Seismic retrofitting assessment of historical churches : The reconstruction of The Basilica of Santa Maria di Collemaggio after the 2009 L’Aquila earthquake

Abstract: This study summarizes previous research to evaluate and verify the results of the extensive restoration of The Basilica of Santa Maria di Collemaggio after the 2009 L’Aquila earthquake. In addition, it aims at identifying the vulnerability factors and challenges in preserving these buildings. The research is based on scientific reports in the field as well as a on sight study of a selected church and two reference churches. After the 2009 L’Aquila earthquake most part of the city was destroyed, including a big part of the cultural heritage.  The Basilica of Santa Maria di Collemaggio that is considered an important symbol for the city of L’Aquila suffered severe damages during the 2009 L’Aquila Earthquake, including shear damages in the façade, crushing of nave pillars, and a total collapse of the transept, probably caused by the failure of the two main pillars. An extensive rehabilitation work begun to restore The Basilica of Santa Maria di Collemaggio, directed by Italian universities, ENI and the municipality of L’Aquila. To not conflict with the cultural heritage, new technology was combined with traditional seismic retrofit action. In the case of The Basilica of Santa Maria di Collemaggio many damages occurred on weak elements that previously had been damages and rebuilt. This underlines the importance of correct seismic retrofit actions and verification of the effect of the implementation. In the rehabilitation work parts of the church was completely rebuilt, among which the transept and the main pillars meanwhile other parts of the church was repaired or exchanged. Further enhancements were made, including modern technology such as installing a structural health monitoring system. In previous research the system has been used to make synthetic test to for evaluating the work. The results from those tests suggests that the rehabilitation project has been successfully completed and that the global seismic resistance of the Basilica has been improved. The present study concludes that incorrect performed seismic retrofit can have devastating result on the structural health of the building. Modern technology such as structural health monitoring system can be used for a more accurate analysis of the building. It also concludes that structural building evaluations are crucial in order to avoid repeating previous mistakes and to validate safety, sustainable interventions and correct implementation for seismic retrofitting. However, if the interventions will affect invasively and if the building will resist stronger earthquakes in the future can still not be said.