(1) Department of Structural Engineering, Politecnico di Milano, Italy
(2) ZAG – Slovenian National Building and Civil Engineering Institute, Ljubljana, Slovenia

The structural performance of a masonry wall structure can be understood provided the following factors are known: (i) its geometry; (ii) the characteristics of its masonry such as the connection between the leaves, joints empty or filled with mortar, physical, chemical and mechanical characteristics of the components (bricks, stones, mortar); (iii) the characteristics of masonry as a composite material. In order to fulfil these requirements, an on-site investigation, recommended by codes of standards in several countries, is needed. Nevertheless, to apply non destructive advanced techniques to masonry, which is a highly non homogeneous composite material, can be frustrating due to the difficulty of interpreting the data collected. In many cases, the solution of very difficult problems cannot be reached with a single investigation technique, but with the complementary use of different techniques.
To this purpose the development of new and more appropriate software for the elaboration and interpretation of data, particularly from NDT, is needed together with the production of guidelines for the correct application of investigation techniques to the different classes of problem of masonry and of masonry structures. Furthermore, when a complex investigation is carried out using different techniques, the greatest difficulty is caused not only by the interpretation of the results of the single technique but also by the harmonisation of all the collected data. Some typical problems solved by the authors within an EC contract (ONSITEFORMASONRY) with the combination and complement of different techniques such as boroscopy, radar and sonic tests, flat-jack and sonic tests, sonic and radar tomography, in-situ shear test and others are presented here.