Comparative study of seismic response of offshore tetrapod jacket systems with semi-rigid and flexible piles under environmental loads

Tetrapod piled jacket (TPJ) foundations, featuring large-diameter semi-rigid piles have been employed to support offshore wind turbines (OWTs), but limited research exists on their dynamic response under seismic excitations in marine environments. Thus, this study employs advanced 3D finite element simulations to analyze and compare the seismic responses of flexible and semi-rigid piled TPJ systems under combined dynamic loads. Under seismic loads, the semi-rigid piled system experience higher compressive stress on the tower but lower maximum stress at X-brace and battered leg joints compared to flexible piled systems. Additionally, soil shear strain in the semi-rigid pile system displays a punch-through failure pattern at the pile end. The impacts of increasing scour depth and clay shear strength on semi-rigid-piled systems are distinctly characterized by greater pile top settlement, augmented bending moment responses, and diminished rotational deformation, compared to those of flexible ones. These findings offer valuable insights into semi-rigid-piled TPJ system dynamic response in complex marine environments.