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 Kunpeng Wang,Chunyan Ji.Helical Wire Stress Analysis of Unbonded Flexible Riser Under Irregular Response[J].Journal of Marine Science and Application,2017,(2):208-215.[doi:10.1007/s11804-017-1404-z]
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Helical Wire Stress Analysis of Unbonded Flexible Riser Under Irregular Response


Helical Wire Stress Analysis of Unbonded Flexible Riser Under Irregular Response
Kunpeng Wang Chunyan Ji
Kunpeng Wang Chunyan Ji
School of Naval Architecture and Ocean Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003, China
unbonded flexible riserinterlayer interactionhelical wire stresslocal flexurebending stiffness variationirregular response
A helical wire is a critical component of an unbonded flexible riser prone to fatigue failure. The helical wire has been the focus of much research work in recent years because of the complex multilayer construction of the flexible riser. The present study establishes an analytical model for the axisymmetric and bending analyses of an unbonded flexible riser. The interlayer contact under axisymmetric loads in this model is modeled by setting radial dummy springs between adjacent layers. The contact pressure is constant during the bending response and applied to determine the slipping friction force per unit helical wire. The model tracks the axial stress around the angular position at each time step to calculate the axial force gradient, then compares the axial force gradient with the slipping friction force to judge the helical wire slipping region, which would be applied to determine the bending stiffness for the next time step. The proposed model is verified against the experimental data in the literature. The bending moment-curvature relationship under irregular response is also qualitatively discussed. The stress at the critical point of the helical wire is investigated based on the model by considering the local flexure. The results indicate that the present model can well simulate the bending stiffness variation during irregular response, which has significant effect on the stress of helical wire.


Bahtui A, Bahai H,Alfano G, 2009. Numerical and analytical modeling of unbonded flexible risers.Journal of Offshore Mechanics and Arctic Engineering, 131(2),021401.
DOI: 10.1115/1.3058700
Benasciutti D, 2014. Some analytical expressions to measure the accuracy of the equivalent von Mises stress in vibration multiaxial fatigue. Journal of Sound and Vibration, 333(18), 4326-4340.
De Sousa JRM, Campello GC,Kwietniewski CEF, 2014. Structural response of a flexible pipe with damaged tensile armor wires under pure tension.Marine Structures, 39, 1-38.
De Sousa JRM, De Sousa FJM,De Siqueira MQ, 2012. A theoretical approach to predict the fatigue life of flexible pipes. Journal of AppliedMathemathics, 2012(6),1927-1936.
de Sousa JRM, Magluta C,Roitman N, 2009. On the response of flexible risers to loads imposed by hydraulic collars.Applied Ocean Research, 31(3), 157-170.
Dong LL, Huang Y, Zhang Q, 2013.An analytical model to predict the bending behavior of unbonded flexible pipes.Journal of Ship Research, 57(3), 171-177.
Dong LL, Tu SS, Huang Y, Dong GH, Zhang Q, 2015.A model for the biaxial dynamic bending of unbonded flexible pipes.Marine Structures, 43, 125-137.
Hobbs RE, Ghavami K, 1982. The fatigue of structural wire strands.InternationalJournal of Fatigue, 4(2), 69-72.
DOI: 10.1016/0142-1123(82)90062-7
Kraincanic I,Kebadze E, 2001. Slip initiation and progression in helical armoring layers of unbonded flexible pipes and its effect on pipe bending behavior.Journal of Strain Analysis for Engineering Design, 36(3), 365-275.
DOI: 10.1243/0309324011514458
Lanteigne J, 1985. Theoretical estimation of the response of helically armored cables to tension, torsion, and bending.Journal of Applied Mechanics, 52(2), 423-432.
DOI: 10.1115/1.3169064
Leroy JM,Estrier P, 2001. Calculation of stresses and slips in helical layers of dynamically bent flexible pipes.Oil and Gas Science and Technology, 56(6), 545-554.
DOI: 10.2516/ogst:2001044
McNamara JF, Harte AM, 1989. Three dimensional analytical simulation of flexible pipe wall structure.Journal of Offshore Mechanics and Arctic Engineering, 114(2), 69-75.
DOI: 10.1115/1.2919961
S?vik S, 2011. Theoretical and experimental studies of stresses in flexible pipes.Computers and Structures, 89(23-24),2273-2291.
S?vik S, Berge S, 1995. Fatigue testing and theoretical studies of two 4 inch flexible pipes.Engineering Structures, 17(4),276-292.
DOI: 10.1016/0141-0296(95)00026-4
Skeie G, S?dahl N, Steinkjer O, 2012. Efficient fatigue analysis of helix elements in umbilicals and flexible risers: Theory and applications.Journal of Applied Mathematics, 2012(1), 246812.
Tan ZM, Quiggin P, Sheldrake T, 2007. Time domain simulation of the 3D bending hysteresis behavior of an unbonded flexible riser, Journal of Offshore Mechanics and Arctic Engineering, 131(3), 307-314.
DOI: 10.1115/1.3058698
Tang MG, Yang C, Yan J, Yue QJ, 2015. Validity and limitation of analytical models for the bending stress of a helical wire in unbonded flexible pipes. Applied Ocean Research, 50, 58-68.
Wang W, Chen G, 2011. Analytical and numerical modeling for flexible pipes.China Ocean Engineering, 25(4), 737-746.
DOI: 10.1007/s13344-011-0059-9
Witz JA, 1996. A case study in the cross-section analysis of flexible risers.Marine Structures, 9(9), 885-904.
DOI: 10.1016/0951-8339(95)00035-6
Witz JA, Tan Z, 1992a. On the axial-torsional structural behavior of flexible pipe, umbilicals and marine cables.Marine Structures, 5(2), 205-227.
DOI: 10.1016/0951-8339(92)90029-O
Witz JA, Tan Z, 1992b. On the flexural structural behaviour of flexible pipes, umbilicals and marine cables.MarineStructures, 5(2-3), 229-249.
DOI: 10.1016/0951-8339(92)90030-S


Received date:2016-11-29;Accepted date:2017-3-7。
Foundation item:Supported by the Natural Science Foundation of Jiangsu Province under Grant No. BK20160557, and the General Program for Colleges and Universities in Jiangsu Province under Grant No. 16KJD570001
Corresponding author:Kunpeng Wang, Email: wangkunpeng@just.edu.cn
Last Update: 2017-05-09