Experimental investigation on vibrations of a drilling riser in a jack-up platform under environmental and operating loads

摘要

In this study, a series of experiments were conducted in a wave/currentflume to investigate the dynamic responses of a drilling riser for a jackupplatform under the environmental loads and operating loads, whichinclude wave, current, top tension and combined conditions. The straindue to the vibration of the drilling riser in both in-line and cross-flowdirections were measured with FBG strain sensors at four locationsalong the water depth. With the Fast Fourier Analysis to the strain data,the amplitude-frequency characteristics of the strain are obtained andthe variation of the strain amplitude at the near-water surface of thecylinder with the wave factors, top tension and water depth is analyzed.Furthermore, the trajectory of the feature locations in the horizontalplane is obtained through modal analysis. It was found that thesuperimposition of the current on waves enhances the vibration of theriser compared with the pure wave condition; the trajectories of thecharacteristic locations are offset along IL direction under thecombined action of wave and current.