Retrofitting of Roncole bell tower with high performace materials: A comparative numerical study

Historic masonry bell towers are a significant component of the built cultural heritage but are particularly vulnerable to seismic actions due to their slender geometry, material degradation, and limited tensile capacity. Their preservation requires strengthening solutions that enhance structural safety while complying with the principles of compatibility, reversibility, and minimum intervention. This study presents a comparative numerical investigation of the seismic retrofitting of the Roncole Bell Tower using three strengthening techniques: Fabric-Reinforced Cementitious Matrix (FRCM), Fiber-Reinforced Polymer (FRP) composites, and steel tie systems. The structural performance of the tower is evaluated through a multi-level numerical approach that combines three-dimensional finite element analysis with simplified mechanical models and limit analysis. The detailed finite element model reproduces the global and local structural response under gravity and seismic loading, while the simplified approaches are employed to identify collapse mechanisms, estimate structural capacity, and provide efficient tools for engineering assessment. The integration of these methods enables a comprehensive evaluation of the retrofit strategies, balancing computational efficiency with predictive accuracy. The strengthening techniques are comparatively assessed in terms of stiffness enhancement, stress redistribution, displacement reduction, crack control, and seismic capacity. The comparison also considers compatibility with the existing masonry, degree of invasiveness, durability, ease of installation, and compliance with internationally recognized conservation principles. The numerical results show that all three retrofit systems significantly enhance the structural performance and seismic resistance of the Roncole Bell Tower, although each technique offers specific advantages depending on the required balance between structural effectiveness, conservation objectives, and practical implementation. The proposed integrated assessment methodology provides a reliable framework for the evaluation and design of strengthening interventions for historic masonry bell towers, supporting the development of sustainable and performance-based conservation strategies for cultural heritage structures in seismic regions.