# Bending Moment in ANSYS AQWA

Discussion in 'Hydrodynamics and Aerodynamics' started by Mohsen, Jan 10, 2020.

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### MohsenNew Member

anyone has any idea to calculate Bending moment or Curvature of Mooring Cable in ANSYS AQWA?
There is Just Cable Force ( Tension)

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### MohsenNew Member

Any Ideas? Up...

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### TANSLSenior Member

Sorry if you think I simplify the subject too much. I suppose it will be calculated in the same way as in any other beam, considering the catenary as a beam subjected to pure bending: bending moment at one point of a beam will be equal to the sum of the products of the forces located to the right of that point multiplied by the distance of each force to the point under study.
Without more data, a more concrete answer cannot be given.

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### MohsenNew Member

I want to model Electrical Cable connected the floating body. then I want to calculate fatigue damage of the cable. for calculating the FD from Result ( Solution Section ) there is just two output: A, Cable Force and B, Whole Section Force. Until here is fine, I can calculate Axial Damage by using Tension Force of the Cable. but for calculating fatigue damage I need more than Axial Damage. I need Bending Moment also
Bending moment or Curvature needed for completing the task.
about the modeling: Cable is modeled in Free Hanging configuration.

Last edited: Jan 11, 2020
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That is the usual procedure, establishing the tension in the mooring system. In general you only need to consider tension, no bending.

It has been shown by many authors that bending and torsional effects can be neglected and that bending and torsional elasticity is of negligible importance to the mooring line tension responses, regardless of load case.
For further reading on this subject:-

Hall, M.; Goupee, A. Validation of a lumped-mass mooring line model with DeepCwind semisubmersible
model test data. Ocean Eng. 2015, 104, 590–603.

Hall, M.; Buckham, B.; Crawford, C. Evaluating the importance of mooring line model fidelity in floating
offshore wind turbine simulations. Wind Energy 2014, 17, 1835–1853.

Why are you saying you need more than axial damage for FD?

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### PanJunior Member

Dear Mohsen,

I am also simulating electrical cables and have the exact same problem. I don't know why these people say bending is not important. It is critical in deciding the fatigue of a dynamic submarine power cable. And we need the bending results except for tension, but I can't find bending in AQWA either. Anybody has any idea?

Besides, how can we extract the displacement of the cable? I know we can extract the displacement of the floating structure easily, but I can't find the option for the cable.

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Dear Pan,