scholarly journals Operational Modal Analysis of the Cablestayed Footbridge

2017 ◽  
Vol 13 (2) ◽  
pp. 92-98 ◽  
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.

scholarly journals Non-Invasive Parameter Identification in Rotordynamics via Fluid Film Bearings: Linking Active Lubrication and Operational Modal Analysis

2016 ◽  
Author(s):  
Ilmar Ferreira Santos ◽  
Peter Kjær Svendsen
Keyword(s):  
Parameter Identification ◽  
Modal Analysis ◽  
Natural Frequencies ◽  
Transfer Functions ◽  
Injection Pressure ◽  
Operational Modal Analysis ◽  
Fluid Film ◽  
Non Invasive ◽  
Fluid Film Bearings

In recent years, theoretical and experimental efforts have transformed the conventional tilting-pad journal bearing (TPJB) into a smart mechatronic machine element. The application of electromechanical elements into rotating systems makes feasible the generation of controllable forces over the rotor as a function of a suitable control signal. The servovalve input signal and the radial injection pressure are the two main parameters responsible for dynamically modifying the journal oil film pressure and generating active fluid film forces in controllable fluid film bearings. Such fluid film forces, resulting from a strong coupling between hydrodynamic, hydrostatic and controllable lubrication regimes, can be used either to control or to excite rotor lateral vibrations. If non-invasive forces are generated via lubricant fluid film, in situ parameter identification can be carried out, enabling evaluation of the mechanical condition of the rotating machine. Using the lubricant fluid film as a non-invasive calibrated shaker is troublesome, once several transfer functions among mechanical, hydraulic and electronic components become necessary. In this framework the main original contribution of this paper is to show experimentally that the knowledge about the several transfer functions can be bypassed by using output-only identification techniques. The manuscript links controllable (active) lubrication techniques with operational modal analysis, allowing for in-situ parameter identification in rotordynamics, i.e. estimation of damping ratio and natural frequencies. The experimental analysis is carried out on a rigid rotor-level system supported by one single pair of pads. The estimation of damping and natural frequencies is performed using classical experimental modal analysis (EMA) and operational modal analysis (OMA). Very good agreements between the two experimental approaches are found. Maximum values of the main input parameters, namely servovalve voltage and radial injection pressure, are experimentally found with the objective of defining ranges of non-invasive perturbation forces.

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

Operational Modal Analysis for Dynamic Characterization of a Ro-Lo Ship

2014 ◽  
Vol 58 (04) ◽  
pp. 216-224 ◽  
Author(s):  
Esben Orlowitz ◽  
Anders Brandt
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Operating Conditions ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Dynamic Characterization ◽  
Sea Trial ◽  
Global Modes ◽  
Bending Modes

The dynamic characteristics of ship structures are becoming more important as the flexibility of modern ships increases, for example, to predict reliable design life. This requires an accurate dynamic model of the structure, which, because of complex vibration environment and complex boundary conditions, can only be validated by measurements. In the present paper the use of operational modal analysis (OMA) for dynamic characterization of a ship structure based on experimental data, from a full-scale measurement of a 210-m long Ro-Lo ship during sea trial, is presented. The measurements contain three different data sets obtained under different operating conditions of the ship: 10 knots cruising speed, 18 knots cruising speed, and at anchor. Natural frequencies, modal damping ratios, and mode shapes have been successfully estimated for the first 10 global modes. Damping ratios for the current ship were found within the range 0.9%–1.9% and natural frequencies were found to range from 0.8 to 4.1 Hz for the first 10 global modes of the ship at design speed (18 knots). The three different operating conditions showed, in addition, a speed dependency of the natural frequencies and damping ratios. The natural frequencies were found to be lower for the 18-knots condition compared with the two other conditions, most significantly for the vertical bending modes. Also, for the vertical bending modes, the damping ratios increased by 28%–288% when the speed increased from 10 to 18 knots. Other modes were not found to have the same strong speed dependency.

