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University of Melbourne
1.
Mahmood, S. M. Faisal.
State-space model identification for modal-based damage detection.
Degree: 2012, University of Melbourne
URL: http://hdl.handle.net/11343/37298 
► A modal-based global method for identification, localization and quantification of damage of shear frame structures is presented in this thesis. The method involves identification of…
(more)
▼ A modal-based global method for identification, localization and quantification of damage of shear frame structures is presented in this thesis. The method involves identification of modal parameters from the vibration responses of the structure only (output-only) using a combination of Natural Excitation Technique (NExT) and Eigensystem Realization Algorithm (ERA), and determination of stiffness values using very few identified modes by employing a least squares solution of the eigenvalue problem. Finally, damage is indicated by comparing the stiffnesses of the (possibly) damaged structure with that of the undamaged structure.
The implementation of NExT-ERA requires a reference channel and an order of the state-space model for modal identification, but several limitations of using a single reference channel and a particular order of the state-space model have been identified from the investigation of this study. To overcome the limitations, a new approach called Multi-Reference Based Mode Selection is proposed in this study. The approach makes use of all the available degree-of-freedoms (DOFs) as reference channels, but one at a time, to identify the best representative modes of the structure. An autonomous modal identification algorithm is also developed for fast online application of the approach.
The stiffness values of a shear frame structure can be determined by employing the least squares solution of the eigenvalue problem. Although the solution can be obtained by using a single natural frequency and the corresponding mode shape, it has been found from this study that the errors in the determination of stiffness values are significant when just one mode is used in the calculation. At least two modes are required to determine the stiffness values with reasonable accuracy. Consequently, two modes were used in the determination of stiffness values using the least squares solution of the eigenvalue problem.
The proposed damage detection methodology was implemented on the analytical Phase I and the experimental Phase II of the IASC-ASCE SHM benchmark problem. The negligible errors in the determination of modal parameters affirm that the methodology is robust in the presence of noise, but the methodology is found to be mildly sensitive to modeling errors, and because of that minor damage locations cannot be identified with certainty. Overall, from the investigation, it can be reported that the proposed methodology has an accuracy of around 90% in damage localization, and the determined severities of damages using it are very close to the actual ones.
Subjects/Keywords: damage detection; modal identification; Natural Excitation Technique; NExT; Eigensystem Realization Algorithm; ERA; Multi-Reference Based Mode Selection approach; benchmark problem
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APA (6th Edition):
Mahmood, S. M. F. (2012). State-space model identification for modal-based damage detection. (Masters Thesis). University of Melbourne. Retrieved from http://hdl.handle.net/11343/37298
Chicago Manual of Style (16th Edition):
Mahmood, S M Faisal. “State-space model identification for modal-based damage detection.” 2012. Masters Thesis, University of Melbourne. Accessed January 22, 2021.
http://hdl.handle.net/11343/37298.
MLA Handbook (7th Edition):
Mahmood, S M Faisal. “State-space model identification for modal-based damage detection.” 2012. Web. 22 Jan 2021.
Vancouver:
Mahmood SMF. State-space model identification for modal-based damage detection. [Internet] [Masters thesis]. University of Melbourne; 2012. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/11343/37298.
Council of Science Editors:
Mahmood SMF. State-space model identification for modal-based damage detection. [Masters Thesis]. University of Melbourne; 2012. Available from: http://hdl.handle.net/11343/37298
University of New South Wales
2.
Chowdhury, Mohammad Shakar.
Application of System Identification using ERA/NExT for Damage Assessment in Composite Laminates.
Degree: Engineering & Information Technology, 2017, University of New South Wales
URL: http://handle.unsw.edu.au/1959.4/57569
;
https://unsworks.unsw.edu.au/fapi/datastream/unsworks:44102/SOURCE02?view=true
► Polymer matrix composites are widely used in aircraft structures due to their superior specific stiffness and strength. However, laminated composites are susceptible to delaminations due…
(more)
▼ Polymer matrix composites are widely used in aircraft structures due to their superior specific stiffness and strength. However, laminated composites are susceptible to delaminations due to the low interlaminar fracture toughness of the matrix. Traditional NDI techniques for damage detection involve significant costs due to the requirement for the grounding of aircraft, shutdown time, and labour involved in inspections. Vibration monitoring for damage assessment in aircraft has several advantages such as being applicable in situ, not requiring external
excitation and the potential for application as a continuous structural health monitoring system. Frequency monitoring is employed in modern aircraft for engine diagnostics and identification of major faults; however, when applied to structural components, monitoring frequency shifts only identifies the presence of damage but not its exact location and severity. Eigensystem Realization Algorithm (ERA) has been proposed for application to many structural components but not for assessment of delamination in composites.This thesis proposes the application of ERA coupled with
Natural Excitation Technique (NExT) for delamination assessment in laminated composite structures, including stiffened composite panels. NExT provides the advantages that any type of
excitation of the structure can be employed and the location of the
excitation point need not be known. The algorithm for delamination assessment using ERA coupled with NExT was developed using Matlab code. The proposed method is first investigated and validated using transient vibration response generated by finite element simulation of composite laminates with delaminations. The simulated response is fed into the ERA/NExT algorithm to identify changes in the system parameters to estimate the location and reductions in bending stiffness in the damaged areas. The use of different types of
excitation modes and excitations provided at different locations have been examined. Sensitivity analyses have been performed conducted study the influence of spacing of measurement points on the accuracy of delamination size and severity estimated using responses by numerical modelling of composite beams and laminated plates. The proposed method is validated experimentally with vibration measurements conducted on laminated carbon/epoxy beams, plates and stiffened panels with embedded delaminations and estimating the location, size and severity of the delaminations in the samples from the measured dynamic responses.
