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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 th...
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... results of the tests with the hammer were not consid- ered for the present study because the strokes were totally absorbed by the masonry of the adjacent church. Table 1 shows the significant frequencies obtained, that is the peak at 8.05 Hz in the E-W direction (T = 0.1227 s) and at 4.57 Hz in the N-S direction (T = 0.2188 s). ...
Citations
... For example, Teughels and Roeck [17] made an FE model of a concrete bridge, and Deng and Cai [18] partially modeled a concrete bridge by applying solid-type elements. As well as those, other several similar studies [19,20] carrying out the modelling of concrete structures thought the concrete material was homogeneous. Therefore, this study also applied the material properties of concrete as shown in Table 2. ...
This research article focuses on developing a baseline digital twin model for a wave power generator structure located in Yongsu-ri, Jeju-do, South Korea. First, this study performs a cause analysis on the discrepancy of the dynamic properties from the real structure and an existing simulation model and finds the necessity of modeling the non-structural masses and the environmental factors. The large amounts of the ballast are modeled in the finite element model to enhance the accuracy of the digital twin. Considering the influence of environmental factors such as tide level and wave direction, the added mass effect of structural members, one of the hydrodynamic effects, depending on the change of the ocean environments is calculated based on the rule of Det Norske Veritas and applied. The results indicate that non-structural mass components significantly impact the dynamic characteristics of the structure. Additionally, environmental factors have a greater effect on the dynamic behavior of the box-type structure compared to lightweight offshore structures.
... These small movements allow one to obtain vibration modes, i.e., different patterns in which the system tries to oscillate naturally, described by specific dynamic features, i.e., frequencies, mode shapes and damping ratios. Vibration modes can be tracked over time in a continuous or intermittent way for manifold objectives, including the calibration of realistic numerical models, the validation of strengthening interventions or the assessment of the structural conditions in preand post-seismic scenarios [29][30][31][32][33][34][35][36][37]. Characterizing ancient masonry constructions from a dynamic point of view allows a better interpretation of their structural behavior, which is complex and rather diverse, especially during earthquakes [19,38]. ...
The preservation and seismic risk mitigation of built cultural heritage is considered today as a major priority in the international political agenda. Among the great variety of heritage structures spread worldwide, masonry towers belong to one of the most vulnerable categories against earthquake actions due to their morphological and material singularity. The proper understanding of the structural behavior of these artefacts at the micro, meso and macro scales, combined with a thorough knowledge of the best analysis practices deriving from the shared experience of the scientific community working in this field, is a fundamental prerequisite to appropriately address their seismic assessment. In this context, the present work offers an extensive discussion on the major challenges that slender monumental towers pose in terms of characterization of their actual behavior under seismic actions. A critical appraisal of the principal analysis methods applicable to the study of these structures is also presented along with a brief review of the existing modelling strategies for their numerical representation. Relevant examples are discussed in support of each argument. In spite of being a relatively young discipline, earthquake engineering has made remarkable progress in the last years and appropriate modi operandi have been consolidating to tackle the seismic assessment of unconventional systems, such as slender heritage structures. The work is conceived in a format of interest for both practitioners and researchers approaching the seismic assessment of this type of structures, and for those in need of an overall practical review of the topic.
... In recent years, the Operational Modal Analysis (OMA) has become one of the most utilized techniques, leading to the identification of the unknown modal parameters of a building from the monitoring output-only analysis [1][2][3][4]. This procedure allows us to accurately evaluate in situ the actual behavior of the structures [5,6] in standard environmental conditions, without any applied force; for this reason, it is also used for buildings with monumental and historical value [7][8][9][10][11][12][13][14][15][16][17][18]. In fact, some recent studies [19][20][21][22] demonstrate that the knowledge of the modal parameters of the structure is essential for the evaluation of the seismic vulnerability and the effects of horizontal forces on structural parts and masonry infills during earthquakes. ...
This paper presents the experimental analysis on the “Municipal Headquarters” of Palagianello Town. This is a strategic building with a high complexity at planimetric and altimetric level, so it is interesting the evaluation of its structural dynamic performance in case of seismic emergency management. To this aim, environmental vibrations have been acquired in situ and accelerometers have been positioned in well-defined points. The data were analyzed with an easy and accurate process that includes the Operational Modal Analysis (OMA), to identify the natural frequencies, the mode shapes and the damping ratios with non-destructive testings. Subsequently, the experimental results were compared with those of two numerical models (with and without infill walls) defined by means of the finite element method (FEM); this allowed for better calibration of the model and to arrive at more realistic conclusions about the behavior of the structure. The paper discusses the influence of the stiffness contribution of masonry infills on the dynamic properties of the building. Moreover, it shows that the adoption of ad hoc chosen locations of the sensors could influence the accuracy of the experimental results, especially for structures characterized by irregularities.
