Response of Foundations to Random Cyclic Loads

Variable amplitude cyclic loads due to natural phenomena are common for laterally loaded piles. A series of small scale cyclic model test have been performed in the Boundary Layer Wind Tunnel Laboratory. Random loads from a boundary layer wind field were applied to a model consisting of a pile, pole and plate. The same setup was also tested under static conditions for comparison. Hyperbolic projection was used to represent the load – displacement relations. Initial stiffness and hyperbolic capacity were obtained from this method. The number of load cycles was found to affect the behavior of the laterally loaded piles. Load cycles were counted using the Rainflow method. Hyperbolic capacity and initial stiffness were found to decrease with increasing numbers of loading cycles. Displacement for laterally loaded piles was greater in the wind tunnel tests compared to static tests. Alternative approaches were used to assess the accumulation of ground-line displacement