1,721,005 research outputs found
Integrated Methodologies Based on Structural Health Monitoring for the Protection of Cutural Heritage Buildings
No full textIn the last decades the need for an effective seismic protection and vulnerability reduction of strategic structures and particularly the architectural heritage determined a growing interest in Structural Health Monitoring (SHM) as a measure of passive mitigation of earthquake effects. The object of monitoring is to identify, locate and classify type and severity of damages induced by external actions or degradation phenomena and to assess their effects on the structural performance. In this way it is possible to take appropriate measures to reduce the danger of collapse and, when necessary, perform strengthening interventions to improve the structural and seismic capacity.
Motivated by the above reasons, this thesis aims at providing a contribution to the development of techniques and integrated methodologies, based on SHM, for the assessment and protection of Cultural Heritage (CH) buildings and monuments.
Firstly, after a detailed state of the art review on specific topics related to SHM of civil engineering structures, a new methodology for the implementation of monitoring techniques on historic masonry structures is proposed. Selected case studies, equipped with distributed sensors and acquisition systems, allowed the definition and successive validation of SHM as a knowledge-based assessment tool, implemented to evaluate intervention needs, following an incremental approach during their execution, and to control the damage states of buildings in a post-seismic scenario.
In order to maximize the benefits of SHM and optimize the entire process, dedicated software for static monitoring and automated algorithms for modal parameters identification have been developed, able to provide almost real time information on the health state of the monitored structure.
Finally integrated procedures based on robust statistical and numerical models have been implemented to interpret and exploit SHM outputs to assess the structural conditions of the investigated CH buildings
Impact of sound-insulated joints in the dynamic behavior of Cross-Laminated Timber structures
Full text linkCross-Laminated Timber (CLT) has gained an increasing success and widespread diffusion among
wood products. Due to the novelty of the components and the dry-assembling techniques, certain
aspects of its behavior and performance remain unexplored; among these, the use of soundinsulated joints and brackets, along with their possible drawbacks on mechanical performance.
In this paper the authors discuss the results of dynamic identification (ID) tests carried out on
twin full-size CLT mockups (two-story), one of which was furnished with sound-insulation details
based on an elastomeric interlayer. Ambient (white noise and random excitations) and forced
vibration (mass shaker) tests were carried out to identify modal parameters.
The paper mainly aims at: i) assessing potential differences in the overall dynamic behavior of
the two mockups, likely due to the introduction of acoustic insulation, ii) detecting possible
drawbacks of insulation layers on mechanical performances, iii) increasing the knowledge about
dynamics of CLT structures.
The results of Operational Modal Analysis (OMA) are presented and the variations in the dynamics between the mockups are discussed. The construction of finite element (FE) models and
their calibration – with joint properties variations – are then presented. The outcomes revealed a
drop of modal frequencies values (at least 20 %) upon the introduction of elastomeric insulation,
whilst no significant alteration was observed in the mode shapes. Model updating based on the FE
models demonstrated that the dynamic response and the frequency variations were mostly
associated with wall-to-wall and wall-to-diaphragms joints, and hold-down connections
Dynamic Identification & Monitoring of the churches of St. Biagio and St. Giuseppe in l’Aquila
No full textIn the framework of a wide investigation campaign carried out by the authors - together with the Polytechnic of Milan - in the churches of St. Biagio d’Amiterno and St. Giuseppe dei Minimi, severely struck by the 6th of April 2009 earthquake, dynamic investigation (Operational Modal Analysis) and structural monitoring were employed in order to obtain a first snapshot of the dynamic characteristics of the aggregate buildings – also for model calibration purposes – and to control their dynamic features with the passing of time.
The st. Biagio church’s main damage was the collapse of the tympanum on top of the facade; other damages involved part of the central nave timber vault, the shallow domes of the lateral naves and some cracking of the pillars and of the apses. The rest of the structures showed an overall satisfying seismic performance. The oratory of St. Giuseppe dei Minimi reported higher – however localized - damage: the façade was subjected to a significant overturning mechanism towards the outside, as indicated by the wide cracks on the two side walls, close to the corners. Few other damage mechanisms were detected, such as shear damage in the façade and in the back wall of the apse. The complex is currently undergoing structural interventions, namely repair and seismic improvement, to correct their deficient - however globally satisfying - seismic performance.
