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Thanks for great explanation. I'll try that soon. Best regards.

Hi, I have some more questions about free field boundaries

1- In a 2D model, when modeling free field columns, the only thing I changed for the FF element is the thickness of the soil element. For example, my main column soil thickness is 1.00 meter but FF column is 10000 meters to simulate high damping of the "infinite" soil medium. Is it correct?

2-In case of a 3D model it is clear that I won't be able to increase thickness of a solid element. So how to model this? Is it enough to increase the properties of soil material? (bulk modulus, shear modulus etc..)

3. In case of a 3D model, how to connect corner elements? I have read Mr. Petraca's paper about SSI bridge and some other materials from web but information about corner elements are limited. Please see the attached corner.jpg file.

My current 2D model is attached. It would be great if you check my ff boundary conditions. Thanks in advance.

Dear vokums,

1. Yes it is correct, in 2D it is sufficient to increase the thickness
2. Yes in 3D what we did is to increase the material properties. In fact in 2D what the element does is just getting the sigma and tangent tensor from the material and multiply them by the thickness before computing internal forces (-integrate(B^T*Sigma*thickness*dA)) and the stiffness matrix (integrate(B^T * C*thickness * B * dV))
3. the corner FF should be connected to the soil model with the same dashpots, but not connected to the side FF

Thank you very much.

Hello,

I have a question. I am attempting to use L-K boundary conditions for my 2-D soil model. I created the model using 9-4 Quad up elements and the PressureIndependMultiYield material. I applied the boundary conditions and conducted a transient gravity analysis, which ran successfully.

However, when I replace the boundary conditions with nodal reactions in the next step, the system goes out of equilibrium and moves downward. I also attempted a static gravity analysis, but it is not working and I'm encountering the error: 'WARNING BandGenLinLapackSolver::solve() -factorization failed, matrix singular U(i,i) = 0, i= 11.' Could someone please help me identify the issue?

Thanks!

Can you try the new ASDAbsorbingBoundary Element? we gave webinars on this topic