Centrifuge modelling of the seismic response of multi-storey buildings on raft foundations to the christchurch earthquake

There were a number of multi-storey buildings on shallow raft foundations in the Central Business District (CBD) of Christchurch that performed well in the 22 February 2011 Christchurch Earthquake. Structural assessments following the earthquake have concluded that some buildings performed significantly better than would have been expected given the intensity of the recorded ground motions in and around the central city. Nonlinear Soil-Foundation-Structure Interaction (SFSI) provides a possible explanation for the good performance of these buildings. Centrifuge experiments were undertaken at the University of Dundee, U.K., to examine the influence of SFSI in the seismic response of multi-storey buildings on raft foundations using a range of equivalent Single Degree of Freedom (SDOF) building models resting on a layer of dense, dry sand. The models were subjected to representative records from the Christchurch Earthquake and it was found that significant energy was dissipated between the soil, foundation and structure. The large raft in conjunction with dense sand meant significant energy could be dissipated through SFSI without the detrimental effects of significant permanent soil deformation.