Structural Safety Assessment of an Existing Steel Bridge After 55 Years of Service

In the 1960s, a unique and modern thin-walled steel superstructure was implemented for several road bridges in Poland. However, the structure has several structural and technological weaknesses that, over time, have led to severe structural damage (e.g., weld cracks, local buckling, etc.). The paper focuses on one of these bridges, which has been in service for over fifty years, where observed damages during detailed inspections necessitated a thorough experimental and numerical investigation to assess the structural safety of the superstructure. For this purpose, the new national guidelines for evaluating the safety of existing road bridges were utilised for the first time. The guidelines were based on the new Eurocode prEN 1990-2, which provides the basis for assessing existing structures. To enable reliable and rational maintenance decisions regarding repair or strengthening, a finite element analysis was conducted considering the condition survey, NDT, and material testing. Based on the experimental and numerical results within this new assessment framework, the final decision was made to close the bridge for service and replace the existing steel structure.