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Dear STKO team,

I try to build a hill with Solids-Structured-Hexa-Linear mesh and stdBrick element.

However, when I run the analysis, it shows something wrong and I hope anyone can help me.

It shows that "Invalid type of elements or number of nodes".

At the same time, it also potentially has the problem that "Matrix is Singular Numerically".

Thanks a lot!

Best Wishes!

Lei Lei

Sorry for wasting everyone's time.

When this problem appears, there may be two reasons, which are the mismatch between element and mesh, and the wrong building of the geometry.

Here, I used the stdbrick element and meshed the model with structured hexa. I checked this and there was no wrong.

The only possible is the geometry so I rebuild my model. Finally, it works.

I hope my mistake can help someone.

Good luck, everyone!

Yes those are the possible source of this issue. We're glad you solved it!

Hi,
I also have the same problem with my model.
Could you please help me to detach the problem? I have attached the model.

If you right-click on your brick Element Property -> Select, you will see that you assigned your Finite Element (Quad) also to some Edges (2-node line element) and vertices. That's why STKO is reporting the error.
When assigning element properties make sure to assign them only to proper sub-geometries (faces in your case).

Another issue is that you modeled your specimen in the X-Z plane. In OpenSees 2D models must be in the XY plane.

Finally pay attention to your BC! the self weight you put in your element properties is not matching the unit system you are using in your material (N-mm)

Dear STKO team,
Thank you for your prompt reply. Could you guide me with assigning the gravity load to masonry prism model?
Since I am doing compressive strength test I put the push load with displacement oriented which is assigned on a point in the middle of top beam, where I couldn’t constrain the point. I will appreciate if you could make sure this part is modeled correctly?
Thank you

First you have to make sure the self weight in the Element property has the correct value.
You put something like 40! It is too much. For example, if you are using N and mm, a self weight of 18kn/m^3 is 1.8e-5 n/mm^3.

Finally you can apply the compressive force as a force and do a displacement control

Dear STKO Team,
Thank you for your response. I modeled the prism again. Now I faced with the error in the screen shot. Please guide me with the solution.
I really appreciate your kind reply.

I have attached the file here for your reference.

Hi, I noticed you have still not modelled the structure in the XY plane. The model geometry should be drawn using the XY plane, as shown in the attached figure.