Comparison of TLP Motion and Tendon Fatigue with versus without VIM or VIV Effects in TLP-Tendon Coupled Analysis

Abstract

This study numerically compares TLP(Tension Leg Platform) motions and fatigue lives of tendons with or without including TLP VIM(Vortex Induced Motion) or tendon VIV(Vortex Induced Vibration) in coupled analysis of TLP with tendons in waves and currents. Equation of motion was solved by HOBEM(Higher Order Boundary Element Method) and convolution for the floater part and by FEM(Finite Element Method) for tendon part. The fatigue life of tendon was calculated by Rainflow method with the tension results from coupled analysis. A cylindrical TLP with tendons was analyzed as a numerical example and the floater motions and tendon tensions were examined for various current speeds to see the trend versus current speed. Four analysis cases such as coupled analysis without TLP VIM nor tendon VIV, coupled analysis without TLP VIM and with tendon VIV, coupled analysis with TLP VIM and without tendon VIV, coupled analysis including both TLP VIM and tendon VIV were compared to discuss which case has larger effects on TLP motion or tendon fatigue.