Design approach for flexural properties of engineered geopolymer composite shield tunnel segments reinforced with GFRP bars

Abstract

To improve the durability and crack resistance of shield tunnel segments, glass fiber-reinforced polymer (GFRP) bars reinforced engineered geopolymer composite (EGC) segments, referred to as EGC-FRP segments, were introduced as a replacement for conventional steel reinforced concrete segments. Experimental study on flexural properties of EGC-FRP segments was conducted. Effects of EGC and reinforcement ratio were analyzed. In addition, a numerical investigation of EGC-FRP segments based on finite element (FE) analysis was performed. The results showed that EGC has more cracks and a smaller crack width than concrete under tensile load and has residual strength after cracking due to the fibers in it, which leads to strong synergistic loading ability between EGC and GFRP bars. The maximum crack width of the EGC-FRP segment is reduced by 66.11% under the same reinforcement ratio. Meanwhile, EGC segments exhibited higher flexural strength, deflection, and post-cracking stiffness than those of the concrete segment. In particular, the ultimate flexural strength is increased by 96.44% compared to that of the concrete segment. A FE model developed based on the experimental results showed a good correlation with the test data. The model was used to analyze the flexural behavior of EGC-FRP segments with different reinforcement ratios. Finally, calculation methods for the flexural strength and deflection of EGC-FRP segments were proposed.