Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(operational mode shape). Showing records 1 – 3 of 3 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters

1. Aghdasi, AmirHossein. Application of transmissibility measurement in estimation of modal parameters for a structure.

Degree: 2013, , School of Engineering

Identification of modal parameters from output-only data is studied in this work. The proposed methodology uses transmissibility functions obtained under different loading conditions to identify resonances and mode shapes. The technique is demonstrated with numerical simulations on a 2-DOF system and a cantilever beam. To underpin the simulations, a real test was done on a beam to show the efficiency of the method. A practical application of the method can be to identify structures subjected to moving loads. This is demonstrated by using FEM-model of a cantilever beam with a moving load.

Operational Modal Analysis (OMA) is being increasingly used as an experimental technique to identify the dynamic properties of many types of large-scale constructed systems. For industrial structures in real operation condition, it is sometimes hard or impossible to measure excitation forces so some identification techniques have been developed to work on response data only. In Operational Modal Analysis (OMA), there is no need to make any assumption about the nature of force and consequently resonance frequencies are recognised. In this thesis, one application of Operational Modal Analysis which is called transmissibility measurement is supposed to be engaged to find resonance frequencies. Operational Modal Analysis has become a valid alternative for structures where a classic forced-vibration test would be difficult to conduct. The use of in-operation modal analysis is particularly interesting because the structure remains in its normal in-operating condition during the test. This is an important advantage because the conditions during a laboratory forced-vibration test are often considerably different from the real working conditions regardless of constraints and limitations. Therefore, this method enables us to find system parameters without any assumption about the nature of the forces.

Phone : +46704997666 E-mail : [email protected]

Subjects/Keywords: Operational Modal Analysis; Transmissibility measurement; mode shape; MATLAB.

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Aghdasi, A. (2013). Application of transmissibility measurement in estimation of modal parameters for a structure. (Thesis). , School of Engineering. Retrieved from http://urn.kb.se/resolve?urn=urn:nbn:se:bth-6188

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Aghdasi, AmirHossein. “Application of transmissibility measurement in estimation of modal parameters for a structure.” 2013. Thesis, , School of Engineering. Accessed July 16, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-6188.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Aghdasi, AmirHossein. “Application of transmissibility measurement in estimation of modal parameters for a structure.” 2013. Web. 16 Jul 2019.

Vancouver:

Aghdasi A. Application of transmissibility measurement in estimation of modal parameters for a structure. [Internet] [Thesis]. , School of Engineering; 2013. [cited 2019 Jul 16]. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:bth-6188.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Aghdasi A. Application of transmissibility measurement in estimation of modal parameters for a structure. [Thesis]. , School of Engineering; 2013. Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:bth-6188

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Queensland University of Technology

2. Wang, Liang. Innovative damage assessment of steel truss bridges using modal strain energy correlation.

Degree: 2012, Queensland University of Technology

As a part of vital infrastructure and transportation network, bridge structures must function safely at all times. Bridges are designed to have a long life span. At any point in time, however, some bridges are aged. The ageing of bridge structures, given the rapidly growing demand of heavy and fast inter-city passages and continuous increase of freight transportation, would require diligence on bridge owners to ensure that the infrastructure is healthy at reasonable cost. In recent decades, a new technique, structural health monitoring (SHM), has emerged to meet this challenge. In this new engineering discipline, structural modal identification and damage detection have formed a vital component. Witnessed by an increasing number of publications is that the change in vibration characteristics is widely and deeply investigated to assess structural damage. Although a number of publications have addressed the feasibility of various methods through experimental verifications, few of them have focused on steel truss bridges. Finding a feasible vibration-based damage indicator for steel truss bridges and solving the difficulties in practical modal identification to support damage detection motivated this research project. This research was to derive an innovative method to assess structural damage in steel truss bridges. First, it proposed a new damage indicator that relies on optimising the correlation between theoretical and measured modal strain energy. The optimisation is powered by a newly proposed multilayer genetic algorithm. In addition, a selection criterion for damage-sensitive modes has been studied to achieve more efficient and accurate damage detection results. Second, in order to support the proposed damage indicator, the research studied the applications of two state-of-the-art modal identification techniques by considering some practical difficulties: the limited instrumentation, the influence of environmental noise, the difficulties in finite element model updating, and the data selection problem in the output-only modal identification methods. The numerical (by a planer truss model) and experimental (by a laboratory through truss bridge) verifications have proved the effectiveness and feasibility of the proposed damage detection scheme. The modal strain energy-based indicator was found to be sensitive to the damage in steel truss bridges with incomplete measurement. It has shown the damage indicator's potential in practical applications of steel truss bridges. Lastly, the achievement and limitation of this study, and lessons learnt from the modal analysis have been summarised.

Subjects/Keywords: steel structures, structural health monitoring, through-truss bridge, natural frequency, mode shape, modal strain energy, damage detection, modal correlation, modal coherence, damage sensitivity, genetic algorithm, operational modal analysis; finite element model, finite element analysis, model updating, modal identification, modal test, vibration test, frequency domain decomposition, stochastic subspace identification, operational modal analysis, ambient vibration, output-only modal analysis; accelerometer, randomness check

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Wang, L. (2012). Innovative damage assessment of steel truss bridges using modal strain energy correlation. (Thesis). Queensland University of Technology. Retrieved from https://eprints.qut.edu.au/53177/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Wang, Liang. “Innovative damage assessment of steel truss bridges using modal strain energy correlation.” 2012. Thesis, Queensland University of Technology. Accessed July 16, 2019. https://eprints.qut.edu.au/53177/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Wang, Liang. “Innovative damage assessment of steel truss bridges using modal strain energy correlation.” 2012. Web. 16 Jul 2019.

Vancouver:

Wang L. Innovative damage assessment of steel truss bridges using modal strain energy correlation. [Internet] [Thesis]. Queensland University of Technology; 2012. [cited 2019 Jul 16]. Available from: https://eprints.qut.edu.au/53177/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Wang L. Innovative damage assessment of steel truss bridges using modal strain energy correlation. [Thesis]. Queensland University of Technology; 2012. Available from: https://eprints.qut.edu.au/53177/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


Brigham Young University

3. Solomon, Brad K. Methods for Identifying Acoustic Emissions From the Front Face of a Small Piezoelectric Blower.

Degree: MS, 2012, Brigham Young University

This thesis focuses on identifying acoustic noise generating components in piezoelectric blowers through transverse velocity measurements and the development of a numerical fluid model. Piezoelectric ceramics have proven useful for many industries and areas of research involving: high precision actuators, noise control, ultrasonic devices, and many other areas. As of late, a unique adaptation of piezoelectric ceramics is surfacing in the area of pumping and cooling. Air pumps that use these ceramics replace the traditional electric motor, resulting in lower power consumption, less moving parts, constant pressure gradients, lower overall weight, and a low profile. The current drawback of this application is the acoustic radiation produced by the blowers. Since these blowers are new to market, little research or development has been done to characterize the noise emissions. This thesis studies the acoustic emissions from the front face of a Murata piezoelectric blower. Jet noise and structural vibrations are two acoustic sources of interest that are studied in this research. A Direct Numerical Simulation (DNS) of the fluid flow through a Murata blower is developed to better identify noise generating mechanisms. The model solutions predict trends in sound pressure levels (SPL) of the jet noise and volumetric flow rates. Both the SPL and flow rate are shown to be functions of critical geometrical dimensions within the flow path of a Murata blower. Important dimensional components are identified as well as non-influential ones. Design guidelines are given to reduce noise emission from the front side of a blower and increase the volumetric flow rate. The results of this research have a direct impact on the piezoelectric blower industry and future blower designs.

Subjects/Keywords: piezoelectric blower; structural vibrations; jet noise; acoustic noise; plate radiation; turbulence; DNS; CFD; transverse velocity; radiation resistance; sound power; sound pressure level; volumetric flow rate; operational mode shape; anechoic; nozzle radius; nozzle length; pumping chamber; Mechanical Engineering

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Solomon, B. K. (2012). Methods for Identifying Acoustic Emissions From the Front Face of a Small Piezoelectric Blower. (Masters Thesis). Brigham Young University. Retrieved from https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4541&context=etd

Chicago Manual of Style (16th Edition):

Solomon, Brad K. “Methods for Identifying Acoustic Emissions From the Front Face of a Small Piezoelectric Blower.” 2012. Masters Thesis, Brigham Young University. Accessed July 16, 2019. https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4541&context=etd.

MLA Handbook (7th Edition):

Solomon, Brad K. “Methods for Identifying Acoustic Emissions From the Front Face of a Small Piezoelectric Blower.” 2012. Web. 16 Jul 2019.

Vancouver:

Solomon BK. Methods for Identifying Acoustic Emissions From the Front Face of a Small Piezoelectric Blower. [Internet] [Masters thesis]. Brigham Young University; 2012. [cited 2019 Jul 16]. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4541&context=etd.

Council of Science Editors:

Solomon BK. Methods for Identifying Acoustic Emissions From the Front Face of a Small Piezoelectric Blower. [Masters Thesis]. Brigham Young University; 2012. Available from: https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=4541&context=etd

.