Use of DFOS to monitor crack opening evolution in FRCM-strengthened reinforced concrete structures

The recent collapses and the general maintenance conditions of bridges have highlighted the urgent need to inspect, maintain, and assess existing infrastructures. Numerous research groups are actively engaged in assessing existing Reinforced concrete (RC) bridges, investigating the primary causes of deterioration by in-situ inspection or laboratory experiments, and developing advanced retrofitting solutions to extend bridge service life. In this field, the two main areas of interest are: on one hand, the development of innovative and performing strengthening and retrofitting solutions, and on the other, the development of inspection and diagnostics techniques for structural health monitoring of RC members. This paper presents a single application that combines the Fabric-Reinforced Cementitious Matrix (FRCM) strengthening and crack control capabilities, with the use of Distributed Fiber Optic Sensors (DFOS) to monitor the crack pattern development. Key advantages of FRCM composites are the better compatibility with irregular surfaces, very important in case of deteriorated concrete covers, and the possibility to work with limited thicknesses, limiting the overall masses increase. In parallel, DFOS technology is recently gaining popularity due to its accuracy, long-term stability, immunity to magnetic fields, and the ability to act as distributed strain sensor. To achieve the goal of an integrated strengthening and monitoring approach, the direct tensile behaviors of plain textiles and FRCM composites are experimentally investigated under monotonic and loading/unloading load conditions, respectively utilizing DFOS to measure the fabric strain and the crack evolution during the tests. Subsequently, at meso-scale, Double-Edge Wedge Splitting (DEWS) tests will be carried out to assess capacity enhancement, crack opening mitigation, and the effectiveness of the DFOS-based approach in tracking crack pattern evolution.