NUMERICAL MODELLING STRATEGIES FOR THE SEISMIC VULNERABILITY ANALYSIS OF CHURCHES AND EVALUATION OF STRENGTHENING INTERVENTIONS

Historic masonry churches represent a class of structures of extraordinary historical, artistic, and architectural significance, exhibiting complex structural behaviours under seismic actions due to their unique geometrical configurations and structural components. Post-earthquake assessments have highlighted that the seismic behaviour of masonry churches is strongly influenced by the activation of typical failure mechanisms of distinct architectural components, known as macroelements, which activate independently during a seismic event. The widespread knowledge on the seismic vulnerability assessment of masonry churches, available in literature, still poses different challenges in terms of assessment of the structure capacity and in terms of preservation. In this context, numerical models based on continuum and discontinuum approaches, have become widely useful tools. The dissertation herein presented, aims at developing different numerical strategies for the assessment of local and global mechanisms in the framework of Finite Element continuum approaches and Discontinuum methods. Starting from the available fragility models of different types of central Italy and Emilia-Romagna churches, and from a detail evaluation of specific case studies surveyed during the Central Italy seismic sequence, three archetypical case studies of the Italian heritage, ranging from simple to complex churches, have been analysed. The detailed seismic assessment is performed in parallel to the evaluation of strengthening solutions, questioning the potential and limitations of various techniques and providing a scientific basis for retrofitting strategies. Among these analyses, a focus on the out-of-plane overturning of the main façade is included. This study proposes an in-depth analysis of the archetypical Italian masonry gabled church facades through a simplified discontinuum formulation implemented in 3DEC software to analyse the nonlinear behaviour of the structure. The methodology, based on previous developments in discrete element modelling (DEM), introduces an optimized formulation that captures both the initial elastic and post peak behaviour of the pushover curve. A custom FISH scripting routine is developed to enhance computational efficiency and data management during simulations. The validation is performed by modelling specific benchmarks available in literature, demonstrating the capability of the DE formulation to accurately replicate the evolution of the mechanism. To systematically explore the influence of specific typological factors, a semi-automated parametric modelling environment was developed using Grasshopper for Rhinoceros 3D. This visual programming framework enables the rapid generation of multiple façade geometries by adjusting wall dimensions, slenderness ratios, interlocking patterns, and roof shapes, facilitating the creation of 54 case-study models, whose geometrical parameters were selected based on a database of over 600 churches surveyed after the 2016 Central Italy seismic sequence. The proposed formulation offers a valuable tool for the seismic assessment of masonry structures, providing deeper insight into the influence of specific typological factors and the intrinsic vulnerability of the archetypical Italian gabled façade churches.