This project is focused on numerical modelling of dynamic problems with basis in a freespanning offshore pipeline located at the Danish area of the North Sea. Hydrodynamic force models are evaluated considering time variation of force coefficients and wake effects. A force model due to vortex lock-in is also considered. Hydrodynamic damping is implemented by a force feedback model. Analytical and numerical models of soil springs have been compared. Transmitting boundary elements for the pipeline and soil springs have been developed and implemented in a numerical Winkler model. Liquefaction problems of the soil have also been evaluated. Free-span analyses are made in a non-linear Winkler model with main focus on fatigue damage due to dynamic excitation from waves and current. Parametric study is performed to detect the governing parameters for the damage of a pipeline free-span. Finally, the project contains multi-span analyses that treat the interaction of two neighbouring free-spans.