Seismic Performance Assessment of Historic Stone Masonry Buildings: The Case of the Angonate Residence, Gjirokastër

Abstract
Historic stone masonry structures constitute a fundamental component of architectural heritage; however, in seismically active regions such as the Balkans, their stability is highly vulnerable to earthquakes, necessitating conservation approaches that balance structural enhancement with the preservation of architectural authenticity. This study provides a general conceptual framework for the assessment and reinforcement of historic stone buildings, using the Angonate House (built around 1880) as a case study. Located in Gjirokastra, a UNESCO World Heritage Site, this building exemplifies the characteristic features of Ottoman architecture.
The methodology used includes digital documentation and structural analysis. The current condition of the building was assessed through field measurements and mapping of identified pathologies, combined with high-resolution photogrammetry to create an accurate three-dimensional geometric model. This model served as the basis for numerical simulations with the Finite Element Method (FEM) in ETABS. Modal and seismic analyses, conducted in accordance with Eurocode 8 and the National Technical Design Codes (KTP), revealed the building’s dynamic behaviour and identified the main structural weaknesses.
Based on these results, a conservative intervention strategy is proposed, aiming at improving the seismic performance in harmony with preserving the historical integrity of the building. The proposed measures include the selective use of Fiber Reinforced Polymers (FRP), the consolidation of the masonry through deep reinforcement and injection with chemically compatible mortar, as well as the installation of discrete fixing elements to improve the diaphragm action. This study shows that the synthesis of digital diagnostics, engineering assessment and conservation ethics constitutes a powerful and applicable methodology for the protection of historic masonry structures in environments with high seismic risk.

Keywords: Architectural Heritage, Heritage Conservation, Structural Reinforcement, Structural Behavior, Finite Element Method (FEM).