Enhanced Seismic Vibration Mitigation Using an Inertial Amplification Mechanism-based Absorber (IAM-A)

Structural vibration mitigation are techniques used to reduce or eliminate vibrations in buildings, bridges, industrial structures, and other engineering constructions. These vibrations can be caused by a variety of sources, including human activities, machinery, wind, earthquakes, and traffic. If not properly managed, vibrations can lead to structural damage, reduce the lifespan of structures and in severe cases lead to catastrophic failures. Passive vibration control methods have long been a focal point in protecting civil engineering structures from dynamic excitations such as earthquakes. Among these methods, the Tuned Mass Damper (TMD) has been recognized for its simplicity and effectiveness. However, traditional TMDs, despite their evolution to include damping effects for enhanced performance, present limitations such as the requirement for additional mass and installation space, and a significant displacement response between the absorber and the primary structure. To address the challenges of TMD, a new study published in the Engineering Structures Journal and conducted by PhD candidate Haomin Ma, Associate Professor Zhibao Cheng, and Professor Zhifei Shi from the Beijing Jiaotong University alongside Professor Alessandro Marzani from the University of Bologna, the researchers developed an innovative approach to mitigating structural vibrations through a novel passive vibration control system called the Inertial Amplification Mechanism-based Absorber (IAM-A).

The researchers initially developed the IAM-A concept by integrating an inertial amplification mechanism (IAM) with the design principles of a TMD. The IAM device, characterized by its triangular-shaped mechanism, amplifies inertial forces of attached masses, offering a novel approach to vibration mitigation. The team used 𝐻₂ and 𝐻_∞ optimization methods, to derive closed-form formulas for the design parameters of the IAM-A. These formulas were based on minimizing the dynamic responses of the primary structure to random and harmonic excitations. This optimization considered factors such as the stiffness, mass, angle, and damping coefficient of the IAM-A. The authors conducted parametric studies to assess the influence of the IAM-A’s design parameters on its vibration mitigation performance. This included variations in the geometrical configuration of the IAM device and its impact on the system’s tuning properties. To validate the theoretical and optimization findings, numerical simulations were performed. These simulations modeled the dynamic response of a primary structure equipped with an IAM-A under seismic excitations, comparing its performance to structures with traditional TMDs and those without any vibration control.

The authors’ numerical results confirmed that the IAM-A outperforms traditional TMDs in reducing the dynamic responses of the primary structure. The IAM-A significantly suppressed both the maximum displacement and acceleration responses of the structure. A critical advantage of the IAM-A over the TMD was its ability to reduce the relative displacement response between the absorber and the primary structure by more than half. This addresses a significant limitation of TMDs, which typically require a large displacement response for effective vibration mitigation. The researchers’ parametric studies highlighted the IAM-A’s flexibility in tuning to achieve optimal vibration mitigation performance. By adjusting the geometrical parameters of the IAM device, the system’s tuning frequency can be effectively matched to the target vibration mitigation frequency region. Moreover, the derived closed-form solutions for the IAM-A’s design parameters provide practical guidelines for the system’s implementation in real-world applications. These solutions facilitate the optimization of the IAM-A’s performance for specific structural requirements and seismic conditions. The research also elucidated the relationship between the IAM-A’s mass ratio, geometric configuration, and its energy dissipation capabilities. It was found that IAM-As with smaller angles (𝜃) and larger mass ratios (𝜇) are more efficient in mitigating vibrations, offering insights into the design trade-offs for achieving optimal performance.

In summary, the works conducted by Professor Zhibao Cheng and colleagues demonstrate the IAM-A’s potential as a highly effective and adaptable solution for passive vibration control in civil engineering structures. By offering a more efficient and adaptable solution to seismic vibration mitigation, the IAM-A has the potential to enhance the safety and resilience of structures against earthquakes. This can lead to safer buildings and infrastructure, reducing the risk of damage and loss of life during seismic events.