Mechanical Performance of Reinforcement Measures for Corrugated Steel Pipe Arch Bridges Under Differential Settlement

This study evaluates the effectiveness of reinforcement measures for a corrugated steel pipe arch bridge subjected to differential settlement induced by underground mining. Using a ten-span continuous corrugated steel pipe arch bridge in Shandong Province as the engineering background, a refined finite element model was developed based on 12 months of in situ settlement monitoring data. The mechanical performance of three reinforcement schemes–inner lining concrete, inner lining concrete with nested steel pipes, and laterally welded steel plates–was systematically compared. The results indicate that under differential settlement, the maximum stress of the unreinforced structure reaches 75.74 MPa, primarily concentrated at the arch foot. Reinforcement with an inner concrete lining significantly improves structural performance; in particular, the 200 mm-thick lining reduces the maximum steel pipe stress by 61.8%, achieves a maximum reduction of 22.1% in crown displacement and approximately 11.2% in sidewall displacement, and limits the circumferential displacement amplitude to 12–17 mm, representing a reduction of 11.7–15%. The nested steel pipe scheme delivers reinforcement effects comparable to the pure inner lining concrete scheme, with a maximum crown displacement reduction of approximately 17.3%, though its overall additional advantages remain limited. In contrast, the laterally welded steel plate scheme reduces the maximum structural stress by 28.3%. While it exhibits favorable control over local displacements, its overall reinforcement effectiveness is inferior to that of the inner lining concrete scheme. These findings provide a useful reference for the reinforcement design and engineering application of corrugated steel pipe arch bridges in mining-induced subsidence areas.