The seismic responses of foundation piles have invoked more and more attention in design.With the finite element method of complete dynamic interaction of pile-soil-structure combined with a typical case study in engineering

a finite element analysis model was created with a visco-elastic boundary set at the artificially truncated boundary to study the effects of soil characteristics on seismic responses of foun- dation piles for the case of horizontal seismic loads.In two cases of top soft and bottom hard and of top hard and bottom soft of the soil profile

seismic responses of foundation piles were studied through the variation of relative thickness and the ratio of elastic moduli of the soil layers.The result shows that cross- sections of the pile at the intersection of pile-rafter foundation and at the interface of soft and hard soil lay- ers might be the sections of maximum internal forces so that these sections of the pile should be considered as the control sections in the design of the pile body.Effects of characteristics of the soil profile on the mo- ment of piles are more significant than those on the shear.