Effects of load-related parameters on the dynamic response of concrete-filled double-skin steel tube K-joints under lateral impact loading

Abstract

Concrete-filled double-skin steel tube (CFDST) structure is gradually applied in jacket foundation of offshore wind turbine (OWT). This study uses experimental and numerical methods to investigate the effect of impact force and axial force on the dynamic response of CFDST-K joints subjected to impact loading. A pendulum test machine is conducted to analyze the deformation property and dynamic response of six K-joints. The results indicate that the impact velocity increases as the impact energy rises, resulting in a significant increase in impact force, displacement, and plastic strain. Improving the axial compression ratio enlarges the second-order effect and the initial stiffness, resulting in a substantial rise in the deformation under a high axial compression ratio. CFDST-K-joints exhibit superior flexural strength, impact resistance, and energy dissipation ability than hollow K-joints in terms of the constraint effect provided by the inner tube to the core concrete. Subsequently, ABAQUS is used for nonlinear analysis and to validate against the test results and explore the energy distribution. Finally, the parametric analysis demonstrates that the optimal hollow rate of CFDST-K joints is between 0.6 and 0.7 and the flexural stiffness is a critical parameter affecting the impact performance.