Physical modelling of dynamic behavior of soil-foundation-superstructure systems

The goal of this paper is to promote the concept of testing centrifuge models that include soil-foundation-superstructure systems. Civil engineering research and practice is often compartmentalized, with structural engineers assuming very simplified foundation behavior, and geotechnical engineers assuming very simplified superstructure behavior. Only in rare cases does a bridge or building designer take account of energy dissipation through foundation yielding. Geotechnical engineers typically design foundations that meet minimum required capacity and stiffness specifications; they do not design foundations that optimize system performance. Large scale centrifuge models offer a unique capability to produce experimental data regarding seismic performance of soil-foundation-superstructure systems. In the centrifuge realistic models of buildings and bridge superstructures can be supported on realistic models of foundations with realistic soil behavior. Soil-foundation-superstructure systems have modes of behavior that are not present in experiments on individual foundation or superstructure components. Examples of two recent series of centrifuge tests demonstrate that system tests are possible and that unique data may be obtained. A spin-off benefit of soil-foundation-superstructure system model tests is the inevitable cross-disciplinary collaboration between structural and geotechnical engineers. It is suggested that this may eventually contribute to an evolution of design philosophy that is based more directly on system performance, with less focus on minimum component specifications.