Stresses analysis at the Altes Museum of Berlin by means of the Hole-Drilling technique (Donostia Method)

The article deals with the application of Hole-Drilling technique on structural elements of the basement floor of the Altes Museum of Berlin (1824–1830 by the Architect Shinkel). In the previous publications, the Hole-Drilling technique was labelled as Donostia Method by the author. The objective of the research is the deduction of the state of the stresses on structural elements of the Architectural Heritage. The method involves glued strain gages at the surface of a stone block. The drilling device is a diamond crown extracting a round material at the centre of a stone block of a masonry. At least three strain gages are placed in the area under consideration. The strain gages record the strains originated by stress relaxation after extracting a round of 36 mm diameter and 36 mm depth. The stresses before drill can be deduced with an appropriate mathematical scheme. The Donostia Method is a minor destructive test providing sufficient information to calculate the principal stresses and their directions around the drill. Two limestone walls, which support the loads of the upper floors introduced in the restoration made after the Second World War, have been analyzed. The tests carried out make it possible to deduce several values of the principal stresses in each analyzed zone.