scholarly journals ESTIMATION OF STRUCTURAL DYNAMICS OF A MODEL BOOM OF DRAGLINE DRE-23 BY OUTPUT-ONLY SYSTEM IDENTIFICATION METHODS

2011 ◽  
Author(s):  
Zakir Faruquee ◽  
Hal Gurgenci
Keyword(s):  
System Identification ◽  
Modal Analysis ◽  
Damping Ratio ◽  
Canonical Variate ◽  
Identification Methods ◽  
Analysis Methods ◽  
Electrodynamic Shaker ◽  
Simulated Field ◽  
Output Only ◽  
Frequency Domain Decomposition

Two output -only system identification methods namely Canonical Variate Analysis (CVA) and Frequency Domain Decomposition (FDD) were used to estimate the dynamics (Mode shape, natural frequency and damping ratio) of the model boom of the dragline DRE 23. The boom was excited separately with an impulse hammer and with an electrodynamic shaker with chirp, random and simulated field excitations. In all cases, the excitations as well as the responses of the model boom were measured. The dynamics were obtained from the response measurements using Output-Only methods as well as from both the excitations and responses using conventional modal analysis methods. In all cases, the estimations of the dynamics by Output-Only methods were comparable if not better than those estimates obtained by the convention modal analysis methods.

Stochastic System Identification for Operational Modal Analysis: A Review

2001 ◽  
Vol 123 (4) ◽  
pp. 659-667 ◽  
Author(s):  
Bart Peeters ◽  
Guido De Roeck
Keyword(s):  
System Identification ◽  
Stochastic System ◽  
Instrumental Variable ◽  
Subspace Identification ◽  
Response Functions ◽  
Impulse Responses ◽  
Identification Methods ◽  
Operational Conditions ◽  
Stochastic Subspace Identification ◽  
Output Only

This paper reviews stochastic system identification methods that have been used to estimate the modal parameters of vibrating structures in operational conditions. It is found that many classical input-output methods have an output-only counterpart. For instance, the Complex Mode Indication Function (CMIF) can be applied both to Frequency Response Functions and output power and cross spectra. The Polyreference Time Domain (PTD) method applied to impulse responses is similar to the Instrumental Variable (IV) method applied to output covariances. The Eigensystem Realization Algorithm (ERA) is equivalent to stochastic subspace identification.

scholarly journals EXPERIMENTAL IDENTIFICATION OF AN ELASTO-MECHANICAL MULTI-DEGREE-OF-FREEDOM-SYSTEM USING STOCHASTIC SIGNALS

2016 ◽  
Vol 7 ◽  
pp. 64 ◽  
Author(s):  
Simon Schleiter ◽  
Okyay Altay ◽  
Sven Klinkel
Keyword(s):  
System Identification ◽  
Civil Engineering ◽  
Moving Average ◽  
Autoregressive Moving Average ◽  
Engineering Structures ◽  
Stochastic Signals ◽  
Identification Methods ◽  
Recent Developments ◽  
Rc Building ◽  
Frequency Domain Decomposition

The determination of dynamic parameters are the central points of the system identification of civil engineering structures under dynamic loading. This paper first gives a brief summary of the recent developments of the system identification methods in civil engineering and describes mathematical models, which enable the identification of the necessary parameters using only stochastic input signals. Relevant methods for this identification use Frequency Domain Decomposition (FDD), Autoregressive Moving Average Models (ARMA) and the Autoregressive Models with eXogenous input (ARX). In a first step an elasto-mechanical mdof-system is numerically modeled using FEM and afterwards tested numerically by above mentioned identification methods using stochastic signals. During the second campaign, dynamic measurements are conducted experimentally on a real 7-story RC-building with ambient signal input using sensors. The results are successfully for the relevant system identification methods.

