Dynamic P-Y Backbone Curves from 1-G Shaking Table Tests

The p-y curve method, which can account for the non linear behavior of soil, is used for modeling dynamically loaded pile foundations in pseudo-static analysis. The p-y curves for static loading conditions are frequently applied even for seismic loading conditions by slight modifications without any further verification, because dynamic p-y curves for seismic loading conditions have not been well established. In this study a series of 1g shaking table tests were carried out in various conditions of acceleration frequency, acceleration amplitude for an input load, flexural stiffness of a pile shaft and a surcharge load at the pile head. The experimental p-y curves for each test condition were evaluated, from which dynamic p-y backbone curves are produced. As a result, two limit backbone curves, due to the big scatter of the test data, were specified as lines connecting the boundary peak points of the experimental p-y curves. In order to represent the upper and lower limit backbone curves numerically, empirical equations were developed for the initial stiffness and the ultimate capacity of soils as a function of a friction angle and a confining stress. The applicability of dynamic p-y backbone curves suggested in this study was evaluated based on the test results of other researchers cited in literature. Also, the backbone curves were compared with the p-y curves that are currently used in practice.