Relative displacements of 3D optical markers for deformations and crack monitoring of a masonry structure under shaking table tests

The application of 3D motion capture systems to shaking table testing provides a unique tool for recording relative displacements of a large number of measurement points of the tested structure. The analysis of 3D relative displacements during dynamic tests allows us to evaluate the structure deformations and to monitor the cracks formation and evolution. The present paper focuses on the processing and analysis of 3D motion capture data to extract accurate displacements between markers positioned on a full-scale model of a masonry cross vault representing a vault of the mosque of Dey, Algiers, tested at the ENEA Casaccia Research Centre. The management and processing of the data acquired through 67 markers located on the vault are described, showing the potentialities of the methodology. Moreover, the possible formulation of damage indices based on the structure deformations and cracks aperture detected from markers relative displacements (MRDs) was explored. In particular, cracks could be counted and classifi ed as a function of the detected apertures, following damage thresholds indicated in the Italian regulations. Moreover, the failure mechanism could be easily visualized and analysed by monitoring the cumulative MRDs. In addition, in-plane and out-of-plane deformations of walls could be monitored during each seismic test, providing accurate information on the torsional and bending effects.