Researchers at Shenzhen University have developed a novel self-sensing steel fiber-reinforced polymer composite bar (SFCB) that integrates distributed fiber-optic sensors (DFOS) for real-time monitoring of cracks and mechanical behavior in reinforced concrete members. This innovative approach, detailed in a recent study published in Engineering, aims to enhance the durability and safety of civil infrastructure by providing a more accurate and reliable method for structural health monitoring.

The study, led by Feng Xing and Zhongfeng Zhu, explores the potential of SFCBs embedded with DFOS technology to monitor strain and detect cracks in concrete structures. Traditional methods for assessing concrete cracking often rely on point sensors, which have limitations in capturing the complex and variable nature of crack development. In contrast, DFOS technology, based on optical frequency-domain reflectometry (OFDR), offers high-resolution strain measurements over a wide area, making it a promising tool for structural health monitoring.

The research team designed a series of tension tests on SFCB-reinforced concrete members to investigate the effects of cover depth, bonding mechanisms, and concrete type on the end effects observed in strain measurements. The tests revealed that using members with small cover depths, surface-treated SFCBs, and geopolymer concrete (GPC) can significantly reduce the impact of end effects, leading to more accurate strain measurements.

A key innovation in this study is the development of a theoretical model for predicting the load response of SFCB-reinforced concrete tension members. The model, validated through experimental data, accounts for the tensile behavior of the concrete and the interaction between the SFCB and the surrounding concrete. This model provides a reliable basis for assessing the structural integrity of reinforced concrete members under tension.

The study also proposes a method for calculating crack widths based on DFOS strain measurements. By analyzing the strain distribution along the SFCB, researchers can identify crack locations and estimate crack widths, providing valuable insights into the damage status of the concrete. This method, which considers both visible and internal cracks, offers a more comprehensive assessment of structural health compared to traditional surface monitoring techniques.

The findings of this research have significant implications for the maintenance and repair of civil infrastructure. By enabling real-time monitoring of cracks and mechanical behavior, self-sensing SFCBs can help engineers detect early signs of damage and take timely measures to prevent catastrophic failures. The study highlights the potential of DFOS technology to transform structural health monitoring, offering a more efficient and reliable alternative to conventional methods.

Future research will focus on expanding the sample size and exploring a broader range of cracking patterns using advanced monitoring techniques. The team also plans to investigate the long-term performance of SFCBs in various environmental conditions, further validating the robustness and applicability of their approach.

The paper “Self-Sensing Steel–FRP Composite Bars for Crack Monitoring and Mechanical Behavior Evaluation in Reinforced Concrete Members,” is authored by Yingwu Zhou, Zenghui Ye, Feng Xing, Zhongfeng Zhu, Xiaoxu Huang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.03.001. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.