Vol.:(0123456789) Journal of Civil Structural Health Monitoring https://doi.org/10.1007/s13349-019-00330-1 123 ORIGINAL PAPER Long‑term performance monitoring of GFRP‑reinforced concrete beams using sensor‑mounted supplemental rebars under harsh environmental conditions Arash Rahmatian 1  · Timir Baran Roy 2  · Amir Mofdi 3  · Ashutosh Bagchi 2  · Michelle Nokken 2 Received: 16 September 2018 / Accepted: 11 March 2019 © Springer-Verlag GmbH Germany, part of Springer Nature 2019 Abstract Fiber-optic sensors (FOS) are increasingly being used in reinforced-concrete (RC) structures for their accuracy and durabil- ity. One of the drawbacks of FOS is their fragility at installation. One recently developed method to address such defciency is to install the FOS on a short bar (supplemental bar) that is rigidly connected to the structural reinforcement bars prior to concrete pouring. However, the durability of such systems under harsh environmental conditions has not been well estab- lished. In order to better understand the behavior of the aforementioned FOS systems under harsh environmental conditions, seven half-scale RC beams with glass fber-reinforced polymer bars were exposed to four diferent exposure regimes, in the present study. After 14 months of exposure to harsh environmental conditions, the RC beams were subjected to static fexural testing to evaluate the FOS system behavior under each environmental condition. In addition, the strain responses of the sensors mounted on the supplemental bars and those in the main bars were monitored to validate the newly developed FOS mounting system. The results of this study show that the proposed FOS mounting system can efciently capture the actual strain in all environmental conditions tested in this study except immersion exposure under high alkali solution. In addition, the fexural deformation and the exposure impact to the beam capacity were evaluated. Keywords FRP · Concrete beam · Weathering · SHM · Sensor · Monitoring 1 Introduction Structural Health Monitoring (SHM) technologies are being used notably in recent years to detect structural damages and evaluate the structural health of the aging and deteriorated civil infrastructure. Many newly constructed structures are also instrumented to monitor their performance over their life span to facilitate their smart maintenance and timely intervention. New construction materials such as Fiber Rein- forced Polymer (FRP) bars and fabrics have also emerged to promote corrosion-free and durable construction. In addi- tion, measurements of strain in the reinforcing bars are of interest to structural engineers to determine the strain profle along the structural elements, in addition to their variation over time. Fiber optic sensors are found to be accurate and, if installed properly and securely, deemed durable under harsh environmental conditions [28]. However, due to fragility of fbers used in the FOS, installation of the FOS inside the structural elements through a durable bond of the sensor to the rebar needs signifcant care. Further investigations are required to propose new FOS installation methods, and to evaluate the durability and the behavior of the installed FOS under diferent harsh environmental conditions. The follow- ing two types of FOS, namely, Fabry–Pérot [35] [FP] and Fiber Bragg Grating [25] [FBG] are found to be commonly used in SHM. Two separate groups, namely Sim et al. [38] and He et al. [21], manually made FRP reinforcement with embedded FBG sensors. They reported that the strain read- ings measured by the sensors correlated with the applied * Arash Rahmatian rahmatiana@uhd.edu 1 Department of Computer Science and Engineering Technology, University of Houston-Downtown, Houston, TX, USA 2 Department of Building, Civil and Environmental Engineering, Concordia University, Montréal, QC, Canada 3 Geotechnics and Structures Group, School of Engineering, Newcastle University, Newcastle upon Tyne, UK