Nonlinear dynamic response analyses of Onshore Wind Turbines with Steel-Concrete Hybrid Tower using a co-simulation approach

The Onshore Wind Turbine (OWT) with a Steel-Concrete Hybrid Tower (SCHT) exhibits unique dynamic characteristics due to its combination of a steel upper section and a concrete lower section, distinguishing it from traditional steel towers. This study proposes a co-simulation approach to develop an integrated, fully-coupled model of OWTs with SCHT, combining multi-body dynamics and finite-element methods for nonlinear dynamic response analysis. First, the multi-flexible body system of the OWT is divided into the blade system and the tower system, with a force-force coupling method applied to manage the interactions between these components. The equation of motion for the blade system is derived using the Euler-Lagrange equations, establishing a multi-body dynamic model. This allows for the detailed simulation of blade dynamics, capturing their flexible behavior and interactions with other turbine components. Then, a finite-element model employing beam elements is developed with OpenSEES software to describe the structural behavior of the SCHT, incorporating material nonlinearity. This model captures the distinct structural responses of the steel and concrete sections. The interactions between these two separate systems are then integrated using an iterative coupling method to formulate the co-simulation approach. This iterative method ensures accurate representation of the dynamic interactions between the two subsystems, leading to amore realistic simulation of the overall turbine behavior. Numerical investigations are conducted to verify the effectiveness of the proposed co-simulation model. Additionally, both linear and nonlinear dynamic response analyses of OWTs with SCHT under extreme wind conditions are performed.