Seismic fragility assessment of historical Khan structures in Izmir (Türkiye)

The province of Izmir in Türkiye is recognized as a city renowned for its rich cultural history. The province boasts numerous Khan masonry monuments, particularly within the Kemeralti commercial district. These structures, which carry cultural significance crucial to architectural heritage, showcase distinctive construction techniques that result in varied seismic behaviors. Conducting seismic assessments of these historic monuments is vital for risk mitigation and preserving them. The initial phase of risk assessment studies involves the development of fragility curves for historical structures. Fragility curves reveal the intricate relations between seismic forces, building features, and potential damage, providing valuable information for risk assessment studies. This paper develops seismic fragility curves for historical Khan masonry monuments through data from visual field observations, structural analysis, and numerical simulations, focusing specifically on the Kemeralti commercial district of Izmir, Türkiye. Using peak ground acceleration (PGA) as the primary intensity measure, the study examines the extent of damage at various PGA levels across different limit states, including Immediate Occupancy (IO), life safety, and collapse prevention. The analysis is conducted in both the X- and Y-directions of the structure using linear time history analysis. Results show higher probabilities of exceedance (PoE) in the Y-direction (perpendicular to the main façade) of the structures compared to the X-direction, which is attributed to the configuration of the structural elements. Furthermore, a strong alignment between the predicted and observed damage patterns during the comparison for the 2020 Samos earthquake (M w =7.0) is noted, indicating an IO performance level. This suggests that the Khan structures sustained only minor non-structural damage, underscoring their resilience in maintaining their structural integrity under low seismic demands. These findings emphasize the necessity of incorporating directional vulnerabilities and observed damage patterns into seismic risk assessments, advocating for targeted retrofitting strategies specifically designed to address the unique structural configurations of historical Khan monuments, thereby enhancing their resilience to higher seismic demands.