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Effects of extensible modelling on composite riser mechanical responses

Effects of extensible modelling on composite riser mechanical responses
Effects of extensible modelling on composite riser mechanical responses
The change from steel risers to composites comes with uncertainties that led to large safety factors. One area of uncertainty is the predicted response and stresses derived from commercial packages that are based on formulations that assume in-extensible riser. However, composite pipes exhibit a lower axial stiffness and therefore the velocity of the axial waves will change with a corresponding change in dynamic response. To determine the effect of this assumption, this paper assesses the effect of extensibility on the time-domain response. It is found that the in-extensible model predicts 3 times the number of high frequency tension cycles in the 20kN tension range. To determine the impact of this change on the stress, the accuracy of available composite pipe models is benchmarked using shell, continuumshell and solid elements. The quadratic and continuum-shell elements provide a maximum percentage difference of 4% compared to solid elements but the continuum-shell is selected as it has a lower computational cost. The response from the extensible and in-extensible models are input into the pipe model, they provide similar Tsai-Wu failure factors, alleviating concerns when modelling the strength. However, the change in dynamics remains a concern for other applications such as machine-learning or digital-twins.
0029-8018
Ragheb, Hossam Ali
0cb06fbc-791d-4535-ba2c-1e3f53ba958b
Sobey, Adam
e850606f-aa79-4c99-8682-2cfffda3cd28
Ragheb, Hossam Ali
0cb06fbc-791d-4535-ba2c-1e3f53ba958b
Sobey, Adam
e850606f-aa79-4c99-8682-2cfffda3cd28

Ragheb, Hossam Ali and Sobey, Adam (2021) Effects of extensible modelling on composite riser mechanical responses. Ocean Engineering, 220, [108426]. (doi:10.1016/j.oceaneng.2020.108426).

Record type: Article

Abstract

The change from steel risers to composites comes with uncertainties that led to large safety factors. One area of uncertainty is the predicted response and stresses derived from commercial packages that are based on formulations that assume in-extensible riser. However, composite pipes exhibit a lower axial stiffness and therefore the velocity of the axial waves will change with a corresponding change in dynamic response. To determine the effect of this assumption, this paper assesses the effect of extensibility on the time-domain response. It is found that the in-extensible model predicts 3 times the number of high frequency tension cycles in the 20kN tension range. To determine the impact of this change on the stress, the accuracy of available composite pipe models is benchmarked using shell, continuumshell and solid elements. The quadratic and continuum-shell elements provide a maximum percentage difference of 4% compared to solid elements but the continuum-shell is selected as it has a lower computational cost. The response from the extensible and in-extensible models are input into the pipe model, they provide similar Tsai-Wu failure factors, alleviating concerns when modelling the strength. However, the change in dynamics remains a concern for other applications such as machine-learning or digital-twins.

Text
Effects of extensible modelling on composite riser mechanical responses pre-print - Accepted Manuscript
Restricted to Repository staff only until 22 December 2021.
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More information

Accepted/In Press date: 26 November 2020
e-pub ahead of print date: 22 December 2020
Published date: 15 January 2021

Identifiers

Local EPrints ID: 445992
URI: http://eprints.soton.ac.uk/id/eprint/445992
ISSN: 0029-8018
PURE UUID: ff15e3e6-cc51-4a2c-9e6a-2ce8214304ee
ORCID for Adam Sobey: ORCID iD orcid.org/0000-0001-6880-8338

Catalogue record

Date deposited: 18 Jan 2021 17:31
Last modified: 18 Feb 2021 17:09

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