BASIC STUDY ON MONITORING TECHNIQUE FOR CONCRETES PRESTRESSED WITH CFRP BY USING FIBER-OPTIC SENSORS

Carbon fiber reinforced plastic prestressed concrete (CFRPC) is a material that utilizes CFRP strand cables as tendons, exhibiting exceptional performance in terms of specific stiffness, strength, and high corrosion resistance [1]. Particularly when used in offshore structures, it is considered to overcome the drawbacks of steel strand cables [2]. In this study, we propose the use of fiber-optic sensors to assess the structural integrity when considering the application of CFRPC to long-life offshore structures. We perform two experiments. First, we conduct tensile tests on three types of CFRP strand cables and one steel strand cable to measure the strain distributions and understand the differences in mechanical properties between the steel and CFRP strand cables, as well as differences between different types of CFRP coatings. Second, we fabricate a CFRPC beam with the CFRP strand cable and bond fiber-optic sensors to a CFRP strand and outside of the concrete beam to measure the strain distribution and verify the feasibility of structural health monitoring of CFRPC. Through these two experiments, we continuously measure the strain along the length of the CFRP strand and the strain distribution of CFRPC from the introduction of prestress until the crack develops. We also investigate the relationship with the breakage behavior and evaluate the mechanical properties, such as the stiffness of the strand cables during the tensile test.