. By other hand, shouldn’t the gap between pretension sections be automatically fixed once the force preload is finished?. If not, the bolt doesn’t develop additional internal tensile force. In fact it “brakes” as soon as the external tensile load reaches the pretension value. That sounds like a bug. It behaves as some kind of perfectly plastic contact if you allow me the comparision. I have made an additional test and it brakes at the exact pretension load. My pretension is two bolts at 700 N each one. The clip blows away when I reach 1400 N of reaction force at the base. ![screenshot.71](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/4/4f39f37648fce22a49d4792a5c57545c7bc4c984.jpeg) ---
**Author:** ![vicmw](https://avatars.discourse-cdn.com/v4/letter/v/6de8d8/32.png) [@vicmw](https://calculix.discourse.group/u/vicmw)\ **Post date:** [February 16, 2024, 9:28pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/23 "2024-02-16T21:28:47Z")
Where can I find this model? It’s one @xyont posted somewhere? Breaking apart at the preload force sounds correct for force pre-tension reacted by contact. Do you have the two steps with displacement applied to pre-tension in the 2nd step? ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [February 16, 2024, 9:49pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/24 "2024-02-16T21:49:00Z")
only some screenshot of example at the thread link provided. The input file and definition can be huge and it need a lot of work, but i have seen the possibility. Below another example case of alternate model of pretension bolt using initial condition type stress. ![2024-02-17 04_41_40-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/b627efda577059e6c965b1cabe36a2a6bfe98d76.png) ![2024-02-17 04_41_57-Calculix keyword editor](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/8/8afc9190f9263513d3fd77b7edeae90876ec23c5.png) ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 16, 2024, 11:50pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/25 "2024-02-16T23:50:44Z")
I have set up the model in Prepomax with two steps but the behaviour is not as expected too. Redefining the pretension to displacement in the second Step and adding FIXED resets the preexisting tensile load on the bolt. It’s well known (although somewhat disconcerting) that a bolt under pretension has a flat transition when the operational load is applied .Tensile do not increase in the bolt until the external load induces a tension=pretension. At that point, tensile increasses again but from the previous pretension value. That drop shown on the graph should be a flat line. Reaction on the bolts base. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/7/7a05fc7c0845e8664f89106d9538794300cf1895.png) Applied ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/8/845af98adb5878df5873d684857cf6a69850eb7d.png) I would appreciate if someone more experienced in Prepomax can take a look if I have properly set up the model. > **[Clamping Hanger.pmx](https://wetransfer.com/downloads/22f3bce8587f6ee5e97a7ab38160084320240216234341/572dd7)** > > 1 file sent via WeTransfer, the simplest way to send your files around the world ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [February 17, 2024, 1:36am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/26 "2024-02-17T01:36:04Z")
actually, i still can not understand the problem from screenshot provided, how purely pre-tension bolt designed to resist tensile load. It’s a friction bolt to be work for shear loads dominant by clamping, some overstrength may exist due to minimum pretension of 70% tensile strength. however, interesting observation when the solver given report in breaks at bolt reaction equal to pretension loads assigned. So it can be assumed as half value of tensile strength (maximum). But the model may incorrect since low pretension load only produce small friction resistance, the plates begin to slide when exceeded, then contact bearing occurs. Is pretension section approach can maintain compatibility of bolt during deformation? i;m not sure whether it can. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 17, 2024, 8:13am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/27 "2024-02-17T08:13:16Z")
> [@xyont](#): > > i still can not understand the problem ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/4/4520f9a56bf65a5d0109bd9b0246f217344cfd65.jpeg) ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/d/dc9fe728f23035305298ebc82eb368167b2a32ca.jpeg) ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/b3f31a8212acc628a6097da9547d6f773627ebd8.png) And so on… ---
