Strain analysis of glass fiber cloth GFRP reinforcement:

① Analysis of the strain of GFRP bars in the longitudinal glass fiber cloth of fatigue specimen B1 The variation of the maximum strain of GFRP bars in specimen Bl with the number of fatigue cycles is shown in Figure 11-23. It can be seen from the figure that the strain of GFRP bars changes in a curve with the number of fatigue cycles. The maximum strain of GFRP reinforcement is 680.3X10-6 at 10000 times ε， The maximum strain of GFRP reinforcement is 745.5X10-6 for 1 million times ε， After 1 million cycles, the strain growth rate of glass fiber cloth GFRP bars becomes larger. After 2 million cycles, the maximum strain of GFRP bars reaches 1000 × 10-6E, 1.5 times the strain of bars at 10000 cycles. At this time, the stress of GFRP bars reaches 48.54 MPa, and the maximum strain value of GFRP bars accounts for 2170. 5 × 10-6 of the strain of bars at the time of static load test piece B0 failure ε 46.1%, far from reaching its design strength.

② Analysis of strain of longitudinal glass fiber cloth GFRP reinforcement of fatigue specimen B2 Fatigue loading of specimen B2 is 1.36 million times at the stress level of 0.25. The relationship between the number of fatigue cycles and the strain of longitudinal GFRP reinforcement is shown in Figure 11-24. At zero static load, the maximum strain of GFRP reinforcement is 1322X 10-6 ε， The maximum strain is higher than that of specimen B1. With the increase of the number of fatigue cycles, the strain of glass fiber cloth GFRP bars increases gradually at 10000 times. This shows that 0 static loading causes more residual strain in GFRP reinforcement. Subsequently, the strain gradually increased, which can fully explain that with the continuous increase of fatigue cycles and the accumulation of fatigue damage of GFRP bars, the strain also gradually increased, and part of the GFRP bars glass fibers broke, which gradually reduced the load bearing capacity of the longitudinal GFRP bars, resulting in the rapid expansion of the main cracks, and finally the brittle failure of the specimen.