Estimation of damping ratios of steel structures by Operational Modal Analysis method

A large number of smart devices make the Internet of Things world smarter. However, currently cloud computing cannot satisfy real-time requirements and fog computing is a promising technique for real-time processing. Operational modal analysis obtains modal parameters that reflect the dynamic properties of the structure from the vibration response signals. In Internet of Things, the operational modal analysis method can be embedded in the smart devices to achieve structural health monitoring and fault detection. In this article, a four-layer framework for combining fog computing and operational modal analysis in Internet of Things is designed. This four-layer framework introduces fog computing to solve tasks that cloud computing cannot handle in real time. Moreover, to reduce the time and space complexity of the operational modal analysis algorithm and support the real-time performance of fog computing, a limited memory eigenvector recursive principal component analysis–based operational modal analysis approach is proposed. In addition, by examining the cumulative percent variance of principal component analysis, this article explains the reasons behind the identified modal order exchange. Finally, the time-varying operational modal identification results from non-stationary random response signals of a cantilever beam whose density changes slowly indicate that the limited memory eigenvector recursive principal component analysis–based operational modal analysis method requires less memory and runtime and has higher stability and identification effect.

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Effect of Vinyl Flooring on the Modal Properties of a Steel Footbridge

Applied Sciences ◽

10.3390/app9071374 ◽

2019 ◽

Vol 9 (7) ◽

pp. 1374 ◽

Cited By ~ 3

Author(s):

Javier Jiménez-Alonso ◽

Jorge Pérez-Aracil ◽

Alejandro Hernández Díaz ◽

Andrés Sáez

Keyword(s):

Modal Analysis ◽

Operational Modal Analysis ◽

Modal Parameters ◽

Vibration Modes ◽

Structural Elements ◽

Average Increase ◽

Analysis Method ◽

Structural Element ◽

Modal Properties

Damping ratios associated with non-structural elements play an important role in mitigating the pedestrian-induced vibrations of slender footbridges. In particular, this paper analyses the effect of vinyl flooring on the modal parameters of steel footbridges. Motivated by the unexpected high experimental damping ratios of the first vibration modes of a real footbridge, whose deck was covered by a vinyl flooring, this paper aims at assessing more accurately the experimental damping ratios generated by this non-structural element on steel footbridges. For this purpose, a laboratory footbridge was built and vinyl flooring was installed on it. Its numerical and experimental modal parameters without and with the vinyl flooring were determined. The operational modal analysis method was used to estimate experimentally the modal parameters of the structure. The damping ratios associated with the vinyl flooring were obtained via the substraction between the experimental damping ratios of the laboratory footbridge with and without the vinyl flooring. An average increase of the damping ratios of 2.069% was observed due to the vinyl flooring installed. According to this result, this type of pavement may be a useful tool to significantly increase the damping ratios of steel footbridges in order to reduce pedestrian-induced vibrations.

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The use of modal analysis to examine the lattice structure

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska ◽

10.22630/pniks.2019.28.3.31 ◽

2019 ◽

Vol 28 (3) ◽

pp. 332-344

Author(s):

Mariusz Żółtowski ◽

Katarzyna Jeleniewicz

Keyword(s):

Modal Analysis ◽

Lattice Structure ◽

Steel Structures ◽

Dynamic Loads ◽

Building Structures ◽

Analysis Method ◽

Safety Factors ◽

Static Loads ◽

Structural Types ◽

Affect State

Steel structures are subject to large dynamic loads clearly reflected by generated vibration processes. The vibrations may affect state of serviceability of structures by lowering comfort of persons working there as well as possible reaching the level hazardous to safety of the structures. The effect of vibrations to structure is mainly manifested by additional stresses in a given cross-section, which are summed up with those resulting from static loads. The dynamic loads may cause damaging effects in buildings of various structural types or even lead to their destruction. Judging the necessity of improving the quality assessment methods of building structures for purposes of estimation of their state as well as safety factors for lattice structures, the author of this work undertook an attempt to investigate destruction process of selected object by using the modal analysis method.

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Obtaining Dynamic Parameters by Using Ambient Vibration Recordings on Model of The Steel Arch Bridge

Periodica Polytechnica Civil Engineering ◽

10.3311/ppci.16422 ◽

2021 ◽

Author(s):

Azer A. Kasimzade ◽

Sertaç Tuhta ◽

Furkan Günday ◽

Hakan Aydın

Keyword(s):

Finite Element Method ◽

Finite Element ◽

Modal Analysis ◽

Dynamic Characteristics ◽

Operational Modal Analysis ◽

Ambient Vibration ◽

Mode Shapes ◽

Dynamic Parameters ◽

Analysis Method ◽

Arch Bridge

Operational Modal Analysis (OMA) is a one of the most popular method to extract the dynamic characteristics from ambient vibration response signals. In this study, the dynamic characteristics of a model of steel arch bridge with a bolt connection constructed in a 6.10 m span and 1.88 m height laboratory were determined by finite element method and operational modal analysis methods. Firstly, finite element model was created in SAP2000 software of model steel system and dynamic characteristic were obtained numerically. Then, accelerometers were placed where the displacements are high on points of the system and dynamic characteristics were determined by operational modal analysis method. The aim of this study is to obtain the dynamic parameters (frequency, damping ratio, mode shapes) of the model of the steel arch bridge accurately and reliably by operational modal analysis method by making use of ambient vibrations in the laboratory conditions. For this purpose, analytical analysis of the model of the steel arch bridge with finite element method and the dynamic parameters obtained as a result of the operational modal analysis of the model steel arch bridge were compared. Also, the modal assurance criterion (MAC) was used. Good compatibility was recognized between the results obtained for experimental and numerical procedures in terms of both the natural frequency and the mode of vibration. At the end of this study, reasonable correlation is obtained between mode shapes, frequencies and damping ratios. Analytical and Operational modal frequencies differences between 0.139 %–7.170 %.

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Operational Modal Analysis of the Cablestayed Footbridge

Civil and Environmental Engineering ◽

10.1515/cee-2017-0012 ◽

2017 ◽

Vol 13 (2) ◽

pp. 92-98 ◽

Cited By ~ 2

Author(s):

Ján Kortiš ◽

Ľuboš Daniel ◽

Matúš Farbák ◽

Lukáš Maliar ◽

Milan Škarupa

Keyword(s):

Modal Analysis ◽

Natural Frequencies ◽

Detection System ◽

Steel Structures ◽

Modern Architecture ◽

Operational Modal Analysis ◽

Vibration Exciter ◽

Operating Load ◽

Acceleration Sensors ◽

Bridge Structures

Abstract Modern architecture leads to design subtle bridge structures that are more sensitive to increased dynamic loading than the massive ones. This phenomenon can be especially observed on lightweight steel structures such as suspended footbridges. As a result, it is necessary to know precisely its dynamic characteristics, such as natural frequencies, natural shapes and damping of construction. This information can be used for further analysis such as damage detection, system identification, health monitoring, etc. or also for the design of new types of construction. For this purpose, classical modal analysis using trigger load or harmonic vibration exciter in combination with acceleration sensors is used in practice. However, there are many situations where it is not possible to stop the traffic or operation of the bridge. The article presents an experimental measurement of the dynamic parameters of the structure at the operating load using the operational modal analysis.

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