Robust Passive and Active Dampers

Robust Passive and Active Dampers: Enhancing Structural Resilience
Flexible structures are prone to natural frequency variations caused by factors such as wind speed, ambient temperatures, and relative humidity fluctuations. However, the design of tuned mass dampers (TMDs) faces challenges due to these uncertainties. To address this issue, we propose a robust approach to TMD design that considers structural uncertainties, optimization objectives, and input excitations such as wind or earthquake. While practical design parameters for TMDs in buildings may deviate from the optimal ones, predetermined optimal parameters for a primary structure with uncertainties are essential for ensuring design robustness. Our proposed approach has demonstrated remarkable robustness and effectiveness in reducing the response of tall buildings to multidirectional wind loads. Additionally, incorporating LQG and fuzzy logic controllers can further improve the performance of TMDs.

The Lever Mechanism: Unlocking Enhanced Vibration Reduction
Our analysis has revealed that smaller damping devices can achieve higher response reductions. In our investigation, we accounted for stiffness uncertainty and damper failure to evaluate the robustness of the mitigation system. Our findings demonstrate that viscous dampers offer a viable solution for vibration attenuation in high-rise buildings, as they effectively reduce both structural and nonstructural damage. Moreover, these dampers enhance the dynamic performance of tall buildings under multiple hazards, contributing to community resiliency.

Vibration Attenuation in Wind Turbines: A Robust Pendulum Pounding TMD
Drawing on Hertz contact law, we propose a pendulum pounding tuned mass damper (PTMD) for vibration suppression in wind turbines. This innovative device incorporates a boundary composed of viscoelastic material to dissipate energy. To facilitate a comprehensive study, we utilize the Lagrangian method to model a wind turbine equipped with the pendulum PTMD. Our investigation encompasses both harmonic and variable frequency excitations, focusing on a 5 MW wind turbine provided by the National Renewable Energy Laboratory (NREL). By optimizing the dominant parameters of the pendulum PTMD across a wide range of frequency ratios and pounding stiffness under variable frequency sinusoidal excitation, we attain optimum values. Evaluating the device against several parameters, including the coefficient of restitution, mass ratio, and stiffness uncertainty in the primary structure, we establish its superior performance compared to classical TMDs. Design charts are developed to enable the selection of optimal device properties for specific optimization objectives. Our results showcase the pendulum PTMD's robustness and capability to reduce maximum accelerations and displacements under earthquakes, outperforming traditional TMDs under multiple hazard loadings and contributing to the dynamic performance of resilient and sustainable infrastructure.


Robust Passive and Active Tuned Mass Dampers

Outer Bracing System


hig-rise ptms

Vibration Attenuation in a High-Rise Hybrid-Timber Building: A Comparative Study
Recent advancements in engineered timber products, alongside their availability, durability, and renewability, have facilitated the construction of taller and more flexible buildings. However, these structures may experience excessive vibrations, leading to safety and serviceability concerns when subjected to wind or earthquake loads. In this paper, we present a dynamic analysis of a 42-story hybrid-timber building and conduct a comparative study on the performance of three damping devices: pendulum pounding tuned mass damper (PTMD), tuned mass damper inerter (TMDI), and tuned mass damper (TMD). We evaluate the vibration reduction capabilities of the TMD and TMDI under filtered white noise and variable frequency sinusoidal excitations. Additionally, we propose a robust pendulum PTMD designed using the Hertz contact law to minimize responses under seismic excitations. By maintaining an equal mass for the TMD, TMDI, and pendulum PTMD, we ensure a fair comparison. Our results demonstrate the pendulum PTMD's superior performance in reducing peak accelerations under earthquake loads, surpassing the capabilities of both TMD and TMDI. This device effectively reduces damage to structural and nonstructural components under seismic loads. Furthermore, we observe that coupling the inerter and TMD to form a TMDI can shift the optimum frequency and damping ratios, leading to reduced performance. Compared to TMD and TMDI, the proposed pendulum PTMD exhibits robustness and higher performance, reducing the base shear, base moment, and inter-story drift ratio. The dominant capabilities of this novel device in a hybrid-timber building under different excitations hold promise for shaping the future of physical infrastructure. They also contribute to climate change adaptation and mitigation efforts, facilitating improved disaster resilience and circular economy policies.


 ptmd exp




Experimental Verification of a Pendulum Pounding Tuned Mass Damper for Seismic Response Reduction
Recent seismic events have underscored the significance of resilient designs in minimizing losses to life and property. While tuned mass dampers (TMDs) have proven effective in reducing structural vibrations, they may have limitations in protecting buildings from non-structural damage caused by earthquakes. Moreover, their effectiveness can be overwhelmed in high-magnitude seismic events. To address these challenges, we propose a novel device called the tuned pendulum pounding mass damper (PTMD), which adapts the TMD device by introducing a pounding surface near its static equilibrium position. Our hypothesis suggests that this modification will result in superior performance in earthquake mitigation. To test this hypothesis, we conducted a shake table experiment on a PTMD installed in a small-scale building model, incorporating a viscoelastic material to model the pounding effects. Our study reveals that the PTMD's tuning frequency ratio can be obtained analytically, while the pounding stiffness and restitution coefficient must be carefully selected for optimal design. With a mass ratio of 1%, the PTMD significantly reduces the acceleration response. Compared to the TMD, the PTMD exhibits greater robustness and effectiveness in reducing responses across a wider band of frequencies. Conversely, the TMD may amplify structural responses when detuned. The superior capabilities of the proposed PTMD make it a promising candidate for shaping the future of infrastructure and contributing to seismic mitigation policies, thereby enhancing disaster resilience.

Selected Publications