Enhancement of fatigue life of steel members by use of prestressed CFRP patches

Due to the requirement of retrofitting and repair for a large number of structures worldwide, research has been directed to innovative techniques of rehabilitation utilizing new materials. One of the most important reasons for upgrading structures is to increase fatigue life in order to preserve and maintain the structure beyond its design life. Carbon fibre reinforced polymers (CFRPs) have been used extensively in civil engineering applications. Many researchers have shown the effectiveness of CFRP strengthening on concrete structures. The effect of CFRP strengthening of steel structures has also shown promising results for fatigue life enhancement. Research proves that this method has more advantages than the traditional methods of strengthening for slowing or stopping crack propagation. Moreover, based on experiments performed by the authors, it has been concluded that various patch configurations have different effects on the fatigue life of steel plates. One of the techniques of strengthening utilizing CFRP patches is prestressing. This technique was introduced in the early days when CFRP materials were introduced for applications in aeronautical, mechanical and structural engineering. Unfortunately, little research has been performed in the area of strengthening steel structures with prestressed CFRP patches. This paper reports on the effect of CFRP strengthening with focus on prestressing CFRP patches. Results for prestressed-CFRP strengthened steel elements show a considerable extension in the fatigue life of these members