Structural Analysis, Retrofitting Design, and In Situ Control of Permanently Damaged Long-Span Timber Beams of a Historical Building in the South of Italy

In 2018, under service conditions, excessive deflections were observed in the long-span timber beams of the first floor of the former Saint Elisabeth Monastery in Palermo (Italy). The building was constructed in the sixteenth century. During the years, it underwent several modifications, and finally in 1900 it became a barrack. In the middle of the twentieth century, it was submitted to maintenance works consisting in rehabilitation of the first floor with timber beams and rehabilitation of the roof with timber trusses. An experimental investigation was carried out to establish the causes of the excessive deflection and to identify a retrofitting design. In this work, details of retrofitting design and strength verification including in situ loading tests are described and discussed. The lesson learned from the case study could help professional engineers to be aware of the main peculiarities and defects of structural systems affected by construction mistakes, and the importance of in situ periodical checks during the useful life of structures. Finally, practical indications for a possible retrofitting technique of this kind of timber structure of historical interest are given, proving to be a simple, rapid, cheap, reversible and effective retrofitting system.