Fatigue behavior of steel plates strengthened with CFRP sheets at different temperatures

Carbon fiber reinforced polymer (CFRP) is a popular material in the area of strengthening steel structures, because it has many advantages such as light weight，high tensile strength, high elastic modulus and ease of installation. Recently, studies have shown that steel plates strengthened with CFRP sheets have improved fatigue performance. However, almost no researches are aimed to study temperature effect on fatigue properties of CFRP reinforcement for steel structures. This paper describes an investigation on the behavior of steel plates strengthened with CFRP at different temperatures. Firstly, through cylinder coupon tests, mechanical properties of the resin were found to vary at different temperatures, especially when the temperature exceeds over the glass transition temperature Tg. Secondly, three cracked bare steel plates and five cracked steel plates strengthened with CFRP sheets were tested under cyclic loading at different temperatures. The results prove the effectiveness of CFRP reinforcement technology, which increased fatigue life by 2 to 3.4 times. It is concluded that the variation of temperature has a great influence on properties of the resin, leading to influence on fatigue life. Finally, the existing analytical method at ambient temperature was modified to predict fatigue lives by considering the temperature effect. Experimental and theoretical results are compared and reasonable agreement is achieved.