Fatigue repair of underwater navigation steel structures using Carbon Fiber Reinforced Polymer (CFRP)

The nation's Steel Hydraulic Structures (SHS) have significant deterioration caused by the effects of complex phenomena including corrosion and fatigue cracking caused by mixed mode loading. Current methods of repair of SHS, adopted primarily from the bridge engineering industry, have proven ineffective because they were developed for Mode 1 loading (tension) only. Various studies have been carried out to assess the use of CFRP for the rehabilitation of the aging and deteriorated infrastructure systems in the United States, however no research has been conducted on submerged steel structures. This paper presents the evaluation and implementation of an innovative retrofit method of CFRP to repair and strengthen the strut arms of a tainter valve. The evaluation of the retrofit method required a Fitness-for-Service fatigue assessment followed by a Finite Element Analysis (FEA) of the tainter valve with and without the retrofit method. Finally, the article presents the installation procedures used to install the CFRP retrofit and describes the advantages of the innovative repair techniques resulting in two to four folds increase of fatigue life.