Wind turbine towers are growing taller to obtain larger thrust load and capture more wind energy at higher elevations. To address the excessive vibration problem of conventional steel tube (ST) towers, a concrete-filled double-skin tubular (CFDST) tower can be a great alternative owing to the advantages of excellent mechanical properties and cost efficiency, especially for tall and slender wind turbines. This paper developed a theoretical model of the CFDST-based wind turbine system by combining the Lagrangian method with the Galerkin method. Subsequently, the analytical solutions of both fundamental frequency and cross-wind displacement response were obtained. The wind tunnel tests of scaled CFDST and ST wind turbine systems, with variations in hollow ratio, tube length, and wind speed, were used to verify the proposed model. The predicted results from the analytical model showed reasonable agreement with the test results. Finally, the validated analytical solutions were employed to further analyze the influence of hollow ratio, length-to-diameter ratio, and tip-mass ratio. This study makes a contribution to the integration analysis of the CFDST-based wind turbine system in theory and experiment, and develops a simplified method to predict its dynamic behavior.

This study presents underwater explosion tests with three different TNT charge weights to investigate the dynamic responses of a fixed steel sheet. A finite element model was established and benchmarked by comparing the bubble development and deformation distribution from the tests. The steel sheet shows a deformation process of hogging, sagging, and hogging again, due to the actions of shock waves, bubble expansion, bubble collapse, and bubble pulsation. The air may be sucked into the bubble during the hogging process, making the bubble collapse earlier and resulting in a relatively lower sagging deformation for large charge weights of TNT. The deformation caused by bubble pulsation is larger than that by the shock waves, owing to the large time duration of bubble pulsation. A parametric analysis was conducted to study the influence of steel grade, plate thickness, detonation distance, and the shape and position of charges on the dynamic behavior of steel plates subjected to underwater explosions. It shows that the damage to the steel plate gradually decreases, with the increase in steel strength, plate thickness, and detonation distance. The influence of the shape and position of charges is limited. The largest deformation is observed when the detonation distance increases to bubble radius.