Passive 3D motion optical data in shaking table tests of a SRG-reinforced masonry wall 3D optical measurement;passive markers;steel reinforced grout;shaking table;structural damage monitoring;modal analysis; Unconventional computer vision and image processing techniques offer significant advantages for experimental applications to shaking table testing, as they allow the overcoming of most typical problems of traditional sensors, such as encumbrance, limitations in the number of devices, range restrictions and risk of damage of the instruments in case of specimen failure. In this study, a 3D motion optical system was applied to analyze shake table tests carried out, up to failure, on a natural-scale masonry structure retrofitted with steel reinforced grout (SRG). The system makes use of wireless passive spherical retro-reflecting markers positioned on several points of the specimen, whose spatial displacements are recorded by near-infrared digital cameras. Analyses in the time domain allowed the monitoring of the deformations of the wall and of crack development through a displacement data processing (DDP) procedure implemented ad hoc. Fundamental frequencies and modal shapes were calculated in the frequency domain through an integrated methodology of experimental/operational modal analysis (EMA/OMA) techniques with 3D finite element analysis (FEA). Meaningful information on the structural response (e.g., displacements, damage development, and dynamic properties) were obtained, profitably integrating the results from conventional measurements. Furthermore, the comparison between 3D motion system and traditional instruments (i.e., displacement transducers and accelerometers) permitted a mutual validation of both experimental data and measurement methods.

The destruction of Amatrice and the surrounding villages in Central Italy after the 2016 seismic sequence was so impressive that engineers, authorities and local communities started sharing the common feeling that historical stone masonry buildings were too below current safety standards. The severe damage caused by the earthquakes led to a general distrust of traditional building techniques, leading to the conclusion that there is nothing to do but demolish and rebuild, perhaps with a false antique. Is there an alternative? Is there a way to combine safety and preservation of architectural heritage? This paper aims contributing to the understanding of the seismic behaviour of stone masonry by reproducing, through simulation on a shake table, the progressive loss of compactness of a real scale rubble masonry wall up to the ruinous collapse with the separation between the two external leaves. The laboratory simulation allowed to evaluate the decrease of the fundamental frequency with increasing damage and estimate the maximum displacement profile and the amount of cracking that the wall is able to sustain before failing. Eventually, two modelling strategies based on finite and discrete element methods were proposed and applied to verify the capability of simulating the out‐of‐plane seismic response and the failure mechanisms of rubble masonry.