Bond behavior between concrete frame beam and large-diameter glass fiber reinforced polymer(GFRP) anchor rod with built-in fiber Bragg grating sensor

Fiber reinforced polymer(FRP) is a new composite material with excellent mechanical properties and corrosion resistance. It is a significant way to solve the durability problem of anchor rod by substituting this polymer for steel bars. Using anchor-rod-structure specimen made from glass fiber reinforced polymer(GFRP) bars with fiber grating installed internally, loaded by hollow hydraulic jack, monitored by grating sensing technology, this paper focuses on the failure mechanism of large-diameter sand-coated GFRP rebar in the frame beams under the condition of anchoring. Research shows that in the experiment, in terms of tensile force and average bond strength, this large-diameter(25 mm) GFRP rebar has reached the design strength of ribbed steel with the same diameter. The most reasonable thickness of frame beam varies from 30 to 40 cm. Transient loading cycles have no obvious influence on GFRP rebar interface-bond state; the degradation of rod body interface-bond state will occur under sustained loads, and it continues to develop and expand to the deeper part. Moreover, the greater the load applied is, the deeper the depth extended to is and the faster the degradation proceeds. Optical fiber grating monitoring technology is an effective method to find and observe the interface-bond state degradation process.