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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
Supervisors
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
a multidisciplinary approach: the basic classical background of structural engineering
meets and supplements itself via classical and advanced signal processing tools, typical of
other branches of engineering. In particular in this work together with the classical fast
Fourier transform (FFT) based algorithm for modal parameters'extraction, a newer, more
advanced and quite well established as well tool based on wavelet transform is experienced.
Reecting its interdisciplinary nature this thesis is made up of two main parts: the former
more analytical and numerical in which some theoretical and practical aspects related with
the application of wavelet transform for modal parameter extraction are faced out and the
latter, purely experimental, in which the methodology is used for studying two historical
masonry structures, a bell tower built in XIII century and a multispans arch bridge built
at the end of XIX century. Both these structures, even if at different scales, can be
considered as belonging to the cultural heritage of their area. This thesis is organized as pointed out in the following:
Chapter 1 sketches out the aims and objectives of the present work;
Chapter 2 sketches some basics of integral transformations and introduces some
basic denitions and terminology common in wavelet analysis. The analytical properties
of a particular wavelet function, Gabor wavelet, are illustrated in detail, being
this function used for the analysis of the data collected during the dynamic tests;
Chapter 3 details some specicities of wavelet based analysis applied to structural
dynamic identification. In particular the inuence of edge-eects in the damping
coecient determination is introduced and studied;
Chapter 4 introduces the rst case study, the Bell tower of St. Niccola'Church
in Pisa. Due to the extensive study carried out on this structure this case study
is split in two distinct chapters, this being the former. This chapter focuses on
the geometrical surveys and on the historical research on materials used in the
construction. Both these information were essential for the preliminary numerical
model;
Chapter 5 describes the way dynamic tests were carried out on the Bell tower of
St. Niccola and details the main results achieved. Then it illustrates results of
static analysis performed on the calibrated numerical model for evaluating reliable
stresses on the materials and on the ground;
Chapter 6 describes the second case study, the main Vara bridge and the wide
dynamic tests campaign that was performed on it. Interesting results regarding the
time variability of equivalent viscous damping coecients and eigenfrequencies are
highlighted;
Chapter 7 summarizes the main results achieved in the present work.
The thesis is completed by two Appendixes labeled A and B that deepens the
properties of sensor used in both dynamic tests and the story of the Private Marble
Railway of Carrara, the Company leader in the past in marble blocks extraction that
at the end of XIX decided to build lots of infrastructures for marble transportation
modernization; among them the main Vara bridge.
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