Blind Modal Identification of Non-Classically Damped Systems from Free or Ambient Vibration Records

2013 ◽  
Vol 29 (4) ◽  
pp. 1137-1157 ◽  
Author(s):  
Fariba Abazarsa ◽  
Fariborz Nateghi ◽  
S. Farid Ghahari ◽  
Ertugrul Taciroglu
Keyword(s):  
Degrees Of Freedom ◽  
Passive Control ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Audio Signals ◽  
Civil Structures ◽  
Ambient Vibration Tests ◽  
Vibration Tests ◽  
Damped Systems

A significant segment of system identification literature on civil structures is devoted to response-only identification, simply because lack of measurements of input excitations for civil structures is a fairly common scenario. In recent years, several researchers have successfully adapted a second-order blind identification (SOBI) technique—a method originally developed for “blind source separation” of audio signals—to response-only identification of mechanical and civil structures. However, this development had been confined to fully instrumented classically damped systems. While several approaches have been proposed recently for extending SOBI to non-classically damped systems, they all require additional data such as velocity or analytic signals. Herein, we present a version of SOBI that requires only acceleration signals recorded during free or ambient vibration tests, and yields the system's complex mode shapes, natural frequencies, and damping ratios. Performance of the proposed technique is demonstrated through two synthetic examples: a ten-story structure possessing a passive control system, and a soil-structure system with seven degrees of freedom (seven-DOF).

scholarly journals Automated band selection for Bayesian FFT modal identification Based on RetinaNet

2021 ◽  
Vol 2078 (1) ◽  
pp. 012058
Author(s):  
Chen Wang ◽  
Zhilin Xue ◽  
Yipeng Su ◽  
Binbin Li
Keyword(s):  
Operation Time ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Band Selection ◽  
Data Sets ◽  
Civil Structures ◽  
Frequency Bands ◽  
Operational Conditions ◽  
Vibration Data

Abstract Bayesian FFT algorithm is a popular method to identify modal parameters, e.g., modal frequencies, damping ratios, and mode shapes, of civil structures under operational conditions. It is efficient and provides the identification uncertainty in terms of posterior distribution. However, in utilizing the Bayesian FFT algorithm, it is tedious to manually select frequency bands and initial frequencies. This step requires professional knowledge and costs most of time, which prevents the automation of Bayesian FFT algorithm. Regarding the band selection as an object detection problem, we design a band selection network based on the RetinaNet to automatically select frequency bands and a peak prediction network to predict the initial frequencies. The designed networks are trained using the singular value spectrum of measured ambient vibration data and verified by various data sets. It can achieve the human accuracy with much less operation time, and thus provides a corner stone for the automation of Bayesian FFT algorithm.

scholarly journals Identification of Modal Parameters of Bridges Using Ambient Vibration Measurements

2015 ◽  
Vol 2015 ◽  
pp. 1-21 ◽  
Author(s):  
Damir Zenunovic ◽  
Mirsad Topalovic ◽  
Radomir Folic
Keyword(s):  
Mathematical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Vibration Measurements ◽  
Ambient Vibration Tests ◽  
Real Nature ◽  
Vibration Tests ◽  
Ambient Vibration Measurements ◽  
Existing Bridges

The paper provides an overview of ambient vibration tests and numerical analysis performed in the framework of Project NATO SfP 983828. The aim of the research is the definition of the dynamic characteristics of bridges on the examples. The paper considers three case studies: two older existing bridges and one newly constructed bridge. A comparative analysis of natural frequencies and mode shapes, obtained by ambient vibration measurements (AVM) and mathematical models (AMs), was carried with the aim to demonstrate the usefulness of ambient vibration tests for identification of the modal parameters of the tested bridge structure. Agreement between AVM and AMs results is very good. The mode shapes are very similar. Some differences between computed and measured frequencies were obtained, which can be attributed to the real nature of the boundary conditions, the uncertainty in the material properties of structure elements, and the mathematical models assumptions.

