Structural and vulnerability analysis aimed at the safeguard of the Ererouyk basilica in Armenia

Also thanks to its inclusion in the list of the 7 most endangered sites in Europe in 2016, the basilica and the archaeological site of Ererouyk 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 Armenia1 (NUACA) to coordinate a group of Italian and Armenian experts headed by: Politecnico di Milano, Centro Studi e Documentazione della Cultura Armena (CSDCA), Europa Nostra and ROCHEMP2. 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. Archaeological excavations and historical-artistic and anthropological studies, conducted by international experts under the supervision of Prof. Donabédian, have allowed us to formulate hypotheses about the original form of the basilica, which has come down to us partially in ruins. In this article, we will describe the path followed to know in a more and more accurate way the structural response and then evaluate the vulnerability: the starting point to define a possible project of seismic risk reduction. 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, we moved on to the identification of the material properties both using data made available by NUACA and referring to literature data. 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) linear kinematic approach, based on the identification of macro-elements and related collapse mechanisms; 2) three-dimensional finite element model with elastic-linear properties of the masonry for the study of dynamic properties of the structure; 3) three-dimensional finite element model with non-linear properties of the masonry, spatially variable according to the analysis of damage and interventions carried out, for the study of seismic response over time. The systemization of all the information collected has allowed giving a complete and exhaustive picture of the vulnerability of the structure.