Dynamic Instability of Pile Foundations Under Real Earthquake Excitation

ABSTRACT This paper investigates the dynamic instability of pile foundations subjected to real seismic excitation through numerical analysis. The seismic input is extracted from ground motion records of the 1966 Peru earthquake, specifically the PER01 station record obtained from the official database of the Instituto Geofísico del Perú. The recorded ground acceleration was processed using the SeismoSignal software and then incorporated into the equation of motion of the pile foundation as a parametric excitation. Because the time‐varying coefficient in the equation of motion is represented by digitally recorded discrete data, conventional methods are not directly applicable. To overcome this limitation, a novel numerical method is proposed for evaluating the dynamic instability of systems whose equation coefficients are available only as digital discrete data. The method approximates the state transition matrix using a cascading matrix technique, enabling accurate stability analysis under arbitrary recorded excitations. A series of parametric studies is then conducted to investigate the effects of key parameters—including static load, soil damping, soil stiffness, excitation frequency, pile elastic modulus, and pile length—on the boundaries of the dynamic instability regions.