Flexural Behavior of CFRP Partially Bonded Reinforced Concrete Beams with Different Anchorage Methods
Qi Cao, Xingchao Wang, Zhimin Wu, Rongxiong Gao, Xin Jiang
Appears on pages(s):
anchorage; concrete beam; flexural performance; partially bonded CFRP; unbonded ratio
Carbon fiber-reinforced polymer (CFRP) is a widely used material for reinforced concrete (RC) beam strengthening. Because of exposure to severe environments and improper construction, the CFRP sheet may separate from the bottom of the RC beam. To analyze the influence of this type of interfacial defect on the mechanical properties of RC beams quantitatively and provide a reference for the rehabilitation of structures, this paper investigated the flexural properties of RC beams strengthened with partially bonded CFRP by experiments and analytical studies. In order to measure the degree of unbonded CFRP, a new parameter called unbonded ratio was established, which is defined as the ratio of unbonded length to the total length of strengthening CFRP in the tension zone. Twenty-six RC beams were fabricated and tested in the present study, and the experimental variables were the unbonded ratio, the thickness of the CFRP sheet, and the anchorage method (vertical U-jacket, inclined U-jacket, and mechanical plate). The cracking load, ultimate load, load-midspan deflection curve, ductility, crack pattern, and failure mods of these specimens were discussed. Also, the coupling effect of the unbonded CFRP and anchorage method on the flexural performance of strengthened beams was investigated. Test results indicated that the ultimate load decreased with the increase of the unbonded ratio before the unbonded ratio reached its critical value. It was also found that the mechanical plate anchorage and inclined U-jacket were superior to traditional vertical U-jacket in terms of load-carrying capacity and flexural stiffness and postponed the debonding of CFRP. Finally, a theoretical model for the ultimate load of RC beams strengthened with an inclined U-jacket was proposed, which showed a good agreement with the test results.