INVESTIGATION OF THE FACTORS AFFECTING THE BOND CHARACTERISTICS BETWEEN CONCRETE AND CARBON FIBER REINFORCED POLYMERS (CFRP)

Abstract

The present study investigated the bond characteristics between R.C concrete beams and CFRP strips. The following summarizes the findings of this investigation: 1. The outcomes of the experimental program on flexural strengthening of RC beams confirmed that FRP externally bonded laminates are an effective technique for increasing the strength of flexural elements 2. The increase of bond length from 600 mm to 900 mm increased the load carrying capacity by 30%, decrease the deflection by 8% and increased the CFRP debonding strain by 80%. 3. While increasing of bond length from 900 mm to 1200 mm had no significant influence on the ultimate capacity. Although decreased the deflection by 5.5%, decreased the steel strain by 15% and increased the CFRP strain by 1.6%. 4. The increase of concrete clear cover thickness from 20 mm to 40 mm had no significant effect on the ultimate capacity, increased deflection by 26% and increased CFRP strain by 13%. While increasing of concrete clear cover thickness from 40 mm to 60 mm decreased the load carrying capacity by 15.5%, decreased the deflection by 14%, and decreased the CFRP strain by 20%. Chapter 7 Summary and Conclusions 878 5. The change of loading pattern from 3-point load to 4-point load decreased moment capacity by 10% and decreased CFRP strain by 10%, this apparent from specimens B2 and B6. 6. The Chinese code equations showed the best correlation with the experimental data, while The Egyptian code equations overestimate the debonding strain and do not consider the bond length as a parameter in determining the debonding strain. Modifications of the approach used are recommended. 7. Using the experimental data and another data available in the literature, a modification factor (λE) was proposed to count for the CFRP bond length to loading span ratio, while 𝜆𝐸 = 0.659 ( 𝐿𝑑 ⁄𝐿) + 0.317 8. The application of proposed factor (λE) enhanced the accuracy of the debonding strain prediction when using ACI 440.2R- 08, Chinese and Egyptian equation. .