Review of structural modelling of deep water jack up structures

The Health and Safety Executive have commissioned KW Ltd to carry out a fundamental assessment of the dynamic characteristics of jack-up structures. The overall objective of the study is to develop an understanding of the possible failure modes of such structures and to prepare a basis for the fundamental modelling of the dynamic interaction of the structure, loading and foundations of jack-up structures on a generic basis. The work presented in this report is concerned with the determination of the non-linear response of jack-up structures to dynamic loading. The analysis includes nonlinearities in the structure, the loading and the interaction between the structure and the seabed. This report and the work it describes were funded by the Health and Safety Executive (HSE). Its contents, including any opinions and/or conclusions expressed, are those of the authors alone and do not necessarily reflect HSE policy. All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means (electronic, mechanical, photocopying, recording or otherwise) without the prior written permission of the copyright owner. The work presented in this report is concerned with the determination of the non-linear response of jack-up structures to dynamic loading. The analysis includes non­ linearities in the structure, the loading and the interaction between the structure and the seabed. The analysis is potentially extremely complex when applied to a detailed model of a practical jack-up structure. In order to enable a wide range of parameters to be studied a simplified model of a jack-up structure has been used. The analysis has been run using a finite element program in which the dynamic response of the structure and foundation to the imposed dynamic loading is calculated. This is considered to represent a series of numerical experiments in which a variety of foundation parameters can be varied. It was concluded from the results of the modelling that a jack-up structure is dynamically self-correcting from a macro-structure, or system, viewpoint. That is, as the magnitude of the loading was increased in the numerical experiments there is an interaction between the dynamics of the structure and loading, resulting in yielding of the soil. Subsequent plastic deformation of the soil appears to prevent a simple form of pushover. A wide range of soil parameters have been considered in the numerical experiments. It is concluded from the results that the use of …