Optical innovative monitoring of masonry testing on site

The recent Italian construction technical legislation for seismic risk reduction in built cultural heritage stresses the role that inspections and testing – especially non invasive or minimally destructive – should have in historic masonry construction diagnose. However, it is well known how difficult it is to deploy suitable testing procedures and equipment for testing masonry on site, especially historic masonry. Further, a correct use should be made of the values and data extracted from such testing. At this purpose, only a user with multidisciplinary knowledge and long experience will be capable of discerning and interpreting the possible behaviour of masonry and the significance of the values obtained from the experiments. A suitable testing technique should help the user to get the full picture of masonry behaviour, in order to gain a better health state condition evaluation of the object. Digital Image Correlation (DIC) is an optical technique allowing obtaining full-field high-definition maps of displacements and deformations on the monitored surface of the test object due for example to thermal distortion or mechanical action. Maps would be obtained by comparing point by point series of photos recorded at different deformation state during the testing. This method is becoming more widely used in the civil engineering sector. In this contribution, an innovative case is presented of DIC monitoring during shear testing on a historic masonry wall on site. The innovations of the case presented consist of applying the DIC method: - to masonry materials; - on site; - during shear testing; - without surface preparation. The reliability of the developed testing approach will be shown by a) comparing data from DIC virtual measurement sensors and real LVDTs; b) presenting high-definition strain maps.