Impact dynamic response analysis of assembled K-joints for jacket offshore wind turbine

Tubular K-joints are critical load-transferring components in jacket offshore wind turbines (OWTs), and their impact resistance is closely related to structural safety and post-impact serviceability. However, the impact behavior of assembled K-joints has not yet been systematically clarified. In this study, a flange-connected assembled K-joint is proposed and experimentally and numerically investigated under lateral impact, with conventional welded K-joints used for comparison. Pendulum impact tests were carried out on two welded joints and two assembled joints under continuous and single-impact conditions, and validated nonlinear finite element models were established in ABAQUS to reproduce the impact response and reveal the underlying damage and energy dissipation mechanisms. The results show that the assembled K-joint exhibits markedly improved impact resistance and deformation control. Compared with the welded joint, it achieves a 1.9-fold increase in peak impact force and an approximately 30% reduction in maximum mid-span displacement. In addition, the local chord indentation depth and residual deformation of the welded joint are 29.4% and 26.8% greater, respectively. The assembled joint attains an energy dissipation rate of 95%, significantly higher than the 68% of the welded joint, owing to the synergistic effects of flange buffering, interfacial friction, and bolt deformation. The proposed connection provides a promising solution for impact-resistant tubular joints in OWT jacket structures.