The new foundation system of the Basilica di Collemaggio's transept

In the seismic retrofitting of historical churches, the realisation of new foundations of collapsed elements represents an important aspect for the interaction with both the underground pre-existing structures and the new structural elements to be rebuilt. For the specific case study of the Basilica di Collemaggio, after an accurate geometrical survey and onsite geotechnical tests, a specific mixed structure foundation system is proposed in order to fulfil the seismicsafety requirements and the Cultural Heritage Office's conservation prescriptions. Nonlinear analyses are performed considering the interaction between the soil and the foundation system, together with the new couple of main pillars and the triumphal arch. The analyses are aimed to verify the capabilities of the new foundation system to bear the transversal seismic actions. The analyses are also completed by some experimental tests on micropiles, which represent the main underground-to-elevation connection elements.