5. Summary of results

We are interested in the first two hundred modes of the structure: these are located in band \(0–7\mathit{Hz}\).

We do find these frequencies with*Code_Aster* with a maximum difference compared to the reference solution of \(\text{1.7\%}\).

Four modes make it possible to obtain an cumulative effective mass according to \(x\) and \(y\) of \(\text{83.2\%}\). The cumulative effective mass following \(z\) is zero over the \(0–7\mathrm{Hz}\) frequency range. These effective mass balances are identical to those obtained with SAMCEF.

For the spectral modal seismic calculation, the displacements obtained are far from the reference solution. However, we can express some doubts about the validity of these reference results in spectral modal analysis, given the poor representation of the mass: in fact, for this reference calculation carried out with Castem2000, the cumulative effective mass in the \(x\) direction represents \(\text{43\%}\) of the total mass. This is why this part of the calculation was commented on in the test case.