US vs EU codes

The forthcoming update of the US AASHTO Specs will agree with the Canadian building code and the US Corps of Engineers code in regard to the analysis and design of piled foundations. Case histories on observations on full-scale piled rafts are reviewed and show that the response of interior and perimeter piles differ. Single piles and perimeter piles engage the soil from the ground downward. In contrast, interior piles engage the soil from the pile toe level upward. Interior piles and soil have strain compatibility, which determines the distribution of load between the piles, the raft contact stress, and the load-transfer movement. Particularly so in subsiding environment, because perimeter piles are subjected to downdrag and drag forces, while neither downdrag nor drag force will affect the interior piles to any appreciable degree. The difference will affect the load distribution and bending moment response across the raft, which is also governed by the degree of rigidity of the raft and by the difference in dishing at the pile toe level and in the dishing of the actual raft. Contact stress under the raft, be it large or small, is incidental to the response of a piled foundation and cannot be considered to reduce the effect of the load applied to the foundation.