Seismic Strengthening of Existing Masonry Buildings with Low-Invasive Techniques

This PhD thesis investigates the seismic performance of historic masonry structures strengthened with Composite Reinforced Mortar (CRM) systems. Despite their growing use in heritage rehabilitation, CRM systems still lack dedicated design provisions, and only limited experimental data are available, particularly for single-sided applications. This research addresses these gaps by combining experimental testing, analytical modelling, and numerical simulations to evaluate the effectiveness, durability, and predictive modelling of CRM-strengthened masonry. An extensive experimental campaign was carried out on material samples, masonry elements (piers, spandrels, and ring beams), and a two-story pilot building, under both in-plane (IP) and out-of-plane (OOP) loading. Tests were performed on unreinforced (URM), single-sided (R1), and double-sided (R2) strengthened specimens. The results confirmed that CRM systems substantially enhance strength, ductility, and energy dissipation capacity, while promoting more distributed cracking and stable post-peak behavior. Two-sided applications provided further improvements in both strength and deformation capacity. The use of transversal connectors effectively prevented wythe separation in two-leaf walls, ensuring composite action between the coating and the substrate. Durability tests on glass-fiber meshes and textile-reinforced mortars highlighted a significant degradation of tensile properties under alkaline exposure and elevated temperature, confirming the importance of environmental effects on long-term performance. However, accelerated ageing protocols still require correlation with real-time exposure to reliably estimate service life. Analytical correlations were developed and calibrated to predict the strength and deformation capacity of CRM-reinforced elements, showing good agreement with the experimental data for both in-plane and out-of-plane behavior. At the structural scale, detailed nonlinear numerical models in Abaqus captured the observed damage mechanisms with high accuracy. Simplified equivalent frame models implemented in Midas Gen provided a computationally efficient tool for evaluating the global seismic performance of CRM-strengthened buildings. The application of this method to benchmark configurations and to the pilot building demonstrated its reliability for practical design purposes. Overall, this research contributes to the understanding and design of CRM interventions for the seismic strengthening of historic masonry. It provides validated experimental evidence, practical analytical correlations, and calibrated numerical approaches that together form a robust basis for future code development and engineering practice. The outcomes also highlight the need for further long-term durability studies and large-scale experimental validation to fully establish CRM systems as a reliable, low-invasive strengthening solution for heritage preservation.