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Bart04 · 2025-02-28T21:48:53+00:00

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Bart04

I am doing an analysis of a Headframe for mining and I have internal bracing set up to be Tension member only but when I am running analysis, I am getting FYI CO074 tension-only truss converted to truss.

in code details I am getting Slenderness ration error 1.4 Fail.

Should I just omit Slenderness, or there is a way of running it with tension only?

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Tayen_Aguilar_57

Hello Bart,

Thank you for your comment.

The FYI you are getting is expected. When running a Linear Analysis, tension-only members are converted to truss elements because the solver considers them axial elements.

You can run a non-linear analysis next if you want to consider the stiffness differently

Regarding the slenderness ratio, take a look at this excerpt from the help system;

With that said, for tension members, S-Steel is overly conservative, using L (member length) instead of the largest unbraced segment so you may want to adjust the ratio for braced members in tension, or use Scratch Pad, where the numerator of the ratio (both compression and tension) = buckling lengths, which you can adjust on a per case basis.

Hopefully this addresses your questions, let me know if you have any additional comments or issues,

Best,

Tayen Aguilar

Altair Support

Headframe calculations.zip

Bart04

Hi Tayen,

I run non-linear and got the same results like with linear analysis. So no difference there.

BTW the membranes I have problem are RB not L shape. should I just turn off slenderness off or if should I increase slenderness what's the recommended ratio?

Headframe calculations.zip

Tayen_Aguilar_57

Hi Bart,

Would you mind sharing your model so we can take a closer look? Please fill this form and send any related files along:

https://community.altair.com/categories/support

The lack of differences might be due to the forces the member is experiencing and the releases and other factors of the member itself or even the negligible forces. Running different types of analyses will help us understand the behavior you are expecting.

As for your second question, it depends on the code you are using and the forces the member is exposed to, You might want to use the Scratch Pad feature for that:

We could provide a more specific answer if you share your model with us,

Best,

Tayen Aguilar

Altair Support

Headframe calculations.zip

Bart04

Headframe calculations.zip

here you will find my model.

thank you for your help

Matthew_Sauer1

Hi Bart,

We ran a code check using a nonlinear analysis with your model. We did observe some high utilizations in some of your bracing. Upon investigation, we did notice that your members seemed to be failing due to slenderness. It should be noted that the relatively small loads in your bracing are actually below your default negligible force limit in S-STEEL (found by right clicking the design constraints tool). This is causing the member to be considered 'unloaded' by S-STEEL. If you lower the negligible force limits to zero, the member will be classified as being in 'Tension', but will still fail the slenderness check due to the relatively small profile, and large length.

If this is not a concern for you, you can ignore the slenderness checks from the report (at your discretion) using the design constraints tool once again.

Should you like to discuss further, please open up a support ticket, and we'd be happy to further discuss:

https://community.altair.com/categories/support

Regards,
Matthew Sauer

Altair Support

Headframe calculations.zip