Shaking table scale model tests of nonlinear soil-pile-superstructure interaction in soft clay

A significant number of cases of damage to piles and pile-supported structures during earthquakes have been observed, but few instrumented records of the response and performance of such structures during earthquakes have been obtained. To expand the database of pile performance during strong shaking, a series of scale model shaking table tests of model piles in soft clay was performed. This research effort had the goals of providing insight into a variety of soil-pile-supestructure interaction (SSPSI) topics, and generating a data set with which to calibrate advanced SSPSI analysis tools being developed at U.C. Berkeley in a parallel effort.;The single piles were seen to respond with components of inertial and kinematic interaction, with the inertial components producing upper bound bending moments. The response of pile groups was highly frequency dependent, which calls into question the applicability of applying pseudo-static analyses to such problems. Pile cap and free field motion variations illustrated wave scattering effects and the necessity of developing modified foundation input motions for substructuring analyses. Moderate effects of pile cap embedment were observed, particularly in contributing to pile group rocking stiffness.;The influences of two-directional shaking were seen to be minimal, as structural inertial forces tended to resolve the motion to a strong axis for the simple single degree of freedom models tested. For single piles, full perimeter soil resistance was not engaged, as the piles preferentially followed gaps developed in previous cycles.;Estimates of pile head lateral stiffness derived from a suite of pile head loading tests differed over a wide range, and were a function of loading level and consequent soil-pile nonlinearity. The methods examined for computing dynamic stiffness from elastic theory provided unrealistically high estimates of stiffness for the model tests. Appropriately selected secant stiffness values from the static lateral load tests provided more realistic descriptions of the observed soil-pile dynamic response for moderate levels of shaking. ATC-32 chart solutions provided marginally acceptable lower bound pile head stiffness estimates for very strong shaking events. (Abstract shortened by UMI.)...