This Faculty Early Career Development (CAREER) grant will advance understanding of passive control strategies for structural protection from vibration damage due to natural hazards, such as windstorms and earthquakes, by investigating methodologies that utilize variable inertance mechanisms. Variable inertance mechanisms are nonlinear devices that transfer one kind of energy (in this case vibration) to another (in this case rotation). The result is an added mass effect that variably changes the system frequencies, which protects the structure by disrupting harmful interactions between the structure and applied dynamic loads. This mechanism of protection differs significantly from current state-of-the-art passive structural control methods that seek to mitigate damage with precisely tuned devices or dissipate energy through dampers or devices designed to absorb damage. This project will enable new variable inertance-based designs that allow for safer and more economically constructed buildings, thus advancing public welfare and prosperity. The research will be integrated as hands-on curriculum into undergraduate and graduate courses to stimulate interest and advance training in structural engineering. Additionally, outreach activities will help close a critical gap in the training of engineering students by promoting the transition of community college students to four-year engineering programs. Data from this award will be archived and made publicly available in the Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (www.DesignSafe-ci.org). This award supports the National Science Foundation role in the National Earthquake Hazards Reduction Program (NEHRP) and the National Windstorm Impact Reduction Program (NWIRP).
Rotational inertial mechanisms feature the transformation of the translational motion to the rotational motion of a flywheel and can produce large effective mass, known as inertance, with small physical mass. This project will evaluate the hypothesis that variations in effective mass achieved by variable inertance rotational inertia devices can be used to protect structures from dynamic loads. Variable inertance in structures will be considered through state-switching mechanisms in which the rotational mechanism passively engages and disengages with a structure and functionally varied inertance mechanisms in which the inertance passively varies as a function of the response of the mechanism. This research will include analytical modeling, numerical simulations, and experimental testing. Specific intellectual contributions will include: 1) determination of state-switching and functionally varied inertance mechanisms that can be used to produce variable inertance devices, 2) characterization of the effect on natural frequencies of variable inertance strategies, 3) evaluation and characterization of the structural control effectiveness of variable inertance strategies, and 4) assessment of effectiveness of variable inertance strategies in realistic building structures.
This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
