Application of empirical mode decomposition to determine pile lengths subject to lateral impact

Currently, flexural wave impulse response (IR) tests, which provide better accessibility for inspecting the partially exposed foundations of in-service bridges or buildings, are not used for frequency analysis due to the dispersion characteristics of bending waves at low frequencies. Despite a drawback at low frequencies, both the velocity and frequency span become constant in the high-frequency range. This article uses frequency spectrum-based analysis to evaluate the lengths of three partially embedded model concrete piles subject to lateral impact. The empirical mode decomposition (EMD) approach is used to determine the lower bound frequency, where two requirements, ie constant velocity and regular frequency span, can be fulfilled in order to apply the one-dimensional (1D) wave concept at high frequencies. Beyond the lower bound frequency, the 1D wave concept is reasonably used to predict the pile lengths, with an estimated error below 5% based on frequency analysis.