ABSTRACT
Existing masonry buildings are often the result of multi-epoch layers of construction cycles, modifications, and alterations that were made over the span of long-periods. Identifying the possible causes of existing damage and ongoing damage processes in historical structures is a complex task that typically involves the integration of different approaches including historical analysis, geotechnical and structural field inspections and investigations, geotechnical and structural monitoring, and structural analysis involving soil-structure interaction effects. Existing cracks and deformation patterns in ancient structures are often due to the combined effect of various recent and past stressing phenomena. Construction processes, natural events as well as anthropic actions, may affect current equilibrium conditions, causing damage to the structure. Such phenomena may be classified into four main triggering categories: (1) recent and ongoing (i.e., new alterations resulting in ongoing deformation patterns), (2) recent but stopped (typically one-time events that produce an effect while they act, such as earthquakes), (3) old but ongoing (i.e., excavations made centuries ago but still influencing the observed damage patterns), and (4) old but stopped (i.e., alterations made in the past but for which remediation measures were already implemented). As a result, the analysis of ancient structures should include the analysis of past events and alterations from historical sources.
The Saint Francis of Paola church in Rome is located to the west of the San Pietro in Vincoli church in the Monti neighborhood, about 300 m from the Colosseum. It was built in 1645-50 and was designed by architect Giovanni Pietro Morandi. Structural damage patterns have affected the church over the last century and the evolution of the health of the structure recently forced local authorities to close the church to the public.
This paper provides a detailed historical analysis of the church from which a series of past alterations that likely triggered the ongoing deformation process that is causing substantial structural damage to the church were identified. The analysis presented in this study was performed using a step-by-step approach based on the traditional scientific method. After analyzing all historical alterations made in the area, field inspections were performed, and hypotheses on the mechanisms responsible for the current damage pattern were made. To corroborate these hypotheses and exclude (or include) other causes, a structural and geotechnical investigation program was carried out. Three borings were drilled at a depth of ~25 m. They were equipped with inclinometers and piezometer. Cracks in structural members of the church were monitored by means of a real-time crack monitoring gauge system. This study shows that thee ongoing deformation mechanism is likely due to a variety of causes including geotechnical issues pertaining to nearby retaining structures and local structural deficiencies. Interestingly, the analysis of the monitoring system shows that the 2016 Central Italy earthquake sequence produced non-negligible displacements to the structures. This observation confirms that strong earthquakes in the Central Apennines may have an impact on monumental structures located in Rome.
