Intervention criteria for historic masonry constructions subjected to seismic actions

The acknowledgment of the scientific community that the structural safety aspects of constructions belonging to the cultural heritage can not be treated according to standard procedures that are fitted for new constructions, is leading to new, specific approaches for assessing their actual structural performances and then for developing new, more appropriate methodologies and design criteria for their repair and strengthening. Over-designing interventions on existing structures could in fact imply in general unacceptable costs and, in the case of the historical heritage, unacceptable losses of cultural (historic, artistic) values. On this respect, the seismic condition presents the most delicate implications, as the very extreme resources of the structure are mobilized. The consciousness that any calculation imply over-design has as relevant consequence that the formal match between code requirements and formally demonstrated structural performances can be misleading, and not necessarily required. Assessment is an articulated and combined use of structural models, historical informations, surveys and investigations, personal, qualitative judgments (based on past experiences, specific training, comparisons, evaluations of past performances of a constructions) in a multidisciplinary context, ensuring that all the values (economical, social, historic, artistic) of the constructions are taken into account, leading to a final decisions on if and how to intervene.