| Summary: | An experimental and numerical investigation into the structural performance of reinforced concrete box sewers with typical corrosion-related extreme defects localized at the ceiling was conducted. Firstly, during the large-scale laboratory test, some key structural responses were captured and evaluated, including the crack width development process (via digital image correlation measurement), ceiling deflection, and material strains of both complete and typical defective boxes. The failure modes and load-carrying mechanism throughout the specimen loading phases were analyzed. Furthermore, the specimen failure process was simulated using a damage-based finite element method, and a related parameter sensitivity analysis was performed. The results indicate that the defective ceiling cracked at mid-span under a low load value, but the bending capacity loss can be substituted by two shoulders and carry three to five times more load before completely collapsing. The simulation matched the lab test qualitatively, and with the suggested set strategy of material parameters, the load-deflection feature curve could provide a practical prediction of the ultimate bearing capacity of the defective sewers, with a 10–15% error on the safe side. Keywords: Defective reinforced concrete box sewer, Corrosion, Structural performance, Large-scale model test, Digital image correlation measurement, Failure simulation
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