Research Of Mechanical Property Of CFRP-Concrete Interface Under Elevated Temperatures

CFRP -retrofitting technology has been widely employed in the retrofitting project. CFRP is sticked to the tensile face of the concrete beam with adhesive to increase the bearing capacity of the beam, as CFRP has very high elasitic modulus. The adhesive layer plays the role of transferring shear force to make CFRP work.However, the fire-enduring-capacity of CFRP-reinforced beam is not ideal. When exposed to fire, CFRP is easy to get oxigated in high temperature, which will induce the reduction of its strength. On the other hand, adhesive will intenerate in high temperature. To protect the CFRP-reinforced beam, some fire protections are employed to the beam to isolate the CFRP from the oxygen, but the temperature of the adhesive layer will still increase. To research the mechanical properties of CFRP-concrete interface under elevated temperatures, the following researches have been done in this paper.(1) The double-slap shear test under elevated temperature is designed, the test was excuted under 4℃,40℃,60℃,80℃,100℃,120℃,140℃,160℃,180℃, the failure type, influence of the temperature on the glue and CFRP are studied, and analyze the falure mechanism of the interface.(2) Research of the changing regulation of the interface strength with temperature has been done. The analysis of the test data shows, the interface bond strength under 40℃is higher than which under 4℃, but after 40℃, the interface strength will decrease with the increase of temperature and become stable after 100℃.(3) Differential equation has been established, by solving the equation with the assumption of the linearτ-δmodel the analytic answer of the stress distribution along the interface and CFRP is found, using which the theoretical P-Δcurve is deduced.(4)τ-δmodle under different temperatures are found, the relation of interface bond strength and stiffness with temperature are studied, as well as the effective bond length. The computing model of the CFRP-concrete interface carrying capacity under elevated temperatures has been established.