On the importance of slamming during installation of structures with large suction anchors

Abstract The dynamic loads experienced when deploying structures with large suction anchors from an offshore construction vessel has been studied. Both model tests and CFD-analyses have been used to calibrate a numerical model of a typical Integrated Template Structure (ITS). The numerical model has then been used in time domain analyses in order to study the dynamic loads in the main lift wire when the ITS is lowered through the splash zone. An overall conclusion from this study is that from a lifting point of view neither the structural integrity of the ITS nor the crane will be jeopardized when crossing the splash zone in a typical deployment operation on the Norwegian Continental Shelf (NCS). The CFD analyses reveal the importance of entrapped air and water when the top of the suction anchor is crossing the splash zone. For the Gjoa ITS suction anchors used in the study, the openings on top of the suction anchors are quite large (perforation of 6%) which limits the amount of entrapped air during the water entry phase and also the amount of entrapped water in the water exit phase.