scholarly journals A New Criterion for the Stabilization Diagram Used with Stochastic Subspace Identification Methods: An Application to an Aircraft Skeleton

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
E. Mrabet ◽  
M. Abdelghani ◽  
N. Ben Kahla
Keyword(s):  
Ambient Vibration ◽  
Subspace Identification ◽  
Identification Methods ◽  
Stochastic Subspace Identification ◽  
Correct Model ◽  
Power Spectral ◽  
Stabilization Diagram ◽  
Ambient Vibration Measurements ◽  
New Criterion ◽  
Spurious Modes

The modal parameters of a structure that is estimated from ambient vibration measurements are always subject to bias and variance errors. Accordingly the concept of the stabilization diagram is introduced to help users identify the correct model. One of the most important problems using this diagram is the appearance of spurious modes that should be discriminated to simplify modes selections. This study presents a new stabilization criterion obtained through a novel numerical implementation of the stabilization diagram and the discussion of model validation employing the power spectral density. As an application, an aircraft skeleton is used.

Investigation of modal damping ratios for stay cables based on stochastic subspace identification with ambient vibration measurements

2019 ◽  
Vol 22 (16) ◽  
pp. 3444-3460 ◽  
Author(s):  
Chien-Chou Chen ◽  
Wen-Hwa Wu ◽  
Szu-Ting Yu ◽  
Gwolong Lai
Keyword(s):  
Energy Dissipation ◽  
Damping Ratio ◽  
Ambient Vibration ◽  
Subspace Identification ◽  
Stochastic Subspace Identification ◽  
Modal Damping Ratio ◽  
Stay Cables ◽  
Modal Damping ◽  
Ambient Vibration Measurements ◽  
Cable Stayed Bridges

The stability assessment of stay cables based on the damping ratios of lower cable modes has attracted a large amount of research efforts. An accurate determination of those modal damping ratios is consequently required for the analysis or health monitoring of cable-stayed bridges. The aim of this study was to explore the challenge in accurately identifying the modal damping ratios of stay cable. The ambient vibration measurements collected from the stay cables of four cable-stayed bridges are investigated to cover different characteristics. A recently developed methodology based on stochastic subspace identification is adopted to determine the modal damping ratios of the cable. With the identified modal damping ratios for the stay cables of four bridges, comparison is made to examine the range of cable damping in different cable-stayed bridges and discuss the effects of several influence factors. It is found that the modal damping ratios for the stay cables of investigated bridges typically fall between 0% and 0.7%, close to the range from 0.05% to 0.5% reported by Post-Tensioning Institute. Moreover, it is also discovered that the modal damping ratio of the cable would decrease with increasing cable length if the energy dissipation mechanism of the cable principally comes from the anchorage device. In the cases where the middle free length section of the cable is filled with effective grouting materials, the modal damping ratio of the cable is not necessarily correlated with the cable length. Finally, the obtained results also indicate that the grouting material filled in the middle free length section of the cable defines the primary contribution to energy dissipation ranked by a descending order of ceresine wax, flexible polymer-modified cement and polyurethane foam.

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 OUTPUT-ONLY MODAL IDENTIFICATION OF TENSEGRITY STRUCTURES

2016 ◽  
Vol 8 (2) ◽  
pp. 52-64 ◽  
Author(s):  
Miniar Attig ◽  
Maher Abdelghani ◽  
Nabil ben Kahla
Keyword(s):  
Natural Frequencies ◽  
Modal Identification ◽  
Mode Shapes ◽  
Subspace Identification ◽  
Balanced Realization ◽  
Stochastic Subspace Identification ◽  
Tensegrity Systems ◽  
Stabilization Diagram ◽  
Subspace Algorithms ◽  
Output Only

Tensegrity systems are a special class of spatial reticulated structures that are composed of struts in compression and cables in tension. In this paper, the performance of stochastic subspace algorithms for modal identification of complex tensegrity systems is investigated. A sub-class algorithm of the Stochastic Subspace Identification family: the Balanced Realization Algorithm is investigated for modal identification of a tripod simplex structure and a Geiger dome. The presented algorithm is combined with a stabilization diagram with combined criteria (frequency, damping and mode shapes). It is shown that although the studied structures present closely spaced modes, the Balanced Realization Algorithm performs well and guarantees separation between closely-spaced natural frequencies. Modal identification results are validated through comparisons of the correlations (empirical vs. model based) showing effectiveness of the proposed methodology.

