Earthquake-induced structural response output-only identification by two different Operational Modal Analysis techniques

2017 ◽  
Vol 47 (1) ◽  
pp. 257-264 ◽  
Author(s):  
Fabio Pioldi ◽  
Egidio Rizzi
Keyword(s):  
Modal Analysis ◽  
Structural Response ◽  
Operational Modal Analysis ◽  
Analysis Techniques ◽  
Output Only ◽  
Response Output

Brake Moan Noise Study through Experimental and Operational Modal Analysis Techniques in a Passenger Car

2017 ◽  
Author(s):  
Alexis Klauber Chaia Kléperon ◽  
Robson Demétrius Araújo Abreu ◽  
Rômulo Morais Bitencourt ◽  
Francis José Marochi Almeida
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Passenger Car ◽  
Analysis Techniques

Operational Modal Analysis of Aluminum Beams

2007 ◽  
Vol 50 (1) ◽  
pp. 74-85 ◽  
Author(s):  
S. Rudroju ◽  
A. Gupta ◽  
S. Yandamuri
Keyword(s):  
Modal Analysis ◽  
Impact Test ◽  
Force Measurement ◽  
Operating Conditions ◽  
Impact Testing ◽  
Operational Modal Analysis ◽  
Normal Functioning ◽  
Large Structures ◽  
Output Only ◽  
Ambient Excitation

Natural frequencies obtained by modal analysis are important to engineers interested in predicting the dynamic behavior of structures. Traditional modal analysis involves impact testing or shaker testing, where response signal and input force are measured to obtain the transfer function. However, for large structures, input excitation force measurement may be difficult, if not impossible. Large structures may be subjected to ambient excitation; operational modal analysis (OMA), also known as output-only modal analysis, has been used for extracting modal parameters of these types of structures. The main advantage of operational modal analysis is that no artificial excitation is needed, and the analysis is based on measurements of only the output data of the system. Operational modal analysis tests are performed under the actual operating conditions of the system without any change of boundary conditions; the tests use the ambient loads as input and thus do not interfere with the normal functioning of the system. In this study, six aluminum beams of different configurations (beams with and without cuts of various lengths) were used for conducting experiments. Results based on impact test, shaker test, and operational modal analysis are presented.

scholarly journals Transmissibilty-Based Operational Modal Analysis for Flight Flutter Testing Using Exogenous Inputs

2012 ◽  
Vol 19 (5) ◽  
pp. 1071-1083 ◽  
Author(s):  
Christof Devriendt ◽  
Tim De Troyer ◽  
Gert De Sitter ◽  
Patrick Guillaume
Keyword(s):  
Modal Analysis ◽  
Frequency Domain ◽  
Experimental Modal Analysis ◽  
Operational Modal Analysis ◽  
Modal Parameters ◽  
Input Output ◽  
Output Only ◽  
Flutter Testing

During the recent years several new tools have been introduced by the Vrije Universiteit Brussel in the field of Operational Modal Analysis (OMA) such as the transmissibility based approach and the the frequency-domain OMAX concept. One advantage of the transmissibility based approach is that the ambient forces may be coloured (non-white), if they are fully correlated. The main advantage of the OMAX concept is the fact that it combines the advantages of Operational and Experimental Modal Analysis: ambient (unknown) forces as well as artificial (known) forces are processed simultaneously resulting in improved modal parameters. In this paper, the transmissibility based output-only approach is combined with the input/output OMAX concept. This results in a new methodology in the field of operational modal analysis allowing the estimation of (scaled) modal parameters in the presence of arbitrary ambient (unknown) forces and artificial (known) forces.

Estimating Loads From Breaking Waves Using Operational Modal Analysis

2020 ◽  
Author(s):  
Michael Vigsø ◽  
Christos Georgakis
Keyword(s):  
Modal Analysis ◽  
Wave Breaking ◽  
Dynamic Properties ◽  
Structural Response ◽  
Wave Theory ◽  
Breaking Waves ◽  
Offshore Structures ◽  
Operational Modal Analysis ◽  
Wave Flume ◽  
Load Effects

Abstract Load effects from breaking waves on offshore structures may be a driving point for the design. It is hence important to assess the likelihood of occurrence along the magnitude of the loads in the event of an impact. Traditionally, loads are predicted using wave theory combined with a load model such as the Morison. This paper features an alternative approach in determining the loads from wave breaking. It is demonstrated how the structural response can be used for (indirectly) estimating the magnitude of the loads caused by wave breaking. The theory is applied to an experimental setup in a wave flume, where a flexible model is subjected to loads from breaking waves. The dynamic properties are mapped using operational modal analysis and it is consequently shown that the loads can be identified using the vibration measurements.

