Output‐only modal testing of simple residential structures and acoustic cavities using the response to simulated sonic booms and 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.

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A Full-Field Non-Contact Thermal Modal Testing Technique Under Ambient Excitation

Experimental Techniques ◽

10.1007/s40799-021-00441-9 ◽

2021 ◽

Author(s):

Y. J. Hu ◽

Z. S. Huang ◽

W. D. Zhu ◽

H. L. Li

Keyword(s):

Modal Testing ◽

Testing Technique ◽

Full Field ◽

Ambient Excitation

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Modelling of Sprayer Boom Dynamics by Means of Maximum Likelihood Identification Techniques, Part 1: A Comparison of Input-output and Output-only Modal Testing

Biosystems Engineering ◽

10.1016/s1537-5110(03)00044-8 ◽

2003 ◽

Vol 85 (2) ◽

pp. 163-171 ◽

Cited By ~ 13

Author(s):

E. Parloo ◽

P. Guillaume ◽

J. Anthonis ◽

W. Heylen ◽

J. Swevers

Keyword(s):

Maximum Likelihood ◽

Modal Testing ◽

Input Output ◽

Output Only ◽

Identification Techniques

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An Identification Method for Damping Ratio of In Situ Building

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.446-449.556 ◽

2012 ◽

Vol 446-449 ◽

pp. 556-560

Author(s):

Zhi Ying Zhang ◽

Qing Sun ◽

Zheng Yang

Keyword(s):

Time Domain ◽

Damping Ratio ◽

Modal Parameter ◽

Identification Methods ◽

Random Decrement ◽

Random Decrement Method ◽

Output Only ◽

Ambient Excitation

Damping evaluation is of great importance in predicting the dynamic response of systems. To get the accurate damping ratios of a system, many identification methods have been proposed and developed. But only few of them achieved accurate results for in-situ buildings due to the fact that the responses are significantly influenced by noise. This paper proposes a new method to accurately identify the damping ratios of in-situ buildings. The method is based on ambient excitation technique which requires no artificial excitation applied to SSI system and to measure output-only. The damping ratio identification is then performed by combining the improved random decrement method and Ibrahim time domain method. To demonstrate the validity of the proposed approach, a case study is performed and the results are compared with the conventional peak-peaking method results. The results show the proposed method can effectively identify the modal parameter of either frequencies or damping ratios of in-situ buildings subjected to ambient excitation.

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Modal testing and detection of pretension deviation in a cable dome structure

Advances in Structural Engineering ◽

10.1177/1369433218789197 ◽

2018 ◽

Vol 22 (2) ◽

pp. 413-426

Author(s):

Hong-Chuang Liu ◽

Shi-Lin Dong ◽

Hao-Qing Liang

Keyword(s):

Element Model ◽

Modal Identification ◽

Modal Testing ◽

Stiffness Degradation ◽

Test Model ◽

Scaled Model ◽

Modal Strain Energy ◽

Dome Structure ◽

Cable Dome ◽

Output Only

Pretension deviation may cause stiffness degradation and overstress that can compromise the safety of tensile structures, which can be diagnosed by modal identification. This article presents modal tests on a 1:10 scaled model of a herringbone-ribbed cable dome structure. An optimal sensor placement scheme is proposed to observe the geometric stiffness change induced by pretension deviation. Based on the tests, different output-only modal identification techniques were implemented. A substructure strategy was adopted to overcome the limited measurement quantity and provide localized diagnoses. The experimental results show that operational modal analysis methods based on output-only data can effectively identify major modes of massive structures. The sensitivity of modal characteristics to pretension deviation is also evaluated via experimental comparisons, and modifications are implemented in an analytical finite element model to approximate the test model. The identified modal information can help locate stiffness degradation and thereby pretension loss in tensile structures. A modified modal strain energy method is proposed to detect pretension loss from decentralized testing and is verified by the test results.

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Analytical and Experimental Study Using Output-Only Modal Testing for On-Orbit Satellite Appendages

Advances in Acoustics and Vibration ◽

10.1155/2009/538731 ◽

2009 ◽

Vol 2009 ◽

pp. 1-10 ◽

Cited By ~ 1

Author(s):

Mashiul Alam ◽

Ramin Sedaghati ◽

Yvan Soucy ◽

Rama B. Bhat

Keyword(s):

Experimental Study ◽

Model Updating ◽

Flexible Structures ◽

Modal Testing ◽

Modal Parameters ◽

Operational Conditions ◽

Orbit Satellite ◽

Potential Applications ◽

Output Only

Output-only modal testing is an effective technique to identify the modal parameters of structural systems under ambient or operational conditions and has potential applications in civil, mechanical, and aerospace engineering. It may effectively be used for model validation, model updating, quality control, and health monitoring through the determination of modal characteristics of the structures. This approach to modal testing has great potential for ground and on-orbit modal testing of space hardware, especially for flexible structures such as membrane payloads where the operating and ambient excitations, such as firing of AC thrusters and ambient thermal shock, are difficult or impossible to measure. The main objective of this work is to conduct analytical and experimental study on output-only modal testing and to demonstrate its potential application to effectively extract modal parameters of an on-orbit satellite appendage.

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