Fatigue Test Behavior of Welded Connections Repaired by Grinding and Wet Welding

This paper presents the results of an experimental fatigue behavior study, conducted on round standard specimens, which were machined from T-welded connections, which are extensively employed in the repair of offshore oil & gas structures. For the analysis, two different grinding/wet welding repair conditions were performed. Hence, the tested grinding depths conditions are 6 and 10 mm, which were subsequently filled with wet welding at three immersion water depths of 50, 70, and 100 m. The round specimens were subjected to high cycle fatigue tension tests, and the S–N curves were measured for air-repair an immersion repair condition. The results reveal a decrease of cycles number in the S–N data with water depth increment, compared with air repair condition. For the wet repair condition, the lowest stresses were obtained for the connections with a grinding depth of 10 mm and filled with wet welding at 50 m of water depth, however the stresses where higher to those obtained at repair air conditions. Nonetheless, for the case of a 6 mm grinding depth repaired with wet welding at 50 m of water depth, the stresses were similar to those at air repair conditions, therefore this last grinding-wet welding combined repair condition can effectively restore the original service life of T-shaped connections, damaged and repaired by the combination of grinding and wet welding. In contrast, for water depths of 70 and 100 m, significantly lower fatigue results were observed compared for both grinding and wet welding repair conditions.