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Truss node connection / cross section class 3

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Message 1 of 7
Ridehard
1771 Views, 6 Replies

Truss node connection / cross section class 3

In Eurocodes 1993-1-8 says that for joints outside range of validity given in Table 7.8, should secondary moments in the joints caused by their rotational stiffness should be taken into account..

 

So If you modeling your truss like continous chords and pinned diagonals/posts you don't have that moment in your joint calculations, so I ask should there be some kinda warning for that?

 

And in 7.1.2.(2) says that compressions elements of members should be class 1 or 2, Robot don't give any warning of that condition too..

 

Am I missing something or should there be a warning for that?

 

See attachment..

6 REPLIES 6
Message 2 of 7
Artur.Kosakowski
in reply to: Ridehard

c1.png

 

c2.png

c3.png

 

For the section class warning: I agree that it should be displayed and I have sent this request to our development team.

 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

 



Artur Kosakowski
Message 3 of 7
Ridehard
in reply to: Ridehard

True, it divide moments caused by Eccentricity but  in my opinion Robot dont take a count "secondary moments" 

 

See attacment pics 🙂

 

Message 4 of 7
Artur.Kosakowski
in reply to: Ridehard

Let me write this again so that I'm sure I understand your request correctly.

 

Scenario 1:

A user defines truss with pinned connections among bars (no bending moments calculated during static analysis).

5.1.5(3) not satisfied

Robot gives warning about the secondary moments not being taken into account during the verification of  a connection

 

Scenario 2:

A user defines truss with elastic releases of fixed connections among bars (bending moments calculated during static analysis).

5.1.5(3) not satisfied

No warning displayed during the verification of  a connection

 

BTW: what is the source of the table that is located at the top of the picture you attached?

 

If you find your post answered press the Accept as Solution button please. This will help other users to find solutions much faster. Thank you.

 

 



Artur Kosakowski
Message 5 of 7
Ridehard
in reply to: Ridehard

source: EN 1993-1-8:2005

And I correct myself, it's not table 5.1.5(3) , Its table 7.20 see attacment..

 

Don't know which one is better, warning always or warning only when modeled as a pin connection.. that flexible is  difficult to take account and there is not many listed values or formulas to calculate that C-value (kNm/rad value) of joint because so many things affects on it.

 

 

 

 

Message 6 of 7
Artur.Kosakowski
in reply to: Ridehard

 Don't know which one is better, warning always or warning only when modeled as a pin connection..  

 

In the situation when bending moments calculated based on stiffness of elements are considered in the verification of a connection display of the warning that the secondary moments are not taken into account would be IMHO sort of strange. I think that it may be assumed that a structural engineer deciding on using fully fixed or partially released connection among bars of the model already decided on the 'stiffness' of the connection Smiley Happy 

 



Artur Kosakowski
Message 7 of 7
Ridehard
in reply to: Artur.Kosakowski

True 🙂 and that situation would be also frustrating, if you think that you know what you are doing 🙂

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