High-resolution distributed acoustic sensing for full-scale monitoring of an FRP–concrete composite bridge deck

This study presents a combined experimental and numerical validation of a high-resolution distributed acoustic sensing (HR-DAS) system for continuous strain monitoring in a full-scale fibre-reinforced polymer (FRP)–concrete composite bridge deck. The deck specimen, representative of a typical road bridge configuration, comprised a glass-carbon FRP trapezoidal girder integrated with a cast-in-place concrete slab. A four-point quasi-static bending test was conducted to assess the performance of HR-DAS in capturing distributed strain profiles along the girder. Five ultra-low-loss enhanced back-reflecting (ULEB) optical fibres with embedded reflectors were bonded to the girder surface and interrogated using an HR-DAS system. Conventional sensors, including strain gauges and linear variable differential transformers (LVDTs), were used in parallel for validation. A 3D finite element model (FE) was developed in ABAQUS and validated against experimental strain and deflection data. Close correlation was observed between HR-DAS measurements, strain gauges, LVDTs, and FE predictions, with strain and deflection ratios showing mean errors within 10 %. Additionally, the HR-DAS system demonstrated capability for capturing spatiotemporal strain profiles with a 1 kHz sampling rate. These results confirm the accuracy, resolution, and scalability of HR-DAS for structural health monitoring of FRP–concrete composite bridge structures, supporting its application in long-term, real-time monitoring under service conditions.