Keynote Lecture: US vs EU codes-PPT Presentation

PPT Presentation

Pdf Summary

The presentation proposes a unified, settlement-based method for analyzing single piles and wide pile groups under applied loads and long-term ground subsidence.<br /><br />It argues that negative skin friction (NSF) creates drag force, an environmental action that may affect pile structural strength but does not reduce bearing capacity. Drag force should not be added to the sustained supported load. The key design concern is downdrag: settlement of the foundation, which can become severe even when the pile itself remains structurally sound. For a single pile, force and settlement equilibrium must be considered together with the pile’s toe load–movement response. Their compatible intersection defines the neutral plane.<br /><br />For wide pile groups, the presentation models the piles and surrounding soil as a combined pier, with an equivalent raft at pile-toe level. Settlement depends on soil compression below the pile toes, pile compression, raft rigidity, load distribution, and pile-toe movement. Perimeter piles tend to behave like single piles, while interior piles transfer load differently: toe movement mobilizes shaft resistance upward from near the toe. Load sharing between piles and raft contact stress is governed by stiffness and strain compatibility.<br /><br />Case histories and numerical simulations are presented in support of these principles. The author rejects capacity-based “group efficiency” as unreliable and argues that settlement analysis is the appropriate basis for design. Long-term subsidence is especially important because it can make perimeter piles settle more than interior piles, increasing differential settlement. Adjacent loads, fills, and excavations must also be considered.

Keywords

settlement analysis

single piles

pile groups

negative skin friction

downdrag

neutral plane

bearing capacity

pile-soil interaction

long-term subsidence

differential settlement