The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

Mooring system reliability in tropical cyclone and North Sea winter storm environments

Mooring system reliability in tropical cyclone and North Sea winter storm environments
Mooring system reliability in tropical cyclone and North Sea winter storm environments

The characteristics of waves, winds and currents in a tropical cyclone environment differ significantly from those in a winter storm environment, like the North Sea. This can have a significant effect on the reliability of a mooring system that is designed to satisfy 100 yr conditions with specified Factors of Safety in accordance with ISO19901-7 or API RP 2SK. This paper presents reliability analysis of the mooring system of a permanently connected Floating LNG vessel, placed at two locations: (a)a tropical cyclone environment of the North West Shelf of Australia and (b)a winter storm environment of the North Sea. It is demonstrated that as a result of differences in the long term distribution of environmental parameters (waves, winds)between a North Sea environment and a tropical cyclone environment, the long term distribution of the mooring line response differs significantly in these two locations. This paper shows that a mooring system which is designed in accordance with ISO (or API), in these two environments, will achieve very different reliability levels because of the significant differences in environmental characteristics. In order to achieve the same reliability for the mooring system at these two geographical locations, Factors of Safety for use with 100 yr environmental conditions (Ultimate Limit State)were derived to achieve the same target probability of failure of 10 −4 /annum. It was found that for the North Sea environment, a factor of 1.5 is required for both the mooring chain and the pile, while for the tropical cyclone environment the required Factor of Safety has to be increased to 2.1. These differences are very significant and design standards need to be revised to reflect these findings.

Cyclonic environment, Factors of safety, Mooring lines, Piles, Reliability, Winter storm
0141-1187
306-316
Stanisic, Dunja
cd348460-7097-49e3-9f5d-765354e4eb53
Efthymiou, Mike
acaa9a55-c6d9-41b5-a01d-0b7cb4ed40c6
White, David J.
a986033d-d26d-4419-a3f3-20dc54efce93
Kimiaei, Mehrdad
8324495a-122a-43d8-a8d0-d38182a39104
Stanisic, Dunja
cd348460-7097-49e3-9f5d-765354e4eb53
Efthymiou, Mike
acaa9a55-c6d9-41b5-a01d-0b7cb4ed40c6
White, David J.
a986033d-d26d-4419-a3f3-20dc54efce93
Kimiaei, Mehrdad
8324495a-122a-43d8-a8d0-d38182a39104

Stanisic, Dunja, Efthymiou, Mike, White, David J. and Kimiaei, Mehrdad (2019) Mooring system reliability in tropical cyclone and North Sea winter storm environments. Applied Ocean Research, 88, 306-316. (doi:10.1016/j.apor.2019.05.004).

Record type: Article

Abstract

The characteristics of waves, winds and currents in a tropical cyclone environment differ significantly from those in a winter storm environment, like the North Sea. This can have a significant effect on the reliability of a mooring system that is designed to satisfy 100 yr conditions with specified Factors of Safety in accordance with ISO19901-7 or API RP 2SK. This paper presents reliability analysis of the mooring system of a permanently connected Floating LNG vessel, placed at two locations: (a)a tropical cyclone environment of the North West Shelf of Australia and (b)a winter storm environment of the North Sea. It is demonstrated that as a result of differences in the long term distribution of environmental parameters (waves, winds)between a North Sea environment and a tropical cyclone environment, the long term distribution of the mooring line response differs significantly in these two locations. This paper shows that a mooring system which is designed in accordance with ISO (or API), in these two environments, will achieve very different reliability levels because of the significant differences in environmental characteristics. In order to achieve the same reliability for the mooring system at these two geographical locations, Factors of Safety for use with 100 yr environmental conditions (Ultimate Limit State)were derived to achieve the same target probability of failure of 10 −4 /annum. It was found that for the North Sea environment, a factor of 1.5 is required for both the mooring chain and the pile, while for the tropical cyclone environment the required Factor of Safety has to be increased to 2.1. These differences are very significant and design standards need to be revised to reflect these findings.

Text
Stanisic et al. 2019 AM - Accepted Manuscript
Download (1MB)

More information

Accepted/In Press date: 6 May 2019
e-pub ahead of print date: 15 May 2019
Published date: July 2019
Keywords: Cyclonic environment, Factors of safety, Mooring lines, Piles, Reliability, Winter storm

Identifiers

Local EPrints ID: 431930
URI: http://eprints.soton.ac.uk/id/eprint/431930
ISSN: 0141-1187
PURE UUID: c51077fd-9778-421a-b3f7-74737d922f73
ORCID for David J. White: ORCID iD orcid.org/0000-0002-2968-582X

Catalogue record

Date deposited: 21 Jun 2019 16:30
Last modified: 10 Jan 2022 06:10

Export record

Altmetrics

Contributors

Author: Dunja Stanisic
Author: Mike Efthymiou
Author: David J. White ORCID iD
Author: Mehrdad Kimiaei

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×