1,721,039 research outputs found
Investigation strategy for structural assessment of historic towers
Full text linkHistorical masonry towers are relevant architectural heritage often in a strategic position within city centres. Their height and position require specific controls in order to define the state of preservation. The paper describes the investigation procedures developed by the authors in selected case studies. According to the timing and to the complexity of the structure, the approach requires preliminary visual inspections, geometric, crack pattern survey supplemented by historical research and stratigraphic survey. Operational modal testing evaluates the overall structural behaviour, indicating eventual local (or global) problems to study in depth by monitoring or further local tests. Emergency operations, such as controls after earthquakes, could require prompt procedures. In this case, the combination of visual inspection, geometric and damage survey with dynamic testing is a reliable procedure for structural assessment. Additional investigation increases the knowledge of local problems or gives information for further activity such as structural modelling. For instance, relevant data are the evaluation of the masonry quality or the control of the local state of stress to estimate through non-destructive or minor destructive testing in selected positions. Nevertheless, such activities require accurate projects of the investigation too, planning and localising several tests in order to solve the problems detected in the preliminary steps of the diagnosis process
The rural architectonic heritage of the province of Mantua and the 2012 earthquake: Chronicle of a death foretold
No full textThe research concerns the study of the rural architectonic heritage in the Mantua province damaged by the seismic sequence started on May 2012. Within each investigated complex, the analysis starts with the identification of the main building, structural and material typologies and the reconstruction of the recursive interventions occurred in time. These preliminary steps are fundamental for the recognising of potential weaknesses affecting the seismic response. The rural heritage in the area is arranged around courtyards and is composed by different building types: the residential building, the stable, the “barchessa” for the storing of goods and animals, one of more small building for specific activity (e.g. warehouse, woodshed, etc.). Each building type has a specific function but also clear architectonic and structural layout. Furthermore, the agriculture recent evolution has involved changes in the use of the buildings and then, important building transformations. In particular, the agricultural machinery has required wider space but also a decreasing of the number of farmers. The result of the process is the partial or complete neglecting of several rural buildings. The following steps of the research involved a survey of selected case studies, some of them of meaningful historical and cultural importance; the study focused on the evaluation of the structural damage, recognising, when possible, the state of preservation before the earthquake, the common damage mechanism and the local vulnerabilities. The aim is both the catalogue the failures and the suggesting of possible interventions to reduce the seismic risks. This last item is strategic, bridging the safety requirements with the preservation issues respectful the historical architecture. Further observations involved the post seismic interventions for the safety of structure, some of them positive and other negative
Structural diagnosis of the architectural heritage: The key role of historical research
No full textModern approach to the diagnosis and structural assessment of historic structure involves several aspects, including information resulting from historic documentation. This item is normally far from the traditional procedures for the structural assessment. Nevertheless, the recent versions of the Italian seismic code require the collection of specific historical information to include in the seismic analysis. In fact, the damage surveyed after the 1997-98 earthquakes documented several brittle structural failures due to defects related to the building transformations. When not considered in the intervention, lack of restrains between masonry portions, fragmentary masonry portions or changes of the building technology can trigger damage but also collapse. The paper focuses the main information resulting from bibliographic and historical research based on available source. Furthermore, the paper underlines the importance of a continuous and direct comparison between the collected data and the building itself. The recognizing of potential discontinuities or irregularity of the structural layout, in fact, could require the planning of further controls to support the safety assessment and analysis
Galleria degli Antichi and Palazzo Giardino at Sabbioneta: Remarks from archive research and direct survey
No full textThe paper focus on two historical building, the Galleria degli Antichi and Palazzo Giardino at Sabbioneta, the capital of the duchy of Vespasiano Gonzaga, included in the UNESCO Word Heritage list in 2008, along with the city of Mantua. Sabbioneta was built in the 16th century in about 35 years, transforming the existing fortification and the traces of the ancient settlements into an Ideal City, recognisable as one of the higher examples of the Renaissance principles in urban planning. After the death of the Duke Vespasiano Gonzaga in 1591, the town was neglected for long time with positive and negative outcomes. From one side we can observe few changes in the general urban layout; from the other sides the single buildings underwent maintenance problem. The “Galleria degli Antichi”, the Gallery of the Ancients, built between 1583 and 1584 to host the art collection of the Duke, and connected through a flyover passage to a former building, “Palazzo Giardino”. The sequence of the recent interventions, which are affecting the present state of preservation of the buildings, is presented and discussed. The research was carried out through an accurate comparison of the archive documents and the direct inspection of the buildings. The investigation of the architectural complex included geometrical survey, analysis of the materials, of their decay, of the building technique and of the structural condition. An important step of the research is the evaluation of the building evolution in the XX century, resulting from the different interventions, uses and ownerships
Investigation strategy for the structural assessment of historic towers
