How to properly calculate and use the stiffness of a steel connection in IDEA StatiCa Connection?

How to properly calculate and use the stiffness of a steel connection in IDEA StatiCa Connection, the impact of the connection stiffness on the internal forces, results of the stiffness analysis.

[@Zeno89100]

If there is tension force in connection, should I apply this force in rotational stiffness analysis?

[@ideastatica_en]

Hello, it depends on what you want to calculate.
1) only pure rotational stiffness My - input only My (not N)
2) rotational stiffness My (and Mz and Mx) under certain load conditions - input all internal forces including N
generaly tension force N does not affect the rotational stiffness of a connection

[@amrabdullah1995]

Thank you for the useful video.
I have a question please.
How can one compare the stresses obtained from IDEA and the uni-axial stress provided by the code ?
FEA runs with equivalent stresses multi axial stress state, so they are different from the yield and ultimate stresses used while defining the material.
do you judge the failure of the connection using the 5% equivalent strain only and ignore the equivalent stress ?
Thank you

[@ideastatica_en]

"The yield stress fyd that is mentioned in the code and which is derived from uni axial tests is also valid as the yield stress for multi axial stress states:
√(σx^2 + σy^2 - σx ∙ σy + 3τxy^2) ≤ fyd
The uniaxial stress state is just a special case of a multi axial stress state. The plates in IDEA StatiCa Connection are modeled with elastic-plastic material with a nominal yielding plateau slope according to EN1993-1-5, Par. C.6, (2), tan-1 (E/1000). The material behavior is based on the von Mises yield criterion. It is assumed to be elastic before reaching the design yield strength, fyd. (for more info, see: www.ideastatica.com/support-center/material-model )
In IDEA, the equivalent stresses are not used for checking, but rather reaching the 5% limit value of the principal membrane strain is used for checking, this is in accordance with EN 1993-1-5 App. C. par. C.8 (1)."

[@xokylemurilloxo]

Is it possible to analyze for torsional stiffness?

[@ideastatica_en]

Yes, for torsional stiffness, you input Mx to the load effects.
See the theoretical backrground:
www.ideastatica.com/support-center/general-theoretical-background#Stiffness_analysis_and_deformation_capacity_of_steel_joints
An article:
www.ideastatica.com/support-center/stiffness-analysis
and tutorial on how to do it:
www.ideastatica.com/support-center/stiffness-analysis-of-a-connection-with-a-custom-cross-section-en

[@arekstachyra5167]

Why the value of Sj,ini is not equal to the one from Eurocode? (20 MN/rad -> 15 in statica, for example)

[@ideastatica_en]

Hello, our values Sj are computed using FEM analysis, so there can some differencies

[@JorgeOrtega-uf9pm]

Where Can I specify if the system Is braced or unbraced on version 10?????????????!?!

[@ideastatica_en]

Hello, all settings can be found in the Code setup