DYNAMIC BEHAVIOUR
FLOATING PRODUCTION PLATFORM
V O L U M E I
by
JITENDRA VERMA
Department of Civil Engineering
THESIS SUBMITTED
IN FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
INDIAN INSTITUTE OF TECHNOLOGY, DELHI I N D I A
JU L Y , 1 9 0 0
OF
to the
Dedicated
to my beloved Parents and wife
LIST OF CONTENTS
Volume I Certificate
A ckn o w 1 edge ments
ABSTRACT
CHAPTER - I
Introduction
CHAPTER - II
Mooring Line Analysis
Volume II
CHAPTER - III
Hydrodynamic Characteristics
CHAPTER - IV
Dynamic Analysis of Floating Production Platform
CHAPTER - V
Page No.
1 - 2 9
30-241
242-41
4 2 9-5:
Conclusion & Recommendations For Future Work 573-5
CERTIFICATE
This is to certify that the thesis entitled DYNAMIC BEHAVIOUR OF FLOATING PRODUCTION PLATFORM being submitted by Mr. Jitendra Verma to the Indian Institute of Technology, Delhi for the award of the degree of Doctor of Philosophy is a record of the bonafide research work carried out by him. Mr. Jitendra Verma has worked under my guidance and supervision and has fulfilled the requirements for the submission of this thesis which to my knowledge has reached the requisite standard.
The thesis, or any part thereof, has not been submitted to any other University or Institute for the award of any degree or diploma.
[R.P.SINGH]
Professor Department of Civil Engineering Indian Institute of Technology, Delhi Hauz Khas, New Delhi - 110 01G
ACKNOWLEDGEMENT
This thesis was supervised by Prof. R. P.Singh to whom I express my profound sense of gratitude and sincere appreciat ion for his invaluahle guidance and encouragement throughout the course of work.
I am thankful to the competent authority of 'Indian Institute of Technology, Delhi’ for giving me the permi ssion to carry out this work as a part time . search scholar. Cooperation extended by Civil Engineer ing Department and Computer Services Center. l.I.T. Delhi is also duly acknowledged.
The author would like to express his gratitude to Prof. Subhash Chander, Civil Engineering Department, l.I.T. Delhi for his kind help and encouragements during the difficult periods of his work. I would further thank Dr. A.K. Gosain and Hr. B.P. Parida for allowing me to use the Computer facilities of the department. His sincere thanks to Dr. A.K. Jain, Dr. A. Gupta, Mr. Sunil Saxena, Hr. V. R. Sharma, Mr. Krishna Prasad for their friendship and help. He would also like to express his appreciat ion to Mr.
R.P. Shahi and Mr. R.V. Aggarwal.
Finally, I would like to express my sincere thanks to Mr. A.K. Seth for excellent typing.
JITENDRA VERMA
ABSTRACT
The aim of the present work is to analyse the floating production platforms subjected to regular waves. The study involves the understanding of the force-excursion characterist ics of chain/clump - mooring system, the hydrodynamic properties of the floating structural body and the dynamic response characteristics of the platform under ocean waves. The static behaviour of the mooring system is taken into the consideration. To start with, the work related to offshore platforms is reviewed with particular emphasis on the literature survey of the mooring cable systems and the floating platforms.
To find the analytical results of multi-component mooring line, the mathematical formulations are presented for both the small strain elastic catenary approach and the finite element method. The parameti : study related to the properties of various cable components and the sloping sea bed are carried out in case of clump - mooring line, undergoing small strains. In the finite
line, undergoing small strains. In the finite element method, an efficient solution procedure is proposed in which the compatible starting configuration is chose in a straight forward and simple manner. The effects of discretization on the results are investigated. A flexible mooring line constituted of expansive rope and steel wire rope is analyzed by both the finite - element
and catenary approach in order to understand the limitation of the elastic catenary approach in the analysis of deeper water - mooring system.
Jhe wave-source method is used in the calculation of the added mass, the potential damping and the wave-excited force for the axisymmetric body of floating platform. The effects of discretization of the generating curve and the number of series terms of wave source approach on the results are investigated in order to estimate the correct properties of the platform. A set of four platform-body of different configurations is selected to carry out the comparative study of their hydrodynamic characteristics. The accuracy of results is investigated in case of the wave-excited force calculated by using Haskind relation and the retardation functions computed from the known potential damping function of frequency. The effects of water depth is
investigated for the properties of the chosen platform.
The accuracy of the added mass at infinite frequency is investigated. Two types of mooring system are taken into the consideration in getting the dynamic response of floating production platform. The chain-system is flexible in comparison to the clump-system. In each case of mooring-system,its stiffness is also taken to be constant in finding the results. The characteristics of the platform-motion and mooring - forces are investigated in case of the chain - system and its linearized
version. The results are also compared in case of the clump - system and its linearized version. Finally, the dynamic responses, as obtained in the cases of chain and clump - systems are studied and compared with each other in order to evaluate the overall influence of the mooring system on the behaviour of floating production platform under regular waves.
