Abstract:In order to carry out the performance-based design of the deepwater steel catenary risers, the evaluation of their dynamic responses to top excitation is imperative. In this study, the energy function of the risers conveying fluid is derived from variational principle. Nonlinear equations of motion influenced by the nonlinear Morison waveform are obtained through Hamilton’s principle in combination with Lagrangian-strain definition. Investigation of the in-line dynamic responses of steel catenary risers is achieved using the finite element method and Newmark Average Acceleration Method. It is found that the bending stiffness and internal fluid velocity plays a major role in the responses, while the flow rate and drag force coefficients remarkably affects the displacement amplitudes of the marine risers’ resonant responses. Outflow velocity produce a significant effect on the bending moment and stress of the riser’s bottom end.