The majority of offshore platforms have passed their design lives. The ageing related problems and how to manage these problems is a key concern for oil and gas offshore structures. For this reason, offshore structures, especially fixed jacket platforms, should be appropriate conditions for its intended use through their service life. The need to maintain offshore structural integrity has been increased in recent years and plays a significant role in continuous integrity and life extension. Early detection of damaged items can prolong the life of platforms by replacing them and results reducing maintenance expenses and increasing safety. Therefore, SI monitoring techniques, especially non-destructive techniques (NDT), are widely used for the early detection of damage in offshore structures.