RESEARCH ARTICLE An investigation on the impacts of passive and semiactive structural control on a fixed bottom and a floating offshore wind turbine Semyung Park 1 | Matthew A. Lackner 1 | Pariya Pourazarm 1 | Arturo Rodríguez Tsouroukdissian 2 | John Cross‐Whiter 3 1 Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, Massachusetts, USA 2 GE Renewable Energy, Richmond, Virginia, USA 3 Glosten INC., Seattle, Washington, USA Correspondence Matthew A. Lackner, Department of Mechanical and Industrial Engineering, University of Massachusetts, 160 Governors Drive, Amherst, MA 01003‐2210, USA. Email: lackner@ecs.umass.edu Funding information U.S. Department of Energy (Office of Science, Office of Basic Energy Sciences and Energy Efficiency and Renewable Energy, Solar Energy Technology Program), Grant/Award Number: DEEE0005494 Abstract The application of structural control to offshore wind turbines (OWTs) using tuned mass dampers (TMDs) has shown to be effective in reducing the system loads. The parameters of a magnetorheological (MR) damper modeled by the Bouc‐Wen model are modified to utilize it as a damping device of the TMD. Rather than showcasing the intricate design policy, this research focuses on the availability of the MR damper model on TMDs and its significance on structural control. The impact of passive and semiactive (S‐A) TMDs applied to both fixed bottom and floating OWTs is evaluated under the fatigue limit state (FLS) and the ultimate limit state (ULS). Different S‐A con- trol logics based on the ground hook (GH) control policy are implemented, and the fre- quency response of each algorithm is investigated. It is shown that the performance of each algorithm varies according to the load conditions such as a normal operation and an extreme case. Fully coupled time domain simulations are conducted through a newly developed simulation tool, integrated into FASTv8. Compared with the passive TMD, it is shown that the S‐A TMD results in higher load reductions with smaller strokes under both the FLS and the ULS conditions. The S‐A TMD using displacement‐based GH con- trol is capable of reducing the fore‐aft and side‐to‐side damage equivalent loads for the monopile by approximately 12% and 64%, respectively. The ultimate loadings at the tower base for the floating substructure are reduced by 9% with the S‐A TMD followed by inverse velocity‐based GH control (IVB‐GH). KEYWORDS magnetorheological damper, offshore wind turbines, pendulum‐tuned mass damper, semiactive control, stroke constraints, structural control 1 | INTRODUCTION Offshore wind energy has the potential to generate substantial amounts of renewable energy due to the high‐quality wind resource compared with onshore locations. 1,2 Recent offshore wind turbine (OWT) foundation types can be classified into two categories: fixed‐bottom substructures, which are a relatively mature commercial technology, and floating platforms. Fixed‐bottom OWTs are only commercially viable only in shallow water depths that are typically less than 60 m but are no longer feasible in deeper water sites. 3 For deployment of OWTs in deeper water sites, floating platforms are necessary, and a growing number of proposed projects plan to use floating technology. 4 Received: 26 September 2018 Revised: 29 January 2019 Accepted: 3 June 2019 DOI: 10.1002/we.2381 Wind Energy. 2019;1–21. © 2019 John Wiley & Sons, Ltd. wileyonlinelibrary.com/journal/we 1