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Tesi etd-11192009-192500


Thesis type
Tesi di dottorato di ricerca
Author
MENGOZZI, MASSIMO
URN
etd-11192009-192500
Title
APPLICATION OF A WAVELET BASED METHODOLOGY FOR STRUCTURAL DYNAMIC IDENTIFICATION IN HISTORICAL MASONRY STRUCTURES
Settore scientifico disciplinare
ICAR/09
Corso di studi
SCIENZE E TECNICHE DELL'INGEGNERIA CIVILE
Commissione
tutor Prof. Croce, Pietro
correlatore Prof. Luise, Marco
Parole chiave
  • operational modal analysis
  • historical masonry structures
  • experimental dynamic
  • experimental modal analysis
  • edge effects
  • dynamic analysis
  • damping detection via CWT
  • wavelet transform
Data inizio appello
18/12/2009;
Consultabilità
parziale
Data di rilascio
18/12/2049
Riassunto analitico
This thesis deals with the problem of dynamic tests in historical masonry structures via<br>a multidisciplinary approach: the basic classical background of structural engineering<br>meets and supplements itself via classical and advanced signal processing tools, typical of<br>other branches of engineering. In particular in this work together with the classical fast<br>Fourier transform (FFT) based algorithm for modal parameters&#39;extraction, a newer, more<br>advanced and quite well established as well tool based on wavelet transform is experienced.<br>Reecting its interdisciplinary nature this thesis is made up of two main parts: the former<br>more analytical and numerical in which some theoretical and practical aspects related with<br>the application of wavelet transform for modal parameter extraction are faced out and the<br>latter, purely experimental, in which the methodology is used for studying two historical<br>masonry structures, a bell tower built in XIII century and a multispans arch bridge built<br>at the end of XIX century. Both these structures, even if at different scales, can be<br>considered as belonging to the cultural heritage of their area. This thesis is organized as pointed out in the following:<br>Chapter 1 sketches out the aims and objectives of the present work;<br>Chapter 2 sketches some basics of integral transformations and introduces some<br>basic denitions and terminology common in wavelet analysis. The analytical properties<br>of a particular wavelet function, Gabor wavelet, are illustrated in detail, being<br>this function used for the analysis of the data collected during the dynamic tests;<br>Chapter 3 details some specicities of wavelet based analysis applied to structural<br>dynamic identification. In particular the inuence of edge-eects in the damping<br>coecient determination is introduced and studied;<br>Chapter 4 introduces the rst case study, the Bell tower of St. Niccola&#39;Church<br>in Pisa. Due to the extensive study carried out on this structure this case study<br>is split in two distinct chapters, this being the former. This chapter focuses on<br>the geometrical surveys and on the historical research on materials used in the<br>construction. Both these information were essential for the preliminary numerical<br>model;<br>Chapter 5 describes the way dynamic tests were carried out on the Bell tower of<br>St. Niccola and details the main results achieved. Then it illustrates results of<br>static analysis performed on the calibrated numerical model for evaluating reliable<br>stresses on the materials and on the ground;<br>Chapter 6 describes the second case study, the main Vara bridge and the wide<br>dynamic tests campaign that was performed on it. Interesting results regarding the<br>time variability of equivalent viscous damping coecients and eigenfrequencies are<br>highlighted;<br>Chapter 7 summarizes the main results achieved in the present work.<br>The thesis is completed by two Appendixes labeled A and B that deepens the<br>properties of sensor used in both dynamic tests and the story of the Private Marble<br>Railway of Carrara, the Company leader in the past in marble blocks extraction that<br>at the end of XIX decided to build lots of infrastructures for marble transportation<br>modernization; among them the main Vara bridge.
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