i am uploading this files, and I appreciate if anyone would accept to check it for me, I am trying to model a model of beam to column joint but the beam is bolted to the web column, I am facing a problem in the step of bolts pretensioning, it does not converge from the first increment, it indicates singularity warning along with zero pivot warning in the region of the bolts. I am confused because it's the same value of the force and the same bolts as another model i did in the past with the beam bolted to the flange, and it worked perfectly fine,only the materials are changed because of the experimental work. Waiting for any reponse.
When encountering convergence issues during the pretensioning step of a bolted joint simulation, there are a few potential reasons and troubleshooting steps to consider:
If the above steps do not resolve the convergence issues, it may be necessary to seek assistance from experienced users or ABAQUS support. They can provide more specific guidance based on the details of your model and the specific error messages you are encountering.
Zero pivot means that your model is not sufficiently constrained and rigid body modes are allowed
I checked your model and I found that your surfaces contacts are totally incorrect, for example, the contact between the bolt head and the surface of the corresponding plate, bolt hole and bolt thread surfaces .........., so I think the main things you have to check are:
1. The boundary condition must be set according to the test type (axial loads, bending moment and so on);
2. In the case of static general steps, the defined steps for the pretension forces of loads and the pretension force values based on the real case;
3. No need to define the boundary conditions of the column as a rigid body, it is better to use BC (boundary condition option);
4. For the material plastic the first values should be zero for stress and zero for strain, but as I checked you used the value 0.001 for the first stress of bolts and 0.0001 for the other materials;
5. The definition of the history output is missing please check it and define it correctly.
Waleed Mashrah can you tell me please how are the contact surfaces incorrect because the same surfaces was defined in another model and it worked perfectly?
as for boundary concitions i tried with coupled reference point rigid bidy and without any reference point the same warning persists.
for the material plastic abaqus doesnt not accept zero as the first value of stress so i defined 0.0001 as a small value, again those material values worked with another model and gave me same results as experimental tests
the history outpout is not a problem i will define them, they are not the reason for the divergence.
Denis Benasciutti i know sir its meaning but i dont understand where shoud i add constraints ?
If the model is insufficiently contrained, the structure stiffness matrix [K] is singular, zero pivolts are present and the displacement solution cannot be found.
Please check for unconstrained model (translations + rotations).
Hello Sara, when I checked your model I didn't find any contact definition between surfaces, the analysis is very sensitive to the surface's contacts. So, I advise you to use surface-surface contact and define all contacts through your model, especially those between the bolt and the other component surfaces. I did a writing mistake for the materials, but when we define material plasticity the first value should be the yield stress value not 0.001.
I recommend you a video on youtube with a close model to yours (https://www.youtube.com/watch?v=mQPJmyAM6pc)
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