Initial deformation of Braces

[Andre Tenchini]

Dear Seismostruct group,

I am desiging a concentrically braced frame, thus I need to put in a initial deformation in braces for to analyze through pushover. However, in my model, I am putting small initial deformation (L/250 = 20 mm) in braces, and I can not run it. But, when i put big deformation ( for example: 70 mm ), the program can run the model. What do you think?

Model descriptions:

- 8 storey;
- composite columns, steel beams and braces;
- Braces are pinned by links;
- elements:
infrmDB - Columns
infrmFB - Beamns and braces

Best Regards,

Andre Silva

[Andre Tenchini]

When I say "the program does not run" this means that it sotp in given step, ie I can found the maximum load (yield load) from plastic mechanism.

Best regards

[seismosoft]

Dear André,

We checked quickly the model you sent us, and noticed that you are using four infrmFB elements with 5 integration points to model beams, which contradicts the suggestions in the Help System. Any particular reason for that?

The same goes for the braces, any particular reason for using two infrmFB elements with 5 integration points?

Note that the above issues are not necessarily related to the difficulties you report, but might nonetheless be worth addressing before progressing any further.

Seismosoft Support

PS: if you could replace the one out-of-plane non-structural node that you currently have in your model with an in-plane one (obviously adjusting the local axes of the related elements), the out-of-plane restraints will no longer be visualised in the renderings.