Updated Group Reduction Factors for Large Pile Groups under Lateral Loads

A recent study in Japan presented lateral load tests on a large pile group of seven rows by nine columns. Results from this study show current design methods overestimate the p-multipliers of trailing piles and hence, overestimate the pile capacity in the tested pile group. In this study, 3D finite element models are developed to study the interaction between two piles at various pile spacings and loading directions. Results from the finite element studies are utilized to modify the p-multiplier model. The GROUP computer program is used to calculate the pile cap load-deflection curves with the modified p-multiplier model. The resulting load-deflection curves compare well with experimental curves, especially for pile groups with a large number of piles (≥18 piles) or pile groups with more than five rows of piles.