The basilica and the archaeological site of Ererouyk, also because included in the list of the 7 most endangered sites in Europe in 2016, have finally attracted the attention of the Armenian government, which has decided to promote its preservation by commissioning the National University of Architecture and Construction of Armenia to coordinate a group of Italian and Armenian experts headed by: Politecnico di Milano, Centro Studi e Documentazione della Cultura Armena, Europa Nostra and Armenian regional Office for Cultural Heritage Preservation.

Built in the sixth century, the three-nave basilica of Ererouyk is unique in Armenia for its size, importance, and typology, which suggests relations with Syrian architecture. For this reason, it has interested many scholars since the late 19th century. In this work, the path followed to know in an accurate way the structural response and to evaluate the vulnerability will be described. The first phase of the study consisted in an in-depth analysis of the damages and restoration interventions that the basilica has undergone during its history, conducted through an accurate collection of archival data and the visual observation of the wall faces and mortar. Subsequently, the identification of the material properties both using results of tests performed on the basilica material and referring to literature data was performed. Then the seismic input was defined, following Armenian standards. Aware of the huge uncertainties inherent in the behaviour of a sack masonry building that has undergone changes over the centuries, it was decided to perform the structural analysis using methods/models of increasing complexity described here in order:

1.       i. linear kinematic approach, based on the identification of macroelements and related collapse mechanisms

2.    ii.   modal analyses using three-dimensional finite element models with elastic-linear properties of the masonry for the study of dynamic properties of the structure;

3.    iii.   nonlinear time history analyses using three-dimensional finite element model with non-linear properties of the masonry, spatially variable according to the survey of damage and interventions carried out in the past, as well as locally variable according to the uncertainties of the material properties, for the study of seismic response over time.

The systematization of all the information collected has allowed giving a complete and exhaustive picture of the vulnerability of the structure, highlighting the necessity to intervene for the improvement of its structural behavior towards seismic action.