# Bolt pre-tension

**URL:** <https://prepomax.discourse.group/t/bolt-pre-tension/1520>\
**Category:** General Questions\
**Created:** [February 16, 2024, 3:22pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520 "2024-02-16T15:22:53Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Trevor](https://avatars.discourse-cdn.com/v4/letter/t/258eb7/32.png) [@Trevor](https://prepomax.discourse.group/u/Trevor)\
**Post date:** [February 16, 2024, 3:22pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520/1 "2024-02-16T15:22:53Z")

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Is there an established process in prepomax for maintaining bolt pre-tension in subsequent steps ?

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**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 16, 2024, 3:31pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520/2 "2024-02-16T15:31:41Z")

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In the second step, you should change the pre-tension type to displacement (if it’s not of this kind already in the first step) and set displacement to Fixed:

![fixed](https://global.discourse-cdn.com/free1/uploads/prepomax/original/2X/5/5c18ad0e6ee48935ee6a2abf4bca1cf2976af0b2.png)

There is a long discussion on how pre-tension works with other loads in CalculiX here: [Pretension shear/tensile resistance - CalculiX (official versions are on www.calculix.de, the official GitHub repository is at https://github.com/Dhondtguido/CalculiX).](https://calculix.discourse.group/t/pretension-shear-tensile-resistance/2091)

So far, the conclusion is that it’s better to use displacement type in the first step.

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**Author:** ![Trevor](https://avatars.discourse-cdn.com/v4/letter/t/258eb7/32.png) [@Trevor](https://prepomax.discourse.group/u/Trevor)\
**Post date:** [February 16, 2024, 3:51pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520/3 "2024-02-16T15:51:58Z")

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The implementation in prepomax seems to be the same as I was doing manually. Thanks.

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<div class="post-metadata">

**Author:** ![Trevor](https://avatars.discourse-cdn.com/v4/letter/t/258eb7/32.png) [@Trevor](https://prepomax.discourse.group/u/Trevor)\
**Post date:** [February 18, 2024, 9:37pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520/4 "2024-02-18T21:37:22Z")

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I had a look at one of the posted models “Clamping Hanger” and thought it odd that the 2nd step contained the correct “\*boundary, fixed” for the pretension section but also an amplitude referring back to the initial load application in step 1. This may have led to much confusion for the pretension and associated reactions.

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**Author:** ![ANYS](https://yyz2.discourse-cdn.com/free1/user_avatar/prepomax.discourse.group/anys/32/7737_2.png) [@ANYS](https://prepomax.discourse.group/u/ANYS)\
**Post date:** [February 18, 2024, 10:26pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520/5 "2024-02-18T22:26:46Z")

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Yep, I removed them. It’s kind of strange that the amplitude were affecting as the value was set to Fixed but it interferes.

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<div class="post-metadata">

**Author:** ![Trevor](https://avatars.discourse-cdn.com/v4/letter/t/258eb7/32.png) [@Trevor](https://prepomax.discourse.group/u/Trevor)\
**Post date:** [February 18, 2024, 10:31pm UTC](https://prepomax.discourse.group/t/bolt-pre-tension/1520/6 "2024-02-18T22:31:31Z")

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I guess its a numerical value fixed from the last step but scaled according to amplitude. I think that’s what I would expect to happen to be consistent but i guess some care is needed.