Strategies for Modeling Partial Pile Head Fixity in Laterally Loaded Pier Foundations

When designing pile groups subjected to lateral loading, modeling and analysis of the connections between piles and the overlying pile caps require careful consideration. For a given pier foundation, characterization of the pile-to-cap connections typically corresponds to one of: pinned (no moment transfer); fixed (moment transfer up to pile rotational capacity); or, partially fixed pile head conditions. The present study aims to provide bridge engineers with practical resources for modeling laterally loaded pile group behaviors, in association with partially fixed pile head conditions. Modeling strategies are presented for both relatively simple (i.e., highly idealized) configurations, as well as for an array of conceivable pier foundations. In particular, an analytical approach is presented, which is suitable for preliminary design of configurations analyzed in a linear elastic manner, and on a representative-pile basis. For nonlinear analysis of pile groups (including soil–structure interaction), a search algorithm is developed that converges on a given target level of partial pile head fixity and associated pile group response (e.g., group lateral displacements, pile head moments). The search algorithm is utilized to investigate 20 unique pier foundation configurations under various lateral load intensities and across target levels of partial fixity. Pairing of the computed foundation responses with the levels of partial fixity, in the ensemble, is intended to serve as a resource to bridge engineers when making initial estimates to model partially fixed pile head conditions.