LATERAL CYCLIC RESPONSE OF PILE IN VISCOELASTIC WINKLER SUBGRADE

The lateral cyclic response of a pile foundation is formulated by treating the subgrade as a viscoelastic Winkler model for simplicity. Viscoelastic characterization of the model is convenient for the computation of a cyclic response exhibiting the hysteresis nature. The governing equation of a pile foundation is solved for a cyclic force applied at the pile head with the Laplace transformation. The inverse integration is evaluated on a complex plane using a contour integration. The residue of the integration around the pole is associated with the steady-state response. With this solution, simple expressions are developed for the maximum responses along the depth and for the spring and dashpot parameters of a pile at its head. Applications of these simple expressions are demonstrated for the evaluation of pile responses observed in shake table tests, in which the soil was liquefied or semiliquefied during the shaking. The responses are evaluated both in a conservative way and in a straightforward manner. The observed responses along the pile shafts are somewhat higher than the computed results but less than those computed in a conservative way.