Mehdi Behzad, Manoochehr Rad, Reza Taghipour, Seyed Meysam Mousavi Rad, Seyed Hamid Sadat Hosseini,
Volume 1, Issue 1 (9-2004)
Abstract
This paper holds a parametric study on seakeeping performance for one kind of submersible vehicles, a tourist submarine. This analyis has been performed from the aspect of motion sickness incidence by using a strip theory hydrodynamics solver. The parameters include sea state, sea direction, depth, speed and duration of operation. Results prove head seas to be more violative than following seas. Moreover, Effect of trip duration, operating depth and vessel forward speed on operability index has been investigated.
Mehdi Shafieefar, Mehdi Adjami,
Volume 5, Issue 10 (3-2010)
Abstract
Development of a simple fast-solving method based on the popular Morrison approach for prediction of semi-submersibles' motion response is the main purpose of the current research. The oblique seas' hydrodynamic specifications are modeled using small amplitude wave theory. The velocity forces and moments have been shown to be small and are therefore neglected. The damping coefficients are obtained from experimental results while added-mass is evaluated using known experimental and theoretical data. Also the interference effects of the various volume elements of the semi-submersible on the flow field are neglected. Comparison of this approximate method shows quite a good agreement with those carried out by other researcher or softwares except for pitch motion which gives a much higher prediction. Spectral analysis is discussed in detail and is applied in predicting the short-term and long-term extreme motion response. The short-term extreme response is based on 50 and 100 years return design sea states while long-term prediction is based on the anticipated life of the semi-submersible. At the end for verification of the model and for showing the method capabilities, "AKER H-4-2 P" semisubmersible is analyzed. The approximate method results are in relatively good agreement with the output results of MOSES Ultramarine software as shown.
Dr. Mohammad Saeed Seif, Dr. Hamid Mehdigholi, Dr. Homayoon E. Estekanchi, Mr. Mohammad Ali Dastan Diznab,
Volume 8, Issue 15 (10-2012)
Abstract
Evaluation of seismic behavior of offshore platforms is one of the important design steps in seismic regions. Nevertheless, because of complication and time cost of these methods, engineers usually do not study them deeply. Endurance Time (ET) method is a good solution for this problem. In this method, with acceptance of a reasonable region of errors, the time of analysis can be reduced considerably. Besides with one ET analysis, the behavior of structure can be evaluated in different seismic levels. In this paper, the ET and other usual methods in standards are introduced and then the seismic behavior of three platforms is compared with ET and response spectrum method. In this comparison, the acceleration function which is generated base on Iranian cod (2800 standard), is used and the differences are considered in relation to spectral analysis of 2800 standard. The results show appropriate conformity between two methods.
