fe-analyst-static-analysis

name	fe-analyst-static-analysis
description	Sub-skill of fe-analyst: Static Analysis (+3).
version	1.0.0
category	engineering
type	reference
scripts_exempt	true

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 / D where 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)

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