Geotechnical seismic isolation based on high-damping polyurethane: centrifuge modelling

Geotechnical seismic isolation (GSI) is a new category of low-damage resilient design methods that are in direct contact with geomaterials and of which the isolation mechanism primarily involves geotechnics. Various materials have been explored for placing around the foundation system in layer form to facilitate the beneficial effects of dynamic soil-foundation-structure interaction, as one of the GSI mechanisms. To reduce the thickness of the GSI foundation layer and to ensure uniformity of its material properties, the use of a thin and homogeneous layer of high-damping polyurethane (HDPU) was investigated in this study via centrifuge modelling. HDPU sheets were installed in three different configurations at the interface between the structural foundation and surrounding soils for realising GSI. It was found that using HDPU for GSI can provide excellent seismic isolation effects in all three configurations. The average rates of structural demand reduction amongst the eight earthquake events ranged from 35 to 80%. A clear correlation between the period-lengthening ratio and the demand reduction percentage can be observed amongst the three GSI configurations. One of the configurations with HDPU around the periphery of the foundation only is particularly suitable for retrofitting existing structures and does not require making changes to the structural systems or architectural features.