A comprehensive long term monitoring system of an iconic heritage complex: the Assisi Basilica case study

The Basilica of Assisi (Italy), built in 1228, has been a UNESCO World Heritage Site of unparalleled historical and artistic value since 2000. Located in one of Italy’s most seismically active areas, it was damaged during the 1997 earthquake (Mw 6.0), when part of the nave collapsed. The Basilica was restored over the following years. To safeguard this iconic structure, the authors implemented a long-term monitoring system on bell tower between 2022 and 2023. The sensor network includes six triaxial ultra-low-noise Epson M-A552 accelerometers on the bell tower, and an INGV OSU seismic station, equipped with an ETL3D/5s velocimeter and ultra-low-noise Epson M-A352 accelerometer, installed at the base of the structure. All the collected data, managed through the Wise Robotics cloud-based platform for efficient analysis and accessibility, contributes to identifying the structure’s dynamic behavior and potential anomalies. This research analyses the modal behavior of the bell tower that was tracked in the last two years, effects of recent seismic events on the tower are discussed and the effect of weather parameters on frequencies is exposed. Looking ahead to future expansion of the monitoring network, the project contributes to the preservation of the Basilica of Assisi and in advancing knowledge of the long-term behavior of monumental structures under complex loading conditions.