Fatigue Performance of Coped Steel Beams, Retrofitted with Carbon Fibre Reinforced Polymers

摘要

Fatigue performance of coped steel beams, repaired with two forms of carbon fibre reinforced polymers (CFRP), was studied experimentally. The two forms included: fabric form, with elastic tensile modulus of 70.9 GPa; plate form, with elastic tensile modulus of 165 GPa. The CFRP was applied on a 10 mm fatigue crack at the cope location and the beams were tested in a 3-point bending condition, with applied stress range (Δσ) of 80 MPa, stress ratio (R) of 0.2 and frequency of 4 Hz. Main parameters included effective thickness ratio (ETR), repair eccentricity (single and double sided repairs), elastic tensile modulus of CFRP (E_(CFRP)) and the CFRP orientation. Both single sided and double sided repairs were found effective in enhancing the fatigue life of coped beams with ETR to be the most effective parameter. Fatigue life enhancement of double sided repaired beams, with plate type CFRP and ETR of 0.264, was 4.8 times, compared to the 2.85 times achieved with fabric type CFRP. Single sided repairs, with fabric type CFRP and ETR of 0.264, showed a 35% fatigue life enhancement. For specimen with fabric type CFRP and ETR of 0.264, double sided repair was found to be twice as effective as the single sided repair. Repair using larger ETR of 0.52, with plate type CFRP, resulted in complete crack arrest condition for the double sided repaired specimen. The test was stopped after achieving 14 times fatigue life enhancement, without any indication of CFRP delamination.