A Macro-element for Pile Groups Subjected to Vertical Eccentric Load

This work proposes a mathematical approach to derive the displacement pattern of pile groups subjected to vertical eccentric load. To this end, a new macro-element is formulated in the framework of strain-hardening elasto-plasticity. The equations are developed by assuming an associated flow rule for the evaluation of the plastic deformations and an exponential relationship for the load-displacement curve of the group. The collapse domain is approximated by a parabolic equation while the yield surface has the same shape of the collapse surface and is scaled homothetically through a hardening function accounting for the past load history of the foundation. The evolution of this state variable is expressed by a pertinent hardening law. The proposed approach is validated against data from centrifuge experiments on pile groups embedded in clay.