Comparative Study on Modal Identification of a 10 Story RC Structure Using Free, Ambient and Forced Vibration Data

2017 ◽  
pp. 267-276
Author(s):  
Seyedsina Yousefianmoghadam ◽  
Andreas Stavridis ◽  
Babak Moaveni
Keyword(s):  
Comparative Study ◽  
Forced Vibration ◽  
Modal Identification ◽  
Vibration Data ◽  
Rc Structure

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.

Modal identification of a bridge-abutment system using forced vibration testing

2012 ◽  
Vol 45 (4) ◽  
pp. 161-170
Author(s):  
L.S. Hogan ◽  
L.M. Wotherspoon ◽  
S. Beskhyroun ◽  
J.M. Ingham
Keyword(s):  
System Identification ◽  
Forced Vibration ◽  
Experimental Testing ◽  
Principal Direction ◽  
Lateral Spreading ◽  
Modal Identification ◽  
Vibration Testing ◽  
Longitudinal Response ◽  
Bridge Superstructure ◽  
Forced Vibration Testing

During the 2010 Mw7.1 Darfield earthquake, the single span Davis Road Bridge located 5 km southeast of Lincoln, New Zealand, sustained significant lateral spreading damage to the western approach. While lateral spreading resulted in up to 450 mm of approach settlement and evidence of damage to the pile foundations, the bridge superstructure sustained no significant damage. Prior to reinstating traffic, the bridge was used for full scale dynamic testing to characterise the influence of different substructure components on the lateral dynamic behaviour of the bridge superstructure. The bridge was characterised using an eccentric mass shaker and an array of accelerometers to perform lateral forced vibration testing in both the transverse and longitudinal directions. Modal properties were extracted from these tests using multiple system identification algorithms. The experimental testing and system identification methodology are described here. Forced vibration testing was able to detect one mode in each principal direction of the bridge, with the fundamental modes for the transverse and longitudinal direction occurring at a period of 0.118 s and 0.092 s respectively. The torsional response found during the transverse direction shaking was most likely due to the effect of gap opening around the piles on the western abutment, while the longitudinal response was dominated by the approach soil.

Extending Blind Modal Identification to the Underdetermined Case for Ambient Vibration

2012 ◽  
Author(s):  
Scot McNeill
Keyword(s):  
Natural Frequencies ◽  
Second Order ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Frequency Domain Method ◽  
Blind Identification ◽  
Vibration Data ◽  
Modal Damping ◽  
Six Dof

The modal identification framework known as Blind Modal Identification (BMID) has recently been developed, drawing on techniques from Blind Source Separation (BSS). Therein, a BSS algorithm known as Second Order Blind Identification (SOBI) was adapted to solve the Modal IDentification (MID) problem. One of the drawbacks of the technique is that the number of modes identified must be less than the number of sensors used to measure the vibration of the equipment or structure. In this paper, an extension of the BMID method is presented for the underdetermined case, where the number of sensors is less than the number of modes to be identified. The analytic signal formed from measured vibration data is formed and the Second Order Blind Identification of Underdetermined Mixtures (SOBIUM) algorithm is applied to estimate the complex-valued modes and modal response autocorrelation functions. The natural frequencies and modal damping ratios are then estimated from the corresponding modal auto spectral density functions using a simple Single Degree Of Freedom (SDOF), frequency-domain method. Theoretical limitations on the number of modes identified given the number of sensors are provided. The method is demonstrated using a simulated six DOF mass-spring-dashpot system excited by white noise, where displacement at four of the six DOF is measured. All six modes are successfully identified using data from only four sensors. The method is also applied to a more realistic simulation of ambient building vibration. Seven modes in the bandwidth of interest are successfully identified using acceleration data from only five DOF. In both examples, the identified modal parameters (natural frequencies, mode shapes, modal damping ratios) are compared to the analytical parameters and are demonstrated to be of good quality.

scholarly journals DETERMINATION OF THE EFFECT OF TiO2 ON THE DYNAMIC BEHAVIOR OF SCALED CONCRETE CHIMNEY BY OMA

2021 ◽  
Vol 55 (3) ◽  
Author(s):  
Sertaç Tuhta ◽  
Furkan Günday
Keyword(s):  
Titanium Dioxide ◽  
Outer Surface ◽  
Ground Level ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes ◽  
Dynamic Parameters ◽  
Vibration Data ◽  
Output Only ◽  
Frequency Domain Decomposition

In this article, the dynamic parameters (frequencies, mode shapes, damping ratios) of a scaled concrete chimney and the dynamic parameters (frequencies, mode shapes, damping ratios) of the entire outer surface of the 80-micron-thick titanium dioxide are compared using the operational modal analysis method. Ambient excitation was provided from micro tremor ambient vibration data at ground level. Enhanced Frequency Domain Decomposition (EFDD) is used for the output-only modal identification. From this study, very best correlation is found between the mode shapes. Titanium dioxide applied to the entire outer surface of the scaled concrete chimney has an average of 16.34 % difference in frequency values and 9.81 % in damping ratios, proving that nanomaterials can be used to increase the rigidity in chimneys, in other words, for reinforcement. Another important result determined in the study is that it has been observed that the adherence of titanium dioxide and similar nanomaterials mentioned in the introduction to concrete chimney surfaces is at the highest level.

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