Jackup Structures Nonlinear Forces and Dynamic Response

Simple analytical methods are shown for stochastic nonlinear dynamic analysis of offshore jacket and jackup structures. Base shear forces are first modelled, and then imposed on a linear 1DOF structural model to predict responses such as deck sway. The force model retains the effects of nonlinear wave kinematics and Morison drag on base shear moments, extremes, and spectral densities. Analytical models are also given for response moments and extremes Good agreement with simulation is found for a sample North Sea jackup. The effects of variations in environmental and structural properties are also studied.