I have a geometry that looks something like this. What will be the combined stiffness of the members?

Figure indicating the geometry

  • $\begingroup$ Which stiffness? Axial? Bending? The full stiffness matrix? Considering p-\delta effects or in the linear regime? $\endgroup$
    – Zegpi
    Oct 30, 2023 at 19:31
  • $\begingroup$ This is basically a slice from cochlea, where the bending part(material 2) is basilar membrane and the material 1, is a bridge tissue. both of them bend but their individual stiffness is different. For our model we are assuming them to be isotropic. I am primarily interested in the bending stiffness. $\endgroup$ Oct 31, 2023 at 3:30
  • $\begingroup$ I get that the materials are different, but what are your expected loads? Are they point loads or distributed loads? What's the loading direction? Are you expecting large deformations? $\endgroup$
    – Zegpi
    Oct 31, 2023 at 16:55
  • $\begingroup$ Load is distributed and given by p = p0*sin(wt) and acting along the length of the slice i.e. from the bottom in the current view. $\endgroup$ Nov 6, 2023 at 18:04

1 Answer 1


Each part stiffness is the $EI$ of that part.

However, calculating the deflection under a certain load analytically by hand could be a term project.


I searched for assembling the global stiffness matrix from member local stiffness matrices. Here is a couple of answers.

global 2

golbal link

  • $\begingroup$ I am using Comsol for simulations but currently I am using the series approximation for the stiffness but my results are way off than the experimentally reported results for deflection values. Currently I am using single value of stiffness for each member. Can you please elaborate how we can get a good formulation for the stiffness matrix? $\endgroup$ Oct 31, 2023 at 16:26
  • $\begingroup$ I added two links to my answer. Take a look. $\endgroup$
    – kamran
    Oct 31, 2023 at 19:19

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