This master thesis shows a study of the waves propagation phenomena inside a layered structure such as the MarkIII cargo containment system (CCS), widely used for the transport of the liquefied natural gas overseas. As a consequence of the wave impacts that take place inside the LNG tanks, strain waves start propagating, reflecting and transmitting at the interfaces which compose the layered structure. The aim of the thesis is to better understand how the propagation of strain waves inside a material resolves the discontinuity between liquid and structure at the moment of the impact, and how the theory of strain waves propagation can be applied to a theoretical model in order to define the deformation of the structure.

When a grounding incident occurs, the officer of the watch is usually unable to assess the severity of the damage. Most ships do have damage response procedures in place. In case of military ships these are well developed, where a well-trained crew, in the form of damage parties, is available to respond adequately. For non-navy ships, this is hardly possible, mostly due to crew restrictions. But even for navy vessels, underwater damage is hard to assess because of accessibility issues of flooded compartments. This is undesirable because it needs to be known which compartments have flooded in order to assess the situation with respect to residual buoyancy and stability. Based on the outcome, the officer in charge can decide whether to evacuate or to stay on board and control the situation. For establishing which compartments will flood the extent of the raking damage must be known. It is proposed that the accelerations (or rather, decelerations) measured on board during a grounding incident can be used to make a prediction of the extent of raking damage.

A three degree of freedom external dynamics calculation model for ship grounding has been made, which is used to predict the extent of bottom raking damage and the grounding force with associated decelerations of the ship in terms of surge, sway and yaw. When the ship decelerates, caused by a grounding event, these motions can be logged through continuous ship motion measurements. From these deceleration time traces it is possible to calculate the bottom damage path through a double integration with respect to time. Moreover, with these decelerations, the location of the raking damage along the ship’s bottom can be calculated as well. A straight forward method is proposed, which is validated against data on ship grounding external dynamics from earlier research and data from large-scale grounding experiments, both carried out in the nineties of the previous century.

The structures which HMC installs offshore are fabricated onshore and subsequently moved onto a barge or ship, seafastened and then transported to the offshore location. The process of moving a structure from the onshore quayside to the barge or ship is called the load-out. This load-out can be performed by lifting, skidding or using a trailer (SPMT). This thesis research focused only on a skidded load-out onto a barge.
During the load-out the weight of the jacket or topside is gradually transferred from the quay to the barge. The barge gradually takes more of the load so ballast water needs to be continuously pumped or discharged depending on the location of the structure and the location of the ballast tank concerned. Improper ballasting during this process will cause the alignment between the quay and the barge to be disrupted which in turn causes peak loads in the topside or jacket and the barge. It is questioned if there are more suitable ballasting methods or a structural solution in order to lower these peak loads? It is also modeled what the effects are of quayside stiffness and the best method to model this stiffness.
Therefore a 2-D representation of the entire load-out is made. This model will be made using the finite element method, via a numerical model, in MATLAB. A base case load-out of a topside will be applied to this model. Using this model, optimizing the ballast configuration will be researched. Several different criteria for the optimization were tested and its different effects on the forces during the load-out were researched and quantified. The structural solution of relocating the skidbeams to an area of lower deck stiffness was also tested and the results studied. The effects of the quayside stiffness and modelling methods were also quantified using the 2-D MATLAB model.
The conclusion derived from the optimizations is that there are other ballast configurations which perform better in reducing the peak forces experienced during the load-out. The key to these optimizations is that they keep the barge-quay alignment as perfect as possible. If a critical element is present in the load-out the ballast configuration can be adjusted to lower the forces in this specific element. The results of the simulation in which the skidbeams were relocated show that this approach has no beneficial effects in reducing the forces during the load-out, mainly due to the presence of the transverse bulkheads in het barge. Furthermore for the modelling of the quayside it was proven that especially when using a low stiffness quayside, modelling the quayside without taking into account the foundation layer stiffness is inaccurate and can lead to lower forces in the model than which occur in reality.