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Suppression of Wave-Excited Vibration of Offshore Platform by Use of Tuned Liquid Dampers

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China Ocean Engineering 2001年第2期16卷 165-176页

作者：董胜李华军 tomotsuka takayama College of Engineering Ocean University of Qingdao Qingdao 266003 China Disaster Prevention Research Institute Kyoto University Gokasho Uji Kyoto 611-0011 Japan

This paper describes experimental and theoretical investigations of Tuned Liquid Damper (TLD) characteristics for suppressing the wave-excited structural vibration. The structural model for the experiments is scaled according to a full size offshore platform by matching their dynamic properties. Rectangular TLDs of different sizes with partially filled liquid are examined. By observing the performance and behavior of TLDs through laboratory experiments, the Study investigates the influence of a number of parameters, including container size, container shape, frequency ratio, and incident wave characteristics. In an analytical study, a mathematical model that describes the nonlinear behavior of liquid in TLD and the interaction of TLD and structure is prerequisite. The validity of the model is evaluated and simulating results can reasonably match the corresponding experimental results.

关键词： numerical simulation offshore platform tuned liquid damper structural vibration rectangular container shallow water wave theory

ADCP application for long-term monitoring of coastal water

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Acta Oceanologica Sinica 2005年第1期24卷 95-100页

作者： YOSHIOKA Hiroshi takayama tomotsuka SERIZAWA Shigeatsu Faculty of Information Science and Technology Aichi Prefectural University Aichi 480-1198 JapanDisaster Prevention Research Institute Kyoto-University Kyoto 611-0011 JapanDisaster Prevention Research Institute Kyoto-University Kyoto 611-0011 Japan

Three kind of application of ADCP is reported for long-term monitoring in coastal sea.(1)The routine monitoring of water qualities. The water quality and ADCP echo data (600 kHz) observed in the long-term are analgzed at MT (Marine Tower) Station of Kansai International Airport in the Osaka Bay, Japan. The correlation between the turbidity and echo intensity in the surface layer is not good because air bubbles generated by breaking wave are not detected by the turbidity meter, but detected well by ADCP. When estimating the turbidity consists of plankton population from echo intensity, the effect of bubbles have to be eliminated. (2) Monitoring stirring up of bottom sediment. The special observation was carried out by using following two ADCP in the Osaka Bay, One ADCP was installed upward on the sea. The other ADCP was hanged downward at the gate type stand about 3 m above from the bottom. At the spring tide, high echo intensities indicating the stirring up of bottom sediment were observed. (3) The monitoring for the boundary condition of water mixing at an estuary. In summer season, the ADCP was set at the mouth of Tanabe Bay in Wakayama Prefecture, Japan. During the observation, water temperature near the bottom showed remarkable falls with interval of about 5-7 d. When the bottom temperature fell, the inflow current with low echo intensity water appears at the bottom layer in the ADCP record. It is concluded that when occasional weak northeast wind makes weak coastal upwelling at the mouth of the bay, the combination of upwelling with internal tidal flow causes remarkable water exchange and dispels the red tide.

关键词： ADCP echo intensity monitoring coastal water red tide stirring up

Optimal Design of TMD Under Long-Term Nonstationary Wave Loading

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China Ocean Engineering 2000年第1期15卷 25-32页

作者：李华军蒋济同曹宏生稽春艳 tomotsuka takayama Professor Disaster Prevention Res. Inst. Kyoto Univ. Gokasho Uji

Traditionally, the use of a tuned mass damper (TMD) is to improve the surviability of the primary structure under extraordinary loading environment while the design loading condition is described by either a harmonic function or a stationary random process that can be fully characterized by a power spectral density (PSD) function. Aiming at prolonging the fatigue life of an offshore platform, this study considers an optimal design of TMD for the platform under long-term nonstationary loading due to long-term random sea waves characterized by a probabilistic power spectral density (PPSD) function In principle, a PPSD could be derived based on numerous ordinary PSD functions; and each of them is treated as realization of the corresponding PPSD. This study provides a theoretical development for the optimal TMD design by minimizing the cost function to be the mean square value of the expected long term response. A numerical example is presented to illustrate the developed design procedure.

关键词： optimal design tuned mass damper power spectral density fatigue life offshore platform