Condition assessment of a heritage arch bridge using a novel model updation technique

Abstract

The bridge network on Indian Railways comprises a large number of masonry arch bridges, a significant number of which are more than 100 years old. The traffic intensities and the loads that are imposed on these structures are significantly higher than those for which they were designed. A significant proportion of these arch bridges is still in good condition and might be structurally adequate for the increased traffic conditions and need not be replaced. A robust identification and assessment procedure is, therefore, critical to enable proper decisions to be taken by railway authorities for managing their arch bridges. A comprehensive monitoring of a 75-year-old heritage stone masonry arch was undertaken. The measured responses were used along with a generated finite element model for structural system identification. The finite element model was updated to estimate the properties and associated degradation of the materials in the masonry arch. The condition of the structure was then estimated to be satisfactory as the converged parameters were well within the expected ranges for the materials in question. The updated model can also be used to reliably check the adequacy of the bridge for future design loads. As the monitoring cost is just a fraction of the replacement cost of the system, this process shows promise of being able to be used to validate the existing infrastructure of stone masonry arch railway bridges and to optimize their replacement.