Bond characteristics and modeling of near-surface mounted CFRP in concrete

摘要

This paper presents the direct pull-out test results of twenty-four concrete joint specimens using near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) rods and strips. Investigated in the study was the effect on the bond strength and local bond characteristics due to different cross-sectional shape (rod vs. strip) and surface treatment of NSM reinforcement (roughened, sand-coated, sand-coated and spirally wound), adhesive type, and concrete strength. Specimens using CFRP rods with sand-coated and spirally wound surface condition outperformed others in terms of load-carrying capacity and local bond strength. Increasing the strength of epoxy adhesive or concrete had positive influence on the bond behavior. The observed post-debonding residual bond stress was confirmed to contribute to the load-carrying capacity of the joint. The proposed analytical model based on a proper trilinear local bond stress-slip law (representing the distinctive linear elastic, softening and debonding stages) provided good agreement with the experimental data.