Non-linear FE modelling of seismic pounding and damped-mitigating interconnection between a R/C tower and a masonry church

The finite element analysis of pounding represents one of the most critical issues for the assessment of the seismic performance of R/C structures built at poor distance from adjacent buildings. The effects of pounding can be particularly severe in slender R/C heritage structures, including civic or bell towers. An emblematic case study falling in this class of structures, i.e. a monumental R/C bell tower constructed in the early 1960s in Florence, is analyzed in this paper. Pounding collisions are simulated with a multi-link viscoelastic contact model originally implemented in this study. The results of the non-linear dynamic enquiry carried out with this model show that pounding affects the seismic response of the bell tower and the adjacent church as early as an input seismic action scaled at the amplitude of the normative basic design earthquake level. A retrofit hypothesis to prevent pounding is then proposed, which consists in linking the two structures by means of a pair of fluid-viscous dissipaters. Thanks to the supplemental damping action produced by these devices, the impacts are totally annulled, bringing the structural members of the tower to safe levels.