Exponential strain energy density-based dynamic failure criterion for jacket offshore wind turbines under extreme seismic loading

Abstract

Jacket offshore wind turbines (OWTs) are increasingly deployed in seismically active regions. However, existing failure criteria for OWTs under seismic loading rely on empirical displacement or stress thresholds that lack theoretical justification. To address this, the present study proposes a novel dynamic failure criterion based on exponential strain energy density (ESED) theory to capture the system-level collapse limit state. A three-dimensional elastoplastic finite-element model of a 10 MW jacket OWT is established in ABAQUS using bilinear kinematic hardening and validated through modal analysis. A failure coefficient is derived from the rate of change of the summed ESED with respect to peak ground acceleration (PGA). Nonlinear time-history analyses are conducted under eight recorded ground motions representing site classes I–IV, combined with rated wind and wave loads. The results demonstrate that the proposed ESED-based criterion accurately determines the failure PGA and distinguishes elastic, elastoplastic, and collapse states. The jacket OWT exhibits a three-stage failure mode consisting of plastic-hinge initiation, plastic-hinge propagation, and buckling-induced collapse. Plastic hinges are localized at tower wall-thickness transitions. The failure PGA ranges from 13.75 to 118.49 m/s 2 , with the lowest value observed for site class IV. The proposed criterion provides a theoretically rigorous alternative to conventional empirical thresholds for collapse assessment of fixed-bottom OWTs under extreme seismic loading.