Evaluation of the Flexural Response of Steel Reinforced UHP-FRC Beams Using Distributed Sensing

The interaction between ultra-high-performance fibre-reinforced concrete (UHP-FRC) and steel reinforcement significantly affects the displacement ductility of UHP-FRC beams in flexure, leading to a brittle failure mechanism due to crack localization. Previous studies faced limitations in fully exploring this interaction due to conventional sensors. Distributed fibre-optic sensors (DFOS), particularly based on optical frequency domain reflectometry (OFDR), offer new insights. In our study, DFOS and strain gauges monitored strains along longitudinal reinforcement and support wire during four-point loading tests on beams with varying fibre contents (1% and 3%) and reinforcement ratios (1.5% and 2.3%). Results showed that lower fibre content and higher reinforcement ratio led to greater ductility, indicated by increased curvature and strain peaks. Finite element modelling underestimated experimental responses, suggesting a need for improved material property characterization.