The use of 3D optical motion data for structural dynamics is both promising and challenging. Further developments for on-the-filed applications are still needed, but, at the present stage, such techniques are already feasible for laboratory dynamic tests. A measurement system of this kind was installed for the first time for shaking table testing at the ENEA Casaccia Research Center. This 3D motion capture system is capable of acquiring the positions of more than a hundred passive markers with a constellation of 10 near-infrared cameras. In particular, this paper focuses on filtering and processing the markers displacements. A methodology is proposed for optimizing the displacement data processing to obtain an estimation of markers accelerations. Such methodology implies the optimal choice of the Savitzky-Golay-filter parameters for the implementation of a filtered numerical derivative of displacement data. The optimal parameters are calculated minimizing the error in the estimation of the peak acceleration of a reference marker compared to a conventional accelerometer located at the same measurement point. The accuracy of markers accelerations was estimated in the range of 0.01-0.02 g, which is appropriate for providing interesting indications for studied structures subjected to most shaking table testing. For example, markers displacements data and related estimated accelerations can be combined to obtain the hysteretic behavior of the structure or of portions of it. Markers data were also used for Experimental and Operational Modal Analysis (EMA/OMA) in order to extract the modal parameters and to calibrate/validate the Finite Element Models (FEM) of the structure. In particular, the combined used of OMA by markers data and numerical modal analysis by FEM permits to compare the resulting modal shapes for a more precise dynamic identification. An example of practical application is illustrated on a shaking table experimentation conducted on a twostory tuff-masonry prototype, which reproduces a typical ancient buildings of Central Italy.
|Titolo:||Processing of 3D Optical Motion Data of Shaking Table Tests: Filtering Optimization and Modal Analysis|
|Data di pubblicazione:||2017|
|Appare nelle tipologie:||5.8 Altro|