In this paper

the composite foundation is regarded as homogeneous and the dynamic elastic-plastic soil constitutive model

Davidenkov

is used to describe the dynamic stress-strain relationship of the soil and the composite soil. On the basis of the finite element method software package

ABAQUS

the subroutine of dynamic elastic-plastic soil constitutive model is developed. A representative soft site in Nanjing is selected

and a detailed 2D elastic-plastic seismic response of composite foundation is performed with ABAQUS. A few factors such as the frequency characteristics

acceleration peak value of the input ground motion

the depth and width of composite foundation and the composite module that affect the seismic response of composite foundation are considered. Then some rules are presented:the frequency characteristics and acceleration peak value of the input ground motion have great influence on the seismic response of composite foundation. Contrast with the free site′s

the peak acceleration response on the ground surface of the composite foundation is much smaller. But outside the composite foundation

the peak acceleration response on the ground surface may larger than the free site′s. With the depth of the composite foundation increasing

the peak acceleration response on the composite foundation decreases

and so does the composite module. There seem to be no relationship between the width of composite foundation and the peak acceleration response on the ground surface of composite foundation.