Numerical incremental and limit analysis homogenized discrete element models (HDEM) for the seismic upgrading of masonry churches by means of FRP strips

The paper presents some advanced FE analyses conducted by means of an incremental and limit analysis homogenized discrete element model (HDEM) on a masonry church damaged by the recent Emilia Romagna (Italy) earthquake, occurred from 20th to 29th May 2012. The church, located in the city of Ferrara is a masonry Romanesque structure that has been severely damaged in correspondence of the columns of the central nave for bending actions and on the apse for shear loads. A partial detachment of the façade has been also observed. We present some results obtained with an advanced non-linear FE code already presented by the authors in [1] and [2] in absence of any reinforcement device. First of all, the church is analyzed “as is” under horizontal loads mimicking a seismic action in agreement with Italian code indications (spectral acceleration taken in agreement with NTC 2008 for the region under study, behavior factor q=2.25). The results put in evidence the insufficient strength of the apse for shear actions and of the columns of the naves for bending moments. A strengthening intervention conducted by means of FRP strips (hooping strips on the columns and diagonal reinforcement on the apse) is numerically analyzed in detail, assuming the behavior of the strips –especially for what concerns delamination- in agreement with Italian Guidelines (CNR DT200) for r.c./masonry strengthening with composite materials. It is found a quite reasonable strength improvement of the weak structural elements due to the application of FRP, with levels of strength higher than the minimum ones required by the Italian code.