... Values around 1 Hz or 2 Hz are usually found for all slender structures except columns, although great variability can be found depending on the boundary conditions (see 'Restraint' in Table 1) or the particularities of the element (e.g. [30,31]). ...
... Diaferio et al. [67] updated up to eleven parameters (stiffness of the springs, Young's modulus E values and densities of different materials) in the numerical model of the bell tower of Announziata (Corfu, Greece). Foti et al. [30] used elastic modulus and density for cyclopic masonry as updating parameters and added masses to account for non-structural elements. Casciati and Al-Saleh [69] installed a retrofit solution made of shape memory alloy wires based on the numerical model capturing the dynamic signature of the Soncino bell tower (Italy). ...
... Values around 1 Hz or 2 Hz are usually found for all slender structures except columns, although great variability can be found depending on the boundary conditions (see 'Restraint' in Table 1) or the particularities of the element (e.g. [30,31]). ...
... Diaferio et al. [67] updated up to eleven parameters (stiffness of the springs, Young's modulus E values and densities of different materials) in the numerical model of the bell tower of Announziata (Corfu, Greece). Foti et al. [30] used elastic modulus and density for cyclopic masonry as updating parameters and added masses to account for non-structural elements. Casciati and Al-Saleh [69] installed a retrofit solution made of shape memory alloy wires based on the numerical model capturing the dynamic signature of the Soncino bell tower (Italy). ...
The scientific community is hardly working to propose reliable methodologies of analysis and non-invasive technologies of investigation to assess the current state of conservation of historic buildings to verify their ability to resist future threats. These structures, mostly made of masonry, are difficult to assess due to the heterogeneity of materials and their mechanical behavior, but it is vital to preserve this invaluable cultural heritage by suitable structural assessment techniques. A great deal of research attention has been paid to monitoring their structural health; in many recent publications new advanced technological methods have been provided such as cheaper sensors, wireless connections, non-contact surveys and continuous monitoring. A bibliometric study has shown that more than half of the papers on Structural Health Monitoring (SHM) and Nondestructive Testing (NDT) on masonry have been published between 2018 and 2020, and 30% of those published in 2020 were on ‘slender’ elements like towers, chimneys or minarets. This paper presents a wide-ranging review of static and dynamic studies published on SHM and NDT of slender masonry structures summarizing and discussing the different experimental techniques used. With respect to the dynamic testing, Operational Modal Analysis (OMA) by accelerometers is the mostly frequent used technique by scholars, but other promising methods such as radar interferometry are also reported. This overall discussion is concluded with a short review of some examples on numerical structural health assessment and signal processing tools. An inclusive list of papers is provided describing the most important slender masonry structures characteristics, natural frequencies, experimental and numerical techniques employed and reference values. This paper, set on a practical perspective, is expected to be of interest to those researchers and practitioners who require an extensive and up-to-date review of this topic.
... In this way it is possible to apply simplified boundary conditions instead of modeling the entire adjacent structure". Some examples are [43,44] and [38]. To evaluate the calibrated parameters in the time domain, the real and the numerical response of the tower for the experimental test were compared (Fig. 5), the results of which verified the calibration of the finite element (FE) model in the time and frequency domains [45]. ...
Recent years have seen a growing interest toward implementation and testing of structural health monitoring techniques for cultural heritage structures, and many scientific papers report on the application of operational modal strategies as an effective knowledge-based tool for vulnerability reduction of masonry buildings. Focusing on historic masonry bell-towers, being such structures particularly prone to earthquake-induced damage, the most part of the studies discuss structural monitoring and vibration-based identification methods with the goal of their seismic protection. As a consequence, while there is great number of researches that investigate masonry towers behaviour under earthquake loads, only a few scientific papers discuss their structural response under service loads such as bell-loads. This issue is also of paramount importance, since in many real cases the bell-ringing has been stopped due to the dynamic interaction phenomena that are activate between the bells and the host structure. With the aim to contribute of improving the knowledge in this field, this paper focuses on a methodology for the study of the dynamic interaction between bells and slender masonry towers. The proposed methodology is divided into four phases: (i) Geometric and structural characterization of the tower and bells; (ii) Evaluation of the dynamic forces generated by the swinging bells; (iii) Experimental campaign to characterize the dynamic properties of the tower by means of operational modal analysis; (iv) Parametric finite element analysis. To illustrate the methodology, a real case of masonry bell-tower in which bell-ringing had to be stopped due to a history of strong vibrations is discussed. The paper includes a method of analysing the dynamic properties of masonry bell-towers, in which the dynamic interaction between the harmonic bell forces and the fundamental tower modes is analysed by means of a calibrated numerical model and the dynamic amplification factor.
