Earthquakes induce a lateral loading in a structure. As a result, an effective passive structural control method is required. Typically, base isolation systems have been used to mitigate seismic induced vibrations. This system was developed based on a concept to prevent damage to the structure by decoupling the building from its foundation during earthquakes. Ideally, base isolators introduce flexibility at the base consequently leading to absorption of most of the Earthquake-induced kinetic energy. Base isolation systems are typically adopted within the framework of passive control of structures. Recent research has shown that near-fault earthquakes may induce excessive base displacements and low-frequency resonances, which may cause base isolation systems to exceed the working range and malfunction. One probable solution to overcome this drawback is to attach supplemental control devices to the system, such as bio-inspired actuators and tuned mass damper inerters. Specifically, the tuned mass damper inerter (TMDI) which is based on a structural control strategy that couples the classical tuned mass damper with an inerter has been presented and tested.
A review of recent literature revealed that enhanced base isolation systems equipped with TMDI showed an improved performance in terms of not only meeting the displacement demand of base-isolation systems but also of reducing the structural responses of isolated superstructures. In a quest to further this knowledge, researchers from the Department of Mechanical Engineering, University of California Santa Barbara: Haitao Li, Dr. Isaac Kwon, Franklin Ly and led by Professor Henry Yang developed a new bio-inspired base isolator equipped with a tuned mass damper inerter. Their goal was to demonstrate a numerical model consisting of a bio-inspired tuned mass damper inerter isolation system, structural system model, and energy response equation as an integral system for structural control. Their work is currently published in the research journal, Smart Materials and Structures.
In their work, the structural control performance of the present bio-inspired base isolation system was demonstrated with numerical simulations using both a single-degree-of-freedom model and a multi-degree-of-freedom model under six different samples of earthquake excitations. In addition, a parametric study was performed to explore the effectiveness of the parameters chosen for the structure. Lastly, parametric analyses of maximum bio-inspired damping force, damping coefficient, stiffness and inertance were performed.
The authors noted that the comparative study with three other types of existing base isolators revealed the effectiveness of the present bio-inspired tuned mass damper inerter isolation system in reducing the displacement, acceleration, input energy ratio and base shear force for the illustrative cases. Moreover, the research team reported that based on the comparisons of responses to six different earthquakes selected, one could observe that for the specific parametric studies, the present passive bio-inspired TMDI base isolation system achieved comparable structural control performance to the state-of-the-art base isolators.
In summary, the study by UC Santa Barbara scientists demonstrated an improved structural control strategy using a bio-inspired passive base isolation system with tuned mass damper inerter. In addition to the traditional base isolation system, a bio-inspired actuator and tuned mass damper inerter were adopted in the model. The numerical models of single-degree-of-freedom and multi-degree-of-freedom structures were simulated to demonstrate the effectiveness of the present base isolation system. In a statement to Advances in Engineering, Haitao Li, first author, highlighted that their results illustrated that satisfactory target responses could be achieved for the examples studied by optimizing parameters such as maximum bio-inspired damping force, damping coefficient, stiffness, and inertance of the inerter.
Haitao Li, Henry T Yang, Isaac Y Kwon, Franklin S Ly. Bio-inspired passive base isolator with tuned mass damper inerter for structural control.Smart Materials and Structures, volume 28 (2019) 105008 (19pp)