The 2016 Central Italy seismic sequence: linear and non-linear interpretation models for damage evolution in S. Agostino’s church in Amatrice

An extensive numerical investigation of the structural behavior of the masonry church of Sant’Agostino in Amatrice (Italy) during the 2016–2017 seismic sequence is presented. The seismic performance of the church is studied in relation to the most energetic shocks of the sequence, occurred on August 24th, 2016, and October 30th, 2016, whose seismic parameters (PGA, Trifunac duration, Arias intensity, destructiveness potential factor) are analyzed in detail. In particular, a comparison between ground motion data recorded by different stations is presented in order to evaluate the influence of local amplification effects on the structural behavior. To achieve this goal, the ground motion data recorded by the permanent accelerometric station (AMT) located in Amatrice on type B soil and belonging to the National Accelerometric Network (RAN) are firstly considered. Then, they are critically compared with those provided by an accelerometric station temporarily installed after the first main shock in the downtown area close to the church site, showing a clear amplification due to the site effects. The dynamic behavior of S. Agostino’s church is numerically investigated by carrying out a set of non-linear dynamic analyses on the 3D finite element model of the church developed in Abaqus CAE and considering as seismic input both the accelerograms recorded by the AMT fixed station and those including the local amplification effects. Non-linear properties of materials are taken into account by defining an elasto-plastic constitutive law with reasonable damage parameters in tension. Numerical results are evaluated in terms of displacement time-history of some relevant control points located on the masonry walls and maps of tensile damage cumulated at the end of the simulations. Numerical results are in good agreement with the evidence based behavior of the structure, thus validating numerical simulations as effective tools for seismic analysis of masonry buildings. Furthermore, a hypothetical strengthening intervention concerning the improvement in masonry mechanical properties is implemented in the model to investigate its positive role in preventing collapse. In the latter case, the approach provides useful hints in interpreting the behavior of the church under the application of repeated accelerograms.