RESEARCH ARTICLE


Dynamic Investigation of an Ancient Masonry Bell Tower with Operational Modal Analysis - A Non-Destructive Experimental Technique to Obtain the Dynamic Characteristics of a Structure



Dora Foti1, *, Salvador Ivorra Chorro2, Maria Francesca Sabba3
Technical University of Bari, Department of Civil Engineering and Architecture,Via Orabona 4, 70125 Bari, Italy.
University of Alicante, Department of Construction Engineering, Apartado de Correos 99, 03080 Alicante, Spain.
Civil Engineer, Bari, Italy


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Creative Commons License
© Foti et al.; Licensee Bentham Open

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Technical University of Bari, Department of Civil Engineering and Architecture,Via Orabona 4, 70125 Bari, Italy.Tel: +39-080-5963771; Fax: +39-080-5963719; E-mail: d.foti@poliba.it


Abstract

This paper shows the results of an experimental analysis on the bell tower of “Chiesa della Maddalena” (Mola di Bari, Italy), to better understand the structural behavior of slender masonry structures. The research aims to calibrate a numerical model by means of the Operational Modal Analysis (OMA) method. In this way realistic conclusions about the dynamic behavior of the structure are obtained. The choice of using an OMA derives from the necessity to know the modal parameters of a structure with a non-destructive testing, especially in case of cultural-historical value structures. Therefore by means of an easy and accurate process, it is possible to acquire in-situ environmental vibrations. The data collected are very important to estimate the mode shapes, the natural frequencies and the damping ratios of the structure.

To analyze the data obtained from the monitoring, the Peak Picking method has been applied to the Fast Fourier Transforms (FFT) of the signals in order to identify the values of the effective natural frequencies and damping factors of the structure. The main frequencies and the damping ratios have been determined from measurements at some relevant locations. The responses have been then extrapolated and extended to the entire tower through a 3-D Finite Element Model. In this way, knowing the modes of vibration, it has been possible to understand the overall dynamic behavior of the structure.

Keywords: Bell tower, Dynamic behavior, Environmental vibration, Masonry structure, OMA.