Distributed optic fiber 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, 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 an air bag system and end anchoring system for the strengthening of a full-scale prestressed concrete girder is proposed at first. Then, for the purpose of evaluating the strengthening efficiency of the PBO sheets, performance of the strengthened PC girder, especially the compressive and tensional strain distribution of concrete and PBO sheet under different load levels and bonding performance of PBO sheets on concrete surface, optic fiber sensing system with a strain/loss analyzer based on the Brillouin Optical Time Domain Deflectometry (BOTDR) technique is employed. Two types of bonding methods for optic fiber installation called the Point Fixed (PF) method and Overall Bonding (OB) method are proposed and investigated. Finally, a kind of polynomial curve fitting method is presented to process the field data contaminated with noise.