Experimental Curvature and Moment Response of Pile Foundations: Comparison with p-y Predictions-Paper

Paper

Pdf Summary

The study evaluates conventional p–y predictions against large-scale tests of three 16-inch-diameter piles embedded in loose sand: reinforced concrete, concrete-filled steel tube, and hollow steel pipe. Each pile was instrumented to measure deformation and internal strain, then subjected to reversed cyclic lateral loading through structural failure.<br /><br />The tests showed that soil gaps formed around the piles at small displacements and grew with continued loading. Experimental load–displacement curves had initial stiffness two to three times lower than predicted by LPILE. However, measured peak lateral capacities were up to 20% greater than the predictions, and yielding occurred at displacements roughly 1.6 to 1.8 times those predicted.<br /><br />The central comparison was between measured and predicted curvature and bending-moment profiles. LPILE consistently overpredicted curvature, with discrepancies generally increasing at larger displacements. At one inch of head displacement, predicted curvature was about 2.4–3 times the measured values; at two inches, it was about 2.3–4.3 times greater. Measured curvature was distributed more broadly along the piles, suggesting more gradual strain redistribution and greater ductility than the model captured. Despite magnitude differences, the analysis generally identified the depth of maximum curvature reasonably well, particularly at larger displacements. Predicted maximum moments also tended to exceed measured values, commonly by about a factor of two and sometimes three.<br /><br />The findings highlight limitations of simplified p–y models, which may not adequately represent pile structural behavior, soil stress redistribution, and gapping under large deformation. The authors recommend using cracked moment–curvature relationships when converting measured curvature into moment and suggest that future models account for pile and soil behavior as a coupled system.

Keywords

p-y curves

lateral pile loading

loose sand

large-scale pile tests

reinforced concrete pile

concrete-filled steel tube

hollow steel pipe

LPILE model

curvature overprediction

soil gapping