Distributed Fiber Optic Sensing for a Full-scale PC Girder Strengthened with Prestressed PBO Sheets

Fiber Reinforcement Polymer(FRP) has been widely accepted as an innovative material for renovation and strengthening of existing infrastructures. Among the FRP materials, the Poly-p-phenylene benzobisoxazole (PBO) fiber sheets attracted great attention in recent years because of the high strength, high Young modulus and high energy absorption capability. In this study, a PBO Prestressing Upgrading Technique (P-PUT) including air bag system and end anchoring system for a full-scale prestressed concrete girder is proposed. For the purpose of evaluating the strengthening efficiency of the PBO sheets and the performance of the strengthened PC girder, specially the compressive and tensional strain distribution of concrete and PBO sheet under different load levels and the bonding performance of the PBO sheet on the concrete surface, a fiber optic sensing system with a strain/loss analyzer based on the Brillouin Optical Time Domain Deflectometry (BOTDR) technique has been employed. Two types of bonding methods for optic fiber installation called Point Fixation(PF) method and Overall Bonding(OB) method are proposed and investigated. A kind of polynomial curve fitting method is presented to processing the field data polluted with noise.