Nonlinear Dynamic Analysis of Marine Risers under Random Loads for Deepwater Fields in Indian Offshore

The paper presents a numerical Analysis of deep water Steel Catenary Riser (SCR) under random sea loads. A finite element method is implemented in the time domain using Newmark's-Beta method. The response analysis is based on a simulation technique which duly considers the various non-linear effects such as relative velocity squared drag force, variable added mass due to variable submergence and nonlinearity due to large excursions. It also accounts for variable tension in riser due to variable submergence, variable buoyancy and wave forces. Results are presented which illustrates the effects of nonlinearities, long term drift oscillations and current velocity on the bending stress in the marine risers. The bending stress response time histories are obtained and presented in terms of bending stress envelopes and spectra showing contribution of various harmonics which is significant because of a non-linear system.