This paper presents a bounding surface plasticity model to characterize soil resistance versus displacement, P-y, behavior for laterally loaded piles subjected to cyclic loading. The model describes the evolution in soil stiffness from initial loading, through a transient stage of degrading stiffness under sustained cyclic loading, to a steady state condition. The model incorporates a kinematic hardening component to produce experimentally observed permanent deformations. The model uses four input parameters: ultimate soil load P/sub ult/, yield load P/sub y/, initial stiffness K/sub e/, and a hardening parameter C. Ultimate resistance P/sub ult/ may be estimated using existing, well-established methods. Experimental data show P/sub y/ and K/sub e/ to be proportional to P/sub ult/, and essentially independent of depth and load cycle. The hardening parameter C appears to be a function of depth and load cycle. Functional forms for these input parameters are provided in this paper, along with values calibrated to centrifuge model test measurements in a kaolin test bed. Model estimates of cyclic bending moments agree with measurements to within 10%. Based on this model, relationships are presented in this paper expressing secant stiffness and damping ratio as functions of cyclic displacement amplitude and number of load cycles.
Ahmed Q. O. Al-Ramthan, Charles P. Aubeny and Olusola Komolafe
Keywords: P-y curves, cyclic loading, bounding surface plasticity, Winkler springs, laterally loaded piles
Publisher: DFI