Stress analysis of the piers of the Tarazona Cathedral (Zaragoza - Spain) by means of the hole-drilling technique

The paper deals with the application of the hole-drilling technique on the four piers of the crossing under the dome of the Cathedral of Tarazona (Zaragoza - Spain). The hole-drilling technique in architectural heritage is named the Donostia Method by the author in previous works. The monument (XIIIth Century) is an excellent cathedral not well known because 25 years ago it was closed by its alarming structural situation. In the XVIth century the gothic original cupola was replaced by a new more weighted dome (cimborrio) modifying the typical load transmission of such constructions. The new dome and the four piers that transmit their weight have been fixed by means of a metallic structure from the moment the cathedral was closed. Over the past years several works of structural reinforcement have been made on the piers and their foundations. It is expected for the next few months that the metallic structure can be disassembled allowing access inside the cathedral. The stress states of each pier have been obtained by means of the hole-drilling technique. The two piers at the absydial zone present high compression stresses, whereas the other two piers present a much smaller level of compressions. The tests carried out make it possible to deduce several values of the principal stresses in each pier; this fact makes it possible to analyze the quality of the results.