The b-Value Analysis for the Stability Investigation of the Ancient Athena Temple in Syracuse

Some of the most significant architectural works are monumental masonry constructions. Among these, the Cathedral of Syracuse can be viewed as a fundamental element in the cultural heritage of Europe. For the preservation of these monuments, it is necessary to assess their durability by taking into account cumulative damage and cracking conditions in the structures. The paper describes the methods used by the authors to determine the conditions of the materials and the crack patterns in the stonework structures of the Cathedral. In particular, the acoustic emission (AE) technique is used to evaluate the time dependence of damage and the onset of critical conditions in a pillar, which is part of the vertical load-bearing structures. The authors show that the damage evolution in the stonework structures, experimentally investigated in situ by the AE technique, can be described by a power law characterised by a non-integer exponent, beta(t). In this way, the time dependence of damage is evaluated by working out the beta(t) exponent and making a prediction of the stability conditions of the structure. Furthermore, the achievement of the critical condition is characterised through another synthetic parameter, the b-value of the Gutenberg-Richter law. The b-value systematically changes during the different stages of the failure process and tends to 1.0 as the structure reaches the final collapse. In the present study, this behaviour is documented by several AE tests carried out on specimens of different dimensions extracted from the pillar. In addition, these results are compared with the AE data obtained from the in situ-monitored pillar.