vamseeachanta 1. FEA Fundamentals for Slender Structures
1. FEA Fundamentals for Slender Structures
OrcaFlex models slender structures (pipes, lines, cables) as Euler-Bernoulli beam elements with:
| DOF per node | Description |
|---|---|
| u, v, w | Translational (surge, sway, heave) |
| θx, θy, θz | Rotational (roll, pitch, yaw) |
Element stiffness contributions:
- Axial stiffness:
EA(axial force vs. extension) - Bending stiffness:
EI(moment vs. curvature) - Torsional stiffness:
GJ(torque vs. twist) - Shear stiffness: optional (Timoshenko)
Key non-linearities in slender structure FEA:
- Geometric non-linearity (large displacements, catenary shape)
- Contact non-linearity (seabed, bend stiffeners, clamps)
- Material non-linearity (yield — typically not modelled for fatigue)
- Hydrodynamic drag non-linearity (Morison equation, velocity-squared)