Methods for the assessment of the nonlinear variation in pile foundation stiffnesses are presented. Values of such lateral and vertical/rotational stiffnesses are intended for use for boundary elements springs of a structural dynamic model of a highway bridge undergoing seismic analysis. Conflicts between the FHWA and Applied Technology Council approaches to foundation stiffness evaluation as well as deficiencies in these methods are noted. The methodology presented is demonstrated relative to a number of field case studies that have backcalculated values (or other responses) with which to compare. Such field case studies involve both failing and nonfailing soil responses, different soil conditions, a wide range of deflection amplitudes, and different types of loading (ambient level tests, full-scale, push-back, quick-release bridge tests, and response during earthquake excitation).
Abstract