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Andersen, M. S., Johansson, J., Brandt, A. & Hansen, S. O. (2016). Aerodynamic stability of long span suspension bridges with low torsional natural frequencies. Engineering structures, 120, 82-91
Open this publication in new window or tab >>Aerodynamic stability of long span suspension bridges with low torsional natural frequencies
2016 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 120, p. 82-91Article in journal (Refereed) Published
Abstract [en]

Classical flutter of suspended bridge decks can be avoided if the torsional frequencies are lower than the vertical. Wind tunnel tests of single boxes and twin box section models with torsional natural frequencies above and below the vertical frequency has been conducted. Flutter was avoided in all tests where the torsional frequency was lower than the vertical. But too low torsional stiffness caused large static displacements of the girder at medium–high wind speeds and steady state oscillations driven by a combination of torsional divergence and stalling behavior at the critical wind seed. In order to design aerodynamically stable suspension bridges with low torsional natural frequencies it is suggested to increase the mass moment of inertia and provide adequate torsional stiffness by the main cables spacing.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Long-span bridge, Flutter, Torsional divergence, Aerodynamics, Wind–structure interaction, Aeroelasticity, Wind tunnel experiments, Non-flutter design principle
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56901 (URN)10.1016/j.engstruct.2016.04.025 (DOI)
Available from: 2016-10-03 Created: 2016-09-28 Last updated: 2017-11-30Bibliographically approved
Andersen, M. S. & Brandt, A. (2016). An alternative to the flutter derivatives. In: BBAA VIII, 8th International Colloquium on Bluff Body Aerodynamics and Applications, Northeastern University, Boston, Massachusetts, USA, June 7-11, 2016: colloquium proceedings. Paper presented at BBAA VIII: 8th International Colloquium on Bluff Body Aerodynamics and Applications, Boston, USA, June 7-11, 2016. Boston: Northeastern University, College of Engineering
Open this publication in new window or tab >>An alternative to the flutter derivatives
2016 (English)In: BBAA VIII, 8th International Colloquium on Bluff Body Aerodynamics and Applications, Northeastern University, Boston, Massachusetts, USA, June 7-11, 2016: colloquium proceedings, Boston: Northeastern University, College of Engineering , 2016Conference paper, Published paper (Refereed)
Abstract [en]

A new simplified framework to study flutter and assess the full scale flutter wind speed is suggested. The flutter instability problem is reduced from a problem involving 8 flutter derivatives to only 4 coefficients. With this method it is possible to estimate the self-excited forces with increased precision by using stability diagrams. Furthermore, the physical transparency of the aerodynamic damping and stiffness terms is increased because the development in vertical and torsional damping and stiffness is analysed instead of flutter derivatives.

Place, publisher, year, edition, pages
Boston: Northeastern University, College of Engineering, 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56900 (URN)
Conference
BBAA VIII: 8th International Colloquium on Bluff Body Aerodynamics and Applications, Boston, USA, June 7-11, 2016
Available from: 2016-10-06 Created: 2016-09-28 Last updated: 2016-10-06Bibliographically approved
Brandt, A. & Kjær, C. (2016). Flipping the classroom for a class on experimental vibration analysis. In: James De Clerck & David S. Epp (Ed.), Rotating Machinery, Hybrid Test Methods, Vibro-Acoustics & Laser Vibrometry, Volume 8: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016. Paper presented at IMAC XXXIV: 34th Conference and Exposition on Structural Dynamics of Multiphysical Systems, Orlando, USA, January 25-28, 2016 (pp. 155-159). Springer, 8
Open this publication in new window or tab >>Flipping the classroom for a class on experimental vibration analysis
2016 (English)In: Rotating Machinery, Hybrid Test Methods, Vibro-Acoustics & Laser Vibrometry, Volume 8: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016 / [ed] James De Clerck & David S. Epp, Springer, 2016, Vol. 8, p. 155-159Conference paper, Published paper (Refereed)
Abstract [en]

Flipped classroom is a relatively new teaching form in higher education which is aimed at improving the learning process by engaging students in pre-class video activities fostering more active discussions between lecturer and student in-class. The concept is that the students watch recorded lectures (lower-order thinking skills) at home prior to class. During the class the students work on assignments and discuss the course content which can make better use of the teacher as a facilitator, so the focus can be on the more difficult things (higher-order cognitive skills) in the course content. In the present paper, the design and implementation using the flipped classroom technique for a course on experimental vibration analysis is presented. Some important experiences are discussed and an evaluation of student experiences is presented. The outcome is that the teaching technique is relatively time consuming to implement, but that the students appreciate being able to watch the lectures at their own pace and having more time working with the difficult things together with the teacher. Also, it turned out that the way the videos were used was very different among different students.

Place, publisher, year, edition, pages
Springer, 2016
Series
Conference Proceedings of the Society for Experimental Mechanics Series, ISSN 2191-5644
Keywords
Flipped classroom, Experimental vibration analysis, Video lectures, Multiple-choice questions, Evaluation
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56931 (URN)10.1007/978-3-319-30084-9_14 (DOI)9783319300832 (ISBN)9783319300849 (ISBN)
Conference
IMAC XXXIV: 34th Conference and Exposition on Structural Dynamics of Multiphysical Systems, Orlando, USA, January 25-28, 2016
Available from: 2016-10-06 Created: 2016-09-28 Last updated: 2016-10-06Bibliographically approved
Brandt, A., Berardengo, M., Manzoni, S. & Cigada, A. (2016). Harmonic scaling of mode shapes for operational modal analysis. In: The 28th International Conference on Noise and Vibration Engineering 2016 (ISMA 2016): proceedings of a meeting held 19-21 September 2016, Leuven, Belgium. Including USD 2016. Paper presented at The 28th International Conference on Noise and Vibration Engineering (ISMA 2016), Leuven, Belgium, September 19-21, 2016. Leuven: Katholieke Universiteit Leuven, Department of Mechanical Engineering
Open this publication in new window or tab >>Harmonic scaling of mode shapes for operational modal analysis
2016 (English)In: The 28th International Conference on Noise and Vibration Engineering 2016 (ISMA 2016): proceedings of a meeting held 19-21 September 2016, Leuven, Belgium. Including USD 2016, Leuven: Katholieke Universiteit Leuven, Department of Mechanical Engineering , 2016Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
Leuven: Katholieke Universiteit Leuven, Department of Mechanical Engineering, 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56969 (URN)
Conference
The 28th International Conference on Noise and Vibration Engineering (ISMA 2016), Leuven, Belgium, September 19-21, 2016
Available from: 2016-10-25 Created: 2016-09-28 Last updated: 2016-10-25Bibliographically approved
Brandt, A. & Singhal, R. (Eds.). (2016). Shock & Vibration, Aircraft/Aerospace, Energy Harvesting, Acoustics & Optics, Volume 9: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016 (1ed.). Springer
Open this publication in new window or tab >>Shock & Vibration, Aircraft/Aerospace, Energy Harvesting, Acoustics & Optics, Volume 9: Proceedings of the 34th IMAC, A Conference and Exposition on Structural Dynamics 2016
2016 (English)Collection (editor) (Other academic)
Abstract [en]

Shock Vibration, Aircraft /Aerospace, Energy Harvesting, Acoustics Optics, Volume 9. Proceedings of the 34th IMAC, A Conference and Exposition on Dynamics of Multiphysical Systems: From Active Materials to Vibroacoustics, 2016, the ninth volume of ten from the Conference brings together contributions to this important area of research and engineering. The collection presents early fi ndings and case studies on fundamental and applied aspects of Structural Dynamics, including papers on:• Energy Harvesting• Adaptive Support• Shock Calibration• Operating Data Applications• Aerospace Testing Techniques• Aircraft /Aerospace Applications• Joints• Acoustics & Optics• Other Sensing

Place, publisher, year, edition, pages
Springer, 2016. p. 209 Edition: 1
Series
Conference Proceedings of the Society for Experimental Mechanics Series, ISSN 2191-5644
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56939 (URN)10.1007/978-3-319-30087-0 (DOI)9783319300863 (ISBN)9783319300870 (ISBN)
Available from: 2016-09-28 Created: 2016-09-28 Last updated: 2016-10-03Bibliographically approved
Brandt, A. (2016). Some educational vibration measurement exercises. Sound & vibration (January), 12-14
Open this publication in new window or tab >>Some educational vibration measurement exercises
2016 (English)In: Sound & vibration, ISSN 1541-0161, no January, p. 12-14Article in journal (Other academic) Published
Abstract [en]

Four exercises are presented to teach experimental vibration measurements: mass calibration; accelerometer mounting; singledegree-of-freedom vibration measurement and analysis; and fullscale experimental modal analysis.

Place, publisher, year, edition, pages
Acoustical Publications, Inc., 2016
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56906 (URN)
Available from: 2016-10-03 Created: 2016-09-28 Last updated: 2017-11-30Bibliographically approved
Brandt, A. (2015). Comparison and assessment of Methods to treat harmonics in Operational Modal Analysis. In: Paper presented at ICEDyn 2015, International conference on structural engineering dynamics 2015, Lagos, Portugal, June 22-24, 2015: . Paper presented at ICEDyn 2015, International conference on structural engineering dynamics 2015, Lagos, Portugal, June 22-24, 2015.
Open this publication in new window or tab >>Comparison and assessment of Methods to treat harmonics in Operational Modal Analysis
2015 (English)In: Paper presented at ICEDyn 2015, International conference on structural engineering dynamics 2015, Lagos, Portugal, June 22-24, 2015, 2015Conference paper, Published paper (Refereed)
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56907 (URN)
Conference
ICEDyn 2015, International conference on structural engineering dynamics 2015, Lagos, Portugal, June 22-24, 2015
Available from: 2016-10-25 Created: 2016-09-28 Last updated: 2016-10-25Bibliographically approved
Orlowitz, E., Andersen, P. & Brandt, A. (2015). Comparison of Simultaneous and Multi-setup Measurement Strategies in Operational Modal Analysis. In: 6th International Operational Modal Analysis Conference (IOMAC 2015), Gijón, Spain, 12-14 May 2015: . Paper presented at 6th International Operational Modal Analysis Conference (IOMAC), Gijón, Spain, May 12-14, 2015 (pp. 598-610). International Operational Modal Analysis Conference (IOMAC)
Open this publication in new window or tab >>Comparison of Simultaneous and Multi-setup Measurement Strategies in Operational Modal Analysis
2015 (English)In: 6th International Operational Modal Analysis Conference (IOMAC 2015), Gijón, Spain, 12-14 May 2015, International Operational Modal Analysis Conference (IOMAC) , 2015, p. 598-610Conference paper, Published paper (Refereed)
Abstract [en]

For operational modal analysis (OMA) the multi-setup (or roving sensors) measurements strategy are often applied because the number of wanted measurement DOFs exceeds the number of available sensors. Studies of potential effects of applying the multi-setup strategy in contrast to the optimal simultaneous measurement strategy have, however rarely been reported. Classically, multi-setup datasets are merged together in a post-identification step, known as the patch based approach in experimental modal analysis. Recently, methods for merging the datasets in a pre-identification step has been suggested in the literature, but none of these methods have been compared with simultaneous measurement data. The present paper presents experimental results from an OMA obtained from a measurement consisting of 45 sensors simultaneously measured on a ship in operation. The modal parameters have been estimated for the full dataset, and for three artificially created multi-setup tests based on the full dataset. The first multi-setup test is composed of five datasets that are parallel in time, hence consistency between the datasets is guaranteed. The second test is also parallel in time but with two datasets, and the third test is composed of the same two datasets, but serial in time, hence consistency between the datasets is not guaranteed. For the multi-setup tests merging of the datasets have been done both with pre- and a post-identification methods and the modal parameters are compared with the ones estimated from the simultaneous measurement data. It is shown that using multi-setup tests systematic errors can occur especially in the damping estimates. The tested case where consistency between the datasets could not be guaranteed larger error was observed than when consistency was ensured. In addition, it was found that when mode shapes are of high importance the number of measured DOFs in each dataset should be sufficient larger in order to have a good estimate of the mode shapes.

Place, publisher, year, edition, pages
International Operational Modal Analysis Conference (IOMAC), 2015
Keywords
Operational Modal Analysis, Experimental data, Measurement strategy, Damping estimation, Comparison
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56959 (URN)9781510803671 (ISBN)
Conference
6th International Operational Modal Analysis Conference (IOMAC), Gijón, Spain, May 12-14, 2015
Available from: 2016-10-25 Created: 2016-09-28 Last updated: 2016-10-25Bibliographically approved
Orlowitz, E. & Brandt, A. (2015). Damping Estimation from Operational and Experimental Modal Analysis on a Laboratory Test Plate. In: 6th International Operational Modal Analysis Conference (IOMAC 2015), Gijón, Spain, 12-14 May 2015: . Paper presented at 6th International Operational Modal Analysis Conference (IOMAC), Gijón, Spain, May 12-14, 2015 (pp. 305-318). International Operational Modal Analysis Conference (IOMAC), Article ID 33.
Open this publication in new window or tab >>Damping Estimation from Operational and Experimental Modal Analysis on a Laboratory Test Plate
2015 (English)In: 6th International Operational Modal Analysis Conference (IOMAC 2015), Gijón, Spain, 12-14 May 2015, International Operational Modal Analysis Conference (IOMAC) , 2015, p. 305-318, article id 33Conference paper, Published paper (Refereed)
Abstract [en]

Operational modal analysis (OMA) is widely used whenever the dynamic characteristics of structuresthat do not fit into a laboratory are needed. In addition, OMA offers a test of the structure under itsreal boundary conditions which can be preferable for validation of numerical models. Theoretically, atleast, the natural frequencies and damping ratios should be identically estimated by an OMA test andan experimental modal analysis (EMA) test. However it is still commonly believed that an EMA testis more reliable because of the available information and controlled environment. The present paperpresents an experimental study of EMA and OMA tests of a Plexiglas plate under free-free conditions.The plate which is a simple geometry is designed to have closely spaced modes and is seen as a goodstructure for comparison. Modal parameters are compared between the EMA and OMA test and it isfound that natural frequencies and mode shapes are similar within 0.2 % (MAC), whereas the dampingratios showed differences up to 7.7 % and are consistently lower for the OMA test. This differences indamping were possibly caused by slightly nonlinear boundary conditions combined with the fact that thevibration levels for the EMA test were higher than for the OMA test.

Place, publisher, year, edition, pages
International Operational Modal Analysis Conference (IOMAC), 2015
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56961 (URN)9781510803671 (ISBN)
Conference
6th International Operational Modal Analysis Conference (IOMAC), Gijón, Spain, May 12-14, 2015
Available from: 2016-10-06 Created: 2016-09-28 Last updated: 2016-10-25Bibliographically approved
Chao, O. Z., Kor, M. A. A. & Brandt, A. (2015). Experimental Validation of Phase synchronisation effects in optimising impact-synchronous time averaging. In: International Operational Modal Analysis Conference (IOMAC): . Paper presented at 6th International Operational Modal Analysis Conference (IOMAC 2015), Gijón, Spain, 12-14 May 2015. International Operational Modal Analysis Conference (IOMAC)
Open this publication in new window or tab >>Experimental Validation of Phase synchronisation effects in optimising impact-synchronous time averaging
2015 (English)In: International Operational Modal Analysis Conference (IOMAC), International Operational Modal Analysis Conference (IOMAC) , 2015Conference paper, Published paper (Refereed)
Abstract [en]

A novel modal analysis technique called Impact-Synchronous Modal Analysis (ISMA) was introduced in previous research. With the utilisation of Impact-Synchronous Time Averaging (ISTA), modal testing can be performed in presence of ambient forces whereas the conventional method requires machines to be shut down. However, lack of information of phase angles with respect to impact in ISTA has caused this modal testing method to be labour-intensive and time-consuming. The effect of the phase angle of the disturbance with respect to the impact is found to be very important when performing modal testing on structures with dominant periodic responses from cyclic loads. Synchronisation of phases between impacts and periodic response from cyclic loads should be avoided to enhance the effectiveness of ISTA. The assessment showed that a few averages are sufficient to eliminate the non-synchronous components when the phase angles with respect to the impact are inconsistent for every impact applied.

Place, publisher, year, edition, pages
International Operational Modal Analysis Conference (IOMAC), 2015
Keywords
Experimental Modal Analysis, Impact-Synchronous Modal Analysis, Impact-Synchronous Time Averaging, modal testing, Operational Modal Analysis, Phase Synchronisation
National Category
Mechanical Engineering
Identifiers
urn:nbn:se:lnu:diva-56958 (URN)9781510803671 (ISBN)
Conference
6th International Operational Modal Analysis Conference (IOMAC 2015), Gijón, Spain, 12-14 May 2015
Available from: 2016-10-25 Created: 2016-09-28 Last updated: 2016-10-25Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2025-7842

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