Stay Force Estimation in Cable-Stayed Bridges Using Stochastic Subspace Identification Methods

2017 ◽  
Vol 22 (9) ◽  
pp. 04017055 ◽  
Author(s):  
Seyed Ehsan Haji Agha Mohammad Zarbaf ◽  
Mehdi Norouzi ◽  
Randall J. Allemang ◽  
Victor J. Hunt ◽  
Arthur Helmicki ◽  
...  
Keyword(s):  
Subspace Identification ◽  
Force Estimation ◽  
Identification Methods ◽  
Stochastic Subspace Identification ◽  
Cable Stayed Bridges

scholarly journals Monitoring and Identification of Vibration Frequencies on a Portion of México City Metro Line 12

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Miguel Ángel García-Illescas ◽  
David Murià-Vila ◽  
Luis Alvarez-Icaza
Keyword(s):  
Mexico City ◽  
Frequency Estimation ◽  
Computational Cost ◽  
High Order ◽  
Ambient Vibration ◽  
Vibration Frequencies ◽  
Identification Methods ◽  
Frequency Monitoring ◽  
Ambient Vibration Measurements ◽  
Low Computational Cost

The use of recursive subspace-based identification methods is analyzed in the estimation of the most significant vibration frequencies along an elevated railroad segment of México City Metro Line 12 using ambient vibration measurements recorded from 2012, when the line was opened, to 2018. Due to the railroad characteristics, the use of high-order models and the systematic tuning of the methods are required to achieve low uncertainty in frequency estimation. A frequency history is generated using these high-order models in order to check for variations along the seven years where important events took place: two low- and one high-intensity earthquakes, paving, and construction of sidewalks and planters around the sensor station. Results are consistent for all methods under analysis in the identified frequencies, suggesting that the system has preserved its structural health. To produce independent results, spectral analysis was performed showing that the associated frequency history is again consistent with that generated with recursive subspace-based identification methods. Overall, results indicate that these subspace methods are suitable for frequency monitoring in the studied system offering, in the case of recursive N4SID, important advantages in terms of low computational cost, real-time implementation, and smaller uncertainty.

scholarly journals Experimental and Numerical Investigation on Dynamic Properties and Human-Induced Vibrations of an Asymmetric Steel-Plated Stress-Ribbon Footbridge

2021 ◽  
Vol 2021 ◽  
pp. 1-21
Author(s):  
Yi Zhang ◽  
Wei He ◽  
Jiewen Zhang ◽  
Hua Dong
Keyword(s):  
Dynamic Properties ◽  
Element Model ◽  
Ambient Vibration ◽  
Subspace Identification ◽  
Stochastic Subspace Identification ◽  
Deck Panels ◽  
Single Person ◽  
Ambient Vibration Testing ◽  
Measurement Results ◽  
Comprehensive Study

This paper presents a comprehensive study on dynamic properties and human-induced vibrations of a slender asymmetric steel-plated stress-ribbon footbridge via both experimental and analytical methods. Bridge modal test was conducted using both ambient vibration testing and impact methods. Modal properties of the bridge were identified based on stochastic subspace identification and peak-pick techniques. Results show that the bridge is characterized by closely spaced modes with low natural frequencies and small damping ratios (<0.002). A sophisticated finite element model that incorporates pretension of the stress ribbon and contribution of deck panels is developed and proven to be capable of reflecting the main dynamic characteristics of the bridge. Human-induced vibrations were measured considering synchronization cases, including single-person and small group walking as well as random walking cases. A theoretical model that takes into account human-structure interaction was developed, treating the single walking person as an SDOF system with biomechanical excited force. The validity of the model was further verified by measurement results.

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