An Identification Method for Damping Ratio of In Situ Building

2012 ◽  
Vol 446-449 ◽  
pp. 556-560
Author(s):  
Zhi Ying Zhang ◽  
Qing Sun ◽  
Zheng Yang
Keyword(s):  
Time Domain ◽  
Damping Ratio ◽  
Modal Parameter ◽  
Identification Methods ◽  
Random Decrement ◽  
Random Decrement Method ◽  
Output Only ◽  
Ambient Excitation

Damping evaluation is of great importance in predicting the dynamic response of systems. To get the accurate damping ratios of a system, many identification methods have been proposed and developed. But only few of them achieved accurate results for in-situ buildings due to the fact that the responses are significantly influenced by noise. This paper proposes a new method to accurately identify the damping ratios of in-situ buildings. The method is based on ambient excitation technique which requires no artificial excitation applied to SSI system and to measure output-only. The damping ratio identification is then performed by combining the improved random decrement method and Ibrahim time domain method. To demonstrate the validity of the proposed approach, a case study is performed and the results are compared with the conventional peak-peaking method results. The results show the proposed method can effectively identify the modal parameter of either frequencies or damping ratios of in-situ buildings subjected to ambient excitation.

scholarly journals Monitoring Rock Slope Instabilities Using Frequency Domain Decomposition Modal Analysis

2021 ◽  
Author(s):  
Mauro Häusler ◽  
Clotaire Michel ◽  
Jan Burjánek ◽  
Donat Fäh
Keyword(s):  
Domain Decomposition ◽  
Resonance Frequency ◽  
Modal Analysis ◽  
Frequency Domain ◽  
Normal Mode ◽  
Rock Slope ◽  
Damping Ratio ◽  
Slope Instabilities ◽  
Frequency Domain Decomposition ◽  
Unstable Rock

<p>Measuring ambient seismic vibration provides a promising tool to monitor unstable rock slopes due to its independence from actual surface deformations. It is generally observed that the seismic wavefield, arising from ambient vibrations, polarizes perpendicular to open fractures and that unstable slopes exhibit strong wavefield amplifications compared to stable reference sites. Rock slope instabilities dominated by deep persistent fracture sets exhibit normal mode behaviour due to standing wave phenomena within individual compartments of the unstable volume. Techniques to assess such behavior are well established in mechanical and civil engineering to assess the dynamic response and possibly the structural integrity of the structure studied.</p><p> </p><p>We performed enhanced frequency domain decomposition modal analysis on ambient vibration data acquired in real-time on an unstable rock site with a volume larger than 150,000 m<sup>3</sup> near Preonzo, Switzerland. We tracked the resonance frequency and normal mode polarization of the first two modes over a period of four years. In addition, we show the development of the modal damping ratio of the fundental mode over time, which is a measure of energy dissipation within and out of the system. We found that the dynamic properties of the rock structure experienced annual variations and that they are primarily controlled by temperature and only secondarily by the exension and closure of large-scale fractures. Even though no large slope failure was observed during the monitoring period, the dataset provides a reference model for ongoing slope monitoring, as the resonance frequency and damping ratio is expected to change significantly prior to failure.</p>

Application of Modal Identification Methods to Spatial Structure Using Field Measurement Data

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Wei Liu ◽  
Wei-cheng Gao ◽  
Yi Sun
Keyword(s):  
Finite Element ◽  
System Identification ◽  
Spatial Structure ◽  
Measurement Data ◽  
Element Model ◽  
Modal Identification ◽  
Modal Parameters ◽  
Identification Methods ◽  
Output Only ◽  
Leakage Error

Modal identification with output-only measurements plays a key role in vibration-based damage detection, model updating, and structural health monitoring in civil engineering. This paper addresses the application of modal identification method to a triangle steel tube truss natatorium using the field measurement data. To obtain dynamic characteristics of the spatial structure, four different output-only system identification methods are employed. They are natural excitation technique–eigensystem realization algorithm, data-driven stochastic subspace identification method, frequency-domain decomposition/frequency-spatial domain decomposition method, and half spectra/rational fractional orthogonal polynomial method. First an analytical modal analysis was performed on the three-dimensional finite element model according to the factual layout design to obtain the calculated frequencies and mode shapes. Then the whole procedure of the field vibration tests on the natatorium was presented. Finally, practical issues and efficiency of the four output-only modal identification techniques are investigated, and compared with the results from a finite element model. The system identification results demonstrate that both methods can provide reliable information on dynamic characteristics of the spatial structure. The frequency-domain methods, however, can quickly identify the modal parameters, but the leakage error introduced by power-spectral density estimation is existent due to the limited length of data. And the time-domain methods can avoid the leakage error, but the computational modes and the computational cost are the main two drawbacks in application. The conclusion is that several system identification methods should be consulted to ensure the accuracy of the estimated modal parameters.

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