Application of Operational Modal Analysis on Railway Vehicles Using on Track Measurements

2013 ◽  
Author(s):  
Lara Mª Erviti Calvo ◽  
Gorka Agirre Castellanos ◽  
Igor Alonso Portillo
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Modal Parameters ◽  
Railway Vehicle ◽  
Correct Identification ◽  
Static Test ◽  
Railway Vehicles ◽  
Analysis Techniques ◽  
Behavior Design ◽  
Nonlinear Components

Nowadays the application of experimental modal analysis techniques on railway vehicles is gaining importance. A correct identification of modal characteristics allows improving the dynamic behavior design of the vehicle and so reaching higher running speeds and accomplishing better comfort levels. So far, in the railway sector only conventional modal analysis techniques have been used. With these techniques, the modal parameters are determined during a static test by measuring the responses of the system to one or multiple known forces. This paper presents the application of the Operational Modal Analysis (OMA) technique on a railway vehicle. This technique determines the modal parameters employing only the responses of the system to an unknown excitation. In this way, the data to be used can be acquired during on track test which presents three main advantages. The first one is that the nonlinear components of the suspensions are working in their normal operating condition which is difficult to achieve during a static test. The second one is that the wheel spinning effect is taken into account. Finally, the test can be combined with other type of track tests, reducing the period of time before delivery of the vehicle to the client. In the case under study, the OMA technique is applied by means of commercial software to measurements performed on a passengers train. The modal parameters obtained for the carbody and one of the bogies are presented.

scholarly journals Transmissibility-Based Operational Modal Analysis: Enhanced Stabilisation Diagrams

2012 ◽  
Vol 19 (5) ◽  
pp. 1085-1097 ◽  
Author(s):  
Gert De Sitter ◽  
Christof Devriendt ◽  
Patrick Guillaume
Keyword(s):  
Modal Analysis ◽  
Power Spectra ◽  
Element Model ◽  
Operational Modal Analysis ◽  
Second Step ◽  
New Approach ◽  
Analysis Techniques ◽  
Estimated Parameters ◽  
Using Data ◽  
Acoustical Data

Recently it has been shown that also transmissibilities can be used to identify the modal parameters. This approach has several advantages: because of the deterministic character of the transmissibility functions, the estimated parameters are more accurate than the results obtained with the power spectra based operational modal analysis techniques. Another advantage is that the transmissibility functions do not depend on the colouring of the unknown forces. A disadvantage of the transmissibility based operational modal analysis techniques is that non-physical modes show up in the stabilisation diagrams. In this contribution it will first be shown that those non-physical modes will show up when traditional stabilisation diagrams are used. In a second step, a new approach of selecting the physical modes out of a set of estimated modes will be discussed and the new approach will be validated using data generated with an acoustical Finite Element Model. Finally, the approach will be validated using real acoustical data.

scholarly journals Virtual Structural Monitoring of Wind Turbines Using Operational Modal Analysis Techniques

2013 ◽  
Vol 569-570 ◽  
pp. 523-530 ◽  
Author(s):  
Emilio di Lorenzo ◽  
Simone Manzato ◽  
Bart Peeters ◽  
Herman van der Auweraer
Keyword(s):  
Modal Analysis ◽  
Wind Turbines ◽  
Numerical Models ◽  
Structural Condition ◽  
Operational Modal Analysis ◽  
Critical Aspect ◽  
Operational Conditions ◽  
Open Issue ◽  
Output Only ◽  
Large Wind

Operational Modal Analysis (OMA), also known as output-only modal analysis, allows identifying modal parameters only by using the response measurements of the structures in operational conditions when the input forces cannot be measured. These information can then be used to improve numerical models in order to monitor the operating and structural conditions of the system. This is a critical aspect both for condition monitoring and maintenance of large wind turbines, particularly in the off-shore sector where operation and maintenance represent a high percentage of total costs. Although OMA is widely applied, the wind turbine case still remains an open issue. Numerical aeroelastic models could be used, once they have been validated, to introduce virtual damages to the structures in order to analyze the generated data. Results from such models can then be used as baseline to monitor the operating and structural condition of the machine.

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