DNV-RP-F114 Excel Template – Dynamic Cable Fatigue Life Calculator

DNV-RP-F114 provides industry-recognized guidance for assessing fatigue in flexible risers and dynamic subsea cables—particularly relevant for inter-array and export cables connecting offshore wind turbines to substations. The Excel template translates this guidance into an accessible, auditable computational framework: it accepts user-defined time-domain or frequency-domain environmental data, calculates hydrodynamic loads via Morison equation or diffraction-based methods, derives local bending stresses using cable cross-sectional stiffness (EI) and curvature from dynamic response, and maps stress cycles to S–N (Wöhler) curves per material layer (e.g., copper conductor, armour wires, polymer sheaths). Fatigue damage is accumulated using the Palmgren–Miner linear damage hypothesis, where total damage D = Σ(n_i / N_i), with n_i being the number of cycles at stress range Δσ_i and N_i the corresponding allowable cycles from the S–N curve. The tool supports both deterministic (e.g., extreme sea states) and stochastic (long-term wave spectra) analyses, enabling life prediction over design service periods (typically 20–25 years) and sensitivity studies on key parameters such as soil stiffness, burial depth, and tension setpoints. Validation typically requires cross-checking against time-domain simulations (e.g., in OrcaFlex or Flexcom) and adherence to DNV’s tiered assessment approach (Tier 1 screening vs. Tier 2 detailed analysis).