Reinforced concrete interventions on the collapse mechanism of historical masonry structures with detailed finite element analyses: Kabasakal Mosque

Abstract

This study aims to evaluate the seismic behavior of the historical Kabasakal Mosque in Gaziantep and to understand the effects of reinforced concrete (RC) elements added after the 1950s. Considering the increasing threats to Turkey’s cultural heritage structures, the significance of scientific approaches in the preservation of historical buildings is emphasized. Initially, a detailed finite element model (R-Model) representing the current state of the mosque was developed. The material properties of the reinforced concrete elements were defined based on literature research and material behavior of similar structures. Subsequently, to reconstruct the mosque’s original state, other historical masonry mosques from the same period and region were studied. The architectural similarities and typological features of these structures were compiled. Based on this data, another finite element model (O-Model), entirely composed of masonry elements representing the mosque’s original condition, was created. In both models, macro modeling techniques were employed, and geometric details and material properties were meticulously defined. As part of the modeling studies, modal analyses, nonlinear pushover analyses, and nonlinear time-history analyses were conducted. Modal analysis results revealed that reinforced concrete elements increased the structural stiffness, elevating the modal frequencies and thereby altering the vibration characteristics of the structure. Pushover analyses showed that while reinforced concrete elements contributed marginally to the horizontal force capacity of the structure, they partially reduced displacement demands. Dynamic analyses indicated that the R-Model exhibited a more uniform stress distribution and improved damage mechanisms due to the reinforced concrete elements. However, in scaled 1.25 analyses, significant damage mechanisms were observed in both O-Model and R-Model. This finding demonstrates that while reinforced concrete interventions provide some level of improvement for the structure, they offer limited protection under large-scale earthquake scenarios. Specifically, the R-Model exhibited a “box effect” created by the reinforced concrete slab between the narthex and the north wall, preventing localized collapses. Nevertheless, critical damage mechanisms persisted in other regions of the structure. The results underscore the necessity of meticulous planning for strengthening interventions in the preservation of historical structures. This study highlights the effectiveness of finite element modeling techniques in analyzing historical masonry structures and shows that reinforced concrete elements improve local damage mechanisms. However, the impact of strengthening methods on the global seismic performance requires further investigation.