Bond Characteristics of CFRP Rod Panels Adhered to Concrete under Bending Effects

Abstract

Carbon fiber–reinforced polymer (CFRP) rod panels (CRPs) comprising small-diameter rods at a spacing larger than rod diameter are emerging as an effective adhesively bonded system for retrofit applications. They offer the advantage of a better bond than equivalent CFRP conventional plates due to the increased surface area of the rods. This study aims at characterizing the flexural bond properties of CRPs using the notched concrete beam test specified by the current standard. CRPs with 2-mm rod diameter were used. Rod spacing-to-diameter ratio (S/D) was varied from 3 to 6. CRP width-to-beam width ratio bf/bc was varied from 0.17 to 0.5. The bond length was varied from 25 to 200 mm on one side of the notch. While debonding failure consistently governed, a development length of 80 mm was found, beyond which insignificant change in ultimate load was noticed. The average bond strength was determined to be 5.1 MPa. It was found that the stress in the individual rods at ultimate load increased from 33% to 53% of their ultimate tensile strength as the S/D ratio increased from 3 to 6. A bilinear bond-slip relation was also established for this system.