1,720,998 research outputs found
An automatic damage detection algorithm based on the Short Time Impulse Response Function.
No full textStructural Health Monitoring together with all the dynamic identification techniques and damage detection techniques are increasing in popularity in both scientific and civil community in last years. The basic idea arises from the observation that spectral properties, described in terms of the so-called modal parameters (eigenfrequencies, mode shapes, and modal damping), are functions of the physical properties of the structure (mass, energy dissipation mechanisms and stiffness). Damage detection techniques traditionally consist in visual inspection and/or non-destructive testing. A different approach consists in vibration based methods detecting changes of feature related to damage. Structural damage exhibits its main effects in terms of stiffness and damping variation. Damage detection approach based on dynamic monitoring of structural properties over time has received a considerable attention in recent scientific literature. We focused the attention on the structural damage localization and detection after an earthquake, from the evaluation of the mode curvature difference. The methodology is based on the acquisition of the structural dynamic response through a three-directional accelerometer installed on the top floor of the structure. It is able to assess the presence of any damage on the structure providing also information about the related position and severity of the damage. The procedure is based on a Band-Variable Filter, (Ditommaso et al., 2012), used to extract the dynamic characteristics of systems that evolve over time by acting simultaneously in both time and frequency domain. In this paper using a combined approach based on the Fourier Transform and on the seismic interferometric analysis, an useful tool for the automatic fundamental frequency evaluation of nonlinear structures has been proposed. Moreover, using this kind of approach it is possible to improve some of the existing methods for the automatic damage detection providing stable results also during the strong motion phase. This approach helps to overcome the limitation derived from the use of techniques based on simple Fourier Transform that provide good results when the response of the monitored system is stationary, but fails when the system exhibits a non-stationary behaviour. The main advantage derived from the use of the proposed approach for Structural Health Monitoring is based on the simplicity of the interpretation of the nonlinear variations of the fundamental frequency. The proposed methodology has been tested on numerical models of reinforced concrete structures designed for only gravity loads without and with the presence of infill panels. In order to verify the effectiveness of the proposed approach for the automatic evaluation of the fundamental frequency over time, the results of an experimental campaign of shaking table tests conducted at the seismic laboratory of University of Basilicata (SISLAB) have been used. Acknowledgements This study was partially funded by the Italian Civil Protection Department within the project DPC-RELUIS 2015 - RS4 ''Seismic observatory of structures and health monitoring''. References Ditommaso, R., Mucciarelli, M., Ponzo, F.C. (2012) Analysis of non-stationary structural systems by using a band-variable filter. Bulletin of Earthquake Engineering. DOI: 10.1007/s10518-012-9338-y
Damage assessment on framed structures through regression models retrieved by nonlinear numerical analyses
No full textNowadays, Structural Health Monitoring is certainly a topic of great interest both in the research and in the professional field as evidenced by the large number of applications and systems installed all over the world. A permanent monitoring system could be installed in order to identify a possible damage occurred on framed structures after moderate/destructive earthquake. Furthermore, it could be an useful tool for evaluating the service condition and the remaining service life of a structure. Most of simplified methods for structural damage detection are based on the evaluation of the dynamic characteristics evolution associated to the fundamental mode of vibration of a monitored structure. Particularly, the variation of parameters such as eigenfrequencies, equivalent viscous damping factors and modal and/or operational mode shapes has been evaluated and analyzed in order to identify structural damage. Methods based on frequency variation can be applied to detect damage, but they are not able to localize structural damage. Instead, to this aims, methods based on the evolution of modal shapes and/or of their derivatives such as mode curvatures could be more effective. Aim of this work is the improvement of an existing method for damage localization on framed structures based on the evaluation of the mode curvature change associated to the fundamental mode of vibration during an earthquake. The approach is based on the use of a nonlinear filter, the band-variable filter, able to extract the nonlinear response of each mode of vibration. The paper focuses also on the possibility to quantify the damage occurred on the monitored structure by considering the correlation among maximum value of mode curvature variation and the maximum inter-story drift. The regression model between these two parameters has been defined through nonlinear numerical models for different reinforced concrete framed structures designed for gravity loads only, with and without the presence of infill panels
Valutazioni preliminari su possibili fenomeni di interazione terreno-struttura rilevati nelle aree colpite dal sisma del 24/08/2016
No full textA holistic approach to long term SHM of transport infrastructures.
