ESTIMATION OF MODAL PROPERTIES OF STRUCTURES THROUGH AMBIENT EXCITATION MEASUREMENT USING CONTINUOUS WAVELET TRANSFORM METHOD

Continuous wavelet transform (CWT) has recently emerged as a promising tool for identification of modal properties such as natural frequencies, damping ratios and mode shapes through ambient excitation measurements of structures. This paper mainly discusses the capability of CWT method to identify the modal properties accurately using a practical application in a five storey reinforced concrete structure with masonry infills. Natural frequencies are identified by extracting windows paralleled to the frequency axis at wavelet ridges. Damping ratios are estimated using the wavelet-based logarithmic decrement method. They are further compared with the damping ratios obtained from the random decrement (RD) method. Furthermore, the mode shapes extracted using CWT method is compared with the results of the modal analysis. Finally, a conclusion can be drawn that the CWT used for the output-only system identification of ambient excitation structures yields a good agreement with results of the RD method and the finite element models.