**Author:** ![xyont](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/xyont/32/3553_2.png) [@xyont](https://calculix.discourse.group/u/xyont)\ **Post date:** [February 17, 2024, 10:07am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/28 "2024-02-17T10:07:17Z")
my another example approach of modeling pretension bolt as in SimSolid (Altair) ![2024-02-17 16_28_51-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/d/df9294cdb3f0ba89e58e8273c4cebefd1e396240.png) ![2024-02-17 16_29_02-](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/1/157e2454b9504d9a00d8242158b6c70cd3ef68ad.png) ---
**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\ **Post date:** [February 17, 2024, 10:08am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/29 "2024-02-17T10:08:53Z")
the 2 parts of each bolt have to be merged, the pretension section is a section inside the bolt (coincident nodes). ---
**Author:** ![fgr](https://avatars.discourse-cdn.com/v4/letter/f/f4b2a3/32.png) [@fgr](https://calculix.discourse.group/u/fgr)\ **Post date:** [February 17, 2024, 10:26am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/30 "2024-02-17T10:26:48Z")
@Disla I don’t know if I have understood correct, but I believe what cheat, it’s the reaction force, which really isn’t reaction force but actual external force. At exit of step 1 everything has come into balance, why no external force exists at the beginning of step 2 and for reason RF2 will start from zero again. Plotting deflection in Y-direction close to the bolt verifies that loads really occurs during the 2 step. ![hotpoint](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/bc084cc3885745a998d70c0320c0a20e0778ccae.jpeg) ![disp](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/e/e0b6ca4cf918cd0b5b3839356c0cdfbdd6184320.jpeg) ---
**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\ **Post date:** [February 17, 2024, 11:11am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/31 "2024-02-17T11:11:15Z")
this is an example I developed from abaqus examples problems guide: [http://130.149.89.49:2080/v2016/books/exa/default.htm](http://130.149.89.49:2080/v2016/books/exa/default.htm) example 1.1.1 that has explanation and link to the original publication. You can easily add axial and radial (shear) loads to this model in a further step. > **[boltpipe4\_calculix\_1.inp](https://drive.google.com/file/d/1aho9HreXEHQCSjhpLPc5HqiLk0CcPuLk/view?usp=sharing)** > > Google Drive file. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 18, 2024, 5:01pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/32 "2024-02-18T17:01:35Z")
> [@fgr](#): > > at the beginning of step 2 and for reason RF2 will start from zero again Hi Flemming, It is confirmed that there is an interference between OP=NEW and FIXED card that erase the pretension in Step\_2 in Prepomax. > **[Boundary, Fixed options](https://prepomax.discourse.group/t/boundary-fixed-options/1523/10)** > > hopefully, there is a workaround to eliminate this problem inside PrePoMax. Thank you. I have been able to obtain the behavior I was talking about with Mecway. One can see the flat section in the reaction while the operational tensile load \ [@JuanP74](#): > > You can easily add axial and radial (shear) loads to this model in a further step Adding the axial and radial shear loads in the second step is the problem but thank you anyway. I can see the gasket there. That’s interesting too. Thank you both and all the previous posters for the replies and support. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 18, 2024, 6:36pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/33 "2024-02-18T18:36:39Z")
Also solve it with custom keywords in Prepomax with the help of xyont and Jackub. Pending final values check. Hopefully this can be implemented in a future release. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/6/69657fce3158c3cdc250695e63e809ed6a2df19b.png) ---
**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\ **Post date:** [February 18, 2024, 9:04pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/34 "2024-02-18T21:04:46Z")
> [@vicmw](#): > > But that only works for small rotations because it doesn’t update the MPCs as the normal changes direction, so this large rotation example goes completely wrong. This is right. If my example from Abaqus examples guide is run in CCX there is evident sign that section does not rotate contrary to Abaqus solution that takes it into account. ---
**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\ **Post date:** [February 18, 2024, 9:12pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/35 "2024-02-18T21:12:06Z")
if you exceed the pretension in the bolt the joint undergoes separation and then the contact condition in the joint plates changes, the bolt instead of the joint is taking the axial load, under this condition the pre-tension section model is no longer valid probably. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/9/964157014e27a2ac1907ce07deb2bb594a00d62d.jpeg) ![Bolted Joint Diagrams with External Forces Applied](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/4/4b60dc1f0c618bf01a7f68a2ab7a32914be66bf9.gif) > **[Bolted Joint Diagrams with External Forces Applied](https://www.boltscience.com/pages/basics5.htm)** > > Tutorial on bolted joint analysis - Bolted Joint Diagrams with External Forces Applied ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 19, 2024, 12:34am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/36 "2024-02-19T00:34:53Z")
