Abstract

Current design codes strive to minimise the rocking and sliding movements of shallow foundations during seismic loading despite much research indicating the beneficial nature of allowing such movements. The primary benefit is the partial isolation of the foundation from the soil beneath which leads to a reduced ductility demand on the superstructure, decreased risk of collapse and a more cost effective design. However, further research is required in order to be able to fully model and predict the behaviour of the soil-foundation interface when sliding and rocking are permitted. In this presentation, the results from a series of centrifuge tests which were conducted to investigate the response of shallow foundations located on dry sand and subjected to dynamic loading will be presented. A range of parameters were varied including; relative density, bearing pressure, aspect ratio, structural stiffness, earthquake magnitude and earthquake frequency. Through instrumentation arrays within the soil and on the structure, combined with high-speed photography, the response of the structure and soil were monitored. This data allows the dynamic response of the soil-foundation interface to be analysed and understood by examination of settlement-rotation and moment-rotation plots. Finally, a new analytical model will be proposed which is capable of representing the moment-rotation behaviour.