Study On Mitigating Ice-induced Vibration Of Offshore Platforms Using TLD

It is indicated that the ice-induced vibration of ice-resistant platforms is quite intensive,and directly endangers the structural safety according to the field data monitored on severalplatforms in the Liaodong Bay of Bohai Sea in past years. Bohai bay is a margin oil field. Thetraditional method is improving the intensity and stiffness of structure, which will increase theproduction cost of jacket platforms. In order to reduce vibration of platforms and productioncost, the tuned liquid damper (TLD) is studied in this thesis. TLD is a passive control device.It is a rigid tank that using the hydrodynamic pressure of the tank to reduce the vibratoryresponse. TLD has the characteristic of low fabrication costs, convenient installation, simplemaintenance, it also can be used in storage tank, and has an extensive application prospect onthe platforms in a margin oil field.Therefore, the thesis develops following investigation:The feasibility of the TLD on platform ice-induced vibration suppression isdemonstrated. The researches of basic principle of suppressing structural vibration and thedynamic character of ice-induced vibration of the jacket platforms are presented, and then it isfound that it's possible to mitigate ice-induced vibration of platforms in Bohai bay by usingthe rectangular deep TLD.The effectiveness of TLD in suppressing ice-induced vibration of platform is calculated.The current researches of the theoretical computation is presented and evaluated. The deepwater theory is selected to validate the effectiveness of TLD to mitigate ice-induced vibration.It is showed that responses of the platform under ice excitation can be substantially reduced ifthe parameters of TLD are selected appropriately. The results can provide theoretical basis tothe application of TLD.A half-experiment with half-simulation test system and the test model of TLD aredesigned and set up. The actual structure and excitation can be simulated in the simulationsystem, the results which is the response of the structure is represented by the moving table.The model of TLD is tested on the moving table as the actual part. The feasibility of this testsystem is proved by analyzing the working principle of TMD; the validity of the test modeldesign is verified by compare of the frequency of the swept test and the theoretical one.This text studies the reaction force of the TLD based on the principle of TLD in vibrationcontrol for structure and validated the effectiveness of TLD. Harmonic and simple ice load tunction excitations are used to test the tbrce of TLD, The results show that the experimentalforces results agree well with the theoretical one, and the significant effect to reduce vibrationthrough TLD can be observed in the resonance area of TLD system.However, the test results of TLD system under the random ice load function exciting arenot satisfying due to the small size of the tank. A big size model will be design and testedunder the actual ice load excitation in the future study.