The three-dimensional flow of force in a damaged, skewed masonry arch railway bridge – Insights from fibre Bragg rosettes, videogrammetry, and modelling

• Dynamic principal strain sensing using new Fibre Bragg grating strain rosettes.
• Visualisation of 3D force flow throughout a skewed arch bridge using these rosettes.
• Videogrammetry monitoring of the bridge to study distributed dynamic deflections.
• Analytical modelling of transverse bridge bending, validated with sensor data.
• Evaluation of bridge repair works using modelling results.

Masonry arch bridges are common, especially in the UK and Europe, but interpretation of their structural behaviour can be challenging and is often complicated by histories of damage over their long working lives. Assessing the performance of repair works at these bridges is vital, to provide confidence in their continued use. This paper presents novel applications of fibre-optic sensing and videogrammetry to measure and visualise the three-dimensional, dynamic structural response of a skewed masonry arch railway bridge in unprecedented detail. In particular, fibre-optic strain rosettes are used to map the distributions of principal strains, and hence force flow, throughout the arch, while videogrammetry reveals a secondary load path in the form of transverse arch bending. Monitoring results are then combined with simplified analytical models of this transverse bending, to study the effectiveness of intervention works aimed at restoring structural connectivity between the arch and its spandrel walls.