Case Study: Seismic Retrofitting of a Medieval Bell Tower with FRP

Abstract

Seismic retrofitting of monument structures requires compliance with restrictive constraints related to the preservation of original artistic and structural features. Any conceived intervention must achieve structural performance yet still respect the appearance and structural mechanism of the original and be as minimally invasive as possible. Therefore, traditional retrofit strategies may not be suitable for such purposes, and structural engineers need to develop specific techniques. Innovative materials (e.g., composites) may be helpful, as demonstrated by the case study presented in this paper. Fiber-reinforced plastics (FRPs) were used for the design, analysis, and installation of the retrofit for the medieval bell tower in Serra San Quirico (Ancona, Italy). A FRP tie system is applied to the inner walls and anchored at the base by a reinforced concrete slab, independent of the tower’s foundation. The intervention enhances the seismic capacity of the structure and is fully provisional as it may be removed by heating the FRP with a hot air jet. The design process consisted of preliminary finite-element simulation and on-site structural assessment. Effectiveness is evaluated by a comparison of nonlinear static analyses (pushover) of the retrofitted and original structures. Finally, seismic risk reduction is computed by considering probabilistic seismic hazard at the site. Installation issues and the current appearance of the structure are also discussed.