A simplified calculation method of steel catenary riser fatigue considering slow drifting motion

Abstract

The invention discloses a steel catenary riser fatigue simplification calculation method considering slow drifting motion. The method comprises the following steps that S1, establishing a steel catenary riser platform motion model; S2, carrying out Newmark-beta process and Newton-Raphson iteration to solve a displacement time history at a suspension point; S3, respectively applying displacement time history under wave frequency and slow drift effects at suspension points of the model; S4, calculating the stress time history under the slow drift effect and the stress time history of three standard positions under the wave frequency effect by using Orcaflex software; S5, proposing a position combination superposition method to combine stress time history curves under the action of superposition wave frequency and low frequency; S6, compiling a Matlab program based on a rain flow counting method to obtain a stress amplitude and a stress cycle index; S7, selecting S-N curve and carrying out combined damage fatigue calculation according to the Palmgren-Miner cumulative damage criterion. According to the method, the calculation efficiency is greatly improved while the calculation precision is ensured.

Description

technical field [0001] The invention relates to the field of marine engineering design, in particular to a simplified calculation method for fatigue damage of steel catenary risers considering slow drifting motion. Background technique [0002] The slow drift movement has a great influence on the fatigue damage of the steel catenary riser: ①The slow drift movement will change the position of the bottoming point of the SCR riser and affect the fatigue of the riser; ②The slow drift movement will cause the SCR riser to form a double peak stress Thus causing additional fatigue damage; ③Slow drift movement will affect the formation and development of submarine gullies, which will react on the riser and affect the fatigue damage of the riser. Therefore, it is extremely meaningful to calculate the joint response of slow drift and wave frequency motion to the riser fatigue damage. [0003] According to DNV-RP-F204, the method of calculating the fatigue damage separately according t...

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Problems solved by technology

[0005] In order to overcome the poor accuracy of the existing calculation methods, in order to obtain accurate calculation results, the position change caused by the periodic movement of the steel catenary riser is fully considered, and the present invention proposes the combined action of wave frequency and slow drift response. The simplified calculation method of riser fatigue damage, that is, the position combination superposition method, greatly improves the calculation efficiency while ensuring the calculation accuracy

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