vamseeachanta Static Analysis (+3)
Static Analysis
- Purpose: Establish equilibrium position under static loads (gravity, current, pretension)
- OrcaFlex:
CalculateStatics() - Outputs: Static position, static tensions, static bending moments
- Convergence criteria: max residual force < 1e-3 kN
Dynamic Analysis
- Purpose: Time-domain simulation under wave + current
- OrcaFlex:
RunSimulation(), stage duration, ramp time - Minimum ramp: 1× Tp to settle hydrodynamic transients
- Minimum simulation duration: 3 hours (10,800 s) for statistical convergence
- Output extraction: Every 0.1–0.2 s (Nyquist for 5×Tp minimum)
Modal Analysis
- Purpose: Natural frequencies and mode shapes (VIV susceptibility)
- Key output: Fundamental period T1 [s] vs. wave/vortex shedding period
- Strouhal criterion:
f_vs = St × U / Dwhere St ≈ 0.2 (subcritical) - Flag if
|T1 - T_wave| / T_wave < 0.10(resonance proximity)
Fatigue Analysis
- Purpose: Accumulated damage over service life
- Method: Time-domain rainflow counting OR frequency-domain spectral
- S-N curve: DNV-OS-F101 D-curve for girth welds
- SCF: DNVGL-RP-C203 hot spot or notch stress
- Target: D < 1.0 (design life ≥ 20 yr with factor of 10)