Ambient Vibration Tests of the Mexicali General Hospital

1991 ◽  
Vol 7 (2) ◽  
pp. 281-300 ◽  
Author(s):  
L. Mendoza ◽  
A. Reyes ◽  
J. E. Luco
Keyword(s):  
General Hospital ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Ambient Vibration Tests ◽  
Longitudinal Response ◽  
Modal Damping ◽  
Longitudinal Stiffness ◽  
Before And After ◽  
Vibration Tests ◽  
Transverse Response

Results of ambient vibration tests of the eight-story reinforced-concrete hospitalization tower of the Mexicali General Hospital are described. The structure suffered some damage during the November 1987 Superstition Hills earthquakes. The tests were conducted in April and August 1989 before and after major alterations of the building were made. The frequencies, modal damping ratios and mode shapes of some of the longitudinal, transverse and torsional modes were determined for the April and August 1989 conditions. It was found that the removal of the facade of the building resulted in a reduction of the longitudinal stiffness of the structure of the order of fifty percent. Measurements of the translation and rocking of the base indicate that soil-structure interaction effects play a moderate role in the transverse response of this structure and a negligible role in its longitudinal response.

Forced and Ambient Vibration Tests and Vibration Monitoring of Hakucho Suspension Bridge

2000 ◽  
Vol 1696 (1) ◽  
pp. 57-63 ◽  
Author(s):  
Yozo Fujino ◽  
Masato Abe ◽  
Hajime Shibuya ◽  
Masato Yanagihara ◽  
Masashi Sato ◽  
...  
Keyword(s):  
Natural Frequencies ◽  
Three Dimensional ◽  
Suspension Bridge ◽  
Element Model ◽  
Vibration Monitoring ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Ambient Vibration Tests ◽  
Bending Mode ◽  
Vibration Tests

Forced and ambient dynamic tests of the Hakucho Bridge were carried out to study the dynamic characteristics of this suspension bridge. Dense-array measurement was employed in order to capture not only natural frequencies and damping, but also the mode shapes of the bridge. The natural frequencies and mode shapes obtained from the forced and ambient vibration tests agreed well with those calculated by a three-dimensional finite element model. A new method that combines the random decrement method with the Ibrahim time domain method is proposed to systematically identify the natural frequencies, damping, and mode shapes. This method is successfully applied to ambient vibration data. It is shown that the natural frequency of the first vertical bending mode decreases noticeably as the wind speed increases. It is also shown that the shape of the first vertical bending mode changes slightly near the towers, depending on the wind velocity; this finding indicates that the change may be associated with friction in the bearings at the towers. Finally, application of the Global Positioning System to measure static displacement of the girder is explained.

Ambient vibrations for the assessment of the strengthening intervention of a masonry barrel vault

2020 ◽  
pp. 147592172095206
Author(s):  
Alice Di Primio ◽  
Noemi Fiorini ◽  
Daniele Spina ◽  
Claudio Valente ◽  
Marcello Vasta
Keyword(s):  
Dynamic Behavior ◽  
Ambient Vibration ◽  
Structural Monitoring ◽  
Mode Shapes ◽  
Modal Assurance Criterion ◽  
Existing Structures ◽  
Ambient Vibration Tests ◽  
2009 L’Aquila Earthquake ◽  
Historical Heritage ◽  
Vibration Tests

