Modal analysis by free vibration response only for discrete and continuous systems

2011 ◽  
Vol 330 (16) ◽  
pp. 3913-3929 ◽  
Author(s):  
Bor-Tsuen Wang ◽  
Deng-Kai Cheng
Keyword(s):  
Free Vibration ◽  
Modal Analysis ◽  
Vibration Response ◽  
Continuous Systems ◽  
Free Vibration Response

Reliability of Extracted Modal Parameters by Random Decrement of Acceleration Signatures

2009 ◽  
Author(s):  
Babak Khodabandelou ◽  
Kaveh Abasi ◽  
Masud Asayesh
Keyword(s):  
Numerical Simulation ◽  
Free Vibration ◽  
Modal Analysis ◽  
Correlation Functions ◽  
Vibration Response ◽  
Modal Parameters ◽  
Random Decrement Technique ◽  
Random Decrement ◽  
Free Decay ◽  
Free Vibration Response

Modal parameters provide important information on dynamic properties of structures. In operating condition, since it is difficult to measure input loadings, methods should be applied where don’t require measuring inputs. Such methods which identify modal parameters of structures by measuring their responses are called Operational- or Output Only- Modal Analysis (OMA) techniques. There are many time and frequency domain operational modal analysis techniques. Generally a form of impulse or free vibration response is required to use most of these techniques. However, in practice structures are usually subjected to some immeasurable or unknown random inputs. In these situations Random Decrement (RD) transformation can reduce these responses to equivalent free decay or correlation functions. Therefore, RD technique coupled with those methods, which require a form of impulse or free vibration response offer a valuable tool for identifying the dynamic characteristics of structures from operational or ambient responses. Unfortunately, in the literature there are some constrains on using random decrement signatures. For example by complicated mathematical relations it is shown that random decrement technique is applicable only if the inputs are uncorrelated zero mean Gaussian white noises. In addition, it is proved that only random decrement of displacement and velocity is equivalent to the corresponding free decay responses or correlation functions the random decrement of acceleration response is never equivalent to the corresponding free decay responses or correlation functions. However, there are many papers which have used random decrement of acceleration responses and extracted modal parameters accurately! In this paper it is tried to show simply and clearly whether it is possible to obtain modal parameters from random decrement acceleration signatures or not. To do that, a numerical simulation of a discrete dynamic system with viscous damping is carried out and the results of numerical methods are compared with those come from analytical solution. Numerical simulation is used since it is completely controllable. Finally, it is tried to identify power and the Applicability cases of random decrement method.

Development of "modal analysis free vibration response only" method for randomly excited systems

2015 ◽  
Vol 226 (12) ◽  
pp. 4031-4042 ◽  
Author(s):  
Mousa Rezaee ◽  
Gholamreza Fattahi Yam ◽  
Reza Fathi
Keyword(s):  
Free Vibration ◽  
Modal Analysis ◽  
Vibration Response ◽  
Free Vibration Response

A Study on Structural System Identification and Damage Detection for Free Vibration Response Using the Wavelet Transform

2015 ◽  
Vol 752-753 ◽  
pp. 1029-1034
Author(s):  
Asnizah Sahekhaini ◽  
Pauziah Muhamad ◽  
Masayuki Kohiyama ◽  
Aminuddin Abu ◽  
Lee Kee Quen ◽  
...  
Keyword(s):  
Free Vibration ◽  
Damage Detection ◽  
Vibration Response ◽  
Structural System ◽  
Modal Parameter ◽  
Modal Parameter Identification ◽  
Complex Morlet Wavelet ◽  
Structural System Identification ◽  
Free Vibration Response ◽  
Energy Components

This paper presents a wavelet-based method of identification modal parameter and damage detection in a free vibration response. An algorithm for modal parameter identification and damage detection is purposed and complex Morlet wavelet is chosen as an analysis wavelet function. This paper only focuses on identification of natural frequencies of the structural system. The method utilizes both undamaged and damage experiment data of free vibration response of the truss structure system. Wavelet scalogram is utilizes for damage detection. The change of energy components for undamaged and damage structure is investigated from the plot of wavelet scalogram which corresponded to the detection of damage.

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