Advisors/Committee Members: Shankar, Krishna, Engineering & Information Technology, UNSW Canberra, UNSW, Morozov, Evgeny, Engineering & Information Technology, UNSW Canberra, UNSW.
Subjects/Keywords: Eigensystem Realisation Algorithm; Vibration; Structural Health Monitoring; Natural Excitation Technique; Damage Assessment; Carbon Fiber Reinforced Polymer
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CSE |
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APA (6th Edition):
Chowdhury, M. S. (2017). Application of System Identification using ERA/NExT for Damage Assessment in Composite Laminates. (Doctoral Dissertation). University of New South Wales. Retrieved from http://handle.unsw.edu.au/1959.4/57569 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:44102/SOURCE02?view=true
Chicago Manual of Style (16th Edition):
Chowdhury, Mohammad Shakar. “Application of System Identification using ERA/NExT for Damage Assessment in Composite Laminates.” 2017. Doctoral Dissertation, University of New South Wales. Accessed January 22, 2021.
http://handle.unsw.edu.au/1959.4/57569 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:44102/SOURCE02?view=true.
MLA Handbook (7th Edition):
Chowdhury, Mohammad Shakar. “Application of System Identification using ERA/NExT for Damage Assessment in Composite Laminates.” 2017. Web. 22 Jan 2021.
Vancouver:
Chowdhury MS. Application of System Identification using ERA/NExT for Damage Assessment in Composite Laminates. [Internet] [Doctoral dissertation]. University of New South Wales; 2017. [cited 2021 Jan 22].
Available from: http://handle.unsw.edu.au/1959.4/57569 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:44102/SOURCE02?view=true.
Council of Science Editors:
Chowdhury MS. Application of System Identification using ERA/NExT for Damage Assessment in Composite Laminates. [Doctoral Dissertation]. University of New South Wales; 2017. Available from: http://handle.unsw.edu.au/1959.4/57569 ; https://unsworks.unsw.edu.au/fapi/datastream/unsworks:44102/SOURCE02?view=true
Virginia Tech
3.
Corcoran, Joseph Michael.
Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms.
Degree: MS, Mechanical Engineering, 2010, Virginia Tech
URL: http://hdl.handle.net/10919/31329
► In this thesis, an output-only experimental modal testing and analysis technique known as the Natural Excitation Technique (NExT) is examined for use with large residential…
(more)
▼ In this thesis, an output-only experimental modal testing and analysis
technique known as the
Natural Excitation Technique (NExT) is examined for use with large residential structures and interior cavities. The
technique which assumes a random, stationary input causing the response data is reviewed and extended for the first time to include the assumption of an impulse input. This
technique is examined with respect to the experimental modal analysis of single and two room residential structures. Each structure is first tested using conventional modal testing methods. Then, NExT is applied using each structureâ s response to a simulated sonic boom, an impulsive input. The results of these analyses along with the results obtained from a finite element model are compared. Then, the interior cavities enclosed by the residential structures are examined using NExT. Therefore, this thesis also demonstrates the successful use of NExT on acoustic systems for the first time. Three configurations of the interconnected cavities enclosed by the two room structure are considered to study physical phenomena. Both interior pressure response to random, stationary inputs and the sonic boom response are used with NExT to determine modal properties. The results of these analyses are compared to a theoretical analysis. Advantages to using NExT with both the response to a random, stationary input and an impulsive input are demonstrated for structural and acoustic systems.
Advisors/Committee Members: Burdisso, Ricardo A. (committeechair), Reichard, Georg (committee member), Inman, Daniel J. (committee member).
Subjects/Keywords: acoustic cavity; residential structure; sonic boom; Natural Excitation Technique (NExT); Modal testing
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APA ·
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APA (6th Edition):
Corcoran, J. M. (2010). Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms. (Masters Thesis). Virginia Tech. Retrieved from http://hdl.handle.net/10919/31329
Chicago Manual of Style (16th Edition):
Corcoran, Joseph Michael. “Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms.” 2010. Masters Thesis, Virginia Tech. Accessed January 22, 2021.
http://hdl.handle.net/10919/31329.
