How to get the uncoupled natural frequencies

Hello Everybody,

A wing was simplified with 8 dumbbelss or concentrated mass. The weight of the 8 dumbbells are:

{W}=[1.240 1.050 0.964 0.862 0.733 0.628 0.634 0.457]T

The static unbalance is:

{SA}=[0.2680 0.2910 0.1810 0.1610 0.1220 0.0884 0.0854 0.0598]T

The moment of inertia is:

{IA}=[0.412 0.437 0.272 0.230 0.157 0.143 0.115 0.055]T

The flexibility  influence coefficience for torsional and bending shape is also known, using [CTT] and  [CZZ] for torsion and bending respectively.

The Mass matrix is diagonal:

[M]=[IA SA / SA W]

This is 16*16 Matix.

The stiffness Matrix:

[K]=[CZZ 0 / 0 CTT]-1

The characteristic equation is

([A]-λ[I]){Z}=0, where A=M-1K, Z is displacement.

An eigenvalue subroutine is called to extract the eigenvalues. However, wrong results are obtained.

Because I am new guy in CSD, not sure  that whether the way to creating the mass matrix and stiffness is correct or not. Any help for  the exact matrix for mass and stiffness would be thankful.

Jerry