scholarly journals DYNAMIC BEHAVIOR OF A CABLE-STAYED FOOTBRIDGE OVER RIVER VRBAS IN BANJA LUKA

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Marina Latinović ◽  
Zoran Mišković ◽  
Marko Popović
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Dynamic Behavior ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Fe Model ◽  
Modal Assurance Criterion ◽  
Frequency Domain Decomposition ◽  
Banja Luka

This paper presents a dynamic behavior analysis of an old cable-stayed footbridge over river Vrbasin Banja Luka. Identification of modal parameters, of this prone to vibrations footbridge structure,was performed using Operational Modal Analysis with Frequency Domain Decomposition method.Experimental test setups and obtained results, compared to the numerical values obtained by FEmodel updating, are shown. Modal Assurance Criterion was used for the confirmation of theuniqueness of experimentally obtained mode shapes, and also for the comparison of FE model modeshapes to the experimentally obtained ones, in the locations of measurement.

scholarly journals Operational Modal Analysis on a 3D Scaled Model of a 3-Storey Aluminium Structure

2018 ◽  
Vol 7 (4.27) ◽  
pp. 78
Author(s):  
M. Fadhil Shazmir ◽  
N. Ayuni Safari ◽  
M. Azhan Anuar ◽  
A. A.Mat Isa ◽  
Zamri A.R
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Natural Frequencies ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Modal Assurance Criterion ◽  
Scaled Model ◽  
Frequency Domain Decomposition

Obtaining a good experimental modal data is essential in modal analysis in order to ensure accurate extraction of modal parameters. The parameters are compared with other extraction methods to ascertain its consistency and validity. This paper demonstrates the extraction of modal parameters using various identification algorithms in Operational Modal Analysis (OMA) on a 3D scaled model of a 3-storey aluminium structure. Algorithms such as Frequency Domain Decomposition (FDD), Enhanced Frequency Domain Decomposition (EFDD) and Stochastic Subspace Identification (SSI) are applied in this study to obtain modal parameters. The model test structure is fabricated of aluminium and assembled using bolts and nuts. Accelerometers were used to collect the responses and the commercial post processing software was used to obtain the modal parameters. The resulting natural frequencies and mode shapes using FDD method are then compared with other OMA parametric technique such as EFDD and SSI algorithm by comparing the natural frequencies and Modal Assurance Criterion (MAC). Comparison of these techniques will be shown to justify the validity of each technique used and hence confirming the accuracy of the measurement taken.    

scholarly journals Operational Modal Analysis of Damage Gear

2020 ◽  
Vol 9 (3) ◽  
pp. 2778-2783
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Dynamic Characteristics ◽  
Natural Frequencies ◽  
Helical Gear ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Identification Algorithm ◽  
Frequency Domain Decomposition

As natural frequencies and mode shapes are often a key to understanding dynamic characteristics of structural elements, modal analysis provides a viable means to determine these properties. This paper investigates the dynamic characteristics of a healthy and unhealthy condition of a commercially used helical gear using the Frequency Domain Decomposition (FDD) identification algorithm in Operational Modal Analysis (OMA). For the unhealthy condition, a refined range of percentage of defects are introduced to the helical gear starting from one (1) tooth being defected (1/60 teeth) to six (6) teeth being defected (6/60 teeth). The specimen is tested under a free-free boundary condition for its simplicity and direct investigation purpose. Comparison of the results of these varying conditions of the structure will be shown to justify the validity of the method used. Acceptable modal data are obtained by considering and accentuating on the technical aspects in processing the experimental data which are critical aspects to be addressed. The natural frequencies and mode shapes are obtained through automatic and manual peak-picking process from Singular Value Decomposition (SVD) plot using Frequency Domain Decomposition (FDD) technique and the results are validated using the established Modal Assurance Criterion (MAC) indicator. The results indicate that OMA using FDD algorithm is a good method in identifying the dynamic characteristics and hence, is effective in detection of defects in this rotating element

scholarly journals Comparison of Mode Shapes of Carbon-Fiber-Reinforced Plastic Material Considering Carbon Fiber Direction

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 311
Author(s):  
Chan-Jung Kim
Keyword(s):  
Carbon Fiber ◽  
Modal Analysis ◽  
Dynamic Behavior ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Carbon Fiber Reinforced Plastic ◽  
Fiber Direction ◽  
Fiber Reinforced ◽  
Fiber Reinforced Plastic ◽  
Reinforced Plastic

