FBG sensors for strain-based monitoring of CFRP-strengthened RC beams under quasi-static moving loads

Résumé fourni par la source

This study presents an experimental and finite element (FE) validation investigation of reinforced concrete (RC) beams under quasi-static moving loads, focusing on the applicability of Fiber Bragg Grating (FBG) sensors for low-amplitude strain monitoring. Two full-scale beam specimens with identical dimensions were examined: an unstrengthened control beam and a beam strengthened with an externally bonded carbon-fiber-reinforced polymer (CFRP) laminate. Moving loads of 100, 122, and 150 kg, all within the elastic response range of the beams, were applied using a custom cart system to simulate quasi-static moving-load conditions. FBG sensors installed at embedded and external locations were used to capture real-time strain responses. Collocated conventional electrical strain gauges were also installed; however, the strain amplitudes generated during testing were generally below 10 µε, and reliable strain–time histories could not be extracted from the electrical gauges. Therefore, the detailed strain-response analysis was based on the FBG measurements. The recorded FBG strain–time histories showed clear rise–peak–decay patterns corresponding to load movement along the span. External sensors measured higher strain amplitudes than embedded sensors, consistent with their proximity to the outer tensile fiber rather than the neutral axis. The CFRP-strengthened beam exhibited higher localized surface strain at the laminate level than the control beam, consistent with strain transfer to the bonded CFRP layer. A three-dimensional FE model developed in Abaqus reproduced the experimental strain–time response with good agreement, with peak-strain deviations generally within 15 %. Stress distributions in the concrete, steel reinforcement, and CFRP layer were consistent with the expected elastic flexural response under the applied loading. Within the tested low-amplitude strain range, the FBG system provided clear, high-resolution strain–time histories and supported FE correlation under quasi-static moving-load conditions. The validated FE model provides a basis for future parametric studies of FRP-strengthened RC members under broader loading, damage, and strengthening configurations than those examined in this elastic-range, single-specimen-pair study.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.