Hello,

I am working in Abaqus and I want to run a modal analysis to compare the results with another structure software. This other software use a diagonal lumped mass matrix (DLMM) to resolve the eigenproblem (K-w²M)X=0. I would like to force Abaqus to use the same kind of matrix. I red that, in Abaqus, the default configuration for Euler bernoulli beam elements is a consistent mass matrix ( CCM) whereas the Timoshenko elements require a DLMM. But when I extract the mass matrix for the Timoshenko elements, the off-diagonal terms are not zero, there are around 10^-20. So this can't be a solution for me.

I also tried to define the mass nodes by nodes instead of defining a density for the material, I saw this method on the link "https://zxding.me/archives/d702tw.html"

. With this method, Abaqus returns me only the diagonal terms of the mass matrix but they are null. How can I do to use DLMM in Abaqus ?