Previous studies have demonstrated the sensitivity of the dynamic behavior of carbon-fiber-reinforced plastic (CFRP) material over the carbon fiber direction by performing uniaxial excitation tests on a simple specimen. However, the variations in modal parameters (damping coefficient and resonance frequency) over the direction of carbon fiber have been partially explained in previous studies because all modal parameters have only been calculated using the representative summed frequency response function without modal analysis. In this study, the dynamic behavior of CFRP specimens was identified from experimental modal analysis and compared five CFRP specimens (carbon fiber direction: 0°, 30°, 45°, 60°, and 90°) and an isotropic SCS13A specimen using the modal assurance criterion. The first four modes were derived from the SCS13A specimen; they were used as reference modes after verifying with the analysis results from a finite element model. Most of the four mode shapes were found in all CFRP specimens, and the similarity increased when the carbon fiber direction was more than 45°. The anisotropic nature was dominant in three cases of carbon fiber, from 0° to 45°, and the most sensitive case was found in Specimen #3.

Modal parameter extraction from measured signal by frequency domain decomposition (FDD) technique

2019 ◽  
Vol 11 (2) ◽  
pp. 324-337
Author(s):  
Sk Abdul Kaium ◽  
Sayed Abul Hossain ◽  
Jafar Sadak Ali
Keyword(s):  
Modal Analysis ◽  
Frequency Domain ◽  
Real Life ◽  
Parameter Extraction ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Measured Signal ◽  
Modal Parameter ◽  
Content Type ◽  
Modal Parameter Extraction

Purpose The purpose of this paper is to highlight that the need for improved system identification methods within the domain of modal analysis increases under the impulse of the broadening field of applications, e.g., damage detection and vibro-acoustics, and the increased complexity of today’s structures. Although significant research efforts during the last two decades have resulted in an extensive number of parametric identification algorithms, most of them are certainly not directly applicable for modal parameter extraction. So, based on this, the aim of the present work is to develop a technique for modal parameter extraction from the measured signal. Design/methodology/approach A survey and classification of the different modal analysis methods are made; however, the focus of this thesis is placed on modal parameter extraction from measured time signal. Some of the methods are examined in detail, including both single-degree-of-freedom and multi-degree-of-freedom approaches using single and global frequency-response analysis concepts. The theory behind each of these various analysis methods is presented in depth, together with the development of computer programs, theoretical and experimental examples and discussion, in order to evaluate the capabilities of those methods. The problem of identifying properties of structures that possess close modes is treated in particular detail, as this is a difficult situation to handle and yet a very common one in many structures. It is essential to obtain a good model for the behavior of the structure in order to pursue various applications of experimental modal analysis (EMA), namely: updating of finite element models, structural modification, subsystem-coupling and calculation of real modes from complex modes, to name a few. This last topic is particularly important for the validation of finite element models, and for this reason, a number of different methods to calculate real modes from complex modes are presented and discussed in this paper. Findings In this paper, Modal parameters like mode shapes and natural frequencies are extracted using an FFT analyzer and with the help of ARTeMiS, and subsequently, an algorithm has been developed based on frequency domain decomposition (FDD) technique to check the accuracy of the results as obtained from ARTeMiS. It is observed that the frequency domain-based algorithm shows good agreement with the extracted results. Hence the following conclusion may be drawn: among several frequency domain-based algorithms for modal parameter extraction, the FDD technique is more reliable and it shows a very good agreement with the experimental results. Research limitations/implications In the case of extraction techniques using measured data in the frequency domain, it is reported that the model using derivatives of modal parameters performed better in many situations. Lack of accurate and repeatable dynamic response measurements on complex structures in a real-life situation is a challenging problem to analyze exact modal parameters. Practical implications During the last two decades, there has been a growing interest in the domain of modal analysis. Evolved from a simple technique for troubleshooting, modal analysis has become an established technique to analyze the dynamical behavior of complex mechanical structures. Important examples are found in the automotive (cars, trucks, motorcycles), railway, maritime, aerospace (aircrafts, satellites, space shuttle), civil (bridges, buildings, offshore platforms) and heavy equipment industry. Social implications Presently structural health monitoring has become a significantly important issue in the area of structural engineering particularly in the context of safety and future usefulness of a structure. A lot of research is being carried out in this area incorporating the modern sophisticated instrumentations and efficient numerical techniques. The dynamic approach is mostly employed to detect structural damage, due to its inherent advantage of having global and location-independent responses. EMA has been attempted by many researchers in a controlled laboratory environment. However, measuring input excitation force(s) seems to be very expensive and difficult for the health assessment of an existing real-life structure. So Ambient Vibration Analysis is a good alternative to overcome those difficulties associated with the measurement of input excitation force. Originality/value Three single bay two storey frame structure has been chosen for the experiment. The frame has been divided into six small elements. An algorithm has been developed to determine the natural frequency of those frame structures of which one is undamaged and the rest two damages in single element and double element, respectively. The experimental results from ARTeMIS and from developed algorithm have been compared to verify the effectiveness of the developed algorithm. Modal parameters like mode shapes and natural frequencies are extracted using an FFT analyzer and with the help of ARTeMiS, and subsequently, an algorithm has been programmed in MATLAB based on the FDD technique to check the accuracy of the results as obtained from ARTeMiS. Using singular value decomposition, the power Spectral density function matrix is decomposed using the MATLAB program. It is observed that the frequency domain-based algorithm shows good consistency with the extracted results.

