Field Measurement Results on Dynamic Responses of One-column Type TLP

Abstract

The hull structure of conventional tension leg platforms (TLPs), operating in the Gulf of Mexico and the North Sea, consists of pontoons and four or six columns supporting a wide deck structure on which topside facilities needed for offshore petroleum exploration are installed.In this paper, authors propose a simple TLP having one column structure which can be used, for example, as a minimum size satellite platform for a marginal oil field. Its hydrodynamic behaviors are discussed on the basis of results of theoretical analysis and measured data obtained through one year at-sea measurement of a prototype TLP (water depth: abt 61.0m) performed by JOIA (Japan Ocean Industries Association) according to the committment from the Ministry of International Trade and Industry.The main results of the sea test are as follows; 1) tension fluctuation of each tendon of one-column type TLP are almost same except short wave period range, 2) the relation between the maximum wave height and significant wave height approximately follows the Rayleigh distribution, 3) measured motion responses and tendon tension fluctuations coincide well with theoretical calculation, 4) the assumed design wave height approximately agrees with the maximum wave height estimated from the measured wave data, 5) the minimum tension of each tendon can be kept positive for given return period.