No full textHistorical masonry towers are relevant architectural heritage often in strategic position within the city centres. Their height and position require specific controls in order to define the state of preservation. The paper describes the investigation procedures developed by the Authors in selected case studies. According to the timing and to the complexity of the structure, the approach requires preliminary visual inspections, geometric, crack pattern survey supplemented by historical research and stratigraphic survey. Operational modal testing evaluates the overall structural behaviour, indicating eventual local (or global) problems to study in deep by monitoring or further local tests. Emergency operations, like controls after earthquakes, could require prompt procedures. In this case, the combination of visual inspection, geometric and damage survey with dynamic testing is a reliable procedure for the structural assessment. Additional investigation increases the knowledge of local problems or gives information for further activity like structural modelling. For instance, relevant data are the evaluation of the masonry quality or the control of the local state of stress to estimate through non-destructive or minor destructive testing in selected positions. Nevertheless, such activities require accurate projects of the investigation too, planning and localising the several tests in order to solve the problems detected in the preliminary steps of the diagnosis process
Continuous Dynamic Monitoring to Enhance the Knowledge of a Historic Bell-Tower
Full text linkThe results of the long-term vibration monitoring program, carried out on the bell-tower of Santa Maria del Carrobiolo in Monza (Italy), are reported in the paper. The dynamic monitoring was motivated by the weak structural layout of the historic building, with two fronts of the tower being supported by the load-bearing structures of the apse and South aisle of the adjacent church. Furthermore, closely spaced modes with similar mode shapes were clearly identified from ambient vibration tests, hence, the modal parameters of the bell-tower significantly differ from those obtained in past experimental studies of similar masonry structures. The continuous dynamic monitoring was mainly aimed at enhancing the knowledge of the historic structure, checking the possible evolution of the key resonant frequencies and assessing the effects of changing temperature on the dynamic characteristics of the bell-tower. The main results of the dynamic monitoring for a period of two years highlight distinctive behavior of the bell-tower, such as the frequency veering exhibited by the lower modes with increased temperature. Subsequently, in order to mitigate the effects of the environmental factors on resonant frequencies, the application of the multiple linear regression (MLR) and the principal component analysis (PCA) tools have been investigated
Detecting and localizing anomalies on masonry towers from low-cost vibration monitoring
No full textThe structural health of masonry towers can be monitored by installing few accelerometers (or seismometers) at the top of the building. This cost-effective setup provides continuous and reliable information on the natural frequencies of the structure and allows to detect the occurrence of structural anomalies; however, to move from anomaly detection to localization with such a simplified distribution of sensors, a calibrated numerical model is needed. The paper summarizes the development of a Structural Health Monitoring (SHM) procedure for the model-based damage assessment in masonry towers using frequency data. The proposed methodology involves the subsequent steps: (i) preliminary analysis including geometric survey and ambient vibration tests; (ii) FE modeling and updating based on the identified modal parameters; (iii) creation of a Damage Location Reference Matrix (DLRM) from numerically simulated damage scenarios; (iv) detection of the onset of damage from the analysis of the continuously collected vibration data, and (v) localization of the anomalies through the comparison between the experimentally identified variations of natural frequencies and the above-defined DLRM matrix. The proposed SHM methodology is exemplified on the ancient Zuccaro tower in Mantua, Italy. Pseudo-experimental monitoring data were generated and employed to assess the reliability of the developed algorithm in identifying the damage location. The results show a promise toward the practical applications of the proposed strategy for the early identification of damage in ancient towers
OMA-based structural health monitoring of historic structures
Full text linkStructural Health Monitoring (SHM) is generally defined as a multi-disciplinary process involving: (a) the repeated or continuous measurement of the response of a structural system through arrays of appropriate sensors; (b) the extraction from measured data of features, which are representative of the health condition and (c) the statistical analysis of these features to detect any novelty or abnormal change in the investigated system. Among the different SHM strategies, the fully non-destructive nature and the minimum impact of the vibration monitoring makes the OMA-based approach especially suitable to address the preservation of Cultural Heritage structures and also to avoid, in some cases, inappropriate strengthening interventions. In the paper, the main ideas of OMA-based SHM of historic structures are presented and exemplified through the application to both relatively simple and very complex buildings, such as towers and cathedrals
Determining and Tuning Models of a Masonry Bridge for Structural Assessment
Full text linkThe paper describes a procedure aimed at developing FE models suitable to the seismic assessment of masonry viaducts. The modeling strategy is based on architectural research, non-destructive or minor-destructive tests, operational modal testing and surrogate-based model updating. In more details, the adopted methodology involves the following steps: (i) preliminary investigations including historical research, geomatic survey and local tests on materials; (ii) operational modal testing and analysis; (iii) FE modeling based on the available geometry and selected assumptions; (iv) choice of the uncertain structural parameters of the FE model; (v) identification of the optimal parameters by minimizing the difference between the model responses and the experimental responses using surrogate models. The 19th-century Olla bridge (Gaiola, Italy) is used to exemplify the proposed approach. The investigated structure turns out to be of special interest because the use of a limited number of sensors allows the identification of a relatively large number of normal modes. Consequently, the installation of a dynamic monitoring system on the bridge has been scheduled
Effects of changing temperature in the vibration-based model updating of a masonry bridge
No full textFE model updating of structures is commonly based on the modal parameters evaluated in a single vibration test. Nevertheless, the influence of changing temperatures on modal parameters – especially on natural frequency – is well known. The paper presents an investigation on the effects of (temperature-induced) frequency variations on the estimate of the elastic properties of a historical masonry bridge. Firstly, documentary research, geometric survey, minor destructive tests and ambient vibration tests were performed. Subsequently, the numerical model of the masonry bridge is developed based on the collected data, and the updating procedure is performed by using the two sets of modal parameters identified in July 2018 (average temperature 30.4°C) and April 2021 (average temperature 13.2°C). The results show that the (temperature-induced) frequency decrease seems to affect more significantly the estimate of the Young’s modulus of spandrels and backing
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