Vibration-based structural monitoring is a fundamental tool to assess the conditions of existing structures, in their real operating state. In particular, as concerns masonry buildings, although a large part of the Italian and European historical heritage is composed of vaulted structures, comparatively few papers in the literature are targeted to the study of the dynamic behavior of vaulted systems. The present work focuses on the application of vibration-based structural monitoring to a barrel vault of the Bussi Castle, located in Pescara, Italy, which suffered some damages as a consequence of the 2009 L’Aquila earthquake. Ambient vibration tests were carried out in the damaged state and after repair and strengthening of the vault for evaluating its dynamic behavior in both states. In either conditions, the modal parameters of the vault were identified using operational modal analysis techniques. The comparison of the modes in the two states, carried out with Modal Assurance Criterion index, clearly indicates an enhancement of dynamic behavior of the consolidated vault. In particular, a new index named Modal Symmetry Index is introduced. The index is based on a proper ratio between mode shapes to evaluate the improvement of the structural symmetry after the restoration interventions. The results confirm the effectiveness of the devised index to evaluate the strengthening interventions and, the potential of the structural monitoring to control the behavior of damaged vaulted masonry systems.

Structural Identification and Numerical Models for Slender Historical Structures

2015 ◽  
pp. 674-703 ◽  
Author(s):  
Dora Foti ◽  
Mariella Diaferio ◽  
Nicola Ivan Giannoccaro ◽  
Salvador Ivorra
Keyword(s):  
Model Updating ◽  
Numerical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Fe Model ◽  
Detailed Structural Analysis ◽  
Ambient Vibration Tests ◽  
Great Confidence ◽  
Vibration Tests ◽  
The Time Domain

In the present chapter the theoretical basis of different methods developed for the calibration of FEMs are discussed. In general, Model Updating techniques are based on the use of appropriate functions that iteratively update selected physical properties (characteristics of the materials, stiffness of a link, etc.). In this way the correlation between the simulated response and the target value could improve if compared to an initial value. The FE model thus obtained can be used for a detailed structural analysis with a great confidence. The technique described in the first part of the chapter is applied to the evaluation of the structural properties of the tower of the Provincial Administration Building in Bari (Italy).The final purpose is to predict the performance of the tower to different combinations of static and dynamic loads, i.e. earthquakes or other induced vibrations. Ambient vibration tests have been performed on the above mentioned tower with the aim of determining its dynamic response and developing a procedure for modeling this building (Foti et al., 2012a). The Operation Modal Analysis (OMA) has been carried out both in the frequency domain and in the time domain to extract the dominant frequencies and mode shapes of the tower.

Determination of the dynamic characteristics of the Colquitz River Bridge by full-scale testing

1996 ◽  
Vol 23 (2) ◽  
pp. 536-548 ◽  
Author(s):  
C. E. Ventura ◽  
A. J. Felber ◽  
S. F. Stiemer
Keyword(s):  
British Columbia ◽  
Dynamic Characteristics ◽  
Field Tests ◽  
Free Vibrations ◽  
Full Scale ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Ambient Vibration Tests ◽  
Vibration Tests ◽  
Full Scale Tests

This paper presents the results of full-scale tests performed at the Colquitz River Bridge near Victoria, British Columbia (B.C.), Canada, during September 1992 to determine the dynamic characteristics of the structure. The five-span bridge was completed in 1954 and is part of the Trans-Canada Highway. It is 82.68 m long and 11.89 m wide, and has six continuous steel girders supporting a 175 mm thick concrete deck. This particular bridge was chosen for testing because of its typical nature of many B.C. bridges, its location in an area of high seismic risk, and its excellent site accessibility. The tests included extensive measurements of ambient vibrations induced by traffic and other sources to determine the dynamic characteristics of the bridge. The most significant vertical and lateral mode shapes and associated periods of vibration were determined from vibration measurements at more than 50 different locations of the deck, piers, and abutments. Although a large amount of data were collected, they were quickly processed and analyzed with an innovative system developed at The University of British Columbia. One of the important features of this system is that it permits the identification of the principal modes of vibration immediately after the data have been collected. In addition to the ambient vibration tests, quick release pullback tests were conducted to verify modal frequencies determined from the ambient vibration tests and to determine the damping of the fundamental modes. These tests consisted of loading the bridge at a selected location with a force of about 90 kN and then releasing this load very quickly to induce free vibrations. The information obtained from the field tests was used to refine a computer finite element model of the bridge, which, in turn, was used to gain insight into the dynamic behaviour of specific components of the bridge. Further, this information was used later by the bridge owner to evaluate the bridge's expected response during an earthquake. Key words: steel bridges, dynamic response, full-scale tests.

