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The stabilisation works of the Leaning Tower of Pisa ended in 2001 (Jamiolkowski, 2001; Burland et al., 2000, 2003). The Tower was re-opened to visitors, after a closing period long at least one decade. After re-opening, works related with the material restoration of the Tower, some recovery activities for the monuments located in Piazza dei Miracoli and the monitoring of the Tower displacements were carried out (Burland et al., 2009; Squeglia & Bentivoglio, 2015).
More recently, after the seismic events that hit the regions of Central Italy, especially the Emilia Romagna earthquake in 2012 (Lo Presti et al., 2013; Fioravante et al., 2013), the interest about the seismic response of the Leaning Tower has become relevant for the Italian geotechnical community.
It is well known that the analysis of the complex dynamic soil-foundation-superstructure interaction can be simplified studying separately (Kramer, 1996):
The first step provides an estimate of the seismic motion variation during the propagation of the seismic waves from the bedrock to the ground surface, in terms of amplitude and frequency content, due to the presence of a weaker overlaying soil deposit. Such an analysis neglects the influence of both the foundation and the superstructure.
In this work, the analyses were carried out assuming a one-dimensional geometry, the presence of vertically propagating shear waves (SH-waves) and as constitutive models for the soil deposit: a linear-equivalent and a non-linear model (Ramberg-Osgood model).
The analyses were performed with a linear-equivalent approach using the computer codes EERA (Bardet et al., 2000) and STRATA (Kottke & Rathje, 2010) and with a true non-linear analysis method using the code ONDA (Lo Presti et al., 2006).