Seismic soil–foundation–structure interaction observed in geotechnical centrifuge experiments

This paper reports the experimental results from two geotechnical centrifuge tests examining seismic soil–foundation–structure interaction of frame structures. In the first test, two three-dimensional frame structures were placed apart, and in the second test, the same frame structures were located adjacent to each other. One of the frame structures was founded on shallowly embedded spread footings, and the other was founded on a deeper basement. During the second test, seismic structure–soil–structure interaction was also examined. In this paper, the experimental set-up is described in detail, some kinematic interaction observations are made, and seismic footing response results are reported. The results of the tests indicate that the seismic response of the shallow footings of a flexible frame structure is complex. This result is important because these complexities are not well incorporated in current soil–foundation–structure interaction analysis procedures. The adjacency of two frame structures, and thus structure–soil–structure interaction, further complicates analysis procedures. In the second test, the spread footings rock, slide, and settle less when they are directly adjacent to a deep basement. These results imply that SSSI can be beneficial or detrimental, depending on the earthquake motion and the structural system. In a companion paper, the seismic response of the frame superstructures and the footing force demands are also examined.