Constructive Features and Past Reinforcements: A Critical Analysis of Seismic Damage in Parma Masonry Churches

The Italian territory is characterised by a moderate seismic hazard that threatens its rich historical built heritage. Protection strategies focus on reducing vulnerability, influenced by materials, construction features, maintenance, and past reinforcements. This requires a thorough understanding of the current conditions, including qualitative factors, in order to take advantage as much as possible of the remaining structural resources of the building, thus limiting the intervention to the minimum necessary. However, the structural strengthening of masonry historical buildings during the 20th century was characterised by a different approach, in which new materials and techniques were applied based on structural mechanics theories, considering mainly quantitative factors and often changing significantly the stiffness and the behaviour of parts of the constructions. Recent seismic events have shown that only some of these interventions proved to be effective, while many of them have resulted in a hybrid behaviour of the structure, favouring its partial or total collapse. The paper aims to critically analyse seismic strengthen-ing techniques applied in the second half of the 20th century in relation to local masonry features. In the specific, the influence of construction history and pre-vious interventions on the seismic behaviour of masonry historical buildings is investigated with reference to masonry churches in the province of Parma (Italy). The significant case of Parma’s Cathedral is then analysed to identify the specific “qualitative” factors that could have influenced its seismic behaviour. A critical comparison is made between seismic damage and constructive features, previous reinforcements and coeval standards, with the main objective of developing tools to support the protection of CH against seismic actions.