New p-y model for seismic loading prediction of pile foundations in non-liquefiable and liquefiable soils considering modulus reduction and damping curves
Lilin Wang, Takeshi Ishihara
Abstract
In this study, a new p-y model is proposed for the seismic loading prediction of pile foundations using the Beam on Nonlinear Winkler Foundation (BNWF) method. It matches the desired modulus reduction curve by identifying three parameters in a hyperbolic function and a linear function using a genetic algorithm (GA), and the desired damping curve by applying the Ishihara-Yoshida rule that controls the unloading–reloading curves iteratively through the three parameters. The rate effect is integrated into the proposed PySimple5 model for clay by exerting influence on the ultimate capacity and maximum material damping through a power function, while the pore pressure effect is reflected in the proposed Pyliq5 model for sand by relating the ultimate capacity to the mean effective stress. For a single pile in non-liquefiable soil, the predicted superstructure acceleration and pile bending moment by PySimple5 agree well with those from centrifuge tests for different soil shear strain levels, while the equivalent linear and PySimple1 models underestimate them for soil shear strain levels higher than 1%. For a pile in liquefiable soil, PyLiq5 shows a reasonable agreement with the centrifuge tests in terms of the superstructure acceleration and pile bending moment by considering the pore pressure effect.