Dear all mates here:
I am struggling about a question when I apply pin boundary condition to a solid element steel bar in ABAQUS.
I knew from another mate that as long as I restrain all the nodes on a same surface to a certain value, which is exactly the situation when I set a displacement in axial direction as a displacement control, that end will lose the freedom to rotate, no matter if I restrain the lateral DOF of the nodes.
So, my question is: since I still need to use displacement control as a loading method, How can I get a pin end boundary condition that can make the end freely rotate, and use displacement control at the same time?
Any suggestion is highly appreciated and thanks very very much for that!
Sincerely yours,
Mengli
Dear Mengzi,
At the support you need to define a reference point and constrain all nodes of the solid elements at the support to this reference node. Then apply the boundary conditions and displacement control to that point.
good luck
emad salem
Dear Salem:
Thanks for your reply! it really works! and the fixed end will just rotate as it should be!
But the thing I cannot understand is that: why you constrain all the nodes at support to a reference point, here I take the center point, after that you set a displacement for that point, it can work? I mean when you restrain all the nodes to the center point, the reference point actually governs the whole point, and all the axial displacement of the nodes should be the same value as the reference point, and if the elements are solid without rotational DOF, that end shouldn't rotate, but it just rotates. Can you help me with this question ?
Sincerely yours,
Mengli
Dear song,
what you did is correct to take the center point as a reference point. The rotation at the end is a typical for pin joint even though the solid element you are using does not have rotational dof. It is the relative displacement between nodes that causes the rotation. If you want to eleminate the rotation then you have to constrain the rotation of the center point. In this case you will have a fixed support.
with best regards,
emad salem
Yes, I just want the pin end modelling results, but I cannot understand when you use rigid body to let the reference point control all the nodes on the surface, and you set axial displacement control to the point, then all the nodes should go down with the same displacement, but what happened is just like you said, the different nodes will have different axial displacement that cause the end rotate, which is good, but I cannot understand why....
Thanks very much for your patient explain, I am so appreciate it!
Best Regards,
Mengli
Dear Mengli,
I've found more or less your question. In general, modeling techniques can be different from each other in any given problem. Although the solstice rotation of the finite element method is not computational, the method Emad suggests is a proper and practical method. I also suggest a different way. If your model is a steel frame or a connection, you can use Wire Element to model the boundary. I used this technique in one my paper (Article Evaluation on Eccentrically Braced Frame with Single and Dou...
). Moreover, Yang and Tan used this in (Article Numerical analyses of steel beam–column joints subjected to ...
).Best,
Rohola.
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