Static Load Test and Modal Analysis of Qingshui River Bridge

2012 ◽  
Vol 588-589 ◽  
pp. 166-169
Author(s):  
Jian Rong Yang ◽  
Zuo Xiong Zheng ◽  
He Xian Su ◽  
Zheng Cong Lai
Keyword(s):  
Modal Analysis ◽  
Natural Vibration ◽  
Static Load ◽  
Natural Frequencies ◽  
Load Test ◽  
Static Load Test ◽  
Efficiency Ratio ◽  
Bridge Structures ◽  
T Beam ◽  
Concrete Deck

A load test on a multi-girder concrete bridge of 30m Span having a non-composite deck slab is described. The bridge was designed to have eight simple supported spans, each consisting of a cross section with six RC T beam. Through analyzing the static and dynamic character of bridge structures, calculating efficiency ratio of load test, picking up the results of observation points, it was determined that the girders were acting non-compositely with the concrete deck and that significant restraint was being developed at the bearing supports. Modal analysis and identification ascertain the characteristic properties of bridges from their response. The damage in bridges may be reflected in the changes of their natural frequencies or modes of natural vibration.

scholarly journals Identification of Historical Veziragasi Aqueduct Using the Operational Modal Analysis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
E. Ercan ◽  
A. Nuhoglu
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Model Updating ◽  
Dynamic Properties ◽  
Dynamic Test ◽  
Element Model ◽  
Operational Modal Analysis ◽  
Modal Identification ◽  
Ambient Vibration ◽  
Mode Shapes

This paper describes the results of a model updating study conducted on a historical aqueduct, called Veziragasi, in Turkey. The output-only modal identification results obtained from ambient vibration measurements of the structure were used to update a finite element model of the structure. For the purposes of developing a solid model of the structure, the dimensions of the structure, defects, and material degradations in the structure were determined in detail by making a measurement survey. For evaluation of the material properties of the structure, nondestructive and destructive testing methods were applied. The modal analysis of the structure was calculated by FEM. Then, a nondestructive dynamic test as well as operational modal analysis was carried out and dynamic properties were extracted. The natural frequencies and corresponding mode shapes were determined from both theoretical and experimental modal analyses and compared with each other. A good harmony was attained between mode shapes, but there were some differences between natural frequencies. The sources of the differences were introduced and the FEM model was updated by changing material parameters and boundary conditions. Finally, the real analytical model of the aqueduct was put forward and the results were discussed.

scholarly journals NATURAL FREQUENCIES ESTIMATION USING OPERATIONAL MODAL ANALYSIS

2017 ◽  
Vol 19 (2) ◽  
pp. 21-35 ◽  
Author(s):  
Konstantin Kravchenko ◽  
Sergey Kugaevsky ◽  
Michail Zhuravlev ◽  
Dmitry Elkind
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Operational Modal Analysis

scholarly journals NATURAL FREQUENCIES ESTIMATION USING OPERATIONAL MODAL ANALYSIS

2017 ◽  
pp. 21-35 ◽  
Author(s):  
Konstantin Kravchenko ◽  
Sergey Kugaevsky ◽  
Michail Zhuravlev ◽  
Dmitry Elkind
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Operational Modal Analysis

scholarly journals DIC-Based Operational Modal Analysis of Bridges

2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Gongfa Chen ◽  
Zhihua Wu ◽  
Chunjian Gong ◽  
Jiqiao Zhang ◽  
Xiaoli Sun
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Operational Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Small Displacement ◽  
Dynamic Displacement ◽  
Bridge Model ◽  
Shooting Distance ◽  
Dic Technique