The paper reports the outcomes of the ambient dynamic identification of the two churches (spring-fall 2010) and of some portions of the surrounding aggregate buildings, which showed - according to their different structural configuration - a marked different dynamic behavior, as well as the results of the first months of the structural static and dynamic monitoring (installed in Dec 2010), consisting of 6 accelerometers, 8 displacement transducers and two temperature and relative humidity sensors
Uncertainty quantification in structural health monitoring: applications on cultural heritage buildings
Full text linkIn the last decades the need for an effective seismic protection and vulnerability reduction of cultural heritage buildings and sites determined a growing interest in structural health monitoring (SHM) as a knowledge-based assessment tool to quantify and reduce uncertainties regarding their structural performance. Monitoring can be successfully implemented in some cases as an alternative to interventions or to control the medium- and long-term effectiveness of already applied strengthening solutions. The research group at the University of Padua, in collaboration with public administrations, has recently installed several SHM systems on heritage structures. The paper reports the application of monitoring strategies implemented to avoid (or at least minimize) the execution of strengthening interventions/repairs and control the response as long as a clear worsening or damaging process is detected. Two emblematic case studies are presented and discussed: the Roman Amphitheatre (Arena) of Verona and the Conegliano Cathedral. Both are excellent examples of on-going monitoring activities, performed through static and dynamic approaches in combination with automated procedures to extract mean- ingful structural features from collected data. In parallel to the application of innovative monitoring techniques, statistical models and data processing algorithms have been developed and applied in order to reduce uncertainties and exploit monitoring results for an effective assessment and protection of historical constructions. Processing software for SHM was implemented to perform the continuous real time treatment of static data and the identification of modal parameters based on the structural response to ambient vibrations. Statistical models were also developed to filter out the environmental effects and thermal cycles from the extracted features
SHM for historical buildings: preventive and post-earthquake controls
No full textStructural health monitoring (SHM) is being more and more applied in the study of cultural heritage (CH) buildings, as a key activity to increase the knowledge on their structural behavior and to have a deeper insight on their conditions. This knowledge allows to carry out with more confidence (and only if necessary) possible strengthening interventions, but also to prevent the execution of intrusive repair works, if they are not justified by an experimentally demonstrated worsening of the structural conditions. The use of monitoring systems applied under ordinary conditions and installed on CH structures allows to: (i) validate the functioning of the adopted structural models; (ii) identify the ongoing damaging processes; (iii) validate the effectiveness of the strengthening interventions. In case of a seismic event, SHM can furthermore prove its usefulness in order (i) to quantitatively evaluate the progression of the assessed damage pattern, (ii) to design effective and urgent interventions if an unsafe displacement patterns is recorded, (iii) to define an early warning procedure for the safety of the workers employed in the strengthening interventions. Monitoring can also be effective when implemented on seriously damaged buildings, if the time schedule for the interventions is difficult to be a priori planned. In this framework, the authors (University of Padova, Italy) in collaboration with the officer of the Cultural Heritage Authority, the university of Nagoya (Japan), the National Institute of the Conservation and Restoration (ISCR) designed and installed SHM systems on six representative and emblematic CH buildings in L’Aquila after the devastating earthquake occurred on the 6th of April 2009 in the Abruzzi Region. The selected case studies SHM systems – presented in the paper – will allow to confirm the effectiveness of the use of structural monitoring during and after the emergency activities in case of a seismic event
Structural health monitoring of historical buildings in Italy: applications and uncertainty overview
Full text linkStructural Health Monitoring (SHM) is currently more and more considered (and applied) in It- aly for the study of Cultural Heritage (CH) buildings, as a key activity to increase the knowledge on their structural behavior and to have a deeper insight on their actual conditions, reducing uncertainties connected to material properties and structural capacity. In recent years the research group at the University of Padua, in collaboration with public administrations, has installed several SHM systems on heritage structures: two case studies are presented and discussed within this paper. The Arena of Verona and the Cathedral of Conegliano are excellent examples of ongoing monitoring activities, performed through static and dynamic approaches. In parallel to the application of innovative monitoring techniques, statistical models and data processing proce- dures have been developed and applied in order to eliminate uncertainties and exploit monitoring results for an effective assessment and protection of historical constructions
Structural health monitoring: a tool for managing risks in sub-standard conditions
No full textIn the last decade the number of structural health monitoring (SHM) systems designed and implemented on historic structures increased exponentially. Monitoring perfectly meets principles and guidelines of the recently issued Italian and European seismic codes as it is considered a strategic activity in the knowledge process of historic buildings, in order to understand their structural behavior and have a deeper insight on their health conditions. Thanks to SHM it is possible to intervene on buildings with more confidence (and only when necessary), but also to prevent the execution of intrusive strengthening interventions, in full compliance with the minimum intervention principle, so important in the restoration field. The object of monitoring is to identify, locate and classify type and severity of damages induced by external actions or degradation phenomena and to assess their effects on the structural performance. In this way it is possible to take appropriate measures to reduce the danger of collapse and, when necessary, perform strengthening interventions to improve the structural and seismic capacity. Motivated by the above reasons, the paper provide a contribution to the application of integrated methodologies and techniques, based on SHM, for the assessment and protection of cultural heritage (CH) buildings and existing structures. Selected case studies, equipped with distributed sensors and acquisition systems, allowed the definition and successive validation of SHM as a knowledge-based assessment tool, implemented to: (1) avoid the execution of unnecessary interventions and assess structural vulnerabilities; (2) evaluate intervention needs, following an incremental approach during their execution; (3) control the damage states of buildings in a post- seismic scenario. Monitoring data, automatically processed through dedicated software for static monitoring and automated algorithms for modal parameters extraction, are then used for the assessment of the health conditions and the identification of active damaging processes based on numerical simulations and robust statistical models
New integrated knowledge based approaches to the protection of cultural heritage from earthquake-induced risk
No full textPotential damages on Cultural Heritage (CH) assets are currently too high, mostly due to their intrinsic vulnerability, and to the fact that most of the technologies applied to date are too intrusive, cost-inefficient, and often unreliable and/or non-effective. As so, the need to develop proper strategies to mitigate the risk associated with seismic vulnerability is unquestionable.