Experimental and Numerical Modal Identification of the Fossanova Gothic Cathedral

2007 ◽  
Vol 347 ◽  
pp. 351-358 ◽  
Author(s):  
Gianfranco de Matteis ◽  
I. Langone ◽  
Fabio Colanzi ◽  
Federico M. Mazzolani
Keyword(s):  
Seismic Vulnerability ◽  
Dynamic Behaviour ◽  
Shaking Table Test ◽  
Mediterranean Area ◽  
Modal Identification ◽  
Shaking Table ◽  
Ambient Vibration ◽  
Dynamic Features ◽  
Ambient Vibration Tests ◽  
Vibration Tests

This paper focuses on the dynamic behaviour of the Fossanova cathedral (Latina, ITALY), which represents a magnificent example of pre-Gothic style church, whose structural typology is largely present in the Mediterranean area, especially in many Countries characterised by a High-Medium seismic hazard. In particular, within the European research project PROHITECH, aiming at investigating the seismic vulnerability of such a structural typology, experimental and numerical analyses have been carried out. Firstly, detailed investigations have been devoted to the identification of the geometry of the main constructional parts as well as of the mechanical features of the constituting materials of the cathedral. Then, both Ambient Vibration Tests (AVT) and Numerical Modal Identification analyses by Finite Element Method (FEM) have been applied, allowing the detection of the main dynamic features. Finally, a refined FEM model reproducing the dynamic behaviour of the cathedral by using scaled physical quantities according to the Buckingham theorem has been developed. In fact, the present study has to be intended as a preliminary activity devoted to se up a shaking table test on a reduced scale physical model of Fossanova cathedral, which will be shortly carried out at the IZIIS laboratory (Skopje, Macedonia).

Modal identification of Karun 4 arch dam using ambient vibration tests

2019 ◽  
pp. 2858-2863
Author(s):  
R. Tarinejad ◽  
M. Damadipour ◽  
H. Golmohammadi ◽  
K. Falsafian
Keyword(s):  
Arch Dam ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Ambient Vibration Tests ◽  
Vibration Tests

scholarly journals Structural Identification and Numerical Models for Slender Historical Structures

2016 ◽  
pp. 196-222 ◽  
Author(s):  
Dora Foti ◽  
Mariella Diaferio ◽  
Nicola Ivan Giannoccaro ◽  
Salvador Ivorra
Keyword(s):  
Model Updating ◽  
Numerical Models ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Fe Model ◽  
Detailed Structural Analysis ◽  
Ambient Vibration Tests ◽  
Great Confidence ◽  
Vibration Tests ◽  
The Time Domain

In the present chapter the theoretical basis of different methods developed for the calibration of FEMs are discussed. In general, Model Updating techniques are based on the use of appropriate functions that iteratively update selected physical properties (characteristics of the materials, stiffness of a link, etc.). In this way the correlation between the simulated response and the target value could improve if compared to an initial value. The FE model thus obtained can be used for a detailed structural analysis with a great confidence. The technique described in the first part of the chapter is applied to the evaluation of the structural properties of the tower of the Provincial Administration Building in Bari (Italy).The final purpose is to predict the performance of the tower to different combinations of static and dynamic loads, i.e. earthquakes or other induced vibrations. Ambient vibration tests have been performed on the above mentioned tower with the aim of determining its dynamic response and developing a procedure for modeling this building (Foti et al., 2012a). The Operation Modal Analysis (OMA) has been carried out both in the frequency domain and in the time domain to extract the dominant frequencies and mode shapes of the tower.

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