Abstract: Based on the complex environment and the particular load of the bridge structure, this paper attempts to explore the performance of damaged RC beams strengthened with BFRP sheets in alkali solution environment and fatigue loading. Damaged RC beams strengthened with two layers of BFRP sheets in alkali solution environment where the pH values are 7,9,10 and fatigue loading have been carried out. Test results show that even under the coupling of the alkali solution and the fatigue loading, the BFRP sheets can improve the ultimate bearing capacity and flexural rigidity of damaged RC beams. Under the same fatigue times, in solution environment where the pH value is 9, the deflection of the beams effected by 90 days increased by 23.13% as compared to the beams effected by 60 days. When other parameters are same, the bending strength of beams effected by alkali solution where the pH values are 7 and 10 decreased by 10.06% and 21.15% relative to beams without environment effect. So, with the increase of the concentration of alkali solution and the time of action, the ultimate bearing capacity, flexural rigidity and anti fatigue properties of RC beams decreased significantly. Finally, regarding the deflection changes as fatigue damage index, we fitted deformation modulus of strengthened beams, with the consideration of the pH value and the fatigue times.

Key words: alkali solution, damage reinforced concrete beam, the basalt fiber cloth, coupling effect of environmental fatigue, fatigue deformation modulus