Embedded Steel Wire FRP Smart Bar And Monitoring Prestress Loss

Based on good sensing performances (such as linearity, repeatability, total precision et al) of FRP (Fiber Reinforced Plastic) - OFBG (Optical Fiber Bragg Grating) - OF (Optical Fiber) smart steel strands, prestress loss of the prestressed concrete structure can be monitored effectively. The core component of the smart steel strand is FRP-OFBG-OF intelligent bar. As a result of brittle failure and low Young's modulus of the bar, it has bad security and poor sensing precision.For solving these problems and combining the advantages of the FRP(or steel wire) composite rebars and smart FRP-OFBG(OF) composite bars at the same time, this paper provides a novel FRP intelligent bar which embedded with steel wires. This intelligent bar can be assembled as FRP smart bar(or steel wire) composite strand, and can be utilized for monitoring the prestress loss of prestressed structures. The main contents of this paper include:Embedded steel wire FRP smart bars is made by that multiple steel strands and OF (or OFBG) sensors are embedded in FRP bar. Then the mechanical and sensing properties of the smart bar were studied by tests.On basis of the definite mechanical and sensing characteristics of the embedded steel wire FRP smart bars, steel cable– FRP smart steel strand is developed by utilizing embedded steel wire FRP smart bar instead of common steel wire core. In this paper, the working principle of steel cable– FRP smart steel strand is expounded, and experimental study on its sensing performance is carried out. The concept and common calculation methods of prestress loss are introduced. For application of steel cable-FRP smart steel strand in prestressed concrete structure, the principle of monitoring prestress loss based on smart steel strand is put forward.A steel frame and a concrete beam for post-tension method are designed, which lay the steel cable– FRP smart steel strand and the conventional sensors. The prestress loss of prestressed bars can be monitroed by the smart steel strands. The monitoring result is analyzed and the comparison between the specification calculation and the conventional sensors is made.