Modal state vectors of a free-hanging drilling riser during deployment and retrieval

Abstract To prevent marine risers' resonance and eliminate potential threats, sufficient inherent dynamic characteristics such as natural frequency, modal displacement, slope, bending moment, shear are necessary to be calculated analyzed. However, most studies calculate the frequencies displacements directly rather than slopes forces. The additional calculations of forces likely result in issue complications, time-consuming, or even errors especially when boundaries at both ends solved by a finite difference method. solve above problems, state-vector approach is developed herein based on precise integration Two traditional methods, i.e., differential transformation method element method, utilized verify validation approach. state vectors drilling riser, not only but also slopes, moments, shears, studied detail under four classic cases according hard soft hang-off modes deployment retrieval processes. Besides, versus riser suspension lengths investigated during retrieval. critical discussed via double-peaked sea irregular wave spectrum. Based analyses presented this study their generic findings, powerful tools can designed associated threats operation.