No full textIn the last years, the development of monitoring systems for critical transport infrastructures is gaining an increasing interest, as pointed out by the scientific literature and the significant number of recent research project regarding this specific topic. Therefore, as first topic, the present article discusses about the necessity of holistic approaches/visions that are based not only on the integration of different sensing technologies, but more important on a multidisciplinary approach encompassing
disciplines related to the sensing, ICT, positioning technologies and civil engineering to properly assess existing infrastructures. Afterward, this contribution will provide a brief survey of the different classes of sensing techniques of specific interest for the civil engineering. In this general frame, attention is also focused on the embedded miniaturized sensors, which have the main advantage to ensure an always updated long term monitoring and provide a more reliable early-warning system. Finally, it is
evident how the concepts here specifically considered for transport infrastructures can be easily extended to monitoring other kinds of critical infrastructures, urban areas (built environment) and cultural heritage
Damage Detection and Localization on Real Structures Subjected to Strong Motion Earthquakes Using the Curvature Evolution Method: The Navelli (Italy) Case Study
Full text linkIn recent years, structural health monitoring (SHM) has received increasing interest from both research and professional engineering communities. This is due to the limitations related to the use of traditional methods based on visual inspection for a rapid and effective assessment of structures and infrastructures when compared with the great potential offered by newly developed automatic systems. Most of these kinds of systems allow the continuous estimation of structural modal properties that are strictly correlated to the mechanical characteristics of the monitored structure. These can change as a result of material deterioration and structural damage related to earthquake shaking. Furthermore, a suitable configuration of a dense sensor network in a real-time monitoring system can allow to detect and localize structural and non-structural damage by comparing the initial and a final state of the structure after a critical event, such as a relevant earthquake. In this paper, the modal curvature evaluation method, used for damage detection and localization on framed structures, considering the mode curvature variation due to strong earthquake shaking, is further developed. The modified approach is validated by numerical and experimental case studies. The extended procedure, named "Curvature Evolution Method" (CEM), reduces the required computing time and the uncertainties in the results. Furthermore, in this work, an empirical relationship between curvature variation and damage index has been defined for both bare and infilled frames
Damage detection and quantification using mode curvature variation on framed structures: analysis of the preliminary results
No full textContinuous monitoring based on vibrational identification methods is increasingly employed for the evaluation of the state of health of existing buildings after strong motion earthquake. Different damage identification methods are based on the variations of damage indices defined in terms modal (eigenfrequencies, mode shapes, and modal damping) and/or non-modal parameters. Most of simplified methods for structural health monitoring and damage detection are based on the evaluation of the dynamic characteristics evolution associated to the fundamental mode of vibration of a monitored structure. Aim of this work is the upgrade of an existing method for damage localization on framed structures during a moderate/destructive earthquake. The existing version of the method is based on the comparison of the geometric characteristics (with particular reference to the mode curvature) exhibited by the structures, related to fundamental mode of vibration, before and during an earthquake. The approach is based on the use of a nonlinear filter, the band-variable filter, based on the Stockwell Transform able to extract the nonlinear response of each mode of vibration. The new version of the method provides the possibility to quantify a possible damage occurred on the monitored structure linking the mode curvature variation with the maximum inter-story drift. This paper shows the preliminary results obtained from several simulations on nonlinear numerical models of reinforced concrete framed structures, designed for only gravity loads, without and with the presence of infill panels. Furthermore, a correlation between maximum mode curvature difference and maximum inter-story drift has been defined for the different numerical models in order to quantify the structural damage. Acknowledgements This study was partially funded by the Italian Department of Civil Protection within the project DPC-RELUIS 2016 - RS4 ''Seismic observatory of structures and health monitoring'' and by the "Centre of Integrated Geomorphology for the Mediterranean Area - CGIAM" within the Framework Agreement with the University of Basilicata "Study, Research and Experimentation in the Field of Analysis and Monitoring of Seismic Vulnerability of Strategic and Relevant Buildings for the purposes of Civil Protection and Development of Innovative Strategies of Seismic Reinforcement"
Un approccio integrato per la localizzazione del danno su strutture sottoposte a terremoti di media e forte intensità
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