Wind Turbines: Enhancing Performance and Resilience

Aerodynamic model of 5‐MW National Renewable Energy Laboratory (NREL) wind turbine    Schematic representation of the outer bracing magnetorheological (MR) damper configuration with a lever mechanism connection for displacement amplification to enhance the performance of the dampers

 

 Wind turbine modeling flowchart.  Modeling of MDOF wind turbine.

 

The escalating demand for energy, coupled with the need for sustainable and renewable electricity sources in challenging locations, has led to the widespread deployment of wind turbines. With advancements in materials and construction techniques, modern wind turbines have reached impressive heights while maintaining low structural damping. However, when installed in harsh offshore environments or seismically-active areas, these towering structures face increased risks of failure due to excessive vibrations.

In light of these challenges, our research focuses on evaluating the performance of onshore and offshore wind turbines under multiple hazards, including wind, waves, earthquakes, and mass and aerodynamic imbalances, during both parked and operating conditions. To achieve this, we adopt a Lagrangian approach that incorporates blade/tower coupling to accurately model the behavior of the wind turbine. Additionally, we implement external smart dampers as a mitigation strategy to address the vibrations induced by multihazard loads.

A key contribution of our study is the development of a novel energy-based probabilistic methodology to calibrate semi-active controllers. By applying this methodology, we effectively design and optimize semi-active controllers for wind turbines, enabling effective vibration mitigation across various hazard scenarios. Our findings demonstrate the efficacy of this approach in reducing vibrations and enhancing the resilience of wind turbines exposed to multiple hazards.  

 

High-Rise Buildings: Ensuring Resilient and Sustainable Design

 

tall buildings subjected to multidirectional wind loadsa framework for the calculation of the dynamic response and internal loads

 

Proposed configuration of the MR dampers with bracing system: (a) bracings with dampers between adjacent floors for shear buildings; (b) outer bracings with dampers for cantilever and slender buildings; (c) damping unit consisting of a viscous damper, helical spring, and a lever mechanism for drift amplification across the damper.

 

In recent decades, high-rise buildings have experienced a resurgence in popularity due to their economic and sustainable benefits, particularly in urban areas where land availability is limited. As the construction of tall towers becomes increasingly prevalent worldwide, it is vital to address the challenges posed by multi-hazard disasters and ensure the resilience and safety of these structures.

Our research focuses on comprehending the behavior of high-rise buildings under multi-hazard loading and leveraging this knowledge to inform design practices. Notably, earthquake loads generate higher modes, resulting in lower inter-story drift compared to wind loads. However, wind-induced accelerations may raise concerns regarding occupant comfort and serviceability, while excessive inter-story drifts can compromise structural safety.

To address these concerns, we employ fluid viscous dampers to mitigate the effects of wind and earthquake loads. Through careful analysis, we determine the optimal number and placement of dampers based on modal drifts and targeted response values. Our evaluation encompasses various system-level performance criteria, including displacement, acceleration, inter-story drift ratio, shear force, and base bending moment. By using concise and easily understandable criteria, we facilitate informed decision-making among stakeholders from diverse technical backgrounds.

We find that positioning viscous dampers with a lever mechanism allows for the use of smaller damping devices while achieving higher response reductions. Furthermore, we assess the robustness of the mitigation system by considering uncertainties in stiffness and potential damper failure. The implementation of viscous dampers proves to be a viable solution for attenuating vibrations in high-rise buildings exposed to wind and earthquake loads, effectively minimizing both structural and nonstructural damage. Consequently, these dampers demonstrate their potential to improve the dynamic performance of buildings under multiple hazards, directly contributing to community resilience.

By addressing the challenges faced by wind turbines and high-rise buildings, our research advances the understanding of structural behavior under various hazards and provides valuable insights for the design of resilient and sustainable infrastructure.


 Selected Publications