  We performed a series of 3D N-body simulations where the initial conditions
were chosen to get two sets of models; unbarred and barred ones. In this work,
we analyze the growth of spirals and bar structures using 1D, and 2D Fourier
Transforms FT methods. Spectrograms and diagrams of the amplitude of the
Fourier coefficients as a function of time, radius and pitch angle show that
the general morphology, of our modeled galaxies, is due to the superposition of
structures which have different values of pitch angle and number of arms. Also,
we made in barred models a geometric classification of orbits from the bar
reference frame showing that the barred potential and the Lagrangian points
$L_4$ and $L_5$ catch approximately one-third of the total disk mass.
