Hey everyone, I want to ask about transformation of curves from dynamic time to frequency domain in plaxis 3D because I need it to calculate impedance functions ??
Information on this conversion used in PLAXIS is given in the scientific manual as follows:
Let there be an acceleration time history of size N, defined by a set of accelerations (may be other responses defined in the form of velocities or displacements), [a1,a2,a3,....., aN] recorded at time steps [t1, t2, t3,....., tN] with uniform sampling rate. On performing Fourier Transform on the given series, the time signature can be converted into frequency dependent Fourier spectra like [A1 + iB1, A2 + iB2, A3 + iB3,....., Am + iBM] against the frequency set of [f1, f2, f3,......, fM], where M is defined as follows:
The power spectra of the response may also be obtained as a set of against the frequency set of [f1, f2, f3,......, fM].The quantities angular frequency w, standard frequency f, and wave period T are related as follows:The fast fourier transform method reduces the multiplications required in the Fourier transform method. For detailed steps on how to do a Fourier transformation and then a fast Fourier transformation, you can consult mathematics books that explain these methods in detail.