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Gabriele S.,Third University of Rome | Spina D.,Seismic Risk Office | Valente C.,University of Chieti Pescara | De Leonardis A.,University of Chieti Pescara
Proceedings of ISMA 2010 - International Conference on Noise and Vibration Engineering, including USD 2010 | Year: 2010

Among the numerous identification methods available for operational modal analysis, the CPR (Complex Plane Representation) method proves efficient and effective in the case of sweep tests where the excitation is not measured. The CPR method has been described in a number of papers by the authors and allows for high precise identification of the modal parameters. In spite of this precision there exist cases where the approximations involved by practical applications need further clarification. The paper is devoted to estimate error bounds due to lack of congruence between the theoretical assumptions and the actual system characteristics or field conditions. The dependence of the amplitude and phase values on the modal density is crucial in this respect. Theoretical and numerical solution are used to validate the CPR results.


Gabriele S.,Third University of Rome | Spina D.,Seismic Risk Office | Iezzi F.,University of Chieti Pescara | Valente C.,University of Chieti Pescara
EESMS 2014 - 2014 IEEE Workshop on Environmental, Energy and Structural Monitoring Systems, Proceedings | Year: 2014

The paper aims to review and deepen the effects of the modal density in the dynamical identification with the Complex Plane Representation (CPR) method that is based on the Hilbert transform of the motion response of mechanical systems. It is demonstrated that the strong accuracy in the identification of the modal parameters with the CPR method can be somewhat corrupted for high modal densities. Theoretical and numerical solutions are used to analyze the problem and validate the CPR results. © 2014 IEEE.


Valente C.,University of Chieti Pescara | Spina D.,Seismic Risk Office | Gabriele S.,Third University of Rome | De Leonardis A.,University of Chieti Pescara
Civil-Comp Proceedings | Year: 2010

Modal parameters are often used for damage identification purposes in the dynamic field. Commonly, shifts in the modal parameters between different states are assumed as measures of damage. Frequency shifts are easily detected, but in some circumstances they are not sensible to damage. In spite of its imprecise identification, damping possesses generally a monotonic variation with damage. Modal shapes exhibit increasing complexity along with damping increase. Operational modal shapes are identified using the CPR method and used to construct indicators capable to detect damage. The effectiveness of the method and the indicators is shown against theoretical data and numerical simulation. © Civil-Comp Press, 2010.


Rainieri C.,University of Molise | Fabbrocino G.,University of Molise | Manfredi G.,University of Naples Federico II | Dolce M.,Seismic Risk Office
Proceedings of ISMA 2010 - International Conference on Noise and Vibration Engineering, including USD 2010 | Year: 2010

Operational Modal Analysis relies upon the fundamental assumption that input is unmeasured and consists of a Gaussian white noise characterized by a flat spectrum in the bandwidth of interest. If this assumption is not fulfilled, the modal identification process may fail due to spurious frequencies appearing in response spectra. It is often possible to identify such non-structural frequencies, but they can also sometimes bias estimates. This is basically the case of spurious harmonics close to structural modes. About civil structures, spurious frequencies can be due to rotating machines but also to interaction with adjacent constructions, as discussed herein, where natural frequencies of a given structure are mixed together with those ones due to interaction with similar close structures; as a result, response spectra are characterized by several close peaks in a narrow bandwidth. An integrated use of output-only techniques is proposed to discriminate modal from spurious frequencies and applied to a real test case.


Rainieri C.,University of Molise | Fabbrocino G.,University of Molise | Manfredi G.,University of Naples Federico II | Dolce M.,Seismic Risk Office
Engineering Structures | Year: 2012

A common assumption in the theoretical background of Operational Modal Analysis (OMA) methods concerns the input, which is not measured and consists of a Gaussian white noise characterized by a flat spectrum in the bandwidth of interest. Even if a number of applications have shown that OMA works also when the input spectrum is smooth enough, if this assumption is not fulfilled, the modal identification process may become more complex or even fail due to dominant frequency components of the input appearing in response spectra. Thus, specific techniques and strategies have to be applied to sort out structural dynamic properties from frequencies of the input. It is often possible to identify such non-structural frequencies in the case of spurious harmonics due to rotating equipment, but they can be erroneously identified as structural or even bias the estimates, for instance when such harmonics are close to structural modes. About civil structures, spurious frequencies can be due to rotating machines but also to interaction with adjacent constructions. In the present paper, attention is mainly focused on the issue of modes from surrounding structures appearing in the response of the structure under investigation. Thus, natural frequencies of a sample structure are mixed together with those due to interaction with similar surrounding structures, and its response spectra are characterized by several close peaks in a narrow bandwidth. In order to discriminate modal from spurious frequencies, an integrated use of output-only techniques is illustrated and applied to a real test case. An approach aiming at robust evaluation and monitoring of dynamic properties for fast post-earthquake emergency support is proposed and the experimental field validation is discussed in detail. © 2011 Elsevier Ltd.


Di Cesare A.,University of Basilicata | Ponzo F.C.,University of Basilicata | Nigro D.,University of Basilicata | Dolce M.,Seismic Risk Office | Moroni C.,Seismic Risk Office
Bulletin of Earthquake Engineering | Year: 2012

An extensive program of shaking table tests under the name Project JetPacs (Joint experimental testing on Passive and semi active control systems) has been developed with the goal of assessing the effectiveness of seven different passive and semi-active energy dissipating bracing (EDB) systems in controlling the seismic vibrations of framed buildings. The experimental program, carried out considering a 3D 1/1.5 scaled steel frame, was entirely funded by the Italian Department of Civil Protection as part of the RELUIS 2005-2008 project. The following article focuses on the experimental tests carried out considering only two EDB systems, based on hysteretic dampers (HD) and visco-recentring devices (SMA + VD) respectively. Specially shaped low carbon steel plates were used to provide hysteresis in the HD based devices, while the innovative SMA + VD visco-recentring system was made up of a combination of viscous dampers (VD) and shape memory alloy (SMA) wires. In this paper a displacement focused design procedure based on non linear static analysis has been proposed in order to evaluate the mechanical characteristics of both types of energy dissipating device. The aim of this design procedure is to limit inter-storey drifts after frame yielding. In order to assess the robustness of the design procedure and to evaluate the effects of the viscous and recentring components, two different sets of HD and SMA + VD devices characterized by slight alterations in the mechanical properties have been tested and compared. Finally, the experimental seismic response of the structure equipped with and without the HD and SMA + VD elements is reported and compared with numerical results obtained using non linear time history analysis. © 2012 Springer Science+Business Media B.V.


Dolce M.,Seismic Risk Office
Geotechnical, Geological and Earthquake Engineering | Year: 2010

The activities initiated after the Mw 6.3 Abruzzi Earthquake of April 6, 2010 can be distinguished in three phases: emergency, post-emergency and reconstruction. Although they are not exactly sequential, because of some overlapping between them, it is useful to use such a scheme, also in relation to the objective to be reached at the end of each of them. The management of the emergency and postemergency phases was relied upon a governmental commissioner, that, until January 31, 2010, was the chief of the Civil Protection Department. From February 1, 2010, a new commissioner was enforced, with the full responsibility of the reconstruction phase. In this paper the main problems and solutions dealt with in the three phases are described, with a main concern for engineering aspects. © Springer Science+Business Media B.V. 2010.

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