Effect of initial pretension on dynamic bond behavior of an ultra-high performance concrete-filled anchorage for carbon fiber-reinforced polymer tendons

This paper is focused on the effect of initial pretension on the dynamic bond performance of the anchorage under impact loads. Drop-weight impact tests were conducted on 15 groups of specimens with four embedded lengths and various pretension ratios; the effects of pretension and embedded length on the bond strength and slip of the anchorage are discussed in the paper. The test results show that a higher pretension ratio led to severer surface damage on the CFRP tendons. With the increase of the pretension ratio, the mechanical interlocking between CFRP ribs and UHPC was improved, leading to an increased average bond strength. By contrast, the relatively large shear deformation and severe damage of CFRP ribs induced by pretension formed "initial defects", which resulted in a lower residual bond performance during impact loading. Based on the test results, a pretension ratio-dependent strength retention function was proposed to quantify the shear damage effect of CFRP ribs caused by pretension; by incorporating this function, accurate formulas were developed for determining the dynamic bond strength of a pretensioned anchorage.