The present study is focused on the structural design of steel structures with steel foundation-girders, and the purpose is to propose an appropriate technique for the stress analysis of the structures subjected to static seismic load taking the effect of soil-pilestructure interaction into consideration based on Chang's formulae. It is clarified that the combined approximations of uniform horizontal displacement with the rotational rigidities of the junctions of column-base and foundation-girders give accurate evaluations to the deformations and stresses of both the structures and the pile foundations.