A new method has been proposed to identify the natural frequencies and mode shapes of a bridge model, in which the digital image correlation (DIC) technique is used to track the dynamic displacement. A key issue in vibration-based damage detection for a bridge is to determine its modal parameters. It is difficult to use traditional acceleration sensors to obtain the accurate mode shapes of bridges as the sensors are only deployed on a few measurement points of the bridges. In this article, the DIC technique is used to capture the movement of the entire experimental bridge model. A steel truss is used as a bridge model and stimulated by a hammer; its dynamic displacement is recorded by using a digital video camera. The correlation analysis is used to track the displacement of the points of interest, and their displacement time histories are inputted into a modal analysis system; the natural frequencies and mode shapes of the bridge model were obtained by both operational modal analysis (OMA) and traditional experimental modal analysis (EMA) methods. (1) The DIC results are compared with those obtained by a traditional acceleration sensor-based method; the natural frequencies obtained by the two measurement methods are very close. (2) The DIC results are sensitive to the amplitude of the measured displacement and the shooting distance; small displacement amplitudes and long shooting distance may result in the low quality of the measured time-history curves, and low-frequency noise signals might be observed in their power spectral density (PSD) curves, while they can be easily solved by the filtering method in this article. (3) In addition, the first frequencies obtained by EMA and OMA are very close, which validates the applicability of the DIC measurement under ambient excitation. The research has illustrated the feasibility of the DIC method for obtaining the modal parameters of the bridges.

scholarly journals The Reliability Testing of Brick Infrastructure with Operating Modal Analysis / Badanie Niezawodności Infrastruktury Murowej Z Użyciem Operacyjnej Analizy Modalnej

2013 ◽  
Vol 25 (1) ◽  
pp. 145-164
Author(s):  
Mariusz Żółtowski
Keyword(s):  
Modal Analysis ◽  
Operational Modal Analysis ◽  
Vibration Exciter ◽  
Building Structures ◽  
Structure Modification ◽  
Close Attention ◽  
Concrete Wall ◽  
Existing Building ◽  
Reinforced Concrete Wall ◽  
Engineering Mechanics

Abstract Modal analysis is widely used in the removal of defects caused by vibration of infrastructure, structure modification, updating the analytical model, or the control of the state and is used to monitor the vibration of structures in the aerospace and civil engineering mechanics from early 1990 began to pay close attention to the use of operational modal analysis (OMA) in a study of the existing building structures. In this case, the vibration exciter platforms, buildings, towers, bridges, etc. to force Operating (ambient). Here we measure only the response of the force generated by the environment. OMA is also very attractive for aerospace and mechanical engineering. This article presents the results of the existing building structure (reinforced concrete wall using operational modal analysis software and used to carry out the LMS and visualization of the results of such research.

scholarly journals Isomap-Based Three-Dimensional Operational Modal Analysis

2020 ◽  
Vol 2020 ◽  
pp. 1-18
Author(s):  
Cheng Wang ◽  
Weihua Fu ◽  
Haiyang Huang ◽  
Jianwei Chen
Keyword(s):  
Modal Analysis ◽  
Natural Frequencies ◽  
Three Dimensional ◽  
Transformation Matrix ◽  
Vibration Response ◽  
Operational Modal Analysis ◽  
Modal Parameter ◽  
Matrix Assembly ◽  
Random Decrement Technique ◽  
Low Dimensional

In order to identify the modal parameters of time invariant three-dimensional engineering structures with damping and small nonlinearity, a novel isometric feature mapping (Isomap)-based three-dimensional operational modal analysis (OMA) method is proposed to extract nonlinear features in this paper. Using this Isomap-based OMA method, a low-dimensional embedding matrix is multiplied by a transformation matrix to obtain the original matrix. We find correspondence relationships between the low-dimensional embedding matrix and the modal coordinate response and between the transformation matrix and the modal shapes. From the low-dimensional embedding matrix, the natural frequencies can be determined using a Fourier transform and the damping ratios can be identified by the random decrement technique or natural excitation technique. The modal shapes can be estimated from the Moore–Penrose matrix inverse of the low-dimensional embedding matrix. We also discuss the effects of different parameters (i.e., number of neighbors and matrix assembly) on the results of modal parameter identification. The modal identification results from numerical simulations of the vibration response signals of a cylindrical shell under white noise excitation demonstrate that the proposed method can identify the modal shapes, natural frequencies, and ratios of three-dimensional structures in operational conditions only from the vibration response signals.

Sign in / Sign up

Export Citation Format

Share Document