PAOLA RONCA Politecnico di Milano

The purpose of the paper is to underline, by experimental evidence together with analytical and physical considerations, the significant and critical points concerning the applications of two of probably the most widely discussed in situ tests for old masonry structures, ultrasonic and flatjack methods. In the case of old monumental masonry structures, the estimation of the actual mechanical properties and the correct load paths by means of in situ tests requires a more careful calibration of the different phases of each test than in the case of new masonry. Indeed old masonry may have hidden voids, damaged or poor materials that cause, even for low level stress, fields of non-elastic behaviour which can greatly influence the values of parameters on which reliable test application and results depend.