A case history: seismic analysis of the retaining wall of the “Sacro Convento” in Assisi (Italy)

Trattasi di ristampa della memoria contenuta in: Proc. of Fourth Int. Conf. on Recent Advances in Geotechnical Engineering and Soil Dynamics, San Diego (USA), March 26-31, 2001. ABSTRACT. The aim of the present work is to analyse the seismic behaviour of the retaining wall of the square in front of the Basilica di San Francesco at Assisi that during a long seismic crisis occurred in September 1997 suffered some damage. Static, pseudo-static and dynamic analyses have been carried out on four significant sections of the wall. The data for the analysis derive from the geometric survey of the structures, the survey of the state of the damage, the measurement of the rotation movements of the wall, the collection of stratigraphic and geotechnical data, as well as the accelerometric recordings of the seismic events using instruments that had been in operation on the structures of the «Sacro Convento» since 1995. Built during the first half of the 16th century, the wall is made of stone masonry, is about 93 m long, 4 m thick, and supports an em-bankment, the height of which varies between 9.0 m and 12.5 m. The wall is approximately 18 m high, and is under the ground also in the front part; it has a rectangular transversal section in the lower part and a T-shaped section in the upper part. It is built on cal-careous rock, and supports a covered portico that is about 3.5 m high. In practice, the recorded accelerometric history coincides with the one at the base of the wall. Numerous seismic events were recorded from 4/9/1997 to 6/10/1997, three of which had a PGA exceeding 0.15g. The most evident movement suffered by the wall was a rigid rotation that caused a movement at the top of the wall greater than 20 cm.