OUT-OF-PLANE CAPACITY OF ARCHAEOLOGICAL RUINS IN POMPEII: MORPHOLOGICAL AND TYPOLOGICAL ISSUES

The assessment of safety conditions of archaeological heritage under seismic actions is crucial in preserving its cultural value. Particular attention has to be paid to out-of-plane mechanisms that frequently activate during seismic actions when the connections between masonry walls are absent or lacking. To this aim, the analytical approaches commonly adopted to investigate the response to horizontal actions of masonry buildings located in urban aggregates can be used with some revisions to account for specific features of the archaeological ruins, which could influence the occurrence and the geometry of the failure mechanisms. In this framework, the paper presents some methodological issues aimed at applying a limit analysis-based approach to a selection of recurrent masonry elements in the archaeological site of Pompeii. Such a selection is based on morphological and typological criteria, functional for categorizing the most vulnerable elements to different out-of-plane mechanisms. Indeed, the classification of archaeological elements, based on the survey of their geometrical features and boundary constraints, represents a preliminary step in identifying the most likely failure mechanisms and the most suitable analytical models to predict their behaviour. On the other hand, the analysis of the construction technique is crucial to define the mutual constraint conditions between the elements. After a first classification of the archaeological elements and their potential out-of-plane failure mechanisms, the paper focuses attention on one of the most recurrent typologies in Pompeii (i.e. T-shaped wall systems); a limit analysis-based approach is applied to investigate the influence of some geometrical and mechanical parameters on the activation of the simple rocking-sliding mechanism on such masonry elements. This study represents the kickoff in defining a new methodological approach to assess the seismic vulnerability of archaeological ruins to out-of-plane mechanisms, eventually extendable to whatever archaeological context.