A team at Shenzhen University has developed a self-sensing steel fiber-reinforced polymer composite bar (SFCB) that integrates distributed fiber-optic sensors (DFOS), enabling real-time monitoring of cracks and structural behavior in reinforced concrete. Published in Engineering, the study offers a promising new method for assessing the health of civil infrastructure with greater accuracy and reliability.
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Led by Feng Xing and Zhongfeng Zhu, the research focuses on embedding DFOS technology into SFCBs to monitor strain and detect cracks as they develop. Traditional approaches often rely on point sensors, which can miss the nuances of crack formation due to their limited coverage. In contrast, DFOS, built on optical frequency-domain reflectometry (OFDR), delivers high-resolution strain data across a continuous surface, making it well-suited for capturing the complex behavior of concrete under stress.
To better understand how various factors affect measurement accuracy, the team conducted a series of tension tests on concrete members reinforced with SFCBs. These tests explored the roles of concrete cover depth, bonding mechanisms, and material types. Results showed that using surface-treated SFCBs, shallow cover depths, and geopolymer concrete (GPC) significantly reduced “end effects”—measurement distortions that can occur near the bar’s extremities—ultimately improving the clarity of strain data.
One of the study’s key innovations is a theoretical model designed to predict how SFCB-reinforced concrete responds to tensile forces. This model, supported by experimental validation, accounts for both the tensile behavior of the concrete and its interaction with the embedded bar. It provides engineers with a dependable tool for evaluating structural integrity in real-world applications.
The research also introduces a method to estimate crack widths based on strain readings from the DFOS. By analyzing strain distribution along the SFCB, the team could not only pinpoint where cracks occurred but also approximate their widths, including internal cracks that aren't visible on the surface. This approach gives a more complete picture of structural health than conventional surface-based inspections.
With this technology, civil engineers could more effectively monitor infrastructure in real time, identifying early signs of damage and intervening before problems escalate. The study highlights how integrating DFOS with self-sensing materials could streamline structural health monitoring and make it more precise.
Next steps for the team include expanding the sample size and testing a broader variety of cracking patterns. They also plan to explore how these systems perform under different environmental conditions over time, further testing the durability and applicability of their approach.
Journal Reference:
Zhou, Y., et al. (2025) Self-Sensing Steel–FRP Composite Bars for Crack Monitoring and Mechanical Behavior Evaluation in Reinforced Concrete Members. Engineering. doi.org/10.1016/j.eng.2025.03.001.