scholarly journals Operational Modal Analysis of a Spar-Type Floating Platform Using Frequency Domain Decomposition Method

Energies ◽  
2016 ◽  
Vol 9 (11) ◽  
pp. 870 ◽  
Author(s):  
Carlo Ruzzo ◽  
Giuseppe Failla ◽  
Maurizio Collu ◽  
Vincenzo Nava ◽  
Vincenzo Fiamma ◽  
...  
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Decomposition Method ◽  
Domain Decomposition Method ◽  
Operational Modal Analysis ◽  
Floating Platform ◽  
Frequency Domain Decomposition

Ambient Response Modal Analysis on a CEM-1 Single-Layer Printed Circuit Board

2013 ◽  
Vol 393 ◽  
pp. 683-687
Author(s):  
M. Azhan Anuar ◽  
A.A. Mat Isa ◽  
A.R. Zamri ◽  
M.F.M. Said
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Printed Circuit Boards ◽  
Printed Circuit Board ◽  
Single Layer ◽  
Circuit Board ◽  
Valuable Insight ◽  
Printed Circuit ◽  
Frequency Domain Decomposition

Since the level of vibration always depends on the natural frequencies of the system, it is important to know the modal parameters of such system to control failure and provide prevention actions. The demand for structurally reliable Printed Circuit Boards (PCB) has increased as more functions are required from electronic products along with less weight and smaller size. This imposes certain limitations and critical requirements. In this paper, investigation on the dynamic characteristics of CEM-1 Single-layer PCB using Operational Modal Analysis (OMA, or often called Output-Only or Ambient Modal analysis), is presented. The Frequency Domain Decomposition (FDD) and Enhanced Frequency Domain Decomposition (EFDD) techniques are applied on the PCB with free-free end condition. Comparison of results between both techniques and also with the result from Experimental Modal Analysis (EMA), will be shown. The understanding on dynamic behaviour of this structure provides valuable insight into the nature of the response and remarkable enhancement of its model, strength and vibration.

scholarly journals Análisis de métodos OMA para la extracción de parámetros modales sobre edificios existentes

2021 ◽  
Vol 33 (2) ◽  
pp. 75-93
Author(s):  
Víctor Samaniego Galindo ◽  
Iván Palacios Serrano ◽  
José Placencia León ◽  
Milton Muñoz Calle ◽  
Santiago González Martínez ◽  
...  
Keyword(s):  
Domain Decomposition ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Operational Modal Analysis ◽  
Frequency Domain Decomposition

En este artículo se presenta la aplicación de métodos de análisis modal operacional (OMA, Operational Modal Analysis) con el objetivo de caracterizar los parámetros modales (v.g. frecuencias y modos de vibración) de una edificación. El estudio se realiza sobre un escenario real consistente en un edificio esencial. En concreto se emplea: el método de descomposición en el dominio de la frecuencia (FDD, Frequency Domain Decomposition) y su versión mejorada (EFDD, Enhanced-FDD). En una primera etapa, se lleva a cabo una evaluación estructural preliminar del edificio (empleando el método de inspección visual rápida, RVS), un levantamiento de dimensiones y ensayos en campo para la caracterización mecánica de sus componentes, todo ello con el propósito de conseguir un análisis modal convencional lo más fiable posible en términos de sus parámetros modales. Con base en este análisis modal, se diseña un plan de instrumentación con acelerómetros triaxiales de sistemas microelectromecánicos (MEMS); el proceso de instrumentación abarca tres etapas: la adquisición, el control y el almacenamiento de información. La principal contribución de este trabajo consiste en la evaluación de la aplicación de los métodos FDD y EFDD sobre un edificio esencial, con la particularidad del uso de vibraciones de microsismicidad para la identificación de parámetros modales. El análisis de los resultados obtenidos determina una frecuencia fundamental del edificio de 1.43 Hz, y evidencia un comportamiento modal no recomendado.

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