Hi Juan and Thanks, Yep.That’s the behaviour I was expecting. Big warning cause it’s clearly nonlinear if anyone is interested in loading and looking close to the separation point. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/bd3a4b287397d2db1ab88fa53174d883b07469b2.png) Why do you say is not valid. Do you mean is nonlinear, it’s not valid for service , is not safe? ---
**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\ **Post date:** [February 19, 2024, 7:11am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/37 "2024-02-19T07:11:16Z")
I am saying that probably the model under this condition will yield wrong results, that is, that will not correlate with real world. So you need a different type of model after separation (no pretension section). ---
**Author:** ![JuanP74](https://avatars.discourse-cdn.com/v4/letter/j/b5a626/32.png) [@JuanP74](https://calculix.discourse.group/u/JuanP74)\ **Post date:** [February 25, 2024, 6:21pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/38 "2024-02-25T18:21:03Z")
I think I didn’t read this whole thread carefully enough, so I’ll try to fix what I said. It seems I never tried to run a pretension analysis beyond separation or at least didn’t take much care about the results since usually separation is a failure condition, so I updated the boltpipe4 example, this time in prepomax with axial load in a second step: it is necessary to edit the calculix keywords as shown in the picture, do it after creating the pretension load so you know the node id (seems I always did this directly the .inp file). The results for the bolt load are in the attached picture, same as yours (time 1.0 is full pretension, then at about time 1.5 separation happens, always load a bit bigger that pretension, from then all load is taken by the bolt). Just a small remark, the “flat” portion of the curve is not completely flat but its slope depends on the relative stiffness bolt/grip as explained [here](https://mechanicalc.com/reference/bolted-joint-analysis), and the non-linear behaviour can be described as 2 lines with different slope before and after separation. This is the usual “hand calc” analysis. I provide both the prepomax file and the inp file so anyone can check the results and confirm if appropriate. Contrary to what I said before the pre-tension section model works well beyond the applied pretension load (if CCX keywords are used properly of course). ![Captura de pantalla 2024-02-25 110019](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/3/306cb03fc818504c16e5bfb08eab00877a6e754e.png) ![Captura de pantalla 2024-02-25 105847](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/a/acc9111e08e88c498ee5ad372aabd6a57f3f2fd7.png) > **[boltpipe4\_calculix\_1a.pmx](https://drive.google.com/file/d/1q4LBbRNPhvyTHNH3bMG2IexlXiXXC2-Q/view?usp=sharing)** > > Google Drive file. > **[boltpipe4\_calculix\_1a.inp](https://drive.google.com/file/d/1NsQVhMaMbTmsIoe_kaEGJUB1WU-67cv7/view?usp=sharing)** > > Google Drive file. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [February 25, 2024, 7:23pm UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/39 "2024-02-25T19:23:19Z")
> [@JuanP74](#): > > Just a small remark, the “flat” portion of the curve is not completely flat but its slope depends on the relative stiffness bolt/grip You are absolutely right. It’s not completely flat. And also, the separation happens slightly over the pretension load. In my case the relative stiffness between bolt and plate made the transition almost imperceptible. ![imagen](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/d/dfe6cc1a085a9fec5a00bc1c4ffd584486508eb8.png) Thank you, Juan, I’m sure users will appreciate this valuable applied case. ---
**Author:** ![RDev](https://avatars.discourse-cdn.com/v4/letter/r/c6cbf5/32.png) [@RDev](https://calculix.discourse.group/u/RDev)\ **Post date:** [June 12, 2026, 6:51am UTC](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091/40 "2026-06-12T06:51:25Z")
Hello @Disla and @JuanP74 , The file shared as an example in the above discussion is having the bolt pretension is in compressive direction. But in the tutorials it is always in the tensile side. Can you please share your knowledge on this. Which one should I follow Sorry I am new to Calculix. Exploring and facing this contradiction. [Previous page](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091.md?page=1)