Nonlinear Dynamic Behaviour of Hollow Piles Based on Axial Harmonic Loading

Abstract

The main objective of the current work is to examine the dynamic axial response of three pile group under machine-based harmonic loads. Field tests are carried out under axial harmonic excitations on a group pile with a pile length of 300 cm and an diameter of 11.4 cm in order to accomplish this objective. For various eccentric moments, the frequency versus amplitude responses of the group pile are measured. The field test results of the soil-pile system show non-linear behaviour as their resonant frequencies decrease and their resonant amplitudes disproportionally increase with eccentric forces. The inverse methodology proposed by Novak (1971) is used for the theoretical study. With this methodology, the changes in stiffness, damping, and effective mass of the piles under various eccentric moments are quantified by analyzing the frequency-amplitude response curves of field results. The theoretically back-calculated soil-pile system response curves are compared with the field results, and it is observed that the analytically predicted responses closely match the field responses. It is also found that the values of estimated damping of the pile group increased, while effective mass and average stiffness values decreased with an increase in eccentric moments.