A Novel Numerical Protocol to Assess Possible Strengthening Interventions on Already Damaged Curved Masonry Structures

A streamlined approach for predicting failure in historical masonry vaults that exhibit stability concerns under gravity loads is proposed and applied to a notable case study in Italy. The structure under investigation is a cloister vault with a significant span, supporting a slender load-bearing wall constructed above the keystone. Since a stability assessment to prevent collapse results necessary, the geometrical and material data were gathered through in situ surveys. A comprehensive numerical protocol, based on 2D finite element modeling, is proposed to evaluate the stability, assess the collapse risk, and suggest effective strengthening solutions for the already cracked structure. Masonry blocks are modeled by 4-noded elastic plane-strain elements, while mortar joints are discretized with (i) orthotropic shell elements coupled with (ii) brittle cutoff bars. The backfill influence is accounted for through equivalent forces representing soil self-weight and horizontal earth pressure. To explore the effects of possible retrofitting interventions, analyses are carried out employing a standard FE software starting from the already cracked and deformed masonry curved structure. This approach relies on three steps: (i) applying dead loads and self-weight, (ii) adding live or dead overloads to simulate damage and deformation, and (iii) implementing a retrofitting intervention aimed at enhancing the load capacity of the damaged structure. For the case under investigation, two retrofitting strategies are considered: Thickening the buttresses at the springing and applying CFRP strips to the intrados. The CFRP strips are modeled with elastic perfectly ductile cutoff bars that are bonded to surface nodes, ensuring a perfect adhesion between substrate and reinforcement.