Comparing time domain and frequency domain transfer functions in spectral fatigue design of fixed platforms

Mehrdad Kimiaei, V. Kejriwal

    Research output: Chapter in Book/Conference paperConference paper

    Abstract

    Copyright © 2016 by the International Society of Offshore and Polar Engineers.Offshore platforms during their pre-service and in-service stages are under cumulative damages due to repeated application of time-varying stresses known as fatigue damages. Ocean wave loads usually have the highest contribution as time-varying loads on the jacket part of fixed platforms and therefore fatigue design of jacket structures to wave loading is one of the main structural design challenges. Spectral fatigue analysis is a widely accepted method for fatigue design of fixed offshore platforms mainly for the dynamic sensitive ones. Stress range transfer functions are needed in spectral fatigue analysis and can be obtained using time domain or frequency domain analysis. Time domain analyses usually lead to more accurate transfer functions but they need much more computational efforts compared to frequency domain analyses. Calculations for frequency domain transfer functions are much faster and usually lead to more conservative fatigue results. This paper compares spectral fatigue design results of an example platform using time domain and frequency domain transfer functions. Additional adjustments on the frequency domain analysis to make them less conservative and as close as possible to time domain results are also discussed in detail.
    Original languageEnglish
    Title of host publicationProceedings of the 12th ISOPE Pacific-Asia Offshore Mechanics Symposium
    EditorsJin S. Chung , Hong Zhang
    PublisherInternational Society of Offshore and Polar Engineers
    Pages340-347
    Number of pages8
    ISBN (Print)9781880653982
    Publication statusPublished - 2016
    Event12th ISOPE Pacific-Asia Offshore Mechanics Symposium: PACOMS 2016 - Gold Coast, Australia
    Duration: 4 Oct 20167 Oct 2016

    Conference

    Conference12th ISOPE Pacific-Asia Offshore Mechanics Symposium
    CountryAustralia
    CityGold Coast
    Period4/10/167/10/16

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