Application Cases

Experiment Name: Research on Shear Resistance and Damage Mechanics Model of Joint Surfaces of Prestressed GFRP Anchor Rods

Research Direction: Application of Composite Materials in Civil Engineering

Experiment Content: Based on the double shear test method for anchor rods, this paper designs and conducts shear tests on the joint surfaces of GFRP anchor rods under different prestress levels. The effects of prestress on the failure modes, shear resistance, and shear deformation of the joint surfaces of GFRP anchor rods are analyzed based on the test results. Furthermore, a predictive model for the shear displacement-shear stiffness and shear displacement-shear stress of GFRP anchor rods is established by combining the equivalent strain hypothesis with damage mechanics theory.

Testing Equipment: Strain acquisition instrument, multifunctional fatigue testing machine, ATA-61411 power amplifier, etc.

Experiment Process: Shear tests are conducted on the joint surfaces of GFRP anchor rods under different prestress levels. The shear strain of the GFRP anchor rods is collected using the power amplifier from Aigtek to analyze the shear stress of the joint surfaces. This further investigates the shear mechanical properties of prestressed GFRP anchor rods. Based on the shear stiffness variation and Weibull damage theory, a damage model is established using the enhanced shear strain test results from the Aigtek power amplifier, revealing the shear damage and failure mechanism of prestressed GFRP anchor rods.

Figure 1: Real photo of the experiment on shear resistance and damage mechanics model of joint surfaces of prestressed GFRP anchor rods

Experimental Results: The load-displacement curve is divided into three stages: initial shearing, mid-shearing, and final shearing. The failure mode is characterized by cracks appearing in the left, middle, and right concrete blocks, with significant cracks in the middle block and crushing in the upper compression zone. Some GFRP bars split, and most of them fail in shear after splitting. For GFRP anchor rods without prestress, the load increases relatively gently with increasing shear strain, indicating lower overall stiffness. In contrast, for prestressed GFRP anchor rods, the load initially increases rapidly and then tends to stabilize as the strain increases, showing a higher initial stiffness. The fracture strain of GFRP anchor rods with 20% and 40% prestress decreased by 33% and 44%, respectively, compared to those without prestress. This indicates that prestress has a significant confining effect on the surrounding rock, effectively enhancing the shear resistance of the joint surfaces.

Figure 2: Experimental Results