Fatigue improvements of cracked rectangular hollow section steel beams strengthened with CFRP plates

Concerns over means to improve fatigue behavior of cracked rectangular hollow section (RHS) steel beams exist. This paper presents the details of strengthening schemes that was carried out using prestressed or high modulus carbon fiber reinforced polymer (CFRP) plates. A set of fatigue tests were conducted and results indicated that prestressed CFRP technique could increase fatigue crack propagation life 35.57 times longer than that of unrepaired one. The results also indicated that high modulus CFRP is effective at increasing fatigue life. Following crack propagation lives were calculated based on finite element models and close agreement with test results were observed. Thereafter, a parametric study was conducted considering the influence of various parameters such as the CFRP prestressing level, plate width and modulus on the fatigue life of the strengthened specimens. The findings of this paper can be employed to formulate design guidance for RHS beams under fatigue loading.