2ND-ORDER SUM-FREQUENCY OSCILLATIONS OF TENSION-LEG PLATFORMS - PREDICTION AND MEASUREMENT

A series of model tests has been performed in regular waves to measure second-order sum-frequency oscillations and tether forces of tension- leg platforms (TLPs). These test results are used to validate the pred ictions based on a recently developed second-order diffraction theory for general three-dimensional bodies. It is found that the vertical-pl ane motions and resulting tether forces of the TLPs include second-ord er sum-frequency resonant components which are comparable in magnitude with first-order wave-frequency responses. The correlation between pr edicted and measured results is satisfactory, overall confirming the v alidity of the theoretical predictions.