Collapse investigation of the Arquata del Tronto medieval fortress after the 2016 Central Italy seismic sequence

In this paper, an investigation is presented of the Arquata del Tronto medieval fortress local collapses that occurred due to the 2016 Central Italy seismic sequence. Both historical evolution and damage inspection of the fortress are discussed. Interestingly, the damage reported to the fortress after the 2016 earthquakes appears similar to what occurred more than 300 years before (due to the 1703 Apennine earthquakes), despite the restoration work of the 1920s. Linear kinematic analysis and 3D modal and seismic FE analyses are carried out to evaluate the safety of the local collapse mechanisms that occurred on the towers' crownings. Numerical findings point out that no failure mode passes the safety check. This suggests that the reconstruction of the collapsed parts should be complemented by specific strengthening devices.