Pin joints in a structure

SOFiSTiK Teddy
1

I am using the text editor Teddy of SOFiSTiK for the FE analysis of a 3D bar frame. For the same I need to implement pin joints between different bar elements in space, meaning the displacement of the connecting ends of the beam elements are constrained w.r.t. each other. However the connected beams are free to rotate about each other and also the joint itself can move in space.

I was looking into the kinematic constraints (specifically KP) but wasn’t able to figure out how to implement it for my model using the text editor.

Any help or example is welcome!

2

Hello

Have you tried using a spring with a special worklaw? This worklaw can then be modified to cover the desired material behaviour. Springs and materials can also be defined in SOFiPLUS(-X) and SSD.

SSD / TEDDY > Help > User Manuals > All Manuals… > SOFiMSHA > chapter 3.20 SPRI - Spring Elements

Best regards
Frederik Höller
Your SOFiSTiK Support Team

3

I have used springs before, but don’t know if it’s possible to have a multidirectional spring. That is while defining the work law, I want the work law to apply for all rotational degrees of freedom. Is that possible?

4

That should be possible. In the TEDDY you will find a few examples that cover the possibilities of springs in combination with special work laws. Perhaps these will help you.

TEDDY > File > Examples > ase > english > spring > e.g. a1_spring_overview.dat

5

I did go through those examples but couldn’t figure out anything suitable. I basically want a simple pin joint in a 3D frame structure made out of beams but haven’t been able to figure out a way to implement that is Teddy.
Can you please provide me the syntax for implementing a pin joint between two beams as well as the module its in?

6

Hello,

You may define pin joints between beam elements in SOFIMSHA. Here is the definition of the pin joints at ends of the beam allowing rotation around local Y axis.

BEAM NO 3 NA 3 NE 4 NCS 1 AHIN MY EHIN MY

See, items AHIN and EHIN in 3.16 chapter of SOFIMSHA manual.

7

Thanks for the response. That’s what I ended up doing for now. But is there a way to combine two releases? For example in the above example, is it possible to allow both rotation about Y-axis as well as about Z-axis.

8

I have had similar problem. I ended using AHIN in the BEAM command. The pin behavior is defined in AQUA where you can define different stiffness for different axis. In the following my example:

AQUA definition of hinge material:
SMAT no 101 MTYP - TITL ‘CONEX’
SFLA no 101 TYPE=N S=1000000
SFLA no 101 TYPE=VY S=1000000
SFLA no 101 TYPE=VZ S=1000000
SFLA no 101 TYPE=MT S=1000000
SFLA no 101 TYPE=MY S=1000000
SFLA no 101 TYPE=MZ S=1

I selected a stiffness 1.0 for MZ then i was able to list rotations in the pin just listing MZ moments (MZ=Rotation).

Then in sofimsha the beam command is as follows:
BEAM 101 101 102 NCS 1 DIV 0 AHIN 101

This worked fine for me.

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