MLA Handbook (7th Edition):
Corcoran, Joseph Michael. “Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms.” 2010. Web. 22 Jan 2021.
Vancouver:
Corcoran JM. Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms. [Internet] [Masters thesis]. Virginia Tech; 2010. [cited 2021 Jan 22].
Available from: http://hdl.handle.net/10919/31329.
Council of Science Editors:
Corcoran JM. Output-Only Experimental Modal Testing of Large Residential Structures and Acoustic Cavities Using Sonic Booms. [Masters Thesis]. Virginia Tech; 2010. Available from: http://hdl.handle.net/10919/31329
University of Southern California
4.
Yun, Hae-Bum.
Analytical and experimental studies of modeling and
monitoring uncertain nonlinear systems.
Degree: PhD, Civil Engineering (Structural Mechanics), 2007, University of Southern California
URL: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/528810/rec/819
► The development of effective structural health monitoring (SHM) methodologies is imperative for the efficient maintenance of important structures in aerospace, mechanical and civil engineering. Based…
(more)
▼ The development of effective structural health
monitoring (SHM) methodologies is imperative for the efficient
maintenance of important structures in aerospace, mechanical and
civil engineering. Based on reliable condition assessment, the
owners of monitored structures can expect two important benefits:
to avoid catastrophic accidents by detecting various types of
structural deterioration during operation, and to establish
efficient maintenance means and time schedule to reduce maintenance
costs.; A vibration-based SHM methodology is evaluated for change
detection in nonlinear systems that can be frequently seen in many
engineering fields. The proposed methodology is advantageous over
existing SHM methodologies regarding the following aspects:
feasible to detect small changes in complex nonlinear systems,
possible to make physical interpretation of detected changes, and
possible to quantify the uncertainty associated with the change
detection.; A series of analytical and experimental studies was
performed to investigate various important issues in modeling and
monitoring of uncertain nonlinear systems. Different parametric and
non-parametric identification methods were compared for monitoring
purpose using full-scale nonlinear viscous dampers for seismic
mitigation in civil structures. Then, the effects of uncertainty on
change detection performance were investigated. Two types of
uncertainty were studied: measurement uncertainty and system
characteristic uncertainty. For measurement uncertainty, three
different types of full-scale nonlinear viscous dampers were used
to validate the proposed SHM methodology when the dampers' response
was polluted with random noise. For system characteristic
uncertainty, a semi-active magneto-rheological damper whose system
characteristics were determined through user controllable input
current was used. Statistical pattern recognition methods were
studied to detect relatively small changes in nonlinear systems
with different uncertainty types. The Bootstrap method, a
statistical data resampling
technique, was also studied to estimate
the uncertainty bounds of change detection when the measurement
data are insufficient for reliable statistical inference.; A
web-based real-time bridge monitoring system was developed and used
for a forensic study involving a cargo ship collision with the
Vincent Thomas Bridge, a critical suspension bridge in the
metropolitan Los Angeles region.
Advisors/Committee Members: Sami F. Masri (Committee Chair), Carter Wellford (Committee Member), Jiin-Jen Lee (Committee Member), John P. Caffrey (Committee Member), Roger G. Ghanem (Committee Member).
Subjects/Keywords: structural health monitoring; system identification; Restoring Force Method; artificial neural networks; Hypothesis Test; Bootstrap Method; statistical pattern recognition; support vector machines; k-means clustering; error analysis; detection theory; Natural Excitation Technique; Eigensystem Realization Algorithm; full-scale viscous dampers; magneto-rheological dampers; suspension bridge; web-based real-time bridge monitoring system; ship-bridge collision
Record Details
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Record Details
Similar Records
Cite
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yun, H. (2007). Analytical and experimental studies of modeling and
monitoring uncertain nonlinear systems. (Doctoral Dissertation). University of Southern California. Retrieved from http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/528810/rec/819
Chicago Manual of Style (16th Edition):
Yun, Hae-Bum. “Analytical and experimental studies of modeling and
monitoring uncertain nonlinear systems.” 2007. Doctoral Dissertation, University of Southern California. Accessed January 22, 2021.
http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/528810/rec/819.
MLA Handbook (7th Edition):
Yun, Hae-Bum. “Analytical and experimental studies of modeling and
monitoring uncertain nonlinear systems.” 2007. Web. 22 Jan 2021.
Vancouver:
Yun H. Analytical and experimental studies of modeling and
monitoring uncertain nonlinear systems. [Internet] [Doctoral dissertation]. University of Southern California; 2007. [cited 2021 Jan 22].
Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/528810/rec/819.
Council of Science Editors:
Yun H. Analytical and experimental studies of modeling and
monitoring uncertain nonlinear systems. [Doctoral Dissertation]. University of Southern California; 2007. Available from: http://digitallibrary.usc.edu/cdm/compoundobject/collection/p15799coll127/id/528810/rec/819
. 
Open Access Theses and Dissertations