Analysis of Laterally Loaded Pile Groups with Partial Pile Head Fixity

Deflections of laterally loaded pile groups are strongly affected by the degree of pile head fixity. If the cap provides perfect restraint against rotation, deflections are only about 25% as large as the deflections for no rotational restraint at the tops of the piles. The degree of rotational restraint is governed by (a) the rotation of the piles with respect to the cap, and (b) the rotation of the cap itself. This paper reviews available information on pile head fixity and proposes a simple method for considering pile head fixity in analyses of pile groups. The method includes consideration of nonlinear soil behavior, pile-soil-pile interaction, the resistance to lateral loads provided by pile caps, and the degree of pile head fixity. The proposed method can be implemented through computer programs such as LPILE and COM624P, and spreadsheets based on the Characteristic Load Method.