Estimation of load-sharing ratios for piled rafts in sands that includes interaction effects

A key design component for piled rafts is the proportion of load carried by the raft and piles, as both contribute to the load-carrying behavior of piled rafts. The analysis in the present study of the load-sharing behavior of piled rafts embedded in sands includes consideration of the pile-raft interaction effect. For this purpose, 3D finite element analyses were performed for various foundation and soil conditions. Due to the interactions between raft and piles, the load-carrying capacities of the raft and piles, once combined into a piled raft, become different from those of unpiled rafts and group piles. As pile spacing increased, the load proportion of piles became higher. Based on the results from finite element analyses, a normalized load-sharing model was proposed that introduced the load capacity interaction factor β. Values of β were evaluated, and a design equation was proposed. The values of β decreased logarithmically with increasing settlement, showing a marked decrease within the initial settlement range. Case examples were introduced to confirm the validity of the proposed method. Reasonably close agreement was observed between measured and calculated load-sharing behaviors.