Macroelement modeling of piles in cohesive soil subjected to combined lateral and axial loading

A simple uniaxial stress-strain model based on the Mohr-Coulomb failure criterion is developed for reproducing the macroscopic response of reinforced concrete pile sections in terms of: (a) Bending moment-curvature relationship, and (b) bending moment-axial force (M-N) failure envelopes. An optimization procedure is then proposed for calibrating the model parameters to match the aforementioned pile section response. The developed model is subsequently applied to determine the bearing capacity failure envelopes of single piles subjected to combined axial, rotational and lateral loading at their heads, through 3D finite element analysis with the use of code PLAXIS. The derived M-Q-N failure envelopes (interaction curves) are implemented into a macro-element model by which the response of the pile is represented by a simple set of equations focusing on the pile head. Formulated within the framework of classical elasto-plasticity, the macro-element combines a hardening rule for loading-unloading-reloading of the Bouc-Wen type coupled with an associative plastic flow rule.