Shear Transfer Mechanism of Concrete Strengthened with External CFRP Strips

Abstract

Concrete with reinforcing steel bars across a shear plane was strengthened using carbon fiber–reinforced polymer (CFRP) strips externally bonded to resist shear transfer. Specimens were designed and tested to give insight on shear transfer based on a component model. In this model, five components, i.e., the friction, aggregate interlock, adhesion, shear dilation, and dowel action, contributed to the overall shear resistance. Results indicated that the ultimate shear transfer capacities improved by 6 to 50% for specimens with steel reinforcement ratios varying from 0.46 to 1.20% and CFRP reinforcement ratios varying from 0.224 to 0.298%. The mechanism of shear resistance increase was due to the additional clamping force provided by CFRP strips, which led to a significant increase in the shear component of the adhesion. A best-fitting expression was presented to predict the ultimate shear transfer capacities of CFRP-strengthened concrete with satisfactory accuracy by comparing the calculated results with test data in this study and in literature. A general concept of equivalent reinforcement ratio was proposed to clarify the limitation of strengthening effect for shear transfer.