Modelling and safety assessment of observed sliding damage in a masonry rib vault

Frequently observed damage in historic masonry vaults has always given rise to concerns on their stability. The effect of present damage on masonry vaults structural response should be taken into consideration during structural analysis as it clearly affects its behavior. The aim is to propose a method to study the safety of vaults, setting up a finite element model with a limited number of discontinuities, based on the consideration of the vault construction and damage observation. A case study from Milan cathedral is adopted where damage is documented. A complex damage mechanism characterized by sliding of voussoirs and detachment of the rib from the web was documented in the 1960s. The results show the possibility to analyze the evolution of the observed mechanism and to evaluate numerically its safety in function of the documented settlements. Technical applications of the present work include interpretations of the causes of observed damage, estimation of the level of settlements based on observed damage, and numerical evaluation of the safety of the current mechanical state.