Filtering property of periodic pile barriers under moving loads

Abstract

The attenuation property of periodic pile barriers for elastic-wave propagation in certain direction induced by stationary loading sources has been extensively investigated. However, the corresponding studies under moving-load excitations are rather limited due to the complexity caused by the time-varying feature of the induced wave-propagation directions. To address this issue, this paper investigates the vibration isolation performance of periodic pile barriers under moving loads. Using the periodic structure theory, a novel method for deriving the attenuation zones of periodic pile barriers under harmonic moving loads is proposed, which allows calculation of the directional attenuation zones (DAZs) for waves propagating in different directions. This is realized by combining the moving-load speed line with the dispersion properties of periodic pile barriers. A simplified numerical model is also developed to analyze the dynamic responses of the periodic pile barriers in frequency domain. The responses of periodic pile barriers under different moving loads are also conducted in time domain to validate the theoretical predictions. The two-dimensional (2D) Fourier transform in both time and space domain is used to study the filtering property of periodic pile barriers under harmonic moving loads and to reveal their vibration isolation mechanism. It is found that different from the stationary loading situation, for which the induced elastic waves mostly propagate in one certain direction, the filtering property of periodic pile barriers under moving loads is related to its dispersion properties along each possible wave-propagation direction. Besides, the attenuation zones for the moving loads are dependent not only on the dispersion properties of the periodic pile barriers, but also on the loading itself, namely the velocity and excitation frequency of the moving load.