Technical performance measures for North Sea jacket structures

This report presents the Technical Performance Measures (TPM) methodology that has been developed to enable a first point assessment of North Sea steel jacket structures to be made· ● The methodology de-emphasises the quantitative structural reliability predictions that are currently employed in the North Sea safety case regime and employs a more qualitative approach to assessing the structural reliability of individual installations. The approach takes into consideration the age of the structure, structural configuration and functionality to generate a relative risk index. This index is semi-quantitative and provides an indication of the structure's performance in relation to other steel jacket fixed installations.· ● The measure of platform vulnerability is based upon the load capacity of the undamaged structure and that when the structure's most critical bracing member is severed.· ● The measure of a platform's consequence of failure is based upon a semi-quantitative approach that considers the nature of the field and the platform's functionality. Benefit is taken from a bridge-linked complex. The methodology presented in this report has used a number of arbitrary values in which to derive key components of both the likelihood and consequence measures. These values have been chosen for demonstration purposes only and may not be representative of values that would ultimately be used upon implementing this tool within a screening process. The TPM methodology is based upon environmental loading and does not consider other potential causes of structural failure. Furthermore the likelihood of structural failure makes use of the Long Term Load Distributions developed as part of work conducted in Reference 6. Consideration is not given to airgap erosion, and as such, wave in deck forces are not considered.The TPM methodology has been applied to a number of North Sea jacket structures and a simple risk assessment has been performed. This has demonstrated the ease of applying the technique to a large number of structures.. 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. ISBN 0 7176 2188 X 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. This report presents the Technical Performance Measures …