Given a signal and its Fourier transform, we derive formulas for its polyphase decomposition in the frequency domain and for the reconstruction from the polyphase representation back to the Fourier representation. We present two frequency-domain implementations of the shift-invariant periodic discrete wavelet transform (SI-DWT) and its inverse: one that is based on frequency-domain polyphase de...

The random decrement (RD) technique is a time domain procedure, where the structural responses to operational loads are transformed into random decrement functions, which are proportional to the correlation functions of the system operational responses or can, equivalently, be considered as free vibration responses. This paper presents a general review on the application of the RD technique in ...

In this study, the structural performance of the gravity-type caisson structure is assessed from vibration-based system identification. To achieve the objective, the following approaches are implemented. Firstly, a structural identification algorithm based on the use of vibration characteristics is outlined. Structural stiffness and damping are selected as two key parameters to be identified fo...

The paper summarises the ambient vibration-based assessment of an historic suspension footbridge, dating back to 1928. The footbridge is characterised by the timber floor system supported by two couples of cables, that were recently replaced. After the retrofit, the actual structural behaviour of the bridge were assessed by experimental and theoretical methods. The field tests included geometri...

Operational modal analysis deals with the estimation of modal parameters using vibration data obtained from unknown or ambient excitation sources in operational rather than laboratory conditions. The paper compares three operational modal parameter identification approaches for identifying modal parameters of a multi-span concrete motorway bridge when subjected to either ambient or broad-band l...

spectral decomposition of time series has a significant role in seismic data processing and interpretation. since the earth acts as a low-pass filter, it changes frequency content of passing seismic waves. conventional representing methods of signals in time domain and frequency domain cannot show time and frequency information simultaneously. time-frequency transforms upgraded spectral decompo...

Traditional multicarrier techniques perform a frequency-domain decomposition of a channel characterized by frequency-selective distortion in a plurality of subchannels that are affected by frequency flat distortion. The distortion in each independent subchannel can then be easily compensated by simple gain and phase adjustments. Typically, digital Fourier transform schemes make the implementati...

In operational modal analysis process of the rotating machinery, it is always difficult to adopt usual modal analysis methods in parameter correction because of the modal parameter identification problems caused by harmonic modes. A technique to distinguish harmonic and structural modes is proposed here, that is, through frequency domain decomposition (FDD) of the vibration signals power spectr...

In this paper we compare the performance of different algorithms employed in solving frequency domain blind source separation of convolutive mixtures. The convolutive model is an extension of the instantaneous one and it allows to relax the hypothesis of a linear mixing process in which all the sources are supposed to reach the electrodes at the same time. This test is carried out in the freque...