Abstract:

The three-point bending fatigue tests of 20 reinforced concrete （ RC ） beams strengthened with carbon fiber laminates （CFLs） in 4 groups were carried out to reveal the relationships between the bending stiffness and such parameters as the damage variable, the cyclic number of fatigue loading, the loading level as well as the fatigue life. It is concluded that （ 1 ） the degradation curve of bending stiffness includes a rapid decay phase, a uniform decay phase, and a rapid decay phase after the failure; （2） there is a good linear relationship between the normalized bending stiffness and the cyclic number of fatigue loading in the uniform decay phase; （3） the normalized linear stiffness varies from 0.55 to 0.79, with a mean value of 0.67 ; （4） the normalized fracture stiffness varies from 0.53 to 0.73, with a mean value of 0.63 ; and （ 5 ） the damage variable of the strengthened beams reaches about 0.37 at the fatigue failure point.

Key words: carbon fiber laminate, reinforced concrete beam, fatigue, bending stiffness, degradation rule, damage variable