... e choice of using an operational modal analysis method derives from the necessity to know the modal parameters of a structure with a nondestructive testing method, because the structures have cultural historical value. e technique allows the possibility to extract the modal parameters (natural frequencies, mode shapes, and damping ratios) from output-only experimental data obtained by mean of ambient vibration testing [23]. In this technique, the loads are unknown and the modal identification has to be carried out based on responses only [24]. ...
Timber-framed masonry structures are known as an effective earthquake load resisting system in high seismicity regions such as Bursa, Turkey. Intense earthquakes have occurred throughout history; however, many of the traditional timber structures have been able to survive without significant damage until the present day. In this study, six historic two-storied timber-framed masonry structures dating from the nineteenth century in Bursa City are investigated by using laboratory and in situ structural health monitoring tests. Although the houses have the same construction techniques, different masonry infill materials are used inside the timber frames. Stone, adobe, and brick are used as infill materials. Mud and lime mortars are used as binding materials. Mud mortar is used with stone and adobe materials. Lime mortar is used with brick material. The physical, mechanical, and dynamic parameters such as density, specific gravity, porosity, elastic modulus, frequencies, mode shapes, and damping ratios of the studied structures were investigated and the results were comparatively discussed. It is understood that the use of different infill materials affects the dynamic behaviors of these structures.
... The techniques, developed for a model updating process and also utilized in some recent studies [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], estimate the unknown mechanical properties of the materials and/or the boundary constraints by comparing the identified and the numerical modal parameters and minimizing specific objective functions. ...
... 5a-d and e-h, respectively) illustrate the situation for the bounded and isolated towers, respectively. The points in each case are very close to the empirical functions but it is worth to notice an anomaly for the bounded towers' group with respect to the (20) Maddelena's Cathedral [14] (A-point in 5a-d). In this case, the estimated frequency is highly different from the others obtained in similar cases, this circumstance may be due to various factors that are not easily identifiable and whose evaluation is beyond the scope of the present paper. ...
... The determination coefficient is equal to 0.95, while MSE is equal to 0.035. In this case, Shakya et al. law [4] gives a MSE more than 2 times the one of Eq. (14). In order to evaluate the performance of the obtained formulation, the natural frequencies evaluated by means of Eqs. ...
The aim of the paper is to perform a preliminary assessment of the dynamic behavior of the bell tower of Basilica Church “S.S. Medici”, one of the most important church in the town of Bitonto, Bari, Italy. The tower is 55 m tall and it is made in reinforced concrete. It is totally disconnected from the main structure of the Church. The structural behavior of the tower has been investigated by performing dynamic experimental tests, which have been executed in two different forcing conditions: recording the vibrations induced only by ambient loads, and, then the ones due to ambient loads and to the excitation produced by the bells. Four bells are housed in the lower bell chamber on a concrete bell frame, four more bells are housed at a higher level bell frame. All the bells are directly connected to the tower and swing in the same direction, so that their movement introduces a dynamic excitation on the tower. The experimental records have detected excessive movements on the tower when the bells swing.
... In particular, the first and second rows (i.e. 5 a-d and 5 e-h, respectively) illustrate the situation for the bounded and isolated towers, respectively. The points in each case are very close to the empirical functions but it is worth to notice an anomaly for the bounded towers' group with respect to the (20) Maddelena's Cathedral [19] (A-point in 5 a-d). In this case, the estimated frequency is highly different from the others obtained in similar cases, this circumstance may be due to various factors that are not easily identifiable and whose evaluation is beyond the scope of the present paper. ...
... The technique utilized in presence of an unknown environmental force is the operational modal analysis (OMA). It has been successfully applied in slender structures such as towers [4][5][6][7][8][9][10][11], chimneys [12], minarets [13][14] and bridges [15][16] in order to determine their dynamic characteristics (i.e. natural frequencies and mode shapes). ...
The new cable-stayed bridge built for the North-South axis road of Bari in order to overpass the railway of RFI and Ferrotramviaria s.p.a. has been recently built and opened to the traffic. The bridge is 626 m long and the central cable-stayed bays have a total length of 225 m. They are supported by cables connected to a central upside down Y-shaped pylon. The peculiarity is that this column is about 60° rotated with respect to the axis of the bridge deck. A dynamic load tests was developed previously to open the bridge to conventional traffic. 26 piezoelectric accelerometers have been utilized in different positions of the cables-stayed bays to record the accelerations produced by environmental forces and by the impact produced by a loaded truck passing over a bump. Operational Modal Analysis has been applied by mean of Artemis software to determine the first fundamental frequencies and the mode shapes. The main frequency of this non-symmetric pylon is the main frequency of all the stayed bridge.