The Commission of the European Communities has recently funded a research project, Niker, which aims at developing an integrated methodology for the systemic improvement of the seismic behavior of CH assets and thus improving the general safety level and reducing the loss of artistic value.
The Niker project involves eighteen partners coming from twelve different countries, among which there are universities, research centres, governmental agencies and small and medium enterprises. In the present contribution, an overview of the main objectives and steps of the project is given
Structural Health Monitoring of the Roman Arena of Verona, Italy
No full textAncient structures - especially very old ones - prove their soundness and the correctness of their structural layout by reaching our days in relatively good conditions. This is the case of the Roman Arena in Verona, Italy, built in the I century A.D., and still standing in the historical centre of Verona, being the symbol of the city and open to public use for visits but also for operas, concerts and relevant shows. With a closer look however, it is possible to appraise the damages that the passing of time and the natural or man induced events such as historical earthquakes, floods or wars and sieges left on the structure. The past seismic events (induced serious damage on the Arena, being the cause of the almost complete collapse of the third (external) ring of the monument, today only remaining in the so called “ala” (wing) of the Arena, an isolated portion of stone blocks curved wall characterized by a repetition of arches and massive pillars.
With the purpose of evaluating the structural response of the Arena to static, dynamic (e.g. shows, concerts) and seismic loads, a Structural Health Monitoring system was installed in the Arena in 2011, with state of the art technology for the data recording in relevant positions of the Arena.
A detailed crack pattern survey was carried out in order to locate the main cracks of the structure, and Finite Elements models were employed to define the relevant modal parameters of the Arena: global modes were identified and thus - with a special focus on the wing - acceleration sensors were installed in the areas where significant dynamic amplifications are expected according to the FE modelling approach. Results of the SHM system will be employed for tuning the available behavioural models (FE, but also Limit Analysis), in order to trace the structural response of the monument for assessing the operational conditions and predicting the safety conditions of the Arena in the eventuality of a major earthquake
Structural Health Monitoring of historical buildings: preventive and post-earthquake controls
No full textStructural health monitoring (SHM) has been recently more and more exploited in the study of cultural heritage (CH) buildings, as a key activity to increase the knowledge on their structural behavior and to have a deeper insight on their conditions. This knowledge allows to carry out with more confidence and only if necessary a strengthening intervention, but also to prevent the execution of intrusive repair works, if they are not justified by an experimentally demonstrated worsening of the structural conditions.
The use of monitoring systems applied under ordinary conditions and installed on CH structures allows to: (i) validate the functioning of the adopted structural models; (ii) identify the ongoing damaging processes; (iii) validate the effectiveness of the strengthening interventions. The effectiveness of this approach is demonstrated by the installation of SHM systems on four important monuments in northern Italy (Verona Arena and the stone tomb of “Cansignorio della Scala” in Verona, the “Bertoliana” library in Vicenza and the church of S. Sofia in Padova) and on the Qutb Minar in New Delhi.
In case of a seismic event, SHM can furthermore prove its usefulness in order to: (i) evaluate quantitatively the progression of the damage pattern, (ii) design effective and urgent interventions if an unsafe displacement patterns is recorded; (iii) define an early warning procedure for the safety of the workers employed in the strengthening interventions. Monitoring can also be effective when implemented on seriously damaged buildings, if the time schedule for the interventions is difficult to be a priori planned. A low cost diffused monitoring system permits to proceed more urgently on selected cases, if a worsening of their structural conditions is noted, or to postpone the interventions in a successive phase, if the assessed damage pattern maintains an acceptable stability.
In this framework, the authors and the university of Padova in collaboration with the officer of the Cultural Heritage Authority, the university of Nagoya (Japan), the National Institute of the Conservation and Restoration (ISCR) and the Veneto region designed and installed SHM systems on six representative and emblematic CH buildings in l’Aquila after the devastating earthquake occurred on the 6th of April 2009 in the Abruzzo Region.
The selected case studies (S. Agostino church, S. Biagio church and S.Giuseppe oratory, S. Marco church, Civic Tower and Spanish Fortress) give the possibility to validate the use of monitoring during and after the emergency activities in case of a seismic event
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