2023, Contributo in volume, ENG
Azzara R.M.; Girardi M.; Padovani C.; Pellegrini D.
This chapter describes the experiments carried out on three medieval masonry towers in the historic center of Lucca, Italy. The towers have been continuously monitored by high-sensitivity seismic stations that record the structures' response to the dynamic actions of the surrounding environment. Special attention is devoted to the Guinigi Tower, one of the most iconic monuments in Lucca, whose monitoring campaign started in 2021. The goal of the chapter is to show the effectiveness of dynamic monitoring as a valuable source of information on the structural properties of the towers and sketch the capabilities of experiment-based finite element modeling.
2023, Contributo in volume, ENG
Girardi M.; Padovani C.; Pellegrini D.; Porcelli M.; Robol L.
This chapter presents the finite element code NOSA-ITACA for static and modal analyses of masonry structures of architectural interest. NOSA-ITACA adopts the constitutive equation of masonrylike materials, which considers masonry a non-linear elastic material with zero tensile strength. The capability of modelling restoration and consolidation operations makes the code a helpful tool for maintaining historical buildings. In recent years, long-term vibration monitoring turned out to be an effective non-destructive technique to investigate the dynamic behaviour and check the health status of historical buildings. Changes in their dynamic properties, such as natural frequencies, can represent effective damage indicators. The latest NOSA-ITACA developments are oriented towards structural health monitoring. The availability of the experimental modal properties of a structure makes it possible to calibrate its finite element model via model updating procedures. In particular, the unknown structure's characteristics, such as materials' properties and boundary conditions, can be determined by solving a minimum problem whose objective function is expressed as the discrepancy between experimental frequencies and mode shapes and their numerical counterparts. Several case studies are presented to show the main features of NOSA-ITACA and its effectiveness in the conservation of architectural heritage.
2023, Articolo in rivista, ENG
Pellegrini D.
Masonry vaults are widely employed in ancient constructions and play a crucial role in their static and dynamic behaviour. In the last decades, the scientific community has carried out, on the one hand, several experimental campaigns aimed at characterising the response of masonry vaults to horizontal actions; on the other, it has developed sophisticated numerical models able to catch the crucial features of their structural response. Within the framework of the SERA.TA project (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe), pre and post-diction contests have been organised to assess the capability of numerical methods to predict the seismic response of a 1:1 scale model of a masonry cross vault, realised and tested at LNEC laboratory (Portugal). This paper outlines the numerical analyses performed on two vault models within the pre and post-diction phase of the project. The numerical models have been created and analysed with NOSA-ITACA, a finite element software implemented at ISTI-CNR and devoted to the structural analysis of ancient masonry constructions. Pros and cons of the numerical simulations have been analysed, comparing the prediction and post-diction results with the experimental data in terms of accelerations, displacements, and crack patterns. Numerical results fit the experimental outcomes, and betterment is evident in the post-diction phase
2023, Articolo in rivista, ENG
Azzara R.M.; Girardi M.; Padovani C.; Pellegrini D.
This paper describes the experiments carried out on a medieval masonry tower in the historic centre of Lucca and some finite element numerical simulations of the tower's experimental response. The Guinigi Tower, one of the most iconic monuments in Lucca, has been continuously monitored by high-sensitive seismic stations that recorded the structure's response to the dynamic actions of the surrounding environment. The monitoring campaign results have been analysed to show the effectiveness of dynamic monitoring as a valuable source of information on the structural properties of the tower. The dynamic analyses of the tower and the surrounding palace subjected to some seismic events recorded during the experiments have highlighted the capabilities of experiment-based finite element modelling. The calibration of the finite element model and the numerical analysis have been carried out by resorting to procedures developed at ISTI-CNR and able to consider the nonlinear behaviour of masonry materials.
2023, Rapporto di ricerca (Research report), ENG
Pellegrini D.
Masonry vaults are widely employed in ancient constructions and play a crucial role in their static and dynamic behaviour. In the last decades, the scientific community has carried out, on the one hand, several experimental campaigns aimed at characterising the response of masonry vaults to horizontal actions; on the other, it has developed sophisticated numerical models able to catch the crucial features of their structural response. Within the framework of the SERA.TA project (Seismology and Earthquake Engineering Research Infrastructure Alliance for Europe), pre and post-diction contests have been organised to assess the capability of numerical methods to predict the seismic response of a 1:1 scale model of a masonry cross vault, realised and tested at LNEC laboratory (Portugal). This paper outlines the numerical analyses performed on some vault models within the pre and post-diction phase of the project. The numerical models have been created and analysed with NOSA-ITACA, a finite element software implemented at ISTI-CNR and devoted to the structural analysis of ancient masonry constructions. Pros and cons of the numerical simulations have been analysed, comparing the prediction and post-diction results with the experimental data in terms of accelerations, displacements, and crack patterns. Numerical results fit the experimental outcomes, and betterment is evident in the post-diction phase.
2022, Contributo in atti di convegno, ENG
Azzara R.M.; Cardinali V.; Girardi M.; Marini F.; Padovani C.; Pellegrini D.; Tanganelli M.
The paper presents the first results of an experimental campaign conducted on the Tower of Palazzo dei Vicari, in Scarperia, Italy. The Tower is a slender medieval structure located at the corner of the main façade of Palazzo dei Vicari. Over the centuries, both Tower and Palace have undergone several severe earthquakes; therefore, they have been reinforced with steel tie rods. In 2019 the structure was hit by the Mugello seismic sequence, which occurred between 9th December 2019 and the first half of January 2020. The mainshock was registered as 4.5 ML, with an epicenter 5 km far from the city of Scarperia. The earthquake was felt in Toscana and Emilia Romagna Regions and caused some damage in the area's cities. During the seismic sequence, two seismometers were installed on the Tower to record earthquakes and natural vibrations and evaluate the behavior of the structure under seismic loads. A second monitoring experiment has been more recently performed, in June 2021. Eight seismic stations were deployed along the height of the Tower, to achieve a complete dynamic identification of the structure. The ambient vibration tests before and after the seismic sequence made it possible to exclude the presence of damage and to calibrate the numerical model of the Tower via model updating techniques.
2022, Rapporto di ricerca (Research report), ENG
Azzara R.M.; Girardi M.; Padovani C.; Pellegrini D.
The paper presents the experimental investigations conducted on the carillon tower of the Santissimo Crocifisso Sanctuary in Castel San Pietro (Bologna, Italy) and the analysis of data collected by velocimeters and accelerometers installed on the structure. The main goal is to assess the effects of the swinging bells on the dynamic behaviour of the tower. The paper's novelty relies on the kind of structure monitored, and the approach followed. The structure is a rare example of a carillon tower, subjected to a careful measurement campaign never carried out before. Moreover, the experimental results are complemented by numerical simulations of the dynamic behaviour of the tower subjected to the action of a swinging bell.
2020, Editoriale in rivista, ENG
Palermo M.; Baraccani S.; Girardi M.; Pellegrini D.; Azzara R.M.
2020, Articolo in rivista, ENG
Girardi M.; Padovani C.; Pellegrini D.; Robol L.
Finite element model updating of a structure made of linear elastic materials is based on the solution of a minimization problem. The goal is to find some unknown parameters of the finite element model (elastic moduli, mass densities, constraints and boundary conditions) that minimize an objective function which evaluates the discrepancy between experimental and numerical dynamic properties. The objective function depends nonlinearly on the parameters and may have multiple local minimum points. This paper presents a numerical method able to find a global minimum point and assess its reliability. The numerical method has been tested on two simulated examples - a masonry tower and a domed temple - and validated via a generic genetic algorithm and a global sensitivity analysis tool. A real case study monitored under operational conditions has also been addressed, and the structure's experimental modal properties have been used in the model updating procedure to estimate the mechanical properties of its constituent materials.
2020, Articolo in rivista, ENG
Barsocchi P.; Bartoli G.; Betti M.; Girardi M.; Mammolito S.; Pellegrini D.; Zini G.
The recent developments of micro-electro-mechanical systems and wireless sensor networks allow today the use of low-cost and small-size sensors for continuous monitoring of civil structures. Both these features are very important for the low impact of the sensor grid in heritage structures, ensuring a low-cost and sustainable dynamic monitoring system. Over the last 20 years the use of sensor networks for continuous monitoring has received a growing interest. Anyway, still numerous questions remain opened about the sensitivity of measurement devices, the optimization of number and positioning of sensors, the energy efficiency of the network, and the development of algorithms for real-time data analysis. This paper, based on the aforementioned motivations, discusses about a monitoring system made of micro-electro-mechanical sensors connected through a wireless network. The architecture of the wireless sensor network and the automatized procedure proposed for the continuous processing of the recorded signals are discussed and described with reference to an explicative masonry tower case study. It is believed that the proposed technologies can provide an economical and relatively non-invasive tool for real-time structural monitoring and that, moreover, the availability of large amounts of data from actual measurements can give effective information on the structural behaviour of historic constructions.
2019, Articolo in rivista, ENG
Girardi M.; Padovani C.; Pellegrini D.; Porcelli M.; Robol L.
A novel method for performing model updating on finite element models is presented. The approach is particularly tailored to modal analyses of buildings, by which the lowest frequencies, obtained by using sensors and system identification approaches, need to be matched to the numerical ones predicted by the model. This is done by optimizing some unknown material parameters (such as mass density and Young's modulus) of the materials and/or the boundary conditions, which are often known only approximately. In particular, this is the case when considering historical buildings. The straightforward application of a general-purpose optimizer can be impractical, given the large size of the model involved. In the paper, we show that, by slightly modifying the projection scheme used to compute the eigenvalues at the lowest end of the spectrum one can obtain local parametric reduced order models that, embedded in a trust-region scheme, form the basis for a reliable and efficient specialized algorithm. We describe an optimization strategy based on this approach, and we provide numerical experiments that confirm its effectiveness and accuracy.
2019, Articolo in rivista, ENG
Girardi M.; Padovani C.; Pellegrini D.; Robol L.
This paper describes a model updating procedure implemented in NOSA-ITACA, a finite-element (FE) code for the structural analysis of masonry constructions of historical interest. The procedure, aimed at matching experimental frequencies and mode shapes, allows for fine-tuning the calculations of the free parameters in the model. The numerical method is briefly described, and some issues related to its robustness are addressed. The procedure is then applied to a simple case study and two historical structures in Tuscany, the Clock Tower in Lucca and the Maddalena Bridge in Borgo a Mozzano.
2018, Articolo in rivista, ENG
De Falco A.; Girardi M.; Pellegrini D.; Robol L.; Sevieri G.
Finite element modeling has become common practice for assessing the structural health of historic constructions. However, because of the uncertainties typically affecting our knowledge of the geometrical dimensions, material properties and boundary conditions, numerical models can fail to predict the static and dynamic behavior of such structures. In order to achieve more reliable predictions, important information can be obtained measuring the structural response under ambient vibrations. This wholly non-destructive technique allows obtaining very accurate information on the structure's dynamic properties (Brincker and Ventura (2015)).