Despite global analysis of umbilicals is a well-known area in the offshore systems design, some topics are still opened for discussions. One of these topics refers to the structural damping. Obviously, the viscous damping caused by hydrodynamic drag forces is the major source of damping to the whole system. However, in some severe load cases, the host vessel dynamics may induce high snatch loads to the umbilical top end and these loads are more related to structural damping, specifically in tension–elongation hysteresis, than to viscous damping. The snatch loads must be taken into account in the whole design process, which leads to an umbilical designed to resist to higher tension loads and implies also, in most cases, in over-dimensioned accessories, such as the bending limiters. Actually, due to the high level of friction between layers, the umbilical presents some level of structural damping which is, in fact, related to hysteretic moment-curvature and tension-elongation relations. This intrinsic structural damping may in fact contribute to the reduction of the snatch loads and considering it may reduce the level of conservatism in the design. However, due to the complexity and diversity of umbilical designs, it is not straightforward to come up with general-use hysteretic curves. A simplification then is to apply classic Rayleigh damping. Typically, damping levels of 5% are accepted in the offshore industry when using stiffness-proportional Rayleigh damping (the 5% damping is a percentage of the critical damping and is accounted for at the regular wave period or irregular wave spectral peak period). The problem here is that stiffness-proportional Rayleigh damping increases linearly with the frequency and the damping level at 1Hz, for example, may get to 60%. This fact indicates that the high-frequency part of the response may be simply discarded from the results, which in turn may lead to an incorrect, over-damped analysis. The present work aims tackling the Rayleigh damping issue, evaluating its effects on tension levels and spectral density of the tension time history. A recommendation of how to apply Rayleigh damping is proposed.
Skip Nav Destination
ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering
June 19–24, 2011
Rotterdam, The Netherlands
Conference Sponsors:
- Ocean, Offshore and Arctic Engineering Division
ISBN:
978-0-7918-4436-6
PROCEEDINGS PAPER
Rayleigh Damping Effects on Global Analysis of Umbilicals
Lauro Massao Yamada da Silveira,
Lauro Massao Yamada da Silveira
Prysmian Cables and Systems, ES, Brazil
Search for other works by this author on:
Rafael Loureiro Tanaka,
Rafael Loureiro Tanaka
Prysmian Cables and Systems, ES, Brazil
Search for other works by this author on:
Joa˜o Paulo Zi´lio Novaes
Joa˜o Paulo Zi´lio Novaes
Prysmian Cables and Systems, ES, Brazil
Search for other works by this author on:
Lauro Massao Yamada da Silveira
Prysmian Cables and Systems, ES, Brazil
Rafael Loureiro Tanaka
Prysmian Cables and Systems, ES, Brazil
Joa˜o Paulo Zi´lio Novaes
Prysmian Cables and Systems, ES, Brazil
Paper No:
OMAE2011-49584, pp. 549-559; 11 pages
Published Online:
October 31, 2011
Citation
da Silveira, LMY, Tanaka, RL, & Novaes, JPZ. "Rayleigh Damping Effects on Global Analysis of Umbilicals." Proceedings of the ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering. Volume 4: Pipeline and Riser Technology. Rotterdam, The Netherlands. June 19–24, 2011. pp. 549-559. ASME. https://doi.org/10.1115/OMAE2011-49584
Download citation file:
16
Views
Related Proceedings Papers
Related Articles
Modeling and Analysis of a Novel Offshore Binary Species Free-Floating Longline Macroalgal Farming System
J. Offshore Mech. Arct. Eng (April,2023)
A Semi-Analytical Study of Stick-Slip Oscillations in Drilling Systems
J. Comput. Nonlinear Dynam (April,2011)
Perturbations Methods in Structural Dynamics and Applications to Cyclic Symmetric Domains
J. Eng. Gas Turbines Power (July,2005)
Related Chapters
Basic Concepts
Design & Analysis of ASME Boiler and Pressure Vessel Components in the Creep Range
Tests to Evaluate the Mechanical Properties of the Ureter
Biomaterials' Mechanical Properties
Clamping, Interference, Microslip, and Self-Piercing Rivets
Structural Shear Joints: Analyses, Properties and Design for Repeat Loading