Beneficial effect of soil-structure interaction to structural response derived from two building arrays in New Zealand

The soil site spectra for site classes D and E in the current NZ design code impose a significant increase in the displacement demands, between 50 and 300% for a structure with a period of 1.0s or longer, compared with a rock site (class A/B) at the same location. However, for many structures on deep or soft soil sites, effects of soil-structure interaction may partly offset the site amplification by means of a filtering effect, and the rocking / translation of the building foundation relative to the free-field ground motion. In this study, results derived from 2 building arrays in New Zealand are presented to provide quantified reductions in the displacement demands for the structures.