Health Monitoring of Rehabilitated Concrete Bridges Using Distributed Optical Fiber Sensing

Wei Zhang, Junqi Gao, Bin Shi & Heliang Cui
Center for Engineering Monitoring with Opto-Electric Sensing, Nanjing University
Hong Zhu
College of Civil Engineering, Southeast University
Source: Computer-Aided Civil and Infrastructure Engineering 21 (2006) 411–424

Abstract: It is evident that a health monitoring systemm (HMS) holds a great deal of potential to reduce the inspection and maintenance cost of existing highway bridges by identifying the structural deficiencies at an early stage, as well as verifying the efficacy of repair procedures. As newly developed techniques, distributed optical fiber sensing (DOFS) have gradually played a prominent role in structural health monitoring for the last decade. This article focuses on the employment of two types of DOFS, namely fiber Bragg grating (FBG) and Brillouin optical time domain reflectometry (BOTDR), into an integrated HMS for rehabilitated RC girder bridges by means of a series of static and dynamic loading tests to a simply supported RC T-beam strengthened by externally post-tensioned aramid fiber reinforced polymer (AFRP) tendons. Before the loading tests, a calibration test for FBG and another one for BOTDR were implemented to, respectively, obtain good linearity for both of them. Monitoring data were collected in real time during the process of external strengthening, static loading, and dynamic loading, respectively, all of which well identified the relevant structural state. The beam was finally vibrated for 2 million cycles and then loaded monotonously to failure. Based on the bending strength of externally prestressed members, ultimate values for the test specimen were numerically computed via a newly developed simplified model, which satisfactorily predicted the ultimate structural state of the beam. And then the alert values were adopted to compare with the monitoring results for safety alarm. The investigation results show a great deal of applicability for the integrated SHM by using both DOFS in rehabilitated concrete bridges strengthened by external prestressing.

    Aktan, A. E., Catbas, F. N., Grimmelsman, K. A. & Tsikos, C. J. (2000), Issues in infrastructure health monitoring for management, Journal of Engineering Mechanics-ASCE, 126(7), 711–24.
    Aktan, A. E., Helmicki, A. J. & Hunt, V. J. (1998), Issues in health monitoring for intelligent infrastructure, Smart Materials and Structures, 7(5), 674–92.
    Ansari, F. (1997), State-of-the-art in the applications of fiberoptic sensors to cementitious composites, Cement & Concrete Composites, 19(1), 3–19.
    Bao, X. Y., Demerchant, M., Brown, A. & Bremner, T. (2001), Tensile and compressive strain measurement in the lab and field with the distributed Brillouin scattering sensor, Journal of Lightwave Technology, 19(10), 1698–704.
    Casas, J. R. & Ramos, G. (2002), Intelligent repair of existing concrete structures, Computer-Aided Civil and Infrastructure Engineering, 17(1), 43–52.
    Davis, M. A., Bellemore, D. G. & Kersey, A. D. (1997), Distributed fiber Bragg grating strain sensing in reinforced concrete structural components, Cement & Concrete Composites, 19(1), 45–57.
    Harajli, M., Khairallah, N. & Nassif, H. (1999), Externally prestressed members: Evaluation of second-order effects, Journal of Structural Engineering-ASCE, 125(10), 1151–61.
    Hiroshige, O., Hiroshi, N., Mitsuru, K. & Akiyoshi, S. (2001), Industrial applications of the BOTDR optical fiber strain sensor, Optical Fiber Technology, 7(1), 45–64.
    Komatsu, K., Fujihashi, K.&Okutsu, M. (2002), Application of the optical sensing technology to the civil engineering field with optical fiber strain measurement device (BOTDR), Proceedings of SPIE, 4920, 352–61.
    Kurashima, T., Usu, T., Tanaka, K.&Nobiki, A. (1997), Application of fiber optic distributed sensor for strain measurement in civil engineering, Proceedings of SPIE, 3241, 247–58.
    Lin, Y. B., Chang, K. C., Chern, J. C.&Wang, L. A. (2004), The health monitoring of a prestressed concrete beam by using fiber Bragg grating sensors, Smart Materials and Structures, 13(4), 712–18.
    Maaskant, R., Alavie,T., Measures,R. M.,Tadros,G., Rizkalla, S. H.&Guha-Thakurta, A. (1997), Fiber-optic Bragg grating sensors for bridge monitoring, Cement&Concrete Composites, 19(1), 21–33.
    Naaman, A. E. (1995), Unified bending strength design of concrete members: AASHTO LRFD Code, Journal of Structural Engineering-ASCE, 121(6), 964–70.
    Tan, K. H. & Ng, C. K. (1997), Effects of deviators and tendon configuration on behavior of externally prestressed beams, ACI Structural Journal, 94(1), 13–22.
    Wu, Z. S., Xu, B., Hayashi, K. & Machida, A. (2003), Fiber optic sensing of PC girder strengthened with prestressed PBO fiber sheets, in Z. S.Wu &M. Abe (eds.), Proceedings of the First International Conference on Structural Health Monitoring and Intelligent Infrastructures, Tokyo, 13–15 November 2003, Rotterdam, Balkema.