Topic
Modal testing
About: Modal testing is a research topic. Over the lifetime, 4047 publications have been published within this topic receiving 64772 citations.
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TL;DR: This work investigates the leading order behavior of the ‘posterior uncertainties’ of the modal parameters in a Bayesian identification framework and shows rigorously that, among other results, the posterior c.o.v. of the natural frequency and damping ratio are asymptotically equal.
58 citations
01 Feb 2002
TL;DR: In this paper, Pitney Bowes et al. compared the LM19mblade modal analysis with a FE-modeling of a wind turbine blade and found good agreement for the dominating deflection direction.
Abstract: Modalanalysishasbeenusedtoidentifynaturalfrequencies,damp-ingcharacteristicsandmodeshapesofwindturbineblades.Differentexperimentalprocedureshavebeenconsideredandthemostappropri-ateofthesehasbeenselected.AlthoughthecomparisonisbasedonmeasurementsonaLM19mblade,therecommendationsgivenarebelievedtobevalidforothertypesofwindturbinebladesaswell.Thereliabilityoftheselectedexperimentalanalysishasbeenquantifiedbyes-timating the unsystematicvariations in the experimental findings. Satisfactoryresults have been obtained for natural frequencies, damping characteristics andforthedominatingdeflectiondirectionoftheinvestigatedmodeshapes.Fornon-dominating deflection directions of the investigated mode shapes, however, theobservedexperimental uncertainty may be considerable – especially for the tor-sionaldeflection.TheexperimentalanalysisoftheLM19mbladehasbeencomparedwithresultsfromaFE-modelingofthesameblade.Forsomeofthehighermodessubstantialdiscrepanciesbetween the naturalfrequencies originatingfrom the FE-modelingandthe modal analysis,respectively, areobserved.Comparing the mode shapes(normalized with respect to the tip deflection in the dominating deflection di-rection) good agreement has been demonstrated for the dominating deflectiondirection. For the non-dominating deflection directions, the qualitative features(i.e.theshape)ofmeasuredandcomputedmodesshapesareingoodagreement,whereastheyquantitativelymaydisplayconsiderabledeviations.Finally,suggestionsofpotentialfutureimprovementsofthe experimentalpro-cedurearediscussed.ISBN87–550–2696–6ISBN87–550–2697–4(Internet)ISSN0106–2840Print:PitneyBowesManagementServicesDenmarkA/S,2002
58 citations
TL;DR: In this article, different experimental techniques for obtaining modal parameters of structures are described, focusing on those techniques that may be applicable to in situ concrete structures (e.g. bridges) and the influence of the nonlinear behaviour of the concrete beams is investigated by performing measurements at different excitation amplitudes.
58 citations
TL;DR: A vision-based rotational angle measurement system for large-scale civil structures using commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router with good agreement with an error of less than 1.0% is proposed.
Abstract: In this paper, we propose a vision-based rotational angle measurement system for large-scale civil structures. Despite the fact that during the last decade several rotation angle measurement systems were introduced, they however often required complex and expensive equipment. Therefore, alternative effective solutions with high resolution are in great demand. The proposed system consists of commercial PCs, commercial camcorders, low-cost frame grabbers, and a wireless LAN router. The calculation of rotation angle is obtained by using image processing techniques with pre-measured calibration parameters. Several laboratory tests were conducted to verify the performance of the proposed system. Compared with the commercial rotation angle measurement, the results of the system showed very good agreement with an error of less than 1.0% in all test cases. Furthermore, several tests were conducted on the five-story modal testing tower with a hybrid mass damper to experimentally verify the feasibility of the proposed system.
58 citations
TL;DR: In this article, a two-dimensional Fourier spectral method is employed to conduct the two dimensional modal curvature estimation in composite structures, where the spectral calculations for spatial derivatives are implemented in global space, thus noise can be suppressed.
57 citations