Slamming is a phenomenon that occurs on floating structures. Drillship as floating structures have slamming when moving at a certain speed which resulted in the movement of relative vertical bow that exceeded full of water of the bow. This paper was performed on the drillship 35000 tons with variants of speed is 7 knots, 12 knots, 13 knots and 14 knots. The first stage taken was the design of the drillship structures by using Maxsurf in order to get lines plan. After the offset data of drillship has been obtained, modeling followed by Hydrostar to get the heave and pitch motion RAO’s from head seas. The result of RAO is used to analyze the relative vertical motion of the bow in the form of RAO as well. That result is used to analysis of structural response by multiplying the wave spectra ITTC/ISSC. From these calculations will be known slamming parameters that can generate the probabilities, intensity and pressure of slamming on the drillship 35000 tons. Probabilities, intensities and pressure of slamming, the maximum occures while the drillship moving on 14 knot of speed, ie. each of 0.483 times, 124.451 times/hour and 492,232 kPa at 15 m of significant wave height.
Master Degree Student, Marine Technology Post-Graduate Program, Institut Teknologi Sepuluh Nopember (ITS), Surabaya, Indonesia
Dept. of Ocean Engineering, Institut Teknologi Sepuluh Nopember (ITS), Indonesia
This paper reviewed the capability of the proposed diffraction potential theory with Morison Drag term to predict the Round Shape FPSO heave motion response. From both the self-developed programming code and ANSYS AQWA software, it can be observed that the diffraction potential theory is over predicting the Round Shape FPSO heave motion response when the motion is dominated by damping. In this study, Morison equation drag correction method is applied to adjust the motion response predicted by diffraction potential theory. This paper briefly present the procedure to integrate the Morison equation drag term correction method with the diffraction potential theory and then, the proposed numerical method was applied to simulate the Round Shape FPSO heave motion response. From the comparison, it can be concluded that Morison equation drag correction method is able to estimate the FPSO heave response in the damping dominated region and provides more reasonable motion tendency compare to the diffraction potential theory without consider the drag effect in the calculation.
Department of Aeronautics, Automotive and Ocean Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Malaysia
Ocean and Aerospace Research Institute, Indonesia
Department of Transportation and Environmental Systems, Hiroshima University, Japan
National Research Institute of Fisheries Engineering (NRIFE), Japan
Centre for Marine Technology and Engineering (CENTEC), Instituto Superior Técnico, Universidade de Lisboa, Portugal
This paper presents reassessment of existing offshore platform in the Ardjuna Field, Northwest of Java, Indonesia. The existing platform of B1C was installed in 1975 and owned by PHE ONWJ. The B1C platform is numerically evaluated for service life extension purposes until the next twenty years. The reassessment analyses focus on in-place analysis, seismic analysis and fatigue analysis. These analyses refer to recommended practice issued by American Petroleum Institute standard. The results indicated that the entire value of unity check for all members fulfill the requirements of API RP 2A - WSD. Analysis of fatigue computation showed that three joints have the fatigue life less than 59 years.
Undergraduate Student, Jurusan Teknik Kelautan, Institut Teknologi Sepuluh Nopember (ITS), Surabaya, Indonesia.
Department of Ocean Engineering, Institut Teknologi Sepuluh Nopember (ITS), Surabaya, Indonesia.
