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Bai Y.,Zhejiang University | Kim Y.,Zhejiang University | Yan H.-B.,Zhejiang University | Song X.-F.,Hangzhou OPR Offshore Engineering Co. | Jiang H.,China Oilfield Services Ltd.
Ships and Offshore Structures | Year: 2015

A number of offshore platforms operating in the years were built with the outdated criteria. A reassessment analysis of the structures should be conducted for safety and maintenance. Reassessment of a jacket structure subjected to corrosion damages was analysed in this study. Programme SACS was used for modelling and conducting pushover analysis for the jacket structure. There are two types of corrosion damage, ‘general corrosion’ and ‘localised corrosion’, and the general corrosion was applied on the structure. Corrosion rates of the jacket structure could be divided into three parts, atmospheric zone, splash zone and full immersion zone. Through the pushover analyses using SACS, the relation between time and RSR/RSR0 was established and it was verified which zone had more corrosion influence to the jacket structure. © 2015 Taylor & Francis

Bai Y.,Zhejiang University | Xu W.,Zhejiang University | Ruan W.,Zhejiang University | Tang J.,Hangzhou OPR Offshore Engineering Co.
Ships and Offshore Structures | Year: 2014

This paper discusses the on-bottom stability of subsea lightweight pipeline (LWP) on sand soil seabed subjected to a combined load of wave and current. Hydrodynamic loads were applied on an LWP to test the on-bottom stability of the pipe. The tests of LWP were carried out with different pipe outer diameter (OD) and different pipe submerged weight. The lateral movement of pipe experiences three characteristic periods based on the lateral displacement of pipe: (1) slightly shaking with sand scour; (2) crossover sand breakouts; (3) laterally moving within a displacement of 2.0 × OD or the pipe will continue to lateral movement after the lateral displacement of 2.0 × OD. A lateral displacement of 2.0 × OD is selected as the displacement criteria for the on-bottom stability of LWP because the pipe will be continuously laterally moving in case the lateral displacement of pipe is larger than 2.0 × OD for LWP, which is different from the on-bottom stability of a rigid steel pipe. Based on the test results, an empirical correlation was established to describe pipeline's lateral on-bottom stability. Three-dimensional ABAQUS dynamic finite element simulations of an LWP on flat seabed are carried out. In accordance with the experimental observations, a modified correlation suggested in DNV-RP-F109 code is used for simulating the lateral resistance of LWP on sand soil surface. The effects of lift force on the pipe when the pipe contacts the seabed were considered. A MathCAD worksheet based on the generalised lateral stability method in DNV-RP-F109 was used to assess the pipeline on-bottom stability. The comparison results of MathCAD and finite element analysis (FEA) showed that the FEA simulation gives a good agreement with test results when the lateral pipe displacement is less than 2.0 × OD. The modified FEA model can be used for the on-bottom stability analysis of LWP to reduce conservatism. © 2014 Taylor & Francis

Bai Y.,Zhejiang University | Bai Y.,Hangzhou OPR Offshore Engineering Co. | Ruan W.,Zhejiang University | Yuan S.,Zhejiang University | And 2 more authors.
Ships and Offshore Structures | Year: 2014

Taking the vessel's RAO (response amplitude operator), wave and lowering velocity into consideration, a 3D mechanical analysis of a manifold installation by a drill pipe in deep water is presented in this paper. On the basis of the small-deformation bending theory, the theoretical formulas of displacements, axial tension, bending moment and inclination along the drill pipe are derived by finite-element discretisation. The key results obtained from the proposed method are compared with the ones achieved from the finite-element model using OrcaFlex and the results are in good consistency. A series of sensitivity analyses are also presented to highlight the most influencing parameters in the installation. The proposed method is useful for the feasibility study of the manifold installation. © 2013 © 2013 Taylor & Francis.


Hangzhou Opr Offshore Engineering; Co. | Date: 2013-05-29

Water pipes not of metal; drain pipes not of metal; penstock pipes, not of metal; water-pipe valves, not of metal or plastic; branching pipes, not of metal; caissons for construction work under water; buildings, not of metal; drain traps valves, not of metal or plastic; coatings building materials.

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