Enhanced damage detection in bridge engineering using DFOS

Distributed Fiber-Optic Sensing (DFOS) is emerging as a key technology for Structural Health Monitorings (SHMs). DFOS offers strain and temperature measurement over long range with high spatial resolution. This technology is most suitable for large civil infrastructure such as bridges or tunnels Structural Health Monitoring. But early applications were limited to one-dimensional measurements along principal load paths, but recent work has enhanced DFOS with full-field monitoring through fiber-optic grids or with multi-sensor fusion technics. This paper reviews the state-of-the-art in DFOS-based damage detection for concrete, steel, and steel-composite bridges and highlights new opportunities for enhanced DFOS applications. First, the most common damage characteristics on different bridge types are summarized. A concise collection of published DFOS applications on bridges follows, illustrating integration either surface-bonded or embedded within structural components for short- and long-term monitoring. It is relived that DFOS is routinely used to validate design assumptions, locate crack initiation in concrete members, and monitor crack propagation in steel bridges. Despite these successes, full-field monitoring with fiber-optic grids remains limited to laboratory scale. Consequently, the paper presents enhanced methodologies for monitoring common damage types: bonding failure, surface cracks,tendon breaks, shear failure, debonding of Carbon Fiber Reinforced Polymer (CFRP) strips, based on embedded DFOS, enhanced 2D fiber-optic grids and multi-sensor fusion. These developments are placed in the context of the Cluster ”Damage detection” of the SPP 100+ project “Extending the Lifetime of Complex Engineering Structures through Intelligent Digitalization”, which aims to transfer laboratory advances into robust, field-deployable SHM solutions on the Rhine River bridge ”Nibelungenbr¨ucke Worms”.