Numerical and experimental evaluation of a variable-stiffness wedge anchorage for basalt-fiber-reinforced polymer tendons

Abstract

The small-sized variable-stiffness wedge (VSW) anchorage, a second-generation solution, was numerically optimized to anchor basalt-fiber-reinforced polymer tendons, building upon the previous first-generation anchorage. The static, fatigue, and relaxation characteristics of the anchorage were experimentally evaluated. Results revealed that VSWs effectively mitigated radial stress concentration within the tendons compared to constant stiffness wedges. Bonding optimization techniques involving cross-splitting and sandblasting proved advantageous in accurately assessing the tensile properties of round tendons. The second-generation anchorage demonstrated an 87% anchoring efficiency, surpassing that of a longer commercial steel-wedge anchorage significantly. The tendon-anchorage assembly can sustain 2 million cyclic loadings under a maximum fatigue stress of 0.44 ffpk (standard value for tendon tensile strength) and a stress range of 0.04 ffpk; moreover, sliding between wedges and tendons resulted in negligible stress reduction across various stress ranges. A logarithmic function effectively modeled the relationship between relaxation time and load retention in tendons with R-squared values consistently above 0.94 throughout; furthermore, the million-hour relaxation rate closely aligned with observed tendon behavior. The application of an initial tensile stress of 0.5 ffpk to tendons allowed for simultaneous high strength and minimal prestress loss.