Scour-induced stability risks of the Zogu Bridge: Preservation challenges and policy recommendations for a threatened European heritage

This study aims to investigate the structural condition of the Zogu Bridge, a designated cultural monument in Albania, focusing on the impact of scour phenomena and the recent threat of devastating flood events. Namely, this study aims to assess the potential risks that could lead to the collapse of the bridge. It underlines the urgency of addressing critical issues to preserve this important cultural and engineering heritage. The study is based on an in-depth analysis combining extensive topographical and geotechnical investigations of the site. In addition, numerical analysis are carried out to evaluate the structural risks associated with the settlement that occurred at Pier P2 during the flood of January 11, 2021. The load-bearing capacity of the bridge was analyzed to obtain a comprehensive understanding of the overall structural integrity. The methodology involves a comprehensive approach to collecting data and assessing the various factors contributing to the precarious condition of the Zogu Bridge. The results of the study reveal alarming conditions, particularly in relation to pier P2, which has subsided by more than 2 m, jeopardizing the overall stability of the bridge. The numerical analysis show that Pier P2 had already lost more than 60% of its load-bearing capacity before the settlement occurred. In addition, piers P5, P1, P3, and P4 are in critical condition, with pier P5 teetering on the edge of equilibrium. Urgent action is deemed crucial to prevent further progression of scour depth which would pose a serious threat to the stability of the entire Zogu Bridge. The originality and contribution of this study lie in the comprehensive examination of the Zogu Bridge, which addresses both the technical aspects and the cultural significance of the structure. The identification of specific risks and critical conditions, supported by thorough site investigations and numerical assessments, provides valuable insights for preservation efforts. Our findings suggest that the construction of a rockfill weir downstream of the bridge would be the most effective short-term measure. This approach would mitigate scouring around the bridge piers, lowering the collapse risk of the Zogu Bridge from extreme to medium. The urgent call to take effective action underscores the importance of preserving this centuries-old engineering masterpiece, highlighting its dual significance as an outstanding work of architecture and a treasured cultural monument of both national and international value.