Control of microvibration transmitting from ground to superstructures using a TMD-based pile-in-pile structure

Low-frequency environmental vibrations have attracted growing concern in densely populated cities due to their low attenuation rate and long wavelength. These factors pose a great challenge to the microvibration control for high-technology facilities. In this study, we propose a pile-in-pile (PIP) structure based on the non-conventional Tuned Mass Damper (TMD) concept, aiming to reduce the horizontal microvibration transmitting from the ground to superstructures. The natural modes of PIP structure are solved through the equivalent TMD model, providing an analytical basis to investigate the superstructure-substructure-soil interaction. Then, a numerical model is developed to evaluate the attenuation effectiveness of PIP structure, which is verified through comparison with existing studies. We comprehensively considered two environmental vibration scenarios, i.e., traffic loads and seismic waves, to investigate the attenuation effectiveness of the PIP structure in both the frequency domain and time domain. The results indicate that intense vibrations can be effectively controlled by transferring them to both the inner and outer piles through placing appropriate springs and dashpots. Under the action of traffic loads, the displacement and acceleration responses are primarily concentrated on the outer pile owing to the difficulty in transmitting external vibrations from the outer pile to the inner pile. In the case of seismic waves, the inner and outer piles act as substructures for each other, with vibrations being dissipated through appropriate connected devices. The mutual motion between inner pile and outer pile enhances the effective control of microvibrations, providing more insights towards the